DEVELOPMENT OF LONGITUDINAL GAS OSCILLATIONS IN A CLOSED TUBE

A comparison is made of solutions of the problem of longitudinal gas o scillations in a closed tube for two ideal gas models. The models diff er in their energy equations. This is entropy conservation in the firs t case and total energy conservation in the second one. Unlike in many other works, mainly devoted to the steady state regime, transient pro cesses and the influence of initial conditions are considered. The osc illations are excited by a plane piston with a sine law displacement. The frequency band under consideration lies in the neighborhood of the first natural frequency of the tube where shock waves are known to ap pear. The investigation is made numerically on the basis of the effect ive finite difference method which belongs to the class of high resolu tion schemes of the second order in both space and time. The results o btained are compared with some known theoretical solutions, found by t he small parameter method, and with experimental data corresponding to the steady state regime. (C) 1996 Academic Press Limited