How to Setup and Run an OpenFOAM Project in Interactive Mode using Nimbix

This article describes the workflow and settings/considerations to set-up and run an OpenFOAM project on Linux using the Nimbix cloud.

NOTE: This example uses the “Flow around a cylinder” OpenFOAM tutorial (constant velocity of 1 m/sec, cylinder radius 0.5 m located in the center of a 4mx4m square. Outflow boundary conditions: relative pressure p = 0 bar) with centerline symmetry setup.

Launching an OpenFOAM Job

To access OpenFOAM on Nimbix platform, the following steps are required:

1. Select OpenFOAM release from the Compute dashboard.

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NOTE: If the option is not available in the first-page menu, press on “More” at the bottom of the page as shown in the image below:

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2. A splash window will open. Select the OpenFOAM GUI option as shown below:

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UNDER GENERAL TAB

1. Under Machine type when you click on the caret on the right, you can select the type of machine you want to run your job on. The decision on machine type selection is based on the size and complexity of your model and cost associated with the machine type (some machines will have higher RAM, others will only run the job on single CPU, others will have better graphics and therefore higher cost, etc).

Figure4.JPG

NOTE: When running interactive based applications, you’ll find that selecting an NC9 or any NC* machine types should offer significant visual performance over not selecting an NC machine type. By selecting an NC machine, this places a GPU on your head-node, and offers better visual performance. Another thing to keep in mind, is that when running interactively you can use a web-browser, or in some cases for large models or you might consider using RealVNC.

2. Select the number of cores:

The machine type you selected in the previous step, will dictate the increment in the number of cores that you can choose/select. For a very simple and small model, you can leave default selection, which in this case would be “16” or move the scroll bar to the desired number of cores or simply type over “16” the number of cores you wish to run your job on (we left it default in this case):

Figure5.JPG

NOTE: Do not confuse the number of cores with the number of nodes (nodes represent the number of increment of cores that you selected. In the example above, 1 node represents 16 cores, 2 nodes correspond to 32 cores).

UNDER OPTIONAL TAB

1. Assign a JOB LABEL (give a name that will help you keep track on your running jobs). For example, cylinder as shown below:

Figure6.JPG

2. Leave blank the wall time limit and the IP address. The Window size needs to be kept as default.  Do not enter an Elastic License Server ID unless you use an elastic license on a designated server.

UNDER STORAGE TAB

Select vault type: Default vault is “drop.jarvice.com”

Figure7.JPG

The “drop.jarvice.com” vault is recommended for small to medium size jobs, such as Icepak projects, simple linear Mechanical Analysis projects, some HFSS and simple Fluent projects (not multi-phase). For any complex and computationally heavy jobs, and where partitioning the job over number of cores becomes challenging, the PREMIUM vault is strongly recommended. The PREMIUM vault can be found under the fly-down under “Select Vault” tab (NOTE: requires subscription and extra monthly payment to have access to PREMIUM vault).

Before submitting your job for running, you can preview your settings under the PREVIEW SUBMISSION tab.

Start OpenFOAM on Nimbix by clicking on the SUBMIT button on the bottom-right of the splash window/screen.

Access OpenFOAM terminal by clicking on the preview window in your Dashboard. A new tab/browser window will open.

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Note: A new directory (/openfoam7/run) is created in your data folder the first time you use OpenFOAM. Copy your OpenFOAM case directory (files can be created prior to analysis to save time and cost) in the /data/openfoam7/run directory.

Start Your OpenFOAM Project – Preprocess and Meshing

1. Using Linux commands, navigate to the project directory that contains the required OpenFOAM directories and files.

Figure9.JPG

NOTE: At a minimum the case directory shall contain the 0/, constant/ and system/ folders. The 0/ folder contains initial values for pressure and velocity, constant/ folder contains the polymesh/ folder that contains the blockMeshDict dictionary file and properties that remain constant during analysis such as material properties, and the system/ folder contains the command and solution dictionaries.

2. Mesh your geometry using blockMesh: type blockMesh in the Linux command window and keep and examine the mesher output in the command window paying close attention to error and warning messages. 

