1. Response Prediction of Compliant Structures in Hypersonic Flow
Andrew Crowell (SMART), Brent Miller (SMART),
Zach Riley (NDSEG), Rohit Deshmukh, Abhijit Gogulapati (Post-Doc), Jack J. McNamara
C A E L
Computational AeroElasticity Laboratory
AFOSR Grant FA
AFOSR AT & TT Portfolio Reviews
July 15 – 18, 2013

2. Motivations & Objective
Thin gauge hot structures enable responsive hypersonic platforms
Response prediction of thin gauge structures in high speed flows requires coupled fluid-thermal-structural modeling & analysis.
Fluid-Thermal-Structural response is trajectory dependent (& dependent on operational life w/ damage accumulation).
Testing scaled multi-disciplinary models in wind tunnels is impractical.
Direct coupling of high fidelity numerical techniques for predicting vehicle response over a trajectory and/or life is impractical.
Require Improved Basic Understanding & Tractable Multi-Physics Approaches
AFOSR AT & TT Review

3. Standard Structural Design Practice
Standard Approach: Develop a set of uncoupled load cases and spot check around operating conditions
Aerodynamic heating and damage accumulation introduce large time-scale transients and path-dependence of the response
AFOSR AT & TT Review

4. Specific Research Themes
Consideration of Turbulent Boundary Layer Loading in Structural Response Prediction (Rohit Deshmukh)
Response of Surface Panels to Shock Impingements (Crowell, Miller, Gogulapati, Deshmukh)
Time-marching and Coupling Reduction of Fluid-Thermal-Structural Interactions (FTSI) (Brent Miller, SMART)
Model Reduction of Aerothermodynamics (Andrew Crowell, SMART)
Model Integration (Abhijit Gogulapati, Post-Doc)
The Impact of Fluid-Thermal-Structural Interactions (FTSI) on Hypersonic Boundary Layer Transition (Zach Riley, NDSEG)
Incorporation of Material and Damage Evolution (Abhijit Gogulapati, Post-Doc)
AFOSR AT & TT Review

5. Specific Research Themes
Consideration of Turbulent Boundary Layer Loading in Structural Response Prediction (Rohit Deshmukh)
Response of Surface Panels to Shock Impingements (Crowell, Miller, Gogulapati, Deshmukh)
Time-marching and Coupling Reduction of Fluid-Thermal-Structural Interactions (FTSI) (Brent Miller, SMART)
Model Reduction of Aerothermodynamics (Andrew Crowell, SMART)
Model Integration (Abhijit Gogulapati, Post-Doc)
The Impact of FTSI on Hypersonic Boundary Layer Transition (Zach Riley, NDSEG)
Incorporation of Material and Damage Evolution (Abhijit Gogulapati, Post-Doc)
AFOSR AT & TT Review

6. Influence of Boundary Layer Turbulence on Structural Response
AFOSR AT & TT Review

7. Influence of Boundary Layer Turbulence on Structural Response
Phenomenological Modeling
Aerothermodynamics
Boundary Layer Edge Conditions
Mean Flow Pressure
TBL
Fluctuating Pressure
TBL
Heat Flux
Pressure Loads
Surface Geometry & Dynamics
Surface Temperature
Surface Heat Flux
Structural Dynamics
Heat
Transfer
Structural Temperature

8. Model for Turbulent Boundary Layer Loading
Turbulence boundary layer pressure load:
Phase angle:
PTBL = f(x,t) eθ(x,t)
θ(x,t) = τ(t) ψ(x)
TBL Fluctuating Pressure
Magnitude,
f(x,t)
[Laganelli et al. (1977,1993)]
Spatial Component of Phase Angle, ψ(x)
[Coe and Chyu (1972)]
Temporal Component of Phase Angle, τ(t)
Randomly Prescribed
AFOSR AT & TT Review

9. TBL Load Model PTBL = f(x,t) eθ(x,t) θ(x,t) = τ(t) ψ(x)
Ψ(x) = 1 (Uniform in space )
PTBL = f(x,t) eθ(x,t)
θ(x,t) = τ(t) ψ(x)
Ψ(x) is Random
Ψ(x) modeled [Coe and Chyu (1972)]
Chordwise direction

10. Full Semi-Empirical Model
Influence of Boundary Layer Turbulence on Structural Response (Mach = 4.0, 30 km)
No TBL Model
f(x,t) = 124 dB
ψ(x) = 1
Ad Hoc Model
f(x,0) =131 dB
ψ(x) modeled
Full Semi-Empirical Model
f(x,t) modeled, ψ(x) = 1
Semi-Empirical Magn.
f(x,0) = 131 dB

11. Full Semi-Empirical Model Instability Returns @ ~150 dB
Influence of Boundary Layer Turbulence on Structural Response (Mach 4.0, 30 km)
Full Semi-Empirical Model
f(x,0) = 138 dB
ψ(x) modeled
Scaled Magnitude
Structural Response is dependent on the magnitude, distribution of the magnitude, and the phase angle of the TBL pressure!
f(x,0) =131 dB
ψ(x) modeled
f(x,t) = 143 dB
ψ(x) modeled
Uniform Magnitude
Instability ~150 dB

