APPENDIX
APPENDIX TRIANGULAR PA/_ICLES OF ADHESIVE TAPE FOR BOUNDARY-LAYER TRANSITION Two practical difficulties encountered in the use of carborundum roughness particles are the lack of uniformity of the particle pattern (caused by large variations in size and shape of the individual particles) and the length of time required for application. These problems are accentuated when it is nec- essary to repeat the application of the roughness bands several times as is done in one of the currently used techniques for assessing the particle-drag penalty.
A type of three-dimensional roughness which offers promise of eliminating these difficulties consists of triangular particles cut from adhesive tape.
The size and shape of these particles can be accurately controlled and no addi- tional bonding agent is required to affix the particles to the model surface, with a resultant savings in time for application. Triangular particles of this type have been tested at the University of Maryland in a water tunnel (refs. 6 and 7) and at the Ames Research Center in air. In both studies, the triangular roughness particle was shown to be more effective in promoting artificial tran- sition than spherical roughness particles of the same height.
Results obtained from tests at supersonic speeds at Ames are shown in fig- ure 13. The ratio of minimum spherical trip Reynolds number to minimum trian- gular trip Reynolds number for transition near the roughness is plotted against Mach number for station Reynolds numbers from 0.029 × l06 to 0.6 X l06 and for particles with height greater than the boundary-layer thickness. These results show that for the conditions of figure 15, the particle height required to fix transition near the roughness is less for triangular trips than for spherical trips. At the top of figure 13 is a sketch showing the dimensions and orienta- tion with respect to the free stream of the triangular trips used in the Ames tests. Triangles with apex angles ranging from 49 ° to 139 ° were found to pro- duce only small variations in the transltion-promoting effectiveness in the studies of reference 7- However, it has been found in both the Ames and the University of Maryland studies that a reduction in effectiveness will be real- ized if the apex of the triangle does not point into the flow.
Although the use of triangular roughness appears encouraging, further investigation is required in the following problem areas: (1) The amount of distortion of the boundary layer caused by the trian- gular trips as compared with the spherical trips (2) The drag penalty of the triangular trips compared with the spherical trips (5) The effect of wing leading-edge sweep on the transition-promoting effectiveness of the triangular trips
APPENDIX - Concluded
APPENDIX - Concluded
(4) The effect of pressure gradient on the transition-promoting effec-
tiveness of the triangular trips
(_) The effectiveness of triangular trips with heights less than the
boundary-layer thickness
lO
REFERENCES i. Braslow, Albert L. : Review of the Effect of Distributed Surface Roughness on Boundary-Layer Transition. AGARD Rept. 254, Apr. 1960.
2. Von Doenhoff, Albert E. ; and Braslow, Albert L. : The Effect of Distributed Surface Roughness on Laminar Flow. Boundary Layer and Flow Control, Vol. 2# G. V. Lachmann, ed., Pergamon Press, 1961, pp. 657-681.
3. Fetterman, David E. ; McLellan, Charles H.; Jackson, L. Robert; Henry, Beverly Z., Jr.; and Henry, John R. : A Review of Hypersonic Cruise Vehicles. NASA TM X-1276, 1966. (Also included in NASA SP-124. ) 4. Loving_ Donald L. : Wind-Tunnel--Flight Correlation of Shock-Induced Separated Flow. NASA TN D-3580, 1966. (Also included in NASA SP-124. ) 5. Henderson, William P. : Studies of Various Factors Affecting Drag Due to Lift at Subsonic Speeds. NASA TN D-5584, 1966. (Also included in NASA SP-124. ) 6. Hama, Francis R. : An Efficient Tripping Device. J. Aeron. Sci. (Readers' Forum), vol. 24, no. 3, Mar. 1957, PP. 236-237.
7. Hegarty, John C. ; and Hama, Francis R. : Further Investigations on the Trlangular-Patch Stimulator. Tech. Note BN-107 (AFOSR TN-57-616, ASTIA AD 136 605), Inst. Fluid Dyn. Appl. Math., Univ. of Maryland, June 1957.
ll DEFINITION OF BOUNDARY-LAYER PARAMETERS x_ k-GRIT NATURAL TRANSITION ROUGHNESS REYNOLDS NUMBER
R,--
VALUE OF R k FOR FORWARD MOVEMENT Rk, cr OF TRANSITION Rx = V®__._x REYNOLDS NUMBER BASED ON DISTANCE OF ROUGHNESS FROM LEADING EDGE Figure ].
].2 SUBSONIC VARIATION OF CD, min WITH ROUGHNESS HEIGHT VARIABLE-SWEEP FIGHTER, M=0.7 .025 .020 Co, rain / k=_
_J
.015' .OlO - I I I I I I I I I 0 2 4 6 8 I0 12 14 16 18 x 10 -3 ROUGHNESS HEIGHT, k, IN.
Figure2 SUBSONIC VARIATION OF CD, mi n WITH ROUGHNESS HEIGHT OTHER CONFIGURATIONS; Mm 0.7 CONFIG.
