AN IMPLICIT METHOD FOR TRANSIENT GAS-FLOWS IN PIPE NETWORKS

This paper describes a fully implicit finite-difference method for cal culating the unsteady gas flow in pipeline networks. The algorithm for solving the finite-difference equations of a pipe is based on the New ton-Raphson method. The Von Neumann stability analysis on the finite-d ifference equations of a pipe shows that the equations are uncondition ally stable. An iterative convergence method is applied to the calcula tion of node pressure at junctions in networks. The parameter study on the convergence shows that the stability depends on the convergence t olerance. Calculation results of a few sample cases are compared with those of the method of characteristics and the two-step Lax-Wendroff m ethod. An excellent agreement between the methods is obtained when a s mall time step is used. Computation time can be greatly reduced by usi ng the implicit method.