Computations of highly nonlinear free-surface flows, with applications to arbitrary and complex hull forms.

摘要

Computations of highly nonlinear free-surface flows, such as around arbitrary and complex hull forms, are performed using a desingularized boundary integral method which had been previously limited to simple, mathematical body geometries. Ubiquitous as wave breaking and spray are in nonlinear ship flows, the development of the method has been accompanied by studies into wave breaking, especially on ways to enable the computations to proceed unhindered by the occurrence of spray and wave breaking.; A criterion for the likely occurrence of wave breaking is devised as a means for detecting incipient numerical wave breaking. Once detected, a breaking wave is suppressed though a new technique that simply fairs through the free-surface nodes that are seen as likely to break. The technique is successfully applied to gravity waves in two dimensions.; The feasibility of the technique in suppressing wave breaking in forward-speed calculations is shown using two-dimensional transom stem flow calculations, and grid convergence is also demonstrated. A stable procedure for effecting cleanly-separating transom stem flow within the inviscid flow model is also devised using these two-dimensional calculations.; Calculations for practical hull forms are enabled by a body geometry processor for modeling such forms. Results are presented for arbitrary and complex hull forms as typified by the Series 60, C_B = 0.6 parent hull and two transom-stemed vessels-the DDG5415 naval combatant model and the D1 fast monohull. Specifically, calm water results at representative Froude numbers are presented, grid convergence is shown, and the computed wave profile on the hull, wave field, and wave resistance are shown to agree well with the available experimental data. The calculations also feature the successful suppression of spray and wave breaking in three dimensions.