High-speed air-breathing engines, such as those used in space and supersonic flight, require streamlined airflow in order to work properly. Pressure gradients caused by shock-wave/boundary-layer interactions (SWBLI) can cause these engines to perform poorly and even become unsafe. A new study undertook a numerical simulation of a Mach 2.8 supersonic flow in order to better understand the physics of nanosecond-pulsed dielectric barrier discharge plasma actuators designed to help control SWBLI.
Previous studies of the plasma actuators mainly focused on subsonic flows, but never supersonic boundary layer separation. The new study built on a previous experiment that looked at two actuator configurations in order to find a method of controlling SWBLI by reducing the separation. Since the experiment had finite resolution, to fully understand what was happening the study used large eddy simulations to resolve the vortices generated by the actuators. The experiment and simulation used actuator configurations oriented parallel to the flow and canted at 18 degrees.
In the simulation, the actuators inject energy into the flow, resulting in a temperature increase. The numerical simulations confirmed the experimental finding that the canted orientation was able to reduce boundary layer separation. This orientation produced a counterflow, creating vortices that could transfer momentum to the boundary layer, thus reducing separation and SWBLI in the system. These results, and understanding the consequences of actuator configuration, could greatly help improve high-speed engine designs of the future.
Source: “Numerical investigation of nanosecond pulsed plasma actuators for control of shock-wave/boundary-layer separation,” by Kiyoshi Kinefuchi, Andrey Y. Starikovskiy, and Richard B. Miles, Physics of Fluids (2018). The article can be accessed at https://doi.org/10.1063/1.5051823.