Experimental investigation of gas percolation through porous compressible material under the effect of shock wave

The results of investigations of the shock wave interaction with compressible polyurethane foam in a shock tube by a special optical method of visualization of transparent as well as nontransparent non-uniformities are presented simultaneously. It is shown that the trailing edge of the compressed zone in a sample coincides with the free surface F of the sample (a plane surface of the sample was normally impacted by the shock wave) if the surface F is impenetrable for a gas behind the shock wave. The thickness of compressed zone increases linearly with time. For a sample with a penetrable surface F, the back of the compressed zone does not coincide with F, but lies inside the sample. The result of experiment is given with very thin layer of the foam, when the thickness of the sample was less than the distance of the compression wave formation. In this case the compression wave was not formed inside the sample. If there was a gap between the sample and the close end of the shock tube, then a shock wave was formed after the screen inside the gap. Pressure on the side and back walls of the tube were measured.