Document
June 2014 Reno, NV USA Okinawa, Japan Edwards, CA USA Aerion Corporation Mike Frederick, Dan Banks Andres Garzon, Jason Matisheck NASA Armstrong Flight Research Center International Symposium on Flow Visualization th
Outline
Transition with Mach number Transition with Reynolds number Transition due to roughness elements
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Background and previous research F-15B IR system Experiment overview Flight test results Summary Questions
Partnership with Aerion Corp.
Background
Tradeoffs work best for business jet class at M<2 Low sweep to control CF dp/dx < 0 on both wing surfaces to stabilize TS Thin wing with sharp leading edge to minimize wave drag increase due to reduction in sweep Non-intrusive, global, good spatial resolution Captures significant flow features well Existence of strong spanwise pressure gradient leads to crossflow (CF) while adverse chordwise pressure gradients amplifies and Tollmien-Schlichting (TS) instabilities – – – – – – – NASA has a current goal to eliminate barriers to the development of practical supersonic transport aircraft Drag reduction through the use of supersonic natural laminar flow (S-NLF) is currently being explored as a means of increasing aerodynamic efficiency Conventional high-speed designs minimize inviscid drag at the expense of viscous drag Aerion Corporation has patented a S-NLF wing design (US Patent No. 5322242) NASA and Aerion have partnered to study S-NLF since 1999 Series of S-NLF experiments flown on the NASA F-15B research test bed airplane Infrared (IR) thermography used to characterize transition
Flow SBLT phase 1 (flat-plate)
= 10 million at Mach 1.8
c Flow
Previous Research
SSNLF Bi-convex test article Demonstrated extended runs of S-NLF up to Re Large chord flat-plate test article Measured plate pressures and local inflow conditions up to Mach 2.0 Pressure data used to help design follow on S-NLF test article
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Supersonic Natural Laminar Flow (SSNLF) Supersonic Boundary Layer Transition (SBLT)
AFT IR camera IR camera pod FWD
F-15B IR System
L3 Cincinnati 640x512 NC 640x512 Indium-Antimonide (InSb) focal plane array with 28 micron pitch Mid-wave (3-5 micron spectral range) 13 mm lens Simultaneous 14-bit digital and RS-170 analog output Streamlined pod mounted on starboard armament rail Silicon window with anti-reflection coating Right-angle prism to redirect image to camera 8 mm (Hi-8) recorder for analog output Digital Design Corp. VAADR-1 unit
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Camera Camera pod Onboard Recorders
LE Splitter plate CLIP 80” (204 cm) RTDs
S-NLF Test Article
40” (102 cm) Bay Instrumentation Strong Back
Strong Back Side
Conical probe IR Camera Pod S-NLF Test Article CLIP
F-15B Test Configuration
p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e ep t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t t te p p p p p p p p S S S S S S S S S S S S S S S S S S S S S S S S S S S S St e e e e e e e e ep r r r r r r r r r r r r r r r r r r r r r r r S t t t t t t t t t t te e e e e e e e e e e e e e e e e e e e e e e e e e e er S S S S S St p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p pe r r r r r r r r r r r r S p p p p p p p p p p p p p p p p p p p p p p p p p p p pp e e e e e e e e e e er Upper Step U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U Up w w w w w w w w w w w w w w w w w we o o o o o ow Lower Step L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L Lo 2-D steps (highlighted in blue)
Roughness Elements
Trip dots (highlighted in red) 19 dots were installed near leading edge of the test article Dots were formed from aluminum and polyimide adhesive tapes with thicknesses of 2, 3, and 4.5 mil (0.051, 0.076, and 0.114 mm) Created from 30 inch (76 cm) strips of 4.5 mil (0.114 mm) thick adhesive backed vinyl film Leading edge located approximately 8.5 inches (21.6 mm) back from leading edge Layered to create addition step heights of 13.5 and 22.5 mil (0.343 and 0.572 mm) – – – – – Roughness elements installed during select flights to investigate effects on transition Trip dots 2-D steps
Analog IR image from flight IR image with control points
IR Image Transformation
Target image with control points Wide-angle lens Camera pod mount position – – IR images have perspective distortion (foreshortening) Calibration grid applied to test article for image registration Control point pairs used to transform distorted image into reference perspective Transformation applied frame-by-frame to IR video Shock Train CF Transition Turbulent Wedge CF Transition Shock Camera Pod
Transformed IR Image
M=1.7, 49.5 kft (15.09 km), steady state M=1.4, 49.5 kft (15.09 km), accelerating
Transition with Mach Number
M=1.1, 42 kft (12.8 km) , accelerating M=1.55, 49.5 kft (15.09 km), accelerating =4.31 million/ft (1.31 million/m) ft =2.67 million/ft (0.814 million/m) ft M=1.7, Re M=1.71, Re =3.49 million/ft (1.06 million/m) =2.14 million/ft (0.652 million/m) ft ft
Reynolds Number Effects M=1.7
M=1.7, Re M=1.7, Re =2.67 million/ft (0.814 million/m) =4.31 million/ft (1.31 million/m) ft ft M=1.7, Re M=1.68, Re
Trip Dots M=1.7
=3.49 million/ft (1.06 million/m) ft =2.21 million/ft (0.674 million/m) ft M=1.71, Re M=1.7, Re =4.31 million/ft (1.31 million/m) =2.67 million/ft (0.814 million/m) ft ft M=1.69, Re M=1.73, Re
2-D Steps M=1.7
(upper 0.343 mm, lower 0.114 mm)
=3.49 million/ft (1.06 million/m) =2.14 million/ft (0.68 million/m) ft ft M=1.7, Re M=1.69, Re
Flight 452
Flight 454
Flight 456
Summary
Regions of laminar flow in excess of 80% chord at chord Reynolds numbers greater than 14 million
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IR thermography was used to characterize the transition front on a S-NLF test article at chord Reynolds numbers in excess of 30 million Changes in transition due to Mach number, Reynolds number, and surface roughness were investigated IR thermography clearly showed the transition front and other flow features such as shock waves impinging upon the surface A series of parallel oblique shocks, of yet unknown origin, were found to cause premature transition at higher Reynolds numbers