.025 TRANSPORT A A TRANSPORT B 0 FIGHTER D TRANSPORT C .020 Co, rain .01.'
.010 I I I I I 2 4 6 8XlO -3 ROUGHNESS HEIGHT, k, IN.
Figure3
]-3
DISTRIBUTION OF MEASURED HEIGHTS OF PARTICLES IN A TYPICAL CARBORUNDUM TRANSITION TRIP GRIT NO. 30 TO NO. 80 6o Lr GRIT NO. 30 [- GRIT NO. 60
_ 4o
I t I I I u.e__d_ 4'0601120 GRIT NO. 40 _ 70 0 0 GR,T ."0'.
0 8 16 24 32x10 -3 0 8 16 24 32x10 -3 ROUGHNESS HEIGHT, ko IN.
Figure 4
DISTRIBUTION OF MEASURED HEIGHTS OF PARTICLES IN
A TYPICAL CARBORUNDUM TRANSITION TRIP
GRIT NO. 90 TO NO. 24.0 r',, 601_r GRIT NO. 90 GRIT NO. 150 LU n., / 20 _ ' .....
I I I
d
m i- n,- GRIT NO. 120 GRIT NO. 240 I.I.
o I,- z n.- I.iJ Q..
I I I I I I A I I 0 4 8 12 16xlO -3 0 4 8 12 16xlO "3 ROUGHNESS HEIGHT, k, IN.
Figure 5 EFFECT OF R x ON VARIATION OF CD, mi n WITH k VARIABLE-SWEEP FIGHTER ; M = 0.7 .030 .025 CD, rain _k=( )Z .O20 • R/FT R x / 0 I.OxlO 6 .04xlO 6 / u 3.0 ,ll _--'7 o 5.9 .22 .015 I I I I 20 x 10-`3 0 5 I0 15 ROUGHNESS HEIGHT, k, IN.
Figure 6 EFFECT OF R x ON Rk,cr SUBSONIC 200010 Rk,cr I000 0 ,_ ..... . J-_C,,._- ,-,0 _._. "'_",':__ ..... _",i_ _'." i.... _" I I I - I I 1 I I 6 .SxlO 0 .I .2 .3 .4 .5 .6 .7 Rx Figure I
1.5
EFFECT OF M ON BOUNDARY-LAYER TRANSITION CRITERIA 8OO0 .8 -X 10 6 / / / !
/ TRANSITION I / NEAR / .6 - / 6000_ / ROUGHNESS--,,,/ / I I Rk / I Rx. rain .4 4000_ I / I I / / / / / / .2 2000-
/'
/ //',- R k, cr J 1 I ] I I I 0 2 4 6 2 4 6 M M Figure8 GRIT-DRAG DETERMINATION BY VARIABLE REYNOLDS NUMBER METHOD M = 2.75 RIFT = 3.0 x 106 .0:52 - EXPERIMENT --o-- FREE TRANSITION --c}-- ARTIFICIALLY TRIPPED .024 - C D .016 "010 F "D'DOOC_ ED POLAR
.oo8 _
.OO6 L LTURBULENT THEORY l I l £ I l I J, .I J 2 3 5 6 7xlO 6 4
o .05 .,o .20
RIFT CL Figure 9
GRIT-DRAG DETERMINATION BY VARIABLE
ROUGHNESS SIZE METHOD
M=2.75 ; R/FT= 3.0 x 106 k, IN.
=% cL
.032 - --.o--- .0i08 # --.o--- .0181 _ ...43 _ .._ - _ _ ,_.--- .12 4 ,_0... -o
-_--.o215 .,#'
.02, -- -,_- -- .02 7 .018 .._ __.._--.095 _.o..- .... c]._ Co .01( CD .014 ._.o___..o____ _-A--.060 .001 :_? .....
.006
I I I I ] I I J
05 o .05 ._o .15
.20 0 2 4 6 8xlO -4 CL k 2, SQ IN.
Figure 10
COMPARISON OF CORRECTED POLARS
M =2.75 ; R/FT = 3.0 x I06
.O32 -
METHOD O VAR. REYNOLDS NO.
D VAR. ROUGHNESS .024 - C o .016
.ooa _o._
I 1 I I ,,,,
-,05 0
• 05 .10 .15 .20
CL
Figure 11
z?
SUPERSONIC VARIATION OF CO, o WITH k2 M =2,75 ; R/FT = 3.0 xl06 .016 .012 CD, o .OOe k=g .00 - I I I I I I 14XlO -4 0 2 4 6 8 I0 12 k 2, SQ IN.
Figure 12 RATIO OF MINIMUM SPHERICAL TRIP REYNOLDS NUMBER TO MINIMUM TRIANGULAR TRIP REYNOLDS NUMBER FOR TRANSITION NEAR ROUGHNESS • _>1; Rx=O.025 xl06 TO 0.6xlO 6 VG)-- Rk, sphere 1,4 Rk, triangle 1.2 1.0 I l ] I LL 2.2 2.6 3.0 1.8 0 1.4 M Figuret3 L-5226 NASA- Langley, 1966