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 FA9550-11-1-0036 AFOSR AT & TT Portfolio Reviews July 15 – 18, 2013

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 7-16-2013 AFOSR AT & TT Review

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 7-16-2013 AFOSR AT & TT Review

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) 7-16-2013 AFOSR AT & TT Review

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) 7-16-2013 AFOSR AT & TT Review

Influence of Boundary Layer Turbulence on Structural Response 7-16-2013 AFOSR AT & TT Review

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

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 7-16-2013 AFOSR AT & TT Review

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

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

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 Returns @ ~150 dB

Shock Impinging on a Compliant Panel 7-16-2013 AFOSR AT & TT Review

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 0.7127 kg/m3 Reynolds Number 29.62 x 106 Material ANSI 4150 steel Length 25.4 cm Thickness 0.635 mm Initial Temperature 368 K

Shock Impingement on a Compliant Panel 7-16-2013 AFOSR AT & TT Review

Impact of Fluid-Thermal-Structural Interactions (FTSI) on Hypersonic Boundary Layer Transition (HBLT) & Stability 7-16-2013 AFOSR AT & TT Review

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 7-16-2013 AFOSR AT & TT Review

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 7-16-2013 AFOSR AT & TT Review

Methodology

Methodology Geometry

Methodology Geometry Mesh Flow

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

Study: NASP Ramp Panel Mach 2-12 ascent trajectory Dynamic pressure = 2000 psf Centerline disp. from 90-300 sec (5< M <12) As Mach/altitude ↑ ~Re ↓ Shift in dominant deformation mode between 210-240 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. 2393-2406

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

Study: Spherical Dome Protuberances Aerothermal tests in NASA Langley HTT at Mach 6.5 Dome lengths of 17.8, 35.6, 71.1 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 = 0.0286 H/L = 0.0143 H/L = 0.0071 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

H/L of 1.43-2.86% L = 17.78 cm L = 35.56 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%

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

Study: X-33 Bowed Panel Array

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

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??? 7-16-2013 AFOSR AT & TT Review

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? 7-16-2013 AFOSR AT & TT Review