Use of Potential Flow Theory to Evaluate Subsonic Inlet Data from a Simulator-powered Nacelle at Cruise Conditions
Incompressible potential flow theory corrected for compressibility effects, using the Lieblein-Stockman compressibility correction, was used to predict surface and flow field static pressures for a subsonic inlet at cruise conditions. The calculated internal and external surface static pressures were in good agreement with data at most conditions. The analysis was used to determine the capture stream-tube location and static-pressure distribution. Additive drag coefficients obtained from these results were consistently higher than those obtained using one-dimensional compressible flow theory. Increasing the distance between the inlet and boattail increased the cowl drag force. The effect of the boundary layer on internal and external surface static-pressure distributions was small at the design cruise condition. The analytical results may be used as an aid to data reduction and for predicting inlet mass flow, stagnation point location, and inlet additive drag.
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additive drag coefficients analysis boundary layer boundary-layer effect capture stream tube Circum Comparison of theoretical compressibility correction compressibility effects compressible flow theory compressible velocity corrected for compressibility cowl drag coefficients cowl drag force cowl external surface cowl pressure distributions density Dimensionless axial location discrepancies distributions at free-stream effects of mass-flow experimental cowl internal experimental pressure distributions external cowl external surface static-pressure Figure 17 flow rate flow ratio free-stream Mach 0.75 free-stream Mach number highest mass-flow incompressible indicated inlet additive drag inlet and boattail inlet choked inlet drag coefficients inlet highlight inlet mass inlet mass-flow ratio internal cowl pressure internal pressure distributions Lewis Research Center maximum nacelle NACA NASA TM number of 0.60 one-dimensional compressible flow POTENTIAL FLOW THEORY ratio and free-stream shown in figure stagnation point stagnation-point location static pressure SUBSONIC INLET surface static-pressure distributions theoretical and experimental theoretical pressure distributions theoretical results Turbofan weight flow wind tunnel