A multi-fluid stagnation-flow plasma model with self-consistenttreatment of the collisional sheath

A two-temperature, multifluid model of a plasma in stagnation flow against a cooled, electrically biased surface is presented. The model couples bulk fluid motion, species diffusion and convection, electron and bulk energy equations, and net finite-rate ionization with Poisson's equation for the electric field in a generalized formulation. Application of the model to argon flow reveals important interactions between thermal, hydrodynamic, chemical and electrical boundary layers, with implications for current-limiting regimes of arcjet operation. The response of a planar Langmuir probe in contact with a collisional, flowing plasma is examined. Determinations of current-voltage behavior compare well with simple theory, including dependence on incident plasma velocity. Departures from this theory arise from boundary-layer perturbations near the electrode surface, away from free-stream conditions. The computational model incorporates a finite-rate catalytic recombination of ions and electrons at the electrode surface together with a specified current