Diagnostics of a relaxing medium by an acoustic pulse with shock front

Peculiarities of the propagation of acoustic pulses with shock fronts in a nonlinear medium with relaxation were studied experimentally and numericall y. Evolution of a pulse profile was simulated numerically using a modified spectral approach, which provided an opportunity to perform calculations ef fectively in a wide range of parameters of the relaxation process. Intense submicrosecond pulses excited by a photoacoustic method were used in the ex periment. Measurements were conducted in acetic acid at various temperature s, which provided an opportunity to vary time and strength of the relaxatio n. It was demonstrated that nonlinearity contributes to the persistence of the shock front, and the shape of the signal behind the shock front depends strongly on the relaxation parameters. Based on the latter fact, a techniq ue for the medium diagnostics was developed. This technique was founded on the measurements of two characteristic parameters of the time profile of th e transmitted pulse.