Attenuation of shocked gas flow by porous medium

摘要

Attenuation of shock waves propagating through porous media is investigated experimentally and numerically. Unsteady processes occur when shock waves and expansion waves travel through porous media: such as a polyurethane foam; and a wire mesh. Foams under study have high-porosities φ_g = 0.951 ～ 0.977 and low densities ρ_c = 27.6 ～ 55.8 kg/m~3, while the wire mesh has low-porosity φ_g = 0.36. Shock tube experiments are conducted by using a shock tube of 50 mm in diameter and 6.4m in length. Initial pressures in driver tube, P_4, and driven tube, P_1, are P_4 = 0.4345 MPa and P_1 ≈ 0.1013 MPa, respectively. The resulting shock Mach number is M_s = 1.33. The foam is fixed onto the shock tube side wall surface of the tube at the test section. Pressures behind the fixed foam were decreased in comparison with the incident pressure jump, which implies that the shock wave was well degenerated into compression waves. In experiment, pressure attenuation factor K_a caused by the presence of foam was estimated to be about 60 ～ 75% of the value in the absence of foam value. In such a case, the momentum loss of flows in foam becomes significant if compared with wire mesh case.