OpenFOAM® Meshing

In the automotive and plant construction sector, catalyst systems are used to clean the exhaust gas from the engine. Commonly, the selective catalytic reduction (SCR) system is used to reduce the NOx emissions. For such purpose, the SCR catalyst substrate has to have a defined minimum temperature before the DeNOx reactant is injected (around 280 °C). The following tutorial gives details about the coupling of the fluid and solid region with an energy transfer between these regions.

The descritization of the continous fluid is the essential task in the field of computational fluid dynamics and numerical analysis. Due to the stiff learning curve of OpenFOAM, especially at the beginning, even simple geometry meshing procedures are hard to achieve. Therefore, the following training case provides information for the first steps with snappyHexMesh.

Particular regions in a mesh could require unique properties such as the modeling of porosities or source terms. Therefore, cell zones have to be used in OpenFOAM®. SnappyHexMesh can be one way to define such zones during the meshing stage directly. Based on the snappyHexMeshDict set-up, different quality levels can be achieved. Especially the influence of the »featureEdge« feature is demonstrated in the training case.

Holzmann CFD offers a wide range of different tutorials. Uniquely focused on dynamic meshes and unique features. This training case provides all information that is required to generate a 2D arbitrary mesh interface (AMI) in OpenFOAM. As always, the example uses the popular and clean bash scripts.

SnappyHexMesh allows using different strategies to refine different surfaces and regions. However, discretizing thin gaps in the domain can result in a challenging topic. Particularly if only triangulated surfaces are available, which cannot be split into more different surfaces that can be controlled individually within the snappyHexMesh application. As already mentioned, OpenFOAM allows different techniques to refine thin gaps. One of them is described in this tutorial.

SnappyHexMesh can refine defined feature edges during the refinement stage. However, many people in the community have a lot of problems with the feature edge refinement strategy. Therefore, Holzmann CFD provides the SFR case which meshes a pipe with three different surface feature refinement set-up's. The results, especially the wrong ones, might be familiar.

People all over the world who start in the field of numerical simulation begin investigating a simple pipe flow. However, for new OpenFOAM® users, even the trivial pipe meshing can be challenging. Therefore, Holzmann CFD provides two cases in which a pipe is bent under 45 degrees, and 90 degrees will be discretized. Additionally, the layer generation is applied, while a coverage rate of 99.5 percent is reached.

The in-house mesher of OpenFOAM® named snappyHexMesh is infamous in the community due to meshing problems in more advanced and complex geometries. This might be true if you are not using snappyHexMesh correctly. This training case shows the basic meshing settings for the helix geometry. Additionally, a way of the layer generation is shown which will end up with a coverage above 95 percent.

The generation of the arbitrary mesh interface (AMI) boundary condition is used for rotating mesh behavior. The AMI condition interpolates values from the static mesh part onto the dynamic mesh part or vice-versa. The generation of that particular kind of boundary condition can be achieved using different methods. Commonly, Holzmann CFD uses the mesher of OpenFOAM®, namely snappyHexMesh, to generate high valuable numerical meshes.

2D and 2D rotational axis symmetric numerical meshes are used whenever it is possible. This method is related to the savings in computational effort and simplification at all. However, there are several ways to create 2D rotational axis symmetric geometries in OpenFOAM®. For more complex designs, it is worth to analyze the following training case which uses the 3D meshing tool »snappyHexMesh« to mesh the geometry in 3D first, and afterward derive the 2D rotational axis symmetric model by using other OpenFOAM® tools such as extrudeMesh and so on.