Subsonic Electrically Quasi-Neutral Weakly-Ionized Gas Flow past a Spherical Probe

The electric characteristics of a sphere located in a flow of viscous, electrically quasineutral weakly-ionized gas containing electrons and monovalent ions are investigated theoretically and numerically. As in the majority of applications, the electrogasdynamic (EGD) interaction parameter is assumed to be small. This makes it possible to solve the gasdynamic and electric equations successively. The spherical surface is assumed to be conducting and heat-insulated. At low free-stream Mach numbers the gas temperature is almost constant in the region of flow past the sphere. This makes it possible to use the model of a viscous incompressible medium. The flow past a sphere is analyzed for gasdynamic Reynolds numbers varying over the interval 0 <= Re <= 1000. The electrodynamic equations in which the convection and diffusion of the electrons and ions and their electrical drift are taken into account are reduced to three elliptic equations for the electron and ion concentrations and the electric potential. A constant potential is assigned on the boundary of the computation region simulating infinity. The entire problem is simulated numerically using specially constructed grids. The charged-component, potential, and electric current fields are determined and the volt-ampere characteristics of the sphere are constructed for various gas velocities. The results obtained generalize the available data on the voltampere characteristics of a sphere (probe) in a weakly-ionized medium at rest.