1. ON THE DESIGN OF HYPERSONIC INLETS 3rd Symposium on Integrating CFD & Experiments in Aerodynamics USAFA, CO June, 2007
Capt Barry Croker
Executive Officer to the AFRL Vice Commander Air Force Research Laboratory

2. Acknowledgements
Dr. Datta Gaitonde Ms. Heidi Meicenheimer Mr. Pete Kutschenreuter Air Vehicles Directorate, AFRL
Dr. John Schmisseur AFOSR
DoD HPCMO, ASC MSRC

3. Overview USAF High Speed Vision Hypersonic Design Process
JAWS Inlet Program
Design Methodology
CFD Verification & Validation
Experimental Test Program
Conclusions

4. USAF High Speed Mission
Future Capabilities:
Prompt Global Strike
Long Range Strike
Operationally Responsive Access to Space
There are several missions for high-speed vehicles. These are some of the possibilities.
The emphasis has been renewed with the development of the NAI, with emphasis on these three aspects, of which our interest is principally in the first.
All of these concept vehicles will require key enabling technologies to be developed, before they become operational.
Hypersonic flight will enable unparalleled global reach and power

5. Challenges of High Speed Flight
Balance engine/airframe
over entire speed regime
Boundary layer
transition on external surfaces and inlet
Shock/boundary layer
interactions
Mass capture, contraction
limits in inlet
Nozzle over-expansion
at transonic speeds
Isolator performance
and operability
External burning ignition
and flame-holding
Cowl lip drag
and heat transfer
Going lower to a specific type of system, a joint VA PR systems study identified many outstanding problems that will influence design. Here is a specific concept vehicle, with many of the same issues identified as in the earlier chart, but broken down into more basic elements such as boundary layer transition, etc. It is clear that the vehicle will need to be integrated and the distinction between air vehicle and propulsion is blurred. Design engineering will require high-confidence data on a number of items, including loads, both local and global, the full flow field structure to do configuration optimization, there is a need for flow control methods and finally, it is critical to obtain scaling laws, to be able to extend results from scaled studies to be extrapolated to full systems.
Nozzle recombination
losses
Fuel injection drag,
mixing and heat transfer
Key enabling technologies need to be developed to make sustained hypersonic flight feasible!

6. AFRL Design Core Competency
Engineering Design Tools
Experimental
Ground Testing
High-Fidelity
CFD
“…to establish a core-competency in hypersonic vehicle inlet design…”

7. Invisicid Streamtracing
Engineering Design
SHOCK BOX
Invisicid Streamtracing

8. Computational Verification
AVUS Design Space Exploration 2nd Order Unstructured RANS + SA or BL
FDL3DI High-Fidelity Analysis 3rd Order Structured RANS + k-
Euler Stream Trace Verification Shock Location
Turbulent Viscous Corrections Nonlinear Effects

9. Centerline X-Y Plane

10. 2D Centerline X-Y Plane

11. 2D Centerline X-Y Plane

12. JAWS
Inward-Turning, Circular Cross Section M = Q  = psf

13. Planar Shock Topology Quarter-Section Rectangular AnalogyX Z Y
Secondary Reflection
Secondary Shock
Primary Reflection
Primary Shock
Full Topology

14. Inviscid Results
Mach Number along X-Z Centerline Plane

15. Inviscid Results
Mach Number along X-Y Centerline Plane

16. Viscous Correction
Boundary layer momentum thickness accounted for through each shock

17. Turbulent Results
Mach Number along X-Y Centerline Plane

18. Turbulent Results
Mach Number along X-Z Centerline Plane

19. Comparison of Results Mach Number along X-Y Centerline Plane Invisicid
Viscous

20. Comparison of Results
Mach Number at Exit Plane
Invisicid
Viscous

21. Swept-Shock Boundary Layer Interaction
Isosurface of TKE in Boundary Layer

22. Swept-Shock Boundary Layer Interaction
Separated Boundary Layer
Centerline Vortex
Interaction Flows

23. Conclusions of CFD
Overall shock structure well aligned with prediction
Viscous correction adequate for shock location
Influence of Swept-Shock Boundary Layer Interaction could have implications on performance

24. Experimental Test Program
NASA Langley Aerothermodynamics Branch 20” Mach 6 Tunnel
Originally Planned for May, Slipped to August
Test Goals:
Establish inlet starting parameters
Back-pressure study
Evaluate on and off design performance
Angle of Attack/Yaw
Re & Minf

25. Model Fabrication Instrumentation location based on CFD predictions
Diagnostics include:
Pressure
Temperature
Surface Oil Flow Visualization

26. Conclusions & Future Work
Functional Analytical Design
CFD to check & improve method
EFD to verify computations & improve method
CFD on off-design cases
Comparison of CFD & EFD data
Engineering Design Tools
High-Fidelity
CFD
Experimental
Ground Testing