Bottom Smoothing to Prevent Numerical Instability

Abstract

Numerical simulation of sediment transport and the changes in plan form of the shoreline near coastal structures may produce results where the bottom slope exceeds the maximum slope which would be expected to occur on the real (prototype) shoreline. This may cause instability in the numerical solution and prevent an accurate simulation of the transport processes. A numerical subroutine has been developed to redistribute the sediment at pints where the numerically produced bottom slope exceeds the maximum expected slope. This subroutine has no dependence on time. The smoothing is accomplished numerically after the completion of one or more iterations of time-dependent, numerical simulation of physical processes, e.g., sediment transport associated with wave action or currents. It should be noted that the smoothing subroutine will smooth any input data to reach a maximum slope between points, even random numbers. This subroutine should not be used as a substitute for good simulation of the physical processes, but may be used to smooth errors resulting from the inexact nature of numerical modeling.