FLEXIBLE DISCRETIZATION ALGORITHM FOR FIXED-GRID MOC IN PIPELINES

The problem of selecting a time step that exactly satisfies the Couran t condition arises most commonly when the fixed-grid method of charact eristics (MOC) is applied to multipipe systems. Traditionally, this pr oblem has been solved by employing one of a variety of interpolation t echniques or by allowing small adjustments in the value of wave speed. In this paper, the number of available strategies is increased substa ntially by allowing several new kinds of interpolation as well as blen ded combinations of these interpolation approaches with the wave-speed -adjustment technique. The new hybrid approaches include interpolation along a secondary characteristic line and minimum-point interpolation , which minimizes the distance from the interpolated point to the prim ary characteristic. An intuitively appealing technique involving direc t adjustment of the wave path is rejected because it is potentially un stable. The entire flexible algorithm is implemented as a preprocessor step, uses memory efficiently, executes quickly, and provides a flexi ble tool for investigating the importance of discretization errors in pipeline systems. The properties of the new algorithm are analyzed the oretically and illustrated by example.