Document
NASA/TM-2010-216209
Landing Gear Components Noise Study – PIV
and Hot-Wire Measurements
Florence V. Hutcheson and Casey L. Burley
Langley Research Center, Hampton, Virginia
Daniel J. Stead and La wrence E. Becker
Lockheed Martin Engineering and Sciences, Hampton, Virginia
Jennifer L. Price
National Institute of Aerospace, Hampton, Virginia
March 2010
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NASA/TM-2010-216209
Landing Gear Components Noise Study – PIV
and Hot-Wire Measurements
Florence V. Hutcheson and Casey L. Burley
Langley Research Center, Hampton, Virginia
Daniel J. Stead and La wrence E. Becker
Lockheed Martin Engineering and Sciences, Hampton, Virginia
Jennifer L. Price
National Institute of Aerospace, Hampton, Virginia
National Aeronautics and
Space Administration
Langley Research Center
Hampton, Virginia 23681-2199
March 2010
Available from:
NASA Center for AeroSpace Information (CASI)
7121 Standard Drive
Hanover, MD 21076-1320
443-757-5802
Landing Gear Components Noise Study –
PIV and Hot-Wire Measurements
Florence V. Hutcheson and Casey L. Burley
Aeroacoustics Branch/RTD
Daniel J. Stead and Lawrence E. Becker
Lockheed Martin Engineering and Sciences
Jennifer L. price
National Institute of Aerospace
NASA Langley Research Center
Hampton, VA 23681
Abstract
PIV and hot-wire measurements of the wake flow from rods and bars are
presented. The test models include rods of different diameters and cross sections and a
rod juxtaposed with a plate. The latter is representative of the latch door that is attached
to an aircraft landing gear when the gear is deployed, while the single and multiple rod
configurations tested are representative of some of the various struts and cables
arrangements present on an aircraft landing gear. The test set-up is described and the flow
measurements are presented. The effect of model surface treatment and freestream
turbulence on the spanwise coherence of the vortex shedding is studied for several rod
and bar configurations.
1. Introduction
During airport approach, the noise radiated from aircraft landing gears is a dominant
1-7 8-10
airframe noise source. A number of numerical and experimental studies have been
conducted in order to identify and model the noise generation mechanisms of landing
gear configurations. Noise reduction studies are also ongoing. Since many components
of a landing gear (the struts, the cables, the axles) can be modeled by rods of various
lengths and cross-sections, understanding the generation mechanisms of the noise
radiated from single and multiple rod configurations is of relevance to the landing gear
noise reduction effort.
In the present study, PIV, hot-wire and acoustic measurements were obtained for
single and two rod configurations to investigate the effect of incoming turbulence, yaw
angle, proximity and wake interference on the rod’s vortex shedding a nd on the radiated
noise. The PIV measurements will be used in a subsequent study to characterize the
turbulence in the wake of the rod elements. This information, along with the hot-wire
data, will be used to develop improved flow and noise prediction models. The acquisition
of the PIV and hot-wire measurements is described in this paper and the results obtained
are presented. Results from the acoustic study are presented in ref. 12.
2. Test description
The PIV and hot-wire measurements for this landing gear noise component
experiment were performed at NASA Langley Research Center in the Quiet Flow Facility
(QFF). The QFF is an open jet facility equipped with a 2 by 3 foot rectangular open jet
nozzle. The rods were supported 19” above the nozzle by two vertical side plates that are
mounted to the short sides of the nozzle (see Figure 1).
side
plate
rod
side
plate
nozzle
exit
flow
Figure 1. Test set-up
For some of the rod configurations tested, a turbulence generating grid was mounted
across the exit plane of the nozzle (as shown in Figure 2). The purpose of the grid was to
generate known turbulence upstream of the rods for study of rod configurations in clean
and freestream turbulent flow. Acoustic foam treatment was glued along each bar of the
turbulence grid to attenuate noise from the air flowing through the grid. When a
turbulence grid was used, the rods were mounted 40” downstream of the nozzle exit plan,
in a region of the flow where the generated turbulence is assumed to be homogeneous
based on the grid geometry .
Figure 2. Turbulence grid with acoustic foam mounted on the nozzle.
The turbulence grid, shown in Figure 3, was designed such that it would generate
macro-scales (integral scale) ranging between 0.5” to 0.92” and micro -scales (dissipation
scale) ranging between 0.07” to 0.12”. The grid bars were 0.5”x 0.5” in cross section, and
the spacing (center to center) between consecutive bars was 2.22”.
Figure 3. Grid for generation of small scale turbulence.
2.1 Model configurations
Square and circular aluminum rods of 3 ft length were tested. Measurements were
taken at flow mach numbers of 0.13 and 0.17 (when the turbulence grid was used,
measurements were taken only at 0.13 Mach number). PIV and hot-wire measurements
were taken in the wake of single and multiple rods configurations. These configurations
are listed below in Table 1. Measurements were taken for both smooth and gritted model
surfaces (#90 grit was used for the gritted configurations). Hot-wire measurements were
taken for only a subset of the configurations listed in Table 1, namely configurations 1, 2, 9, 13, 20 and 21.
Several concepts for the reduction of the noise radiating from a cylindrical rod were
examined. These concepts were inspired by an experiment conducted by Ahuja et al. to
reduce the noise radiating from car antennas. In that experiment, protrusions in the form
of O-rings and beads were distributed along the span of a conical rod immersed in a
uniform flow. It was shown that the protrusions reduced the radiated noise by rendering
the vortex shedding along the span of the rod less coherent. It is also mentioned in ref.14 that similar results can be achieved by wrapping a wire along the span of the rod.
In the present study, the effect of collars (configuration 20) and wire wraps
(configuration 21) on the noise radiated by a cylindrical rod was examined. The collars
are uniformly distributed along the span of the rod and the wires are wrapped along the
entire span of the rod. Hot-wire measurements were performed to determine the effect of
the collars and wire wraps on the vortex shedding spanwise coherence. Preliminary
microphone measurements were also acquired to obtain an initial measure of the impact
of the collars and wire wraps on the radiated noise level.
Table 1. Model configurations.
Configuration Sketch Description
(cross - section s )
1 1” diam eter rod
flow
2 ½” diameter rod
3 Two 1” diameter rods together.
4 Two 1” diameter rods , c enters 2” a part.
5 Two 1” diameter rods , c enters 3” a part.
6 1” diameter rod upstream of a ½” rod, centers 3”
apart.
7 ½” diameter rod upstream of a 1” rod, centers 3”
apart.
8 Two 1” diameter rods, centers 1” apart an d
aligned perpendicular to flow .
Two 1” diameter rods, centers 2” apart and
9 aligned perpendicular to flow.
