Henry Bandringa Henry Bandringa
Simulation of wave impacts on offshore structures
The aim of this project is to develop a CFD approach to predict local impact loads on a global structure in realistic and deterministic waves, based on existing methods. In order to accomplish this goal, an assessment and possible extension of the existing CFD methods available at MARIN for the prediction of impact loads (ReFRESCO and ComFLOW) will be made.
The CFD methods will be step-wise validated for multiple offshore applications, with increasing complexity:
• a fixed global structure in regular waves;
• a fixed global structure in irregular and breaking waves;
• a global structure moving interactively in irregular and breaking waves.
An assessment will be made on accuracy of relative wave height, local pressures and global loads, but also in terms of computational costs.

This project is part of the research programme Operations@Sea and Waves & Workability .

Milos Birvalski Milos Birvalski
Development of a Nuclei Measurement System
Cavitation is a physical phenomenon of great relevance to maritime engineering, which can cause vibration and noise on vessels, as well as increase the drag of propellers or cause their deterioration/destruction. It is known that cavitation is initiated by cavitation nuclei, which are fluid or solid micron-sized particles naturally present in the water. The goal of this project is to develop a measurement technique that can determine the diameter spectrum and the concentration of nuclei in model testing conditions. and which has to operate remotely in near-vacuum. The path towards the goal is envisaged in several steps:
• literature study to investigate particle sizing techniques that are suitable for our purpose;
• testing and validation of two or more of the chosen techniques in well controlled conditions;
• building a prototype measurement system to be applied in the DWB based on one selected technique that performed best during testing and validation.

This project is part of the research programme Resistance & Propulsion - Multi-Phase Flows.

Konstantinos Drakopoulos Konstantinos Drakopoulos
Efficient Overlapping-Grids Simulations with ReFRESCO
The goal of this project is to implement an efficient overlapping-grids capability in ReFRESCO. Overlapping-grids have been already implemented in several other codes, and in a general sense, it consists on a generalization of internal/non-conformal/sliding interfaces. Moreover, overlapping-grids do increase the range of complex interaction problems possible to be tackled with ReFRESCO, and even help in the grid generation process. However, overlapping-grids algorithms involve several computational expensive operations, and its calculations are mainly unsteady, which are inherently CPU time consuming. Therefore new homogeneous/hybrid parallelization techniques have to be used in order to improve the efficiency of the overlapping algorithms. As an ultimately complex application to be tackled in this project, consider a ship/offshore construction in waves, fully appended, with working propellers/thrusters and active rudders, sailing/drifting close to a fixed object (harbour or another body).

This project is part of the research programme CFD Development - Basis Functionality and CFD Development - Moving Objects.

James Hawkes James Hawkes
Massively-Parallel Computational Methods in ReFRESCO
The aim of this project is to evolve ReFRESCO to take advantage of emerging hardware trends. A massive shift towards parallelization is under way, due to the stagnation of core clock-speeds, and many CFD codes are trying to address these changes. Part of this work investigates the way in which ReFRESCO is parallelized, identifying more modern parallelization schemes that can improve the scalability of ReFRESCO. These may include hybrid parallelization schemes (mixing multi-processing and multi-threading) or the use of graphics cards and co-processors to accelerate simulations. Another major part of this work looks at the underlying, mathematical algorithms which are responsible for solving the physical model. Many of these algorithms are numerically powerful but have poor scalability due to excessive inter-core communication. There is an opportunity to develop new algorithms which avoid expensive communications, whilst retaining most of their numerical performance, therefore allowing ReFRESCO to scale on massively-parallel computers.

This project is part of the research programme CFD Development - Basis Functionality.

Thomas Lloyd Thomas Lloyd
Cavitating Propeller Analysis Including Noise Radiation Using CFD
The project’s first aim is to derive and implement a version of the mathematical model for noise generation due to Ffowcs-Williams and Hawkings, known as the FW-H method. The implementation is to serve as a post-processing step to CFD computations of the cavitating marine propeller flow field using either MARIN CFD method ReFRESCO, or CRS boundary element method PROCAL. Apart from the computation of radiated noise, the determination of the acoustic loading on nearby structures, principally the ship hull above the propeller, is considered part of this objective.

This project is part of the research programme on Resistance & Propulsion - Noise & Vibrations.

Gem Rotte Gem Rotte
Ship Drag Reduction by Air Lubrication
The main goals for this project are to explore and validate multiphase CFD models to model the flow around air cavities and air chambers. In particular, we intend to:
• Assess the capability of multiphase RaNS and -LES methods available in ReFRESCO to capture the large-scale flow phenomena around air cavities and chambers.
• Compute the pressure- and shear stress distributions around air cavities and air chambers, in order to determine the distribution of drag components and their sensitivity to variations in air chamber/cavity characteristics.

This project is part of the research programme Resistance & Propulsion - Powering Performance.


External Staff

Joao Baltazar (IST, Portugal) Joao Baltazar (IST, Portugal)
Improving Propulsor Computations
Perform cost-effective accurate open water predictions of ducted propellers using boundary element methods (BEM), and using the RANS code REFRESCO on a routine basis.

This project is part of the research programme Resistance & Propulsion - Powering Performance.

Luis Eca (IST, Portugal) Luis Eca (IST, Portugal)
ReFRESCO Verification & Validation
The main goal of the project is to improve the robustness and accuracy of MARIN’s RANS solvers and in particular ReFRESCO. The success of the application of CFD tools to complex geometries typical of industrial applications relies on the use of numerically robust techniques but also on schemes that lead to accurate solutions without the need to use unaffordable or too expensive computer resources. Furthermore, any development of more sophisticated mathematical models to handle turbulence will require an accurate and robust flow solver.

This project is part of the research programme CFD Development - Basis Functionality.

Xin He (TU Delft, the Netherlands) Xin He (TU Delft, the Netherlands)
Fast and Robust Solvers for Maritime Applications
Xin He works on Technologiestichting STW project 13281, entitled "Fast and robust solvers for maritime applications". This project aims at improving the efficiency of the iterative solution method in ReFRESCO by solving the coupled system of mass and momentum equations using modern preconditioners in combination with a Krylov method.

This project is part of the research programme CFD Development - Basis Functionality.

Guilherme Rosetti (USP, Brasil) Guilherme Rosetti (USP, Brasil)
ReFRESCO simulations for Complex Offshore Applications
The goal of this cooperation project is to carry out work on numerical developments, verification and validation exercises and exploratory work within the offshore field. The following topics are of interest:
- Current loads on two vessels in side-by-side configurations including free surface effects;
- Wind loads on two vessels in side-by-side configurations;
- Smoke/gas/fumes dispersion;

These activities shall be developed in the course of three years (2016-2018) and are part of the research programme Operations at Sea.

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