ON THE DESIGN OF HYPERSONIC INLETS 3rd Symposium on Integrating CFD & Experiments in Aerodynamics USAFA, CO 20-21 June, 2007 Capt Barry Croker Executive Officer to the AFRL Vice Commander Air Force Research Laboratory

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

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

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

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!

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

Invisicid Streamtracing Engineering Design SHOCK BOX Invisicid Streamtracing

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

Centerline X-Y Plane

2D Centerline X-Y Plane

2D Centerline X-Y Plane

JAWS Inward-Turning, Circular Cross Section M = 5 - 10 Q  = 1000-1500 psf

Planar Shock Topology Quarter-Section Rectangular Analogy X Z Y Secondary Reflection Secondary Shock Primary Reflection Primary Shock Full Topology

Inviscid Results Mach Number along X-Z Centerline Plane

Inviscid Results Mach Number along X-Y Centerline Plane

Viscous Correction Boundary layer momentum thickness accounted for through each shock

Turbulent Results Mach Number along X-Y Centerline Plane

Turbulent Results Mach Number along X-Z Centerline Plane

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

Comparison of Results Mach Number at Exit Plane Invisicid Viscous

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

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

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

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

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

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