Boundary Layer Flow Control Using Plasma Induced Velocity

摘要

An examination of the effects of plasma induced velocity on boundary layer flow was conducted. A pair of thin copper film electrodes spanned the test section, oriented at thirty degrees from normal to the free stream flow. An adverse pressure gradient was imposed over the electrode configuration using a pressure coefficient profile similar to that associated with suction side of a Pac-B low pressure turbine blade. In addition, suction was applied to keep flow attached on the upper wall, inducing separation over the electrode. The electrode is supplied by an AC source at three different power levels with the free stream flow at three separate chord Reynolds numbers. The chord length was based on the geometry of the simulated airfoil profile used for the upper wall of the test section. The flow turbulence intensity was varied by means of a passive grid in the upstream flow. Velocity data were collected using particle imaging velocimetry as well as with a boundary layer pitot probe. The power levels applied to the plasma were between 20 and 40 watts. The flow regimes studied were between chord Reynolds numbers of 50,000 to 100,000. It was found that the use of plasma to control the boundary layer enabled the flow to remain attached in the presence of an adverse pressure gradient. However, at the studied Reynolds numbers and electrode configuration the plasma was unable to affect an already separated flow regardless of the power input to the electrode. It was finally ascertained that two types of turbulent structures could be resolved, one being a counter-rotating vorticity pair and the other being a counter-rotating vorticity sheet.