10 Square bar (1”x1” cross section) with two sides
parallel to flow.
11 Square bar (1”x1” cross section) with 2 sides at
30 ° with flow .
12 Square bar (1”x1” cross section) with 2 sides at
45 ° with flow.
13 3/4 ” diameter rod with 4” wide by 0.2” thick plate
(same span as rod), no gap. Rod secured to plate
with 17 evenly spaced brackets. The edges of the
plate are beveled down to 0.04” over a distance of
0.27” .
14 3/4 ” diameter rod with 4” wide by 0. 2 ” thick plate
(same span as rod), 0. 1” gap. Rod secured to
plate with 17 evenly spaced brackets. The edges
of the plate are beveled down to 0.04” over a
distance of 0.27”.
Configuration Sketch Description
(spanwise views)
1” diameter rod, axis 15 ° from plan e perpendicular
15 to flow.
1” diameter rod, axis 30 ° from plan e perpendicular
16 to flow.
1” diameter rod perpendicular to flow and 1/2”
17 diameter rod with axis 30 ° from 1” ro d axis.
Distance between rod centers at mid span is 3”.
1/2” diameter rod perpendicular to flow with a
18 1”x1” cylindrical collar (with rounded edges)
located at mid - span.
1/2” diameter rod perpendicular to flow w ith a
19 1”x1” square collar located at mid - span.
1/2” diameter rod perpendicular to flow with eleven
collars (1.5” long, 3/4” in diameter, rounded
20 edges) centered every 3.1”.
1/2” diameter rod perpendicular to flow with 1/8”
2.5”
21 wire wrapped along the full span of the rod.
2.2 PIV system set up
The PIV system set up is described in Figure 4. As shown in this figure, flow field
measurements were performed downstream of the rod elements using stereo PIV. Such
PIV configurations yield three components (3-C) of velocity over a two-dimensional
plane. The PIV measurements were obtained for two PIV window locations downstream
of the models. For most of the configurations, the measurements were taken at the model
mid-span and in a plane parallel to the test section walls (i.e., parallel to the side plates).
The first measurement location, window A, was located directly above the rod (or
directly above the most downstream rod for multiple rods configurations). The distance
between the bottom edge of the measurement location and the rod surface was
approximately 1mm. Window A covered a 10” by 10” area. A second measurement
location, window B, was located 8.5” further downstream. Window B covered also a 10”
by 10” area which overlapped the first measurement area defined as window A by
approximately 1.5”.
side plates
measurement
windows A and B
traverse
traverse
position B
cameras position B
laser 2
position A
laser 1 position A
rod
side plate
U
o
camera
traverse
rod
lasers
nozzle
camera
Side view
Top view
Figure 4. Illustration of PIV system set-up (not to scale).
The PIV measurement planes were illuminated using two Nd:YAG, 120 mJ, double
cavity lasers with a repetition rate of 15 Hz. To minimize laser reflections from the test
model, beam- blocks were used to “chop off” the light sheet as close as possible to the
model surface. The thickness of the light sheet was about 1 mm.
Two Redlake MegaPlus ES 1.0 CCD cameras with 105 mm lenses were used to
record the PIV images with a resolution of 1008 by 1012 pixels. The lasers, optical lenses
and cameras were mounted on a traverse system in order to maintain the distance
between the cameras and the light sheet constant while moving to the different
measurement locations.
The flow was seeded upstream of the low-pressure air fan (i.e., at the beginning of the
flow circuit) to ensure a homogeneous distribution of the seeded particles throughout the
jet flow. Laskin nozzle seeders filled with Bis(2-Ethylhexyl) Sebacate were used to
generate particles of less than 1 m in diameter.
Over 400 image pairs were acquired at each measurement location, at a rate of 15
frames per second (the frame rate was synchronized with that of the laser pulse).
Integrated Design Tools proVISION software (version 2.01.08) was used to process the
PIV images and generate 3-component velocity vector maps. The PIV images were
processed with a 24 by 24 interrogation window size with a 50% overlap, leading to a
resolution of 1 velocity vector for each 1.15 mm by 0.94 mm area. Cross- correlation
techniques were used to compute the velocity vectors from PIV image pairs. The
percentage of interpolated velocity vectors computed in each vector map was kept below
1% (an interpolated vector is the result of a least square interpolation of nearest
neighbors).
2.3 Hot-wire system set up
The hot-wire measurements were acquired using two straight hot-wire probes.
Platinum-plated tungsten wires with a diameter of 5 m and unplated active length of
0.13 cm were used. The resistance of the wires ranged between 3.4 and 3.8 Ohms. An
overheat ratio of 1.8 was used. The wires were operated using a TSI IFA 100 constant
temperature anemometer (CTA) and were tuned for a frequency response of
approximately 80 kHz. The bridge output of the CTA was obtained in NetCDF format
using a NEFF system 495 data acquisition unit using a 12-bit A/D converter. The data
was sampled at a rate of 142.8 kHz. The signal was separated into AC and DC
components to maximize the available system gain. At each measurement location, 2,048,000 data points were taken yielding just over 14 seconds worth of data.
A five-hole pitot-static tube was used in conjunction with the hot-wire probes in order
to verify the hot-wire measurements. The pressure measurements were obtained with a
PSI system 8400 data acquisition unit which was accurate within ±0.0025 psi. The hot-
wires were calibrated frequently throughout the duration of the test. These calibrations
th
were performed measuring both flow velocity and wire voltages. A 4 order polynomial
fit was applied to the data to obtain calibration curves.
The hot-wire measurements were acquired with one wire remaining stationary at the
model mid-span while the second hot-wire traversed the flow in increments in either the
spanwise (x) or cross-stream (z) direction (see Figure 5 and 6). Cross-stream surveys
were performed for configurations 1, 9 and 13 at the following downstream locations:
x 0.5” (i .e., as close as possible to the rod surface), x =1.5” and x =5.5”, where
1 2 3
(x,y,z)=(0,0,0) is on the axis of the rod at the model mid-span. For each of the
aforementioned x locations, the stationary wire was located at (x ,0,0) while the
i, i=1,2,3 i
traversing wire was moved from (x ,0,- 2”) to (x ,0,+2”) with an increment z of 0.5”
i i
between each measurement location. For configuration 9, in which a second rod is placed
parallel to the first one at z=-2, the cross-stream survey extended between z=- 4”and z=2”
with z=0.5”. For configuration 13, because of the plate that is attached to the rod, the
cross-stream survey at x 0.5” extended only between z=0 and z=2”.
Stationary wire
(at model midspan)
pitot tube
traversing wire
Figure 5. Hot-wire probes set-up.
