COOLED PITOT-TUBE IN PLASMA-JET - AN IMPACT-PRESSURE RECOVERY MODEL

The time-dependent axisymmetric Navier-Stokes equations are numericall y integrated to predict the steady-state pressure at the forward criti cal point of a cooled pitot tube immersed in an air plasma flow. The f low is assumed to be in chemical equilibrium. Real gas chemistry is co upled to the gasdynamics by means of a Gibbs free energy minimization package. A Runge-Kutta multistage time integration to the central disc retization of the flux balance is used. Local time stepping and residu al averaging technique are used to accelerate the convergence to the s teady state. Numerical results are presented for subsonic and transoni c air plasma flows at four Mach numbers from 0.1 to 0.8 for gas temper ature in (he range of 300-5000 K. The computed values of the impact pr essure are compared to values obtained from theoretical and semiempiri cal 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 becom es greater for lower freestream Mach number which is consistent with t he experimental results of Hare. Additional calculations also reveal t hat this effect increases as the freestream pressure decreases.