Cooled pitot tube in plasma jet - An impact-pressure recovery model

Abstract

The time-dependent axisymmetric Navier-Stokes equations are numerically integrated to predict the steadystate pressure at the forward critical point of a cooled pitot tube immersed in an air plasma flow. The flow is assumed to be in chemical equilibrium. Real gas chemistry is coupled to the gasdynamics by means of a Gibbs free energy minimization package. A Runge-Kutta multistage time integration to the central discretization of the flux balance is used. Local time stepping and residual averaging technique are used to accelerate the convergence to the steady state. Numerical results are presented for subsonic and transonic air plasma flows at four Mach numbers from 0.1 to 0.8 for gas temperature in the range of 300-5000 K. The computed values of the impact pressure are compared to values obtained from theoretical and semiempirical relations. The comparative examination indicates that the computed impact pressure is much more sensitive to the temperature difference between the gas and the pitot tube. It is found that this effect becomes greater for lower freestream Mach number which is consistent with the experimental results of Hare. Additional calculations also reveal that this effect increases as the freestream pressure decreases.