Cross - stream Spanwise surveys
. … . . . . . ….. . …..
surveys
. … . . . . . ….. . …..
X X
. … . . . . . ….. . …..
z o
rod
Y
rod ( midspan)
M
M
Figure 6. Hot-wire cross-stream and spanwise surveys.
Spanwise surveys were performed for configurations 2, 20 and 21 at downstream
locations x =0.5”, x = 0.75” and x = 1.5” . For configurations 1, 9 and 13 a spanwise
4 5 2
survey was performed only at downstream location x 0.5” . For each of the
aforementioned x locations, the stationary wire was located at (x ,0,0) while the
i, i=1or 2,4,5 i
traversing wire was moved to each of the following spanwise locations: (x ,y,0) where y=
i
0.25 ” , 0.5 ” , 0.75 ”, 1 ” , y=1 ” +0.5 ” k (k =1,2,…8 ), y=5 ” +n ( n=1,2,…5 ) and y=13 ” and 17 ” .
3. Test results
3.1. PIV results
The flow field images obtained from the PIV measurements are presented in figures 7
through 27. The results displayed were obtained with the standard data processing
methodology described in section 2.3. Figures displaying the instantaneous in-plane
ˆ ˆ
velocity field ( u x v y ) (with the free stream velocity subtracted) and the instantaneous
dv du
axial vorticity field ( ) are shown for all the model configurations tested.
z
dx dy
For presentation clarity, the vectors in each map are only shown for every second node in
x and y.
In each plot, the PIV results obtained from measurement windows A and B (see
Figure 5) are shown. The plots from measurement window A show the wake flow up to
250 mm downstream of the model while the second plot shows the wake flow in the
region located between 200 mm and 450 mm downstream of the model. The two plots are
purposely not shown overlapped as the measurements were taken at different instants in
time.
In a follow up study, various spectral decomposition techniques such as POD will be
applied to these PIV measurements to characterize and define the turbulence shed by the
different rod configurations tested in this experiment. This information will be used to
model the turbulence shedding from landing gear components.
3.2. Hot-wire results
The wake flow velocity data obtained from the streamwise and spanwise hot-wire
surveys were acquired to support related CFD model development. In this section only
results drawn from the spanwise survey data are presented. The spanwise surveys were
performed to examine the effect of incoming turbulence, surface treatment and noise
reduction devices (collars and wire wrap) on the vortex shedding spanwise coherence.
These results will subsequently be tied to the acoustic study since the vortex shedding
spanwise coherence is related to the amplitude of the radiated noise .
Cross spectra between the stationary and the traversing hot-wire signals were
generated with a frequency resolution f of 17.4 Hz. These cross-spectra were calculated
when the stationary and traversing hot-wires were located 0.25” apart (along the model
span) at downstream location x (for model configurations 2, 20 and 21) or x (for model
1 4
configurations 1, 9 and 13). Each cross spectrum generally displayed a small correlation
peak at the frequency f = f and a stronger correlation peak at f = 2 f , where f
0 0 0
corresponds to the rod vortex shedding frequency. The cross spectra obtained for the 1”
rod (i.e., configuration 1) are presented in Figure 28.
The spanwise variation of the coherence γ of the vortex shedding was calculated
over a 5-bin frequency band centered at f = 2 f . The coherence is defined as
(f) G
ab
(f) γ (1)
(f) G (f) G
bb aa
where G (f), G (f) and G (f) are the cross spectra and auto spectra of the stationary and
ab aa bb
traversing hot-wire signals.
The spanwise coherence for the smooth and gritted 1” rod, with and without
freestream turbulence is displayed in Figure 29. The flow Mach number is 0.13. It is
seen that for the smooth rod in clean flow some coherence in the vortex shedding is
maintained over a span of approximately 3.5D (where D is the rod diameter). When the
surface of the rod is gritted, the coherence length increases to approximately 6D. When
freestream turbulence is introduced (by the turbulence grid) and the surface of the rod is
smooth, the level of spanwise coherence in the vortex shedding is seen to become very
low. Once the surface of the rod is gritted, the spanwise coherence level recovers and is
close to that for the clean flow test cases.
At a Mach number of 0.13, the Reynolds number for this 1” rod configuration is
77,000 (and 100,000 at Mach number 0.17). For this Reynolds number (and when the rod
surface is smooth), the burst to turbulence occurs in the free shear layers near the side of
the cylinder and the formation of alternate eddies takes place close to the rear of the
15 16,17
cylinder . It has been reported in several experimental studies that in this flow
regime, free stream turbulence will affect the flow past the cylinder when the integral
scale Ts of the turbulence is less than the rod diameter D and a reduction of the vortex
shedding coherence length will result. It was observed in these studies that for Ts/D < 1, a
flow regime that would otherwise occur for higher Reynolds numbers, namely (100k-
200k) < Re < (300k-340k), was triggered. In this new flow regime, transition to
turbulence occurs in the free shear layers along the separation lines. This state of flow is
associated with a drop in the vortex shedding coherence length (and drop in the drag
coefficient) as the three-dimensionality of the onset of the transition to turbulence affects the spanwise “uniformity” of the flow. In the present study, Ts/D is less than 1, therefore,
the reduction in coherence length that was observed for the smooth rod is consistent with
16,17
previous published findings .
As mentioned previously, for the present test case, the vortex shedding coherence
length was found to be high when the rod surface was gritted, regardless of the presence
of freestream turbulence. This behavior is also consistent with a study by Batham who
suggests that the roughness turbulence triggers transition around the separation line more
evenly and in doing so, the separation line is straightened, leading to higher spanwise
coherence levels.
Finally, regarding the hot-wire measurements that were performed on the 1” rod
configuration, it is shown in Figures 30 and 31 that the spanwise coherence scales well
with the Strouhal number.
The cross spectra obtained for configuration 9 are shown in Figure 32 (for this side by
side rod configuration, the two hot-wires were aligned along the span and in the center
plane (z=0) of one of the two rods). It is seen that the cross spectra again display two
correlation peaks, one at the vortex shedding frequency f = f and the other at f = 2 f .
0 0
The correlation peak recorded at f = f is stronger than for the single rod case. This could
be explained by the presence of a bias gap flow between the two rods. Thus, for this side
by side arrangement, narrow and wide wakes often form behind the two cylinders. The
gap flow is then biased towards the narrow wake and is bistable, switching to either side,
leading to an interchange of the narrow and wide near-wake behind the cylinders . This
leads to the presence of a stronger cross-stream velocity component (than in the single
rod case) that the hot-wires are more able to detect, allowing a distinction between the
vortices that are shed from either side of the rod. This leads to a stronger spectral peak at
the vortex shedding frequency. The correlation peaks observed in the cross spectra are
also broader in frequency than in the single rod case. This can probably be explained by
the continuous change between narrow and wide wakes which may cause the vortex
shedding frequency to drift between a higher value for the narrow wake flow and a lower
value for the wider wake flow.