12. Shock Impinging on a Compliant Panel
AFOSR AT & TT Review

13. AFRL RC-19 Experiment: Shock Impingement on a Compliant Panel
Spottswood, Eason, and Beberniss, “Influence of Shock-Boundary Layer Interactions on the Dynamic Response of a Flexible Panel,” ISMA 2012 Conference on Noise and Vibration Engineering, 2012.
Freestream Properties
Panel Properties
Mach Number
2.0
Dynamic Pressure
123 kPa
Temperature
215 K
Density
kg/m3
Reynolds Number
29.62 x 106
Material
ANSI 4150 steel
Length
25.4 cm
Thickness
0.635 mm
Initial Temperature
368 K

14. Shock Impingement on a Compliant Panel
AFOSR AT & TT Review

15. Impact of Fluid-Thermal-Structural Interactions (FTSI) on Hypersonic Boundary Layer Transition (HBLT) & Stability
AFOSR AT & TT Review

16. Impact of FTSI on HBLT & Stability
Goal: Investigate the influence of Fluid-Thermal-Structural Interactions on hypersonic boundary layer stability using geometries and operating conditions extracted from previous work.
Generic Panel (Last Year) [Miller, McNamara, Spottswood, Culler 2011]
NASP Ramp Panel [Culler and McNamara 2011]
Spherical Dome Protuberances [Glass and Hunt 1986]
X-33 Bowed Panel Array [Berry, Horvath, Kowalkowski, and Liechty 1999]
3-D considerations
AFOSR AT & TT Review

17. Impact of FTSI on HBLT & Stability
Goal: Investigate the influence of Fluid-Thermal-Structural Interactions on hypersonic boundary layer stability using geometries and operating conditions extracted from previous work.
Generic Panel (Last Year) [Miller, McNamara, Spottswood, Culler 2011]
NASP Ramp Panel [Culler and McNamara 2011]
Spherical Dome Protuberances [Glass and Hunt 1986]
X-33 Bowed Panel Array [Berry, Horvath, Kowalkowski, and Liechty 1999]
3-D considerations
AFOSR AT & TT Review

18. Methodology

19. Methodology
Geometry

20. Methodology
Geometry
Mesh
Flow

21. Methodology STABL1 Flow Geometry Mesh Flow Solution Stability Analysis
1 Johnson and Candler – 2005

22. Study: NASP Ramp Panel Mach 2-12 ascent trajectory
Dynamic pressure = 2000 psf
Centerline disp. from sec
(5< M <12)
As Mach/altitude ↑ ~Re ↓
Shift in dominant deformation mode between sec
Culler, A.J and McNamara, J.J., “Impact of Fluid-Thermal-Structural Coupling on Response Prediction of Hypersonic Skin Panels,” AIAA Journal, Vol. 49, No. 11, November 2011, pp

23. Study: NASP Ramp Panel 90 sec 180 sec 240 sec 300 sec
Decreased N-factor growth rate for higher mode deformation
N-factors continue to decrease as higher mode deformation increases
Expected Transition
Panel
Panel
240 sec
300 sec
CW: Compliance tends to increase N-factor in vicinity of panel
RE: Compliance tends to decreaes N-factor in vicinity of panel
N-factors return to rigid growth by end of the wedge for 240 and 300 seconds
NEW MODE SHAPE FOR PANEL AT 300 seconds!!!
Panel
Panel

24. Study: Spherical Dome Protuberances
Aerothermal tests in NASA Langley HTT at Mach 6.5
Dome lengths of 17.8, 35.6, cm
Effective altitude of 30.2 km
Unit Re = 3.543x106 m-1
Domes 1-3
LE = 1.89m
Domes 4-6
LE = 1.80m
Domes 7-8
LE = 1.47m
H/L =
H/L =
H/L =
Glass, C.E and Hunt, L.R, “Aerothermal Tests of Spherical Dome Protuberances on a Flat Plate at a Mach Number of 6.5,” NASA TP-2631, 1986

25. H/L of %
L = cm
L = cm
1.43%
Impact on N-factor increases with panel size
As H/L increases a sudden, drastic increase in N-factor growth is observed
2.86%

26. Study: X-33 Bowed Panel Array
Experiments in NASA LaRC 20-Inch Mach 6 Air Tunnel to examine BL transition and impact on aeroheating
14 centerline panels
Mach 6 ReL = 3.5 x 106
Cold wall conditions
0.6 m long panels
15.4 mm peak height
X-33 Bowed Panel Array

27. Study: X-33 Bowed Panel Array

28. 3-D Effects Glass and Hunt Dome 8 X-33 Single Panel Percent Crossflow
%CF ≤4.4% for each geometries
Uedge
Wmax
Glass and Hunt Dome 8
X-33 Single Panel

29. Summary
Response prediction of thin gauge structures in hypersonic flow is dependent on understanding complex unsteady, nonlinear interactions with the environment
Structural response is sensitive to different characteristics of the turbulent boundary layer (as best as we can tell from simplified models!)
We now have the capability to comprehensively model fluid-thermal-structural interactions to shock impingements
RANS surrogates + TBL models for fluctuating pressure
Model integration & verification in progress
Validation will be tricky
Panel scale protuberances reveal interesting interactions with the laminar boundary layer – opportunity to delay transition???
AFOSR AT & TT Review

30. Fundamental Challenges
Experimental validation (particularly from structural POV)
Incorporation of LES/DNS into long time record multi-physical analysis: O(minutes to hours)
Turbulent Boundary Layer Loadings in General
SBLIs
How does the N-factor corresponding to transition change with evolving surface conditions? What about 3-D considerations?
Consequences of damage accumulation & material evolution?
AFOSR AT & TT Review