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)approx=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.