The spanwise coherence for the side by side rod configuration is displayed in Figure
33. The flow Mach number is 0.13. The effects of freestream turbulence and of surface
roughness are found to be similar to that observed for the single rod case. The spanwise
coherence is high for the gritted rods with or without freestream turbulence, and for the
smooth rods in clean flow. The spanwise coherence drops when freestream turbulence is
introduced and the surface of the rods is smooth. Also, as for the single rod configuration,
the vortex shedding spanwise coherence for the side by side rods is found to scale well
with the Strouhal number (see figures 34 and 35).
The spanwise coherence for the smooth and gritted 1/2” rod, with and without
freestream turbulence is displayed in Figure 36. Results are shown for a flow Mach
number of 0.13 for the freestream turbulence cases and for Mach numbers 0.13 and 0.17
for the clean flow cases. It is seen that for the clean flow cases, some coherence in the
vortex shedding is maintained over a span of approximately 5D (where D is the rod
diameter) when the flow Mach number is 0.13 and 6D when the flow Mach number is
0.17. It is also seen that when the surface of the rod is smooth, the coherence levels
measured along the rod span are similar for the three downstream locations surveyed. For
the gritted rod cases, larger variations are noted between the spanwise surveys performed
at different downstream locations. When freestream turbulence is introduced, the
spanwise coherence levels are only slightly reduced (and some coherence in the vortex
shedding is maintained over a span of approximately 4D). This is consistent with
Batham ’s study which found that for the present flow regime, turbulence with integral
scale greater than the rod diameter does not affect the cylinder flow. Based on the design
of the turbulence grid used in this test, 1 Ts/D < 2 for the 1/2” rod . Therefore only a
portion of the eddies generated by the grid (as oppose to probably most of the eddies for
the 1 ” rod test configurations) may be of a scale small enough to modify the cylinder
flow and affect the spanwise coherence of the vortex shedding. This would explain the
limited effect of the freestream turbulence on the spanwise coherence for the 1/2" rod
cases compared to that for the 1” rod cases.
For model configurations 20 and 21 (1/2” rod with collars or wire wrap), the
spanwise coherence of the vortex shedding was nonexistent for the spanwise surveys
performed at 0.5” and 0.75” downstream of the rods . The cross spectra obtained for the
1/2" rod with collars (model configurations 21) are shown in Figure 37. For comparison,
the cross spectra obtained between the stationary and traversing hot-wires for a simple
1/2" rod (model configurations 2) are displayed in figures 38 and 39. For configuration 2,
the cross spectra are showing the expected correlation peaks at the vortex shedding
frequency f and 2f . For configuration 21 (as for configuration 20), the cross spectra do
0 0
not show any correlation peaks for the spanwise surveys performed at x=0.5 ” and 0.75”.
For configuration 20, however, the spanwise coherence of the vortex shedding recovered
at x=1.5”. This was not observed for the wire wrap configuration but it may be that the
spanwise coherence of the vortex shedding may also recover further downstream of the
rod, but just not at x=1.5”. Recovery in vortex shedding spanwise coherence downstream
of the rod should not affect the level of radiated noise since the noise is generated by the
flow (pressure) fluctuations that are occurring directly along the surface of the rod
surface.
The noise spectra obtained for configurations 2, 20 and 21 from preliminary acoustic
measurements show the drastic noise reduction that occurs when collars or the wire
wraps are installed on the rod. The noise spectra for 1/2” rod with smooth or gritted
surface or equipped with collars or with a wire wrap are shown in Figure 40 for a uniform
flow of Mach number 0.17. It is seen from this figure that good broadband noise
reduction is achieved when the surface of the rod is gritted, however the spectral peak at
the vortex shedding frequency is not attenuated. When the collars or the wire wrap are
installed on the rod, about 25 dB reduction is achieved at the shedding frequency and the
large tone generated by the vortex shedding is nearly eliminated. With the collar
configuration, a 7 to 12 dB noise reduction is also achieved at frequencies greater than
the vortex shedding frequency and up to 50 kHz (the cutoff frequency). The same level of
noise reduction is achieved with the wire wrap between the shedding frequency and 18
kHz. Above 18 kHz, the noise reduction achieved is around 3 dB.
For model configuration 13 (rod with side plate) with smooth surface and immersed
in a clean flow, the spanwise hot-wire measurements indicated only a very weak level of
spanwise coherence in the vortex shedding. Thus, a coherence level of about 0.1 is
maintained over a 4D span at the vortex shedding frequency f (for M=0.13 and M=0.17).
Unlike the other model configurations tested, the hot-wire cross-spectra only displayed a
(small) peak at f= f . This results from the fact that the hot-wire probes are located beside
the plate, near the rod surface, and are therefore exposed to the vortices that are shed
from only one side of the rod. When freestream turbulence is introduced, the
measurements indicate an absence of spanwise coherence in the vortex shedding (at the
survey location) for the smooth and gritted models.
5. Conclusion
PIV and hot-wire measurements performed in the wake of single and multiple rods
configurations were presented. Measurements were taken for both smooth or gritted
model surfaces, and with and without freestream turbulence. The effect of model surface
treatment and freestream turbulence on the spanwise coherence of the vortex shedding
was studied for several rod configurations. The results indicate that for a smooth rod and
a flow Mach number of 0.13, the introduction of freestream turbulence led to a large
reduction of the spanwise coherence of the vortex shedding when the turbulence integral
scale Ts is less than the rod diameter D. For 1 Ts/D < 2, the freestream turbulence had
limited effect on the coherence. It was also observed that freestream turbulence had
minimal effect on the spanwise coherence of the vortex shedding for the gritted rods. For
smooth and gritted rods, immersed in a clean flow, the spanwise coherence of the vortex
shedding was found to scale well with Strouhal number.
It was also verified that wrapping a wire or distributing collars along a rod
successfully reduces the spanwise coherence of the vortex shedding, leading to a large
noise reduction.
References
1. Smith, M. G., Chow, L. C. “Prediction method for aerodynamic noise from aircraft
landing gear”, AI AA paper 98-2228.
2. Smith, M. G., Chow, L. C. “Validation of a prediction model for aerodynamic noise
from aircraft landing gear”, AIAA paper 2002 -2581.
