Effect of a forward-facing step on the disturbance amplification in a flat-plate boundary layer

Accurately modeling boundary-layer transitions is a top research priority in the NASA CFD Vision 2030 Study and can help reduce the environmental impact of aviation. Here we apply stability analysis to subsonic flow over a two-dimensional zero-pressure-gradient boundary layer in the presence of a forward-facing step which has varying height, slope, and corner radii. The computational predictions capture the overall trend from experiments associated with a gradual upstream shift in the transition location as the step height increases. However, the critical step height corresponding to a very large upstream shift in the transition location is not well predicted compared to the measured data.