Viscous-inviscid matching for wave-body interaction problems.

摘要

A common feature appearing in computational simulations of wave-body interaction problems in ocean engineering is the presence of an open boundary which separates a region of interest from the rest of a semi-infinite domain. Usually, the phenomenon to be studied is located in a near-field region, where it is desirable to concentrate the available computer resources. Unfortunately, there is no simple way to specify conditions on the flow at the boundary between the near-field or inner region and the outer region such that surface waves propagate across without reflection or attenuation. This thesis addresses this issue by creating a general solution of the outer flow and develops techniques to match this solution to a variety of interior problems and interior solution methods.; The general, outer solution developed here uses a boundary-integral formulation which relies on the existence of an unsteady Green function for inviscid-fluid flow with surface waves. The numerical solution of the resulting integral equation is per formed using a pseudo-spectral method which has not been studied previously. Novel techniques for numerical evaluation of the Green functions that appear in the formulation are developed. The matching of this inviscid solution is then applied to several solution methods for various problems in the inner region.; If the assumption of inviscid flow is made in the interior region; the matching between the inner and outer regions presents no difficulties for the mathematical model of the flow, the same field equation applies to both regions. However, the mechanics of the matching technique do depend upon the solution method used in the interior region and a new, indirect technique is developed for application to field discretization methods that require a point-wise boundary condition.; If the flow in the interior region is modeled as a viscous flow, the manner in which the matching between the inner and outer region should be performed needs to be established. A new matching algorithm which differs from previous attempts at viscous-inviscid matching is developed and success of this technique is demonstrated with numerical results.