3. Souliez, F. J., Long, L. N., Morris, P. J. and Sharma, A. “Landing gear
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25 m/sec (u - u ) 25 m/sec (u - u )
25 m/sec (u - u ) a) b) c )
Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 t = t 450 t = t 450 2 2 t = t 450 2 400 400 350 350 300 300 250 250 t = t t = t t = t 1 1 200 200 150 150 100 100 100 Streamwise direction (mm) 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 -50 -100 -50 -100 -50 -100 50 100 0 50 100 0 50 100 25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 -2000 0 2000 -2000
d ) e ) f )
t = t 450 t = t 450 2 t = t 450 350 350 300 300 t = t t = t 1 t = t 200 200 150 150 100 100 50 50 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 -50 -100 0 50 100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 7. Configuration 1 ( 1” diameter rod ). Axial vorticity contours and in-plane velocity vectors .
a) smooth rod, clean flow, M=0.13; b) smooth rod, clean flow, M=0.17; c) gritted rod, clean flow, M=0.13; d) gritted rod, clean flow, M=0.17 e) smooth rod, turbulent flow, M=0.13; f) gritted rod, turbulent flow, M=0.13.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 2000 -2000 0 2000 t = t 450 t = t 450 2 2
a ) b)
400 400 300 300 t = t t = t 1 1 200 200 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 -50 -100 0 50 100 0 50 100 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 -2000 t = t 450 t = t 450
c ) d )
t = t t = t 50 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 8. Configuration 2 (1/2 ” diameter rod ). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 -2000 t = t 450 t = t 450
a ) b)
400 400 t = t t = t 50 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 t = t 450 t = t 450
c ) d )
t = t t = t 1 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 9. Configuration 3 (two 1” diameter rod s together, streamwise alignment). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u )
a) b) c )
Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 0 2000 -2000 -2000 t = t 450 t = t 450 t = t 450 2 300 300 250 250 t = t t = t t = t 1 1 200 200 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 0 50 100 -50 -100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 0 2000 -2000 -2000
d ) e ) f )
t = t 450 t = t 450 t = t 450 2 2 400 400 350 350 t = t 1 t = t t = t Streamwise direction (mm) 50 Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 0 50 100 -50 -100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 10. Configuration 4 (two 1” diame ter rods, 2” apart , streamwise alignment). Axial vorticity contours and in-plane velocity vectors. a) smooth rod, clean flow, M=0.13; b) smooth rod, clean flow, M=0.17; c) gritted rod, clean flow, M=0.13; d) gritted rod, clean flow, M=0.17; e) smooth rod, turbulent flow, M=0.13; f) gritted rod, turbulent flow, M=0.13.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 0 -2000 -2000 2000 t = t 450 t = t 450 2 2
a ) b)
t = t 1 t = t Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 -50 -100 0 50 100 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) 25 m/sec (u - u ) Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450
t = t 450 c ) d )
t = t t = t 50 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 11. Configuration 5 (two 1” diameter rods, 3” apart , streamwise alignment). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000
a ) b)
t = t 450 t = t 450 t = t t = t 1 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450
c ) d )
t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 12. Configuration 6 (½” rod downstream of 1” rod ). Axial vorticity contours and in-plane velocity vectors. Clean Flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u )
Vorticity a) b) c )
Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -2000 0 2000 0 2000 -2000 t = t 450 2 t = t 450 t = t 450 350 350 250 250 t = t t = t 1 t = t 1 1 200 200 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000
t = t 450 d ) e ) f )
t = t 450 t = t 450 250 250 t = t t = t 1 t = t 100 100 100 50 50 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 0 0 -50 -100 0 50 100 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 13. Configuration 7 ( 1” rod downstream of ½” rod ). Axial vorticity contours and in-plane velocity vectors. a) smooth rod, clean flow, M=0.13; b) smooth rod, clean flow, M=0.17; c) gritted rod, clean flow, M=0.13; d) gritted rod, clean flow, M=0.17; e) smooth rod, turbulent flow, M=0.13; f) gritted rod, turbulent flow, M=0.13.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 t = t 450 t = t 450 2 2
a ) b)
400 400 350 350 300 300 250 250 t = t t = t 1 1 200 200 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 -50 -100 0 50 100 0 50 100 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 t = t 450 t = t 450
c )
d )
t = t t = t 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 -50 -100 0 50 100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm)
Figure 14. Configuration 8 (two 1” diameter rod s together, cross-stream alignment). Axial
vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 t = t 450 t = t 450
a ) b)
t = t t = t 1 1 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 0 50 100 0 100 200 -100 -200 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 0 2000 t = t 450 t = t 450
c ) d )
250 250 t = t t = t 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 -100 -200 0 50 100 0 100 200 Cross-stream direction (mm) Cross-stream direction (mm) Figure 15. Configuration 9 (two 1” diameter rod s, 2” apart , cross-stream alignment). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450
a ) b)
t = t t = t 50 Streamwise direction (mm) Streamwise direction (mm) -100 -200 0 100 200 -50 -100 25 m/sec (u - u ) 0 50 100 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity Cross-stream direction (mm) Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450
2 c )
d )
t = t t = t 150 150 Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 0 100 200 -100 -200 Cross-stream direction (mm) Cross-stream direction (mm) Figure 16. Configuration 10 (square bar). Axial vorticity contours and in-plane velocity vectors.
