PRELIMINARY INVESTIGATION OF POROUS WALLS AS A MEANS OF REDUCING TUNNEL BOUNDARY EFFECTS AT LOW-SUPERSONIC MACH NUMBERS

摘要

The use of porous-walled tunnels at supersonic Mach numbers as a means of avoiding reflection of a stream disturbance extending to the walls is discussed. Calculated shock-reflection characteristics of porous materials are presented in the form of design charts for Mach numbers up to 1.5 and incident shock deviations up to 6°. The charts presented indicate that for walls of a given porosity there exists a range of incident shocks representing certain combinations of stream deviation and Mach number for which no reflected disturbance will occur; for all other incident shocks, reflections occur but the stream deviation across the reflected disturbance is less than that for a solid boundary. Results obtained in experiments in which the bow shock from a 4° wedge at a Mach number of 1.2 was reflected from sintered-bronze and bonded-screen walls are consistent with the calculated characteristics.