CONVERGING SHOCK WAVES IN A VAN DER WAALS GAS OF VARIABLE DENSITY

The converging problem of cylindrically or spherically symmetric strong shock wave collapsing at the axis/centre of symmetry, is studied in a non-ideal inhomogeneous gaseous medium. Here, we assume that the undisturbed medium is spatially variable and the density of a gas is decreasing towards the axis/centre according to a power law. In the present work, we have used the perturbation technique to the implosion problem and obtained a global solution that also admits Guderley's asymptotic solution in a very good agreement which holds only in the vicinity of the axis/centre of implosion. The similarity exponents together with their corresponding amplitudes are determined by expanding the flow parameters in powers of time. We also refined the leading similarity exponents near the axis/centre of convergence. We compared our calculated results with the already existing results and found them in good agreements up to two decimal places. Shock position and flow parameters are analysed graphically with respect to the variation of values of different parameters. It is observed that an increase in the density variation index, adiabatic exponent and Van der Waals excluded volume, causes the time of shock collapse to decrease due to which the shock acceleration gets increased and shock reaches the axis/centre much faster.