Figure10.JPG

NOTE: blockMesh is the OpenFOAM built-in meshing engine. Several commercial FEM software meshers can be used to mesh your geometry and can be imported into OpenFOAM. FluentMeshToFoam Converts a Fluent mesh (in ASCII format) to foam format including multiple region and region boundary. It is necessary to have most of the required files for the simulation within the case directory to create the OpenFOAM mesh. The three main directories (0/, constant/ and system/) and their files are required to run blockMesh. Otherwise, it is also possible to use a solved case as a dummy file to run blockMesh.

Mesh is created in the /data/openfoam7/run/cylinder/constant/polymesh directory:

Figure11.JPG

Inspect Mesh in Graphic Window (optional)

1. Start ParaView from your dashboard. ParaView is a pre and post processing software that can be used to view OpenFOAM files.

Figure12.JPG

2. In the resulting splash window click ParaView button.

Figure13.JPG

UNDER GENERAL TAB

1. Under Machine type when you click on the caret on the right, you can select the type of machine you want to run your job on. The decision on machine type selection is based on size and complexity of your model and cost associated with the machine type (some machines will have higher RAM, others will only run the job on single CPU, others will have better graphics and therefore higher cost, etc).

Figure14.JPG

NOTE: When running interactive based applications, you’ll find that selecting an NC9 or any NC* machine types should offer significant visual performance over not selecting an NC machine type. By selecting an NC machine, this places a GPU on your head-node, and offers better visual performance. Another thing to keep in mind, is that when running interactively you can use a web-browser, or in some cases for large models or you might consider using RealVNC.

2. Select the number of cores:

The machine type you selected in the previous step, will dictate the increment in the number of cores that you can choose/select. For a very simple and small model, you can leave default selection, which in this case would be “16” or move the scroll bar to the desired number of cores or simply type over “16” the number of cores you wish to run your job on (we left it default in this case):

Figure15.JPG

UNDER OPTIONAL TAB

Label your job by adding a name for your job in your “Job Label” text box (cylinder) in this example:

Figure16.JPG

IN THE STORAGE TAB

Select vault type: Default vault is “drop.jarvice.com”

 

Figure17.JPG

The “drop.jarvice.com” vault is recommended for small to medium size jobs, such as Icepak projects, simple linear Mechanical Analysis projects, some HFSS and simple Fluent projects (not multi-phase). For any complex and computationally heavy jobs, and where partitioning the job over number of cores becomes challenging, the PREMIUM vault is strongly recommended. The PREMIUM vault can be found under the fly-down under “Select Vault” tab (NOTE: requires subscription and extra monthly payment to have access to PREMIUM vault).

Before submitting your job for running, you can preview your settings under the PREVIEW SUBMISSION tab.

Start ParaView on NIMBIX by clicking on the SUBMIT button on the bottom right of the splash window.

Open the ParaView by clicking on the preview window. A second tab or browser window will open. You can toggle between ParaView and OpenFOAM windows/tabs during the workflow.

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Open the Mesh File to examine the mesh: Select Open from the graphical toolbar or from File to Open.

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Navigate to the system folder to open the controlDict dictionary file.

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Navigate to OpenFOAMReader in the OpenDataWith pop-up window.

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Click OK to dismiss the window and read in the data. Click Apply to show the geometry.

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NOTE: Alternate ways to open the mesh file is to create a <filename> file with the “.foam” extension (empty file) in the case (in this example cylinder) folder. OpenFOAM will look for the mesh files and will open them accordingly. Name of the file is arbitrary. Additionally, the command checkMesh (as always, you need to be in the case directory to execute the command correctly) will also check the validity of your mesh but will not display it in a graphical window.

Run OpenFOAM (Solver) and Post Process

Switch to OpenFOAM command window. Start the solver from the command prompt (type the solver name and hit “Enter”)

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NOTE: Depending on the problem set-up you will use different solvers for different solution (set up in the fvSolution file in the system/ directory). In this example a steady state potentialFoam solver is used. This solves for the velocity potential, to calculate the flux-field, from which the velocity field is obtained by reconstructing the flux. Several solvers can be used (icoFoam, laplacianFoam, etc.) depending on your problem set-up.

Inspect the output file and analyze any warnings or errors.

Figure24.JPG

POST PROCESS your solution using ParaView using the same steps/procedure outlined in the previous paragraph. Open the solution files from the newly created solution folders post analysis.

 

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