Computational Fluid Dynamics

Introduction

The Wolfson Unit's range of consultancy services encompass Computational Fluid Dynamics (CFD), as well as experimentally based methods. Working closely with a number of partners ranging from academics at the University of Southampton to commercial software vendors, and specialist CFD analysts we have developed our CFD capabilities in order to compliment the experimental testing and other services we provide.

Wolfson Unit engineers have had experience of, and been using, CFD since the early 1990's. This experience ranges from having conducted academic research to assisting designers on best practice to incorporate CFD within their design development, and using a variety of CFD codes to evaluate fluid flow in variety of problems.

Simulation Software

We have access to a wide variety of Computational Fluid Dynamics (CFD) tools, ranging from 2D foil modelling codes to commercial RANS solvers. While OpenFOAM is used in preference for RANS and LES simulations, access to and expertise with CFX and FLUENT is available.

OpenFoam

OpenFOAM CFD Toolbox is a open source CFD software package produced by a commercial company, OpenCFD Ltd. It has a large and expanding user base across most areas of engineering and science. OpenFOAM has an extensive range of features to solve anything from complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics and electromagnetics. OpenFOAM uses finite volume numerics to solve systems of partial differential equations ascribed on any 3D unstructured mesh of polyhedral cells. We have developed a number of approaches and techniques for solving typical marine applications of OpenFOAM. Unlike other leading CFD codes OpenFOAM is open source and there is no licencing costs. It therefore lends itself very well to large, parallel processing simulations.

Computational resources

The Iridis supercomputer at the University of Southampton allows us to provide a fast turn around on a full matrix of simulations for detailed models. The technical specifications of this resource are:

• 1008 Compute Nodes with 2 4-core 2.27 Ghz Nehalem processors (so 8 processor cores per node) providing over 72 TFlops
• at least 22GB of memory available to the user (32 nodes have 45GB), total of 22.4TB RAM
• currently ~110 TB of usable disk space
• Infiniband network throughout

As well as using the Iridis computational resource for undertaking our consultancy services, the Wolfson Unit has the capability of providing a portal to Iridis for clients to run their own simulations.

Integration of results into design process

Any results obtained by CFD should ideally be used in conjunction with experimental or other data sources, with, for example, the experimental data providing the overall forces and the CFD providing an accurate breakdown and distribution of the forces, as well as giving greater understanding of the flow features and any trends to the data. In addition, the various data sources need to be assimilated into the overall design and decision making process easily and accurately. The Wolfson Unit has a range of software, such as BRIO^®, dedicated to this issue as well as extensive experience and knowledge of projects where this has been achieved.

Hydrodynamic studies

Computational models including moving bodies, free surface and Large Eddy Simulations (LES) can all provide valuable information in producing an efficient and effective design. Typical studies that can be conducted include:

• Optimisation of keels for upwind sailing performance
• Prediction of wave drag
• Optimisation of stern gear

Aerodynamics studies

Modelling capabilities include unsteady and twisted flow, allowing an accurate model of sailing yachts, and hot gas outflows. Typical studies that can be conducted include:

• Gas dispersion
• Aerodynamic efficiency of sails
• Performance prediction of sails in unsteady conditions
• Aerodynamic performance of superstructure

Collaboration

We regularly work closely with a number of other CFD consultants and software suppliers in order to provide a complete service to the client, using the latest software, techniques and expertise, be in combining experimental results with CFD results, or to complement computational capabilities.

Please contact the Wolfson Unit to discuss your requirements for computational simulations.