Aerodynamic Characterization of the Jet of an Arc Wind Tunnel

It is well know that, due to a very aggressive environment and to the rather high rarefaction level of the arc wind tunnel jet, the measure of fluid-dynamic quantities is difficult. For this reason, the aerodynamic characterizzation of the jet relies also on computer codes, simulating the operation of the tunnel. The present authors already used successfully such a kind of procedure for the tests in the arc wind tunnel (SPES) in Naples (Italy). In the present work an improved procedure is proposed. Like the former procedure also the present procedure relies on two codes working in tandem: 1) one-dimensional code simulating the inviscid and thermally not-conducting flow field in the heater, in the mix-chamber and in the nozzle up to the position, along the nozzle axis, of continuum breakdown, 2) Direct Simulation Monte Carlo (DSMC) code simulating the flow field in the remaining part of the nozzle. In the present computing procedure, the DSMC simulation includes the simulation both in the nozzle and in the test chamber. An interesting problem, considered in this paper by means of the present computing procedure, has been the simulation of the flow field around a Pitot tube and of the measure of the total pressure. The measure of the total pressure, under rarefied conditions, may be even four times the theoretical value. Therefore a substantial correction must be applied to the measured data. In the present paper a correction factor for the total pressure measured in SPES is proposed. The present analysis relies on twelve tests performed in SPES