Stability study of laminar boundary layers with wall temperature effects using numerical methods

A study was conducted to determine the effect of wall temperature on the stability of the laminar boundary layer along a flat plate as well as the Proof of Concept (POC) supersonic nozzle wall of the low-disturbance wind tunnel at NASA Ames. A boundary layer code and a stability code were used in this study.

The boundary layer over a flat plate was used to verify the accuracy of both codes. Results from the codes were compared to insulated (adiabatic) and non-insulated experimental and analytical data. The agreement was in all cases very good. The flat plate was further used to compare the laminar boundary layer stability when cooling was applied through a linear temperature distribution and a constant uniform wall temperature. It was found that in this cooling process the linear temperature distribution provided more stability than the constant uniform wall temperature.

Since the local warming of the fluid helped stabilize the flow, heat was applied in a stable area of the flat plate. It was found that the heating temperature and length had a significant effect in the increase of the laminar boundary layer stability. This idea was applied to the PoC nozzle and similar results were obtained. We observed a decrease in the N factor of the e^N linear stability theory of approximately fifty percent for the best case.