Experimental Investigation of Intake Surface Geometry Effects on Off-Design Climb Performance

This study investigates the influence of intake surface geometry on intake performance during off-design climb with a quasi-two-dimensional (quasi-2D) experiment representing transonic flow over the lower lip of a civil installation. Twenty-seven test cases are examined within a design-of-experiments structure that incorporates four independent parameters: 1) highlight curvature, 2) surface-curvature distribution, 3) diffuser shape, and 4) mass flow rate. In each test case, a quasi-2D transonic shock-wave–boundary-layer interaction formed on the intake front lip. Intake performance, defined as incompressible boundary-layer displacement thickness ahead of the transonic fan position ([Formula: see text]), is significantly lower, by up to an order of magnitude, when [Formula: see text], which corresponds to the threshold for well-established separation. Leading-edge radius is the surface geometry parameter with the greatest influence on shock strength, and therefore on intake performance, at off-design climb. Setting a smaller leading-edge radius increases surface turning in the initial (subsonic) region near the highlight, thereby reducing surface curvature in the transonic region. The resulting decrease in transonic acceleration weakens the shock, which forms a benign interaction with minimal impact on intake performance across the investigated mass-flow range.