Solving the equations for unsteady gas flow by two methods

The paper discusses briefly a number of methods available to solve the hyperbolic partial differential equations which describe unsteady compressible fluid flow. Equations describing unsteady one-dimensional flow in a pipe, accounting for heat transfer, gradual area change, and friction are presented in conserva tion-law, normal, and characteristic form. The pres sure pulsations at locations in a single-stage reci procating air compressor system are predicted, employ ing both the method of characteristics and a composite scheme utilising the Two-Step Lax-Wendroff method within the pipes and the method of characteristics at the boundaries. The composite scheme was simpler to apply, required much less computational time, and yielded results in closer agreement with data obtained experimentally.