Abstract
The basis of reasonable grid design for water hammer analysis using the method of characteristics is given by clarifying theoretically and numerically the actual error characteristics due to the time-line interpolations and the effect of the boundaries on that error. The theoretical expressions of the errors already known are discussed for the linear valve closure problems in the simple piping systems. In applying the reachback time-line interpolations (RTLI), the theoretical predictions of the numerical damping are valid even in only calculations at boundary grids. With the predictions, the time-step sizes can be determined by the RTLI for a given allowable numerical damping rate. Though the implicit time-line interpolations (ITLI) cause the rapid amplitude damping of waves of time-scales inherent to relatively short pipesÅC the time-step sizes are large enough to justify the rigid column approximations in pipelines. The method combined with the ITLI and RTLI is modified to employ larger the time step sizes.