Clean flow a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 t = t 450 t = t 450
a ) b)
t = t 1 t = t Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 -50 -100 0 50 100 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 0 2000 -2000 t = t 450 t = t 450
c )
d )
t = t t = t 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 0 50 100 -50 -100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 17. Configuration 11 (square bar, rotated 30°). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 0 2000 -2000 t = t 450 t = t 450
a ) b)
350 350 300 300 t = t t = t 1 1 Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 0 50 100 -50 -100 25 m/sec (u - u ) 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 0 2000 -2000 -2000 t = t 450 t = t 450 2 2
c ) d )
400 400 350 350 300 300 250 250 t = t t = t 1 1 200 200 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 18. Configuration 12 (square bar, rotated 45°). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u )
Vorticity a) b) c )
Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 2000 -2000 0 2000 -2000 0 2000 t = t 450 2 t = t 450 t = t 450 400 400 250 250 t = t t = t 1 t = t 1 200 200 150 150 100 100 Streamwise direction (mm) Streamwise direction (mm) 50 Streamwise direction (mm) 0 25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u ) 0 50 100 -50 -100 -50 -100 0 50 100 Vorticity 0 50 100 -50 -100 Vorticity Vorticity Cross-stream direction (mm) Cross-stream direction (mm) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Cross-stream direction (mm) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 0 2000 0 2000 -2000 -2000 t = t 450 t = t 450 2 t = t 450
d ) e ) f )
t = t t = t 1 t = t Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 19a. Configuration 13 ( 1” rod with plate, no gap). Axial vorticity contours and in-plane velocity vectors. Smooth model surface, clean flow. Measurements performed at the following spanwise locations a) center of a bracket, M=0.13; b) bracket side edge, M=0.13; c) between two brackets, M=0.13; d) center of a bracket, M=0.17; e) bracket side edge, M=0.17; f) between two brackets, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity
a) b) c )
Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450 t = t 450 400 400 350 350 300 300 250 250 t = t t = t 1 1 t = t 200 200 150 150 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 t = t 450 t = t 450 2 t = t 450
d ) e )
f )
250 250 t = t t = t t = t 1 1 Streamwise direction (mm) 50 Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 19b. Configuration 13 ( 1” rod with plate, no gap). Axial vorticity contours and in-plane velocity vectors. Gritted model, clean flow. Measurements performed at the following spanwise locations a) center of a bracket, M=0.13; b) bracket side edge, M=0.13; c) between two brackets, M=0.13; d) center of a bracket, M=0.17; e) bracket side edge, M=0.17; f) between two brackets, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u )
a) b) c )
Vorticity Vorticity 25 m/sec (u - u ) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 t = t 450 0 2000 2 -2000 t = t 450 t = t 450 t = t t = t t = t Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 19c. Configuration 13 ( 1” rod with plate, no gap). Axial vorticity contours and in-plane
velocity vectors. Gritted model, turbulent flow. Measurements performed at the following
spanwise locations a) center of a bracket, M=0.13; b) side edge of a bracket, M=0.13; c) between two brackets, M=0.13; 25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u )
a) b) c )
Vorticity Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 0 2000 -2000 2000 -2000 -2000 0 2000 t = t 450 t = t 450 t = t 450 2 400 400 250 250 t = t t = t t = t 200 200 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 -50 -100 0 50 100 25 m/sec (u - u ) -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Cross-stream direction (mm) Cross-stream direction (mm) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 0 2000 -2000 -2000
t = t 450 f )
t = t 450 t = t 450 d ) e )
2 2 400 400 350 350 250 250 t = t 1 t = t t = t 1 1 200 200 100 100 50 50 Streamwise direction (mm) Streamwise direction (mm) Streamwise direction (mm) 0 0 0 -50 -100 -50 -100 0 50 100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 20a. Configuration 14 ( 1” rod with plate, 0.1” gap). Axial vorticity contours and in-plane velocity vectors. Smooth model, clean flow. Measurements performed at the following spanwise locations a) center of a bracket, M=0.13; b) bracket side edge, M=0.13; c) between two brackets, M=0.13; d) center of a bracket, M=0.17; e) bracket side edge, M=0.17; f) between two brackets, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u )
a) b) c )
Vorticity 25 m/sec (u - u ) Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 t = t 450 t = t 450 t = t 450 t = t t = t t = t 200 200 150 150 100 100 Streamwise direction (mm) 50 50 Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 25 m/sec (u - u ) 25 m/sec (u - u ) 25 m/sec (u - u ) -50 -100 0 50 100 -50 -100 0 50 100 Vorticity Cross-stream direction (mm) Vorticity Vorticity Cross-stream direction (mm) Cross-stream direction (mm) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 0 2000 0 2000 -2000 t = t 450 t = t 450 t = t 450 2 2 2
d ) e ) f )
400 400 350 350 300 300 250 250 t = t 1 t = t t = t 1 1 150 150 100 100 Streamwise direction (mm) 50 Streamwise direction (mm) Streamwise direction (mm) 0 0 0 50 100 -50 -100 -50 -100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Cross-stream direction (mm) Figure 20b. Configuration 14 ( 1” rod with plate, 0.1” gap) . Axial vorticity contours and in-plane velocity vectors. Gritted model, clean flow. Measurements performed at the following spanwise locations a) center of a bracket, M=0.13; b) bracket side edge, M=0.13; c) between two brackets, M=0.13; d) center of a bracket, M=0.17; e) bracket side edge, M=0.17; f) between two brackets, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -2000 0 2000 t = t 450 2 t = t 450
a ) b)
t = t t = t 1 1 Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 25 m/sec (u - u ) 0 50 100 -50 -100 Cross-stream direction (mm) Vorticity Cross-stream direction (mm) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 25 m/sec (u - u ) Vorticity t = t 450 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000
0 2000 c )
-2000 d )
t = t 450 t = t t = t Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 21. Configuration 15 (1” rod , 15° with flow). Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) Vorticity 25 m/sec (u - u ) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity -2000 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450
a ) b)
t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 0 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 t = t 450
2 c )
d )
t = t 450 t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 22. Configuration 16 (1” rod , 30° with flow). Axial vorticity contours and in-plane velocity vectors.Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 0 2000 -2000 t = t 450 t = t 450
a ) b)
t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) 25 m/sec (u - u ) Cross-stream direction (mm) Vorticity 25 m/sec (u - u ) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450
c ) d )
t = t 450 t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 23. Configuration 17 (1” rod and ½” rod 30° with flow) . Axial vorticity contours and in- plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 2000 t = t 450 t = t 450
a ) b)
t = t t = t Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 -50 -100 0 50 100 25 m/sec (u - u ) Cross-stream direction (mm) Cross-stream direction (mm) Vorticity 25 m/sec (u - u ) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 t = t 450
c )
d )
t = t 450 t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 24. Configuration 18 (1/2” rod with 1 rounded collar) . Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 0 2000 -2000 -2000 t = t 450 t = t 450 2 2
a ) b)
350 350 t = t t = t Streamwise direction (mm) 50 Streamwise direction (mm) -50 -100 0 50 100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 0 2000 -2000 t = t 450 t = t 450 2
c ) d )
t = t t = t Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 25. Configuration 19 (1” rod with square collar) . Axial vorticity contours and in-plane velocity vectors. Clean flow. a) smooth rod, M=0.13; b) smooth rod, M=0.17; c) gritted rod, M=0.13; d) gritted rod, M=0.17.
25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 Vorticity 0 2000 -2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 t = t 450 t = t 450
a ) b)
t = t t = t Streamwise direction (mm) Streamwise direction (mm) -50 -100 0 50 100 Cross-stream direction (mm) 0 50 100 -50 -100 Cross-stream direction (mm) 25 m/sec (u - u ) 25 m/sec (u - u ) Vorticity Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 0 2000 -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 -2000 2000 t = t 450
2 c ) d )
t = t 450 t = t t = t 1 Streamwise direction (mm) Streamwise direction (mm) 0 0 -50 -100 0 50 100 -50 -100 0 50 100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 26. Configuration 20 (1” rod with 11 collars) . Axial vorticity contours and in-plane velocity
vectors. Smooth model, clean flow. Spanwise location of measurements and flow speed: a) at
center of a collar, M=0.13; b) midway between two collars), M=0.13; c) at center of a collar, M=0.13; d) midway between two collars, M=0.17.
