This is perhaps due to resolution and the kind of mesh (unstructured mesh). Note that the maximum velocity at the center of the tube at the outlet (~ 0.29 m/s) smaller than the theoretical maximum (~ 0.31 m/s). The following pdf shows how to plot the velocity across the outlet of the pipe. Post-processing of results is done with the paraFoam program that is also available on the freecad-openfoam singularity image. Singularity exec /n/seas_computing/scientific_software/freecad-OpenFoam-2021.simg. #SBATCH -mem-per-cpu=500 #Memory per cpu in MB (see also -mem) #SBATCH -p shared #Partition to submit to You can import it into openfoam and run openfoam from the tube_laminar_flow directory as follows: The file also includes a mesh file from gmsh. Unzip the file in a suitable directory, change into it and run singularity from there. The zip file tube_laminar_flow.zip includes the directory structure with all the necessary files set up for laminar pipe flow. The following pdf file illustrates the steps:Ġ3_OpenFOAM_laminar_flow_simulation_v2021.pdf We setup the simulation by copying the folder $FOAM_TUTORIALS/incompressible/simpleFoam/pitzDaily folder and modifying the appropriate files. The mesh file should be converted to the OpenFOAM format with the gmshToFoam utility and the units (which are in mm) need to be converted to SI units (the native units of OpenFOAM) with the transformPoints utility function. Before beginning this part, make yourself familiar with the OpenFOAM directory structure:įor the current simulation, we need the mesh generated with gmsh along with the initial and boundary conditions and fluid transport properties. We set up the simulation of laminar pipe flow by copying a pre-existing incompressible flow simulation directory structure from the directory $FOAM_TUTORIALS. Geometry creation and meshing can also be carried out with other open source packages such as salome (or salome_meca). Solidworks, Onshape, Autodesk, etc.) and exported in STEP format to meshing software. Note that the geometry creation step can also be performed with commercial software (eg. The following pdf shows mesh generation with hexahedra.Ġ2_Openfoam_gmsh_hexahedral_meshing_v2021.pdf While tetrahedral meshes can be generated easily with gmsh, they are not ideal for CFD applications. The following pdf shows how to construct the tube geometry and export it in the STEP format suitable for import into gmsh for meshing.Ġ1_Openfoam_freecad_tube_geometry_v2021.pdf Geometry preparation with freecad and meshing with gmsh Flow in the tube is maintained by applying a pressure of 5000 Pascals above the atmospheric pressure at one end while the other end is exposed to the atmosphere. The kinematic viscosity of the fluid is 0.00047 m^2/s and the density is 850 kg.m^3 (corresponding to some kind of oil). In this example, we consider laminar flow in a pipe (radius 10 mm, length 1000 mm). OpenFOAM with geometry and meshing using other software These steps can be carried out using the singularity container on odyssey. Please familiarize yourself with this model (and the OpenFOAM directory structure) before proceeding further. All steps are carried out in OpenFOAM via command-line interface (CLI). The example of lid-driven cavity flow introduces you to OpenFOAM by taking you through all the steps (geometry creation, meshing, simulation and post-processing) for a simple geometry. Basics of pre-processing, simulation and post-processing in OpenFOAM In the following sections, we will briefly take you through the modeling steps with a simple example. However, it is more convenient to use a CAD software package for creating more complex geometries and use a separate software for meshing. Simple geometries can be created and meshed within OpenFOAM (see the lid-driven cavity flow example below). These include pre-processing (geometry/part creation and meshing), simulation, and post-processing. Modeling with OpenFOAM involves multiple steps.
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