Nonlinear flexural-gravity waves due to a body submerged in the uniform stream

TL;DR

This paper models nonlinear steady flow past a submerged body beneath an elastic sheet, revealing complex wave interactions and nonlinear effects in gravity and elastic waves across various flow regimes.

Contribution

It introduces a coupled nonlinear model using the integral hodograph method to analyze nonlinear flexural-gravity waves around submerged bodies.

Findings

Two types of interface waves identified: gravity and elastic

Nonlinear interaction of waves is significant near critical Froude numbers

Solution convergence issues occur at certain submergence depths near critical flow conditions

Abstract

The two-dimensional nonlinear problem of steady flow past a body submerged beneath an elastic sheet is considered. The mathematical model is based on the velocity potential theory with fully nonlinear boundary conditions on the fluid boundary and on the elastic sheet, which are coupled throughout the numerical procedure. The integral hodograph method is employed to derive the complex velocity potential of the flow which contains the velocity magnitude on the interface in explicit form. The coupled problem has been reduced to a system of nonlinear equations with respect to the unknown magnitude of the velocity on the interface, which is solved using a collocation method. Case studies are undertaken for both subcritical and supercritical flow regimes. Results for interface shape, bending moment and pressure distribution are presented for the wide ranges of Froude numbers and depths of submergence. According to the dispersion equation, two waves on the interface may exist. The first, longest wave is that caused by gravity, and the second, shorter wave is that caused by the elastic sheet. The obtained solution exhibits strongly nonlinear interaction of these waves above the submerged body. It is found that near the critical Froude number, there is a range of submergences in which the solution does not converge.