Numerical Investigation of an Innovative Inward Turning Inlet

Two different strategies for inlet compression, one based on a new innovative elliptic design and the other based on a classic non-axisymetric or rectangular cross-section, are explored numerically. The free-stream Mach number is 7 and the dynamic pressure is 1500 psf. The elliptic cross-section inlet, denoted “Jaws” because of its shape, is designed using compression theory to provide planar shocks emanating from the leading edges. Advantages over the square-duct or traditional design include an absence of shock-on-cowl-lip interactions – which can lead to catastrophic failure of the cowl-lip – and potentially lower losses through viscous-inviscid interactions. Both configurations are chosen to yield similar compression ratios with a dual compression strategy comprised of successive pitch and yaw plane compression. Particular emphasis is placed on understanding the fully three-dimensional viscous/inviscid interaction phenomena encountered, and their impact on distortion is analyzed. The performance of the two designs is compared for a given design condition, and Jaws was analyzed as well as at off design Mach numbers and angles of attack. This unique inward turning inlet was found to result in low boundary layer growth and minimal shock—boundary layer interactions because of the diminished wetted area.