Simulation of scour around arbitrary offshore foundations based on the Volume-of-Fluid method combined with a Bingham model

TL;DR

This paper introduces a novel simulation method for scour around offshore structures using a combined Volume-of-Fluid and Bingham model within OpenFOAM, validated against experimental data and capable of handling arbitrary geometries.

Contribution

It develops a new approach for sediment modeling with a Bingham fluid and internal wall functions, improving scour simulation accuracy around complex offshore structures.

Findings

Good agreement with experimental scour data

Enhanced internal wall modeling improves sediment surface prediction

Applicable to arbitrary offshore structures with complex geometries

Abstract

This paper presents a method for the simulation of scour around arbitrary offshore structures. It is based on the solution of the Reynolds-Averaged-Navier-Stokes equations implemented in the OpenFOAM framework. The sediment is simulated with the help of a Bingham model, which basically models a solid sediment behavior by introducing a very high viscosity. The relative pressure used by the Bingham model is estimated with a new approach based on the solution of a Poisson equation. The position of the sediment surface is calculated with the Volume-of-Fluid approach using a high-resolution scheme. To keep the typical wall characteristics without demanding a fine grid, the common wall functions are transferred to the domain internal sediment walls. Furthermore, additional modifications are applied to model a solid sediment wall inside the solution domain. The new internal wall function implementation is validated with a 2D test case. The results show a very good agreement to common wall functions and a significant improvement compared to its negligence. Furthermore the solver is used to simulate the scour downstream of an apron and the scour around a vertical cylinder in current. The results are compared to experiments presented in the literature and show good agreement. The applicability onto arbitrary structures is demonstrated by applying the solver onto a vertical cylinder with a mudplate. The current development state is able to resolve all important physical flow and scour phenomena. The results also unveil that modeling of the suspension and the treatment of the internal wall need additional attention.