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# Advanced Numerical Modeling of Marine Free Surface Flows

Language

English

Course format On-site
Date 2020-08-17 - 2020-12-20

The course covers the underlying principles of numerical modeling of marine flows with complex free surfaces with a numerical wave tank. In the near-field, these types of flows occur under non-linear waves, where waves steepen up to and beyond the point of breaking. The numerical methods taught capture the complex free surface through two-phase flow modeling and solution of the three-dimensional Navier-Stokes equations. The numerical methods for the interface treatment, spatial and temporal discretization, parallel computing are presented. Essential parts of a numerical wave tank are the wave generation, wave absorption and the unique numerical aspects of simulating wave propagation. The relevant topics for marine and coastal engineering of modeling porous structures, floating bodies and sediment transport are also introduced. In addition, the possibility to use the two-dimensional depth-averaged version of the numerical wave tank is covered, which allows for large scale phase resolved wave modeling in conjunction with a non-hydrostatic pressure solution or additional dispersion terms.

In the exercises, the theoretical knowledge of numerical modeling of marine flows with complex free surfaces is applied by the students. The numerical wave tank used is the open-source hydrodynamics model REEF3D, which is developed at the Department of Civil and Environmental Engineering. Here, all numerical methods addressed in the lectures are implemented. A brief introduction of the object oriented principles and modular code structure of the numerical wave tank is given.

## Prerequisites

Basic knowledge of computational fluid dynamics (CFD), basic numerical methods and basic programming skills are recommended.

Fluid mechanics and wave theory equivalent to TVM4116 Fluid Mechanics and TBA4270 Coastal Engineering respectively in addition to Matlab/Phyton skills are required.

## Learning outcomes

Knowledge:

After completion of this course, the student will have knowledge on:

• the CFD Fundamentals of a numerical wave tank (Navier-Stokes equations, convection discretization, diffusion, time discretization, pressure, turbulence modeling, iterative solver)
• free surface treatment with interface capturing (level set method, volume-of-fluid method)
• Numerical Wave Tanks (wave generation, wave absorption, principles of the calculation of wave propagation with a CFD code)
• parallel computing (domain decomposition, message passing interface, parallel solution of a sparse linear matrix)
• porous media algorithms for breakwater simulations
• sediment transport calculation in a CFD-based numerical wave tank
• 6DOF algorithm for fluid-structure-interaction
• depth-averaged Navier-Stokes equations (with non-hydrostatic pressure or dispersion terms) for large scale phase resolved wave modeling

Skills:

After completion of this course, the student will have skills on:

• practical use of numerical methods for marine flows with complex free surfaces
• selection of physical boundary conditions for wave generation and absorption
• compilation and installation of the open-source hydrodynamics model REEF3D
• setting up simulations for a range of marine flow problems with a complex free surface
• running simulations on NOTUR's supercomputer facilities

General competence:

After completion of this course, the student will have general competence on:

• Insight into CFD-based numerical wave tanks and the critical evaluation of the numerical results.

## ISCED Categories

Scientific modelling