Influence of segmentation and ambipolar diffusion on MHD nonequilibrium boundary layers

The compressible laminar and turbulent boundary-layer equations representing the fiow of cesium seeded argon plasma over successive segments of the cathode wall of an MHD channel were investigated and solved for both finite and intinite rates of reaction. The equations solved include the electron energy and the electron continuity equations as well as the usual global boundary-layer equations. The effects of finite rates of reaction and ambipolar diffusion are considered, and the inner boundary conditions for both the electron energy and the electron continuity equations are obtained by investigating a sheath analysis. The governing equations are solved using a finite-difference scheme without introducing a local similarity assumption. The finite rate results are considerably different from the infinite rate ones. The main reason is the ambipolar diffusion which depletes the electrons near the wall. No special problems have been found in the solution of the turbulent flow equations. This is due to the high mobility of electrons. (auth)