25 m/sec (u - u ) Vorticity 25 m/sec (u - u ) -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 Vorticity -2000 -1714 -1429 -1143 -857 -571 -286 0 286 571 857 1143 1429 1714 2000 0 2000 -2000 t = t 450 t = t 450
a ) b)
t = t t = t Streamwise direction (mm) Streamwise direction (mm) 0 50 100 -50 -100 0 50 100 -50 -100 Cross-stream direction (mm) Cross-stream direction (mm) Figure 27. Configuration 21 (1” rod with wire wrap) . Axial vorticity contours and in-plane velocity
vectors. Smooth rod, clean flow. Measurements performed at model midspan a) M=0.13; b)
M=0.17.
smooth 1" rod
gritted 1" rod
clean flow
clean flow
M=0.13
M=0.13
cross spectral density cross spectral density
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
smooth 1" rod
gritted 1" rod
clean flow
clean flow
M=0.17
M=0.17
4 4
cross spectral density cross spectral density
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
6 6
smooth 1" rod gritted 1" rod
turbulent flow turbulent flow
5 5
M=0.13 M=0.13
4 4
3 3
2 2
cross spectral density cross spectral density
1 1
0 0
0 500 1000 1500 2000 0 500 1000 1500 2000
frequency (Hz) frequency (Hz) Figure 28. 1” rod. Cross spectral density between the stationary and traversing hot-wires. The
two hot-wires are aligned along the span of the rod. The spacing between the two probes is
y=0.25”.
0.9
0.8
1"rod, M=0.13
smooth surface, clean flow
0.7
gritted surface, clean flow
smooth surface, turbulent flow
0.6
gritted surface, turbulent flow
)
0.5
sqrt(
0.4
0.3
0.2
0.1
0 2 4 6 8 10
span/D
Figure 29. Spanwise coherence for a 1” rod . f= 2 f . The flow Mach number is 0.13.
0.9 0.9 0.8
gritted 1"rod
clean flow
0.8 0.7
smooth 1"rod, clean flow
0.7 0.6 ) 0.6 ) 0.5
M=0.13
M=.13 0.5 sqrt( M=.17
0.4 M=0.17
sqrt(
0.4 M=.13 M=0.13
M=.17 0.3
M=0.17
0.3 0.2 0.2 0.1 0.1 0 0 1 2 3 4 0 1 2 3 4
freq*span/U
freq*span/U Figure 30. Spanwise coherence at f= 2 f . Figure 31. Spanwise coherence at f= 2 f .
0 0 1” rod , smooth surface, clean flow. 1” rod , gritted surface, clean flow.
gritted tandem 1" rods
smooth tandem 1" rods
clean flow
clean flow
5 5
M=0.13
M=0.13
cross spectral density cross spectral density
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
smooth tandem 1" rods
gritted tandem 1" rod
clean flow
clean flow
5 5
M=0.17
M=0.17
cross spectral density cross spectral density
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
6 6
gritted tandem 1" rods
smooth tandem 1" rods
turbulent flow
turbulent flow
5 5
M=0.13
M=0.13
4 4
3 3
2 2
cross spectral density cross spectral density
1 1
0 0
0 500 1000 1500 2000 0 500 1000 1500 2000
frequency (Hz) frequency (Hz) Figure 32. Two side by side 1” rods. Spacing center to center is 2”. Cross spectral density between the stationary and traversing hot-wires. The two hot-wires are aligned along the span of one of the two rods. The spacing between the two probes is y=0.25”.
0.9
0.8
two 1"rods side by side, M=0.13
0.7
smooth surface, clean flow
gritted surface, clean flow
0.6
)
smooth surface, turbulent flow
gritted surface, turbulent flow
0.5
sqrt(
0.4
0.3
0.2
0.1
0 2 4 6 8 10
span/D
Figure 33. Spanwise coherence, f= 2 f . Two 1” r od s side by sides, centers 2” apart.
The flow Mach number is 0.13.
0.9 0.9 0.8 0.8
two gritted 1" rods side by side
two smooth 1" rods side by side 0.7
0.7
clean flow
clean flow
0.6 0.6 ) ) 0.5 0.5 sqrt(
sqrt( M=0.13
M=.13 M=.13
0.4 0.4 M=0.13
M=.17
M=0.17
M=.17
M=0.17
0.3 0.3 0.2 0.2 0.1 0.1 0 1 2 3 4 0 0 1 2 3 4 freq*span/U
freq*span/U
Figure 34. Spanwise coherence at f= 2 f . Figure 35. Spanwise coherence at f= 2 f .
0 0 Two 1” rods side by sides, centers 2” apart. Two 1” rod s side by sides, c enters 2” apart.
Smooth surface, clean flow. Gritted surface, clean flow.
gritted 1/2" rod
smooth 1/2" rod
0.9
0.9
clean flow
clean flow
0.8 M=0.13
0.8
M=0.13
0.7
0.7
2 2
γ
γ
0.6
0.6
x=0.5"
x= 0.5"
0.5 x=0.75"
0.5
x=0.75"
x=1.5"
x=1.5"
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0 2 4 6 8 10
0 2 4 6 8 10
span/D
span/D
1 1
smooth 1/2" rod gritted 1/2" rod
0.9
0.9
clean flow clean flow
0.8 0.8
M=0.17 M=0.17
0.7 0.7
2 2
γ γ
0.6 0.6
x= 0.5" x= 0.5"
0.5 0.5
x=0.75" x=0.75"
x=1.5" x=1.5"
0.4 0.4
0.3 0.3
0.2 0.2
0.1 0.1
0 2 4 6 8 10 0 2 4 6 8 10
span/D span/D
smooth 1/2" rod
0.9 gritted 1/2" rod
0.9
turbulent flow
turbulent flow
0.8
0.8
M=0.13
M=0.13
2 2
0.7
0.7
γ γ
0.6
0.6
x= 0.5"
x= 0.5"
0.5
x=0.75" 0.5
x=0.75"
x=1.5"
0.4
x=1.5"
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0 2 4 6 8 10
0 2 4 6 8 10
span/D
span/D
Figure 36. Spanwise coherence for a 1/2 ” rod . f= 2 f .
smooth 1/2" rod with collars
smooth 1/2" rod with collars
3 clean flow
clean flow
M=0.13
M=0.17
x=0.5"
x=0.5"
cross spectral density
1 cross spectral density
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
smooth 1/2" rod with collars smooth 1/2" rod with collars
clean flow clean flow
M=0.13 M=0.17
x=0.75" x=0.75"
cross spectral density cross spectral density
1 1
0 500 1000 1500 2000
0 500 1000 1500 2000
frequency (Hz) frequency (Hz)
4 4
smooth 1/2" rod with collars smooth 1/2" rod with collars
clean flow clean flow
3 3
M=0.17 M=0.13
x=1.5" x=1.5"
2 2
cross spectral density cross spectral density
1 1
0 0
0 500 1000 1500 2000 0 500 1000 1500 2000
frequency (Hz) frequency (Hz) Figure 37. 1/2” rod with collars. Cross spectral density between the stationary and traversing hot- wires. The two hot-wires are aligned along the span of the rod. The spacing between the two probes is y=0.25”.
