One of the main aims of the software suite for hydrogen and fuel cell systems, in addition to the engineering tools made available, is the creation of a state-of-the-art and freely available CFD modelling software suite for hydrogen safety science and engineering. Included in this suite will be a number of physical models, which will be made available through the utilization of the OpenFOAM CFD toolbox produced by OpenCFD Ltd at ESI group. These CFD models are based on the original OpenFOAM solvers, with some modifications made to the original source code in order to tailor them specifically to hydrogen and the scenarios under investigation.

The models implemented are the high pressure hydrogen release and dispersion model and the multi-phenomena deflagration model, both of which were developed at Ulster. Contained within Section 1.6are details of the high pressure hydrogen release and dispersion model.

The following section (Section 1.1) provides a very brief introduction to OpenFOAM and how the program can be used.

1.1       Introduction to OpenFOAM

As the models are based on the OpenFOAM CFD toolbox this section contains a brief introduction to OpenFOAM as well as a general overview of its structure.

OpenFOAM is a free, open source CFD software package and 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. If offers the user complete freedom to customize and extend its existing functionality. It includes over 80 solver applications that can simulate specific problems in engineering mechanics and over 170 utility applications that perform pre- and post-processing tasks. It can be installed on Linux operating systems including ‘Ubuntu’, ‘SuSe’ and ‘Red Hat Enterprise’.

Installation instructions can be found on the OpenFOAM website, www.openfoam.org.

FOAM is short for ‘Field Operation and Manipulation’. At its core is a flexible set of C++ written modules which are used to build solvers and simulate specific problems. It contains numerous pre-configured solvers, utilities and libraries meaning it can be used, initially, as any other typical simulation package. However as OpenFOAM is open, in terms of its design, structure and source code, the solvers, utilities and libraries are fully customisable. It employs finite volume numeric to solve systems of partial differential equations on any structured or unstructured mesh. The fluid flow solvers are developed within an implicit, pressure-velocity, iterative solution framework. Domain decomposition parallelism is fundamental to the design of OpenFOAM meaning there is no need for any parallel specific coding. The overall structure of OpenFOAM is shown in Figure 1.

Figure 1 – Overview of OpenFOAM structure [1]

1.1.1    Basic case setup

Using OpenFOAM all boundary conditions, mesh and case setup are implemented using text files in a specific folder structure. This folder structure is summarised in Figure 2. An example case, such as a steady-state incompressible turbulence model, would require the following setup (this description was obtained from Andersen and Nielson, 2008):

Figure 2 – Overview of OpenFOAM structure [2]