Narrow Results

The program SWAN (Simulating WAves Nearshore) is a third-generation wave model used to compute the spectra of random short-crested, wind-generated waves on Eulerian grids. Presently there is no release of the SWAN code to execute on parallel computers and computations are limited to a single processor. This paper shows how to easily create a version of the SWAN code that can execute on parallel platforms using a simple approximation. The approximation is to solve the transport equation as a stationary problem at every time level. This is referred to as a quasi time-accurate approximation to differentiate it from a truly time-accurate computation where the transport equation is solved as a nonstationary problem. Using this approximation, the individual integrations at different times are independent, and coarse-grain parallelism can be easily exploited using the Message Passing Interface (MPI) parallel programming system.

This study compares the quasi time-accurate method in Part I: Method, with the time-accurate version of SWAN for a simulation of 1995 Hurricane Luis and a Gulf of Mexico storm that occurred in September 2000. Using the quasi time-accurate method, significant reductions in wall times were achieved relative to time-accurate computations. Examination of the error norms show that the quasi time-accurate method agrees well with the time-accurate results. Thus, the MPI quasi time-accurate method, because of its efficiency, can play an important role for cases where the time-dependent forcing terms are the dominant influence on wave conditions.