4 4
4 4
smooth 1/2" rod smooth 1/2" rod
gritted 1/2" rod gr
clean flow clean flow
clean flow cl
3 3 3 3
M=0.13 M=0.17
M=0.13 M
x=0.5" x=0.5" x=0.5" x=
2 2
2 2
cross spectral density cross spectral density
1 cross spectral density 1 cross spectral density
1 1
0 0
0 0
0 500 1000 1500 2000 0 500 1000 1500 2000
0 500 1000 1500 2000 0 500
frequency (Hz) frequency (Hz) frequency (Hz) freq
4 4
4 4
smooth 1/2" rod smooth 1/2" rod
gritted 1/2" rod gr
clean flow clean flow
clean flow cl
3 3 3 3
M=0.13 M=0.17
M=0.13 M
x=0.75" x=0.75"
x=0.75" x=
2 2
2 2
cross spectral density cross spectral density
1 cross spectral density 1 cross spectral density
1 1
0 0
0 0
0 500 1000 1500 2000 0 500 1000 1500 2000
0 500 1000 1500 2000 0 500
frequency (Hz) frequency (Hz) frequency (Hz) freq
4 4 4 4
smooth 1/2" rod gritted 1/2" rod smooth 1/2" rod gr
clean flow clean flow clean flow cl
3 3 3 3
M=0.13 M=0.13 M=0.17 M
x=1.5" x=1.5" x=1.5" x=
2 2 2 2
cross spectral density cross spectral density cross spectral density cross spectral density
1 1 1 1
0 0 0 0
0 500 1000 1500 2000 0 500 1000 1500 2000 0 500 1000 1500 2000 0 500
frequency (Hz) frequency (Hz) frequency (Hz) freq Figure 38. Smooth 1/2” rod. Cross spectral density between the stationary and traversing hot- wires. The two hot-wires are aligned along the span of the rod. The spacing between the two probes is y=0.25”.
4 4
th 1/2" rod smooth 1/2" rod
gritted 1/2" rod gritted 1/2" rod
flow clean flow
clean flow clean flow
3 3 3
13 M=0.17
M=0.13 M=0.17
" x=0.5" x=0.5" x=0.5"
2 2
cross spectral density
cross spectral density 1 cross spectral density
1 1
0 0
0 1500 2000 0 500 1000 1500 2000
0 500 1000 1500 2000 0 500 1000 1500 2000
y (Hz) frequency (Hz) frequency (Hz) frequency (Hz)
4 4
th 1/2" rod smooth 1/2" rod
gritted 1/2" rod gritted 1/2" rod
flow clean flow
clean flow clean flow
3 3 3
13 M=0.17
M=0.13 M=0.17
5" x=0.75"
x=0.75" x=0.75"
2 2
cross spectral density
cross spectral density 1 cross spectral density
1 1
0 0
0 1500 2000 0 500 1000 1500 2000
0 500 1000 1500 2000 0 500 1000 1500 2000
y (Hz) frequency (Hz) frequency (Hz) frequency (Hz)
4 4 4
th 1/2" rod gritted 1/2" rod smooth 1/2" rod gritted 1/2" rod
flow clean flow clean flow clean flow
3 3 3
13 M=0.13 M=0.17 M=0.17
" x=1.5" x=1.5" x=1.5"
2 2 2
cross spectral density cross spectral density cross spectral density
1 1 1
0 0 0
0 1500 2000 0 500 1000 1500 2000 0 500 1000 1500 2000 0 500 1000 1500 2000
y (Hz) frequency (Hz) frequency (Hz) frequency (Hz) Figure 39. Gritted 1/2” rod. Cross spectral density between the stationary and traversing hot- wires. The two hot-wires are aligned along the span of the rod. The spacing between the two probes is y=0.25”.
smooth ½” rod
SPL
(dB)
½” rod with wire wrap
SPL
(d B)
50 ½” rod with collars
0 1 2 3 4 5
Frequency (kHz)
gritted ½” rod
0 10 20 30 40
Frequency (kHz)
Figure 40. Noise spectra for the 1/2" rod. Four configurations: smooth or gritted 1/2" rod, smooth 1/2" rod with collars or with wire wrap. Clean incoming flow. Mach number 0.17.
Form Approved
REPORT DOCUMENTATION PAGE
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1. REPORT DATE (DD-MM-YYYY)
2. REPORT TYPE 3. DATES COVERED (From - To)
03 - 2010 01-
Technical Memorandum
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Landing Gear Components Noise Study - PIV and Hot-Wire Measurements
5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
Hutcheson, Florence V.; Burley, Casey L.; Stead, Daniel J.; Becker, Lawrence E.; Price, Jennifer L.
5e. TASK NUMBER
5f. WORK UNIT NUMBER
561581.02.08.07
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
REPORT NUMBER
NASA Langley Research Center
Hampton, VA 23681-2199
L-19839
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)
National Aeronautics and Space Administration
NASA
Washington, DC 20546-0001
11. SPONSOR/MONITOR'S REPORT
NUMBER(S)
NASA/TM-2010-216209
12. DISTRIBUTION/AVAILABILITY STATEMENT
Unclassified - Unlimited
Subject Category 71
Availability: NASA CASI (443) 757-5802
13. SUPPLEMENTARY NOTES
14. ABSTRACT
PIV and hot-wire measurements of the wake flow from rods and bars are presented. The test models include rods of different diameters and cross sections and a rod juxtaposed to a plate. The latter is representative of the latch door that is attached to an aircraft landing gear when the gear is deployed, while the single and multiple rod configurations tested are representative of some of the various struts and cables configuration present on an aircraft landing gear. The test set up is described and the flow measurements are presented. The effect of model surface treatment and freestream turbulence on the spanwise coherence of the vortex shedding is studied for several rod and bar configurations.
15. SUBJECT TERMS
Noise; Flow measurements; Landing gear; Rod and bar configurations; Wake flow
19a. NAME OF RESPONSIBLE PERSON 18. NUMBER 17. LIMITATION OF
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