How to run COMSOL Multiphysics Workflow On Nimbix - Batch Mode

This article describes the workflow for performing a simple single physics analysis on the Nimbix platform using COMSOL® software. COMSOL® software package offers the capabilities of performing heat transfer, electromagnetic, structural analysis, and multiphysics analysis either as stand-alone or using a high-performance cloud computing service such as the one offered by NIMBIX. The case study presented in this article will demonstrate the Batch mode COMSOL® workflow on NIMBIX using COMSOL® release 5.5

If you ever find yourself creating new models in COMSOL faster than you can launch them interactively, it is time for you to learn how to run your simulations in batch mode.

The example described in this case study is a simple heat transfer problem that was set up and created in COMSOL® release 5.5. The scope of the case study is to show you the workflow for running a COMSOL project on NIMBIX cloud, in batch mode.

The following steps can be followed (for detailed instructions on using COMSOL®, consult COMSOL® user manuals and tutorials):

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1. Select Compute from your Nimbix account menu (the “All Apps” window will be displayed in your browser and all the Nimbix cloud supported software will be shown). Start COMSOL® software by clicking on the COMSOL® 5.5 icon as shown below.

NOTE: If the option (for example latest COMSOL release or any other release) is not available in the first-page menu, click 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 COMSOL® 5.5 (or any other release you prefer) option and choose COMSOL Batch, as shown below:

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NOTE: For the example presented in this article (simple fluids heat transfer problem), COMSOL Multiphysics, Single Host was used to set-up the model and create the .mph file. Once the .mph file was created (which you can also create it on your local computer), you can use it to run your simulation in batch mode. This offers you the advantage of being able to run multiple projects at the same time, much faster than doing it interactively, and it allows you to explore different loads and boundary conditions quicker. The study design is shown below (axisymmetric CFD/heat transfer flow through a heated restriction problem that uses a “velo” parameter as the inlet flow velocity) as shown below:

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3. After clicking on COMSOL Batch, the cloud set-up screen opens and here you must choose some of the settings by clicking on the Tabs on the top of the window (General, Optional, etc) one tab at a time, starting with GENERAL.

UNDER GENERAL TAB

1. Under Machine type drop down, when clicked, you have the choice of selecting 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).

For the example presented here, we selected the Machine type: 2 core 128GB RAM (CPU only) (n32), as shown below:

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NOTE: The Default “1 node” 128GB RAM pops up and the number of nodes can be changed if you want to run it on more nodes. The machine type you selected in this step, will dictate the number of cores allocated. Do not mistake 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 2 cores, 2 nodes represent 4 cores, etc).

2. Select the input file – browse for the “. mph” file that you created by clicking on the “…” ellipsis button:

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3. Browse to the “BatchModel.mph” location in your vault and select the file:

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UNDER OPTIONAL TAB

1. Assign a JOB LABEL (give a name that will help you keep track on your running jobs. For example, My_Batch – optional), a Parameter name under Parameter names (give a meaningful name based on the parameter type, in this case “velo” from velocity), and assign a Parameter value that corresponds to this batch run, as shown below:

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NOTE: Leave all other boxes blank, unless you run multiple physics and wish to give a name to each of the Physics you run, or you have a data file that wants to use in your batch mode simulation. NIMBIX allows users to pass parameters to the COMSOL solvers that overwrite the internal parameters (in this case, the model will run with 0.5 m/sec inlet velocity vs 0.25 m/sec assigned during pre-processing.

UNDER STORAGE TAB

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

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The “drop.jarvice.com” vault is recommended for small to medium size jobs, such as simple 1D, 2D heat transfer, electromagnetic or structural analysis projects. For any complex and computationally heavy jobs, and where partitioning the job over the number of cores becomes challenging, the PREMIUM vault is strongly recommended. The PREMIUM vault can be found under the drop down under “Select Vault” tab (NOTE: requires a subscription and extra monthly payment to have access to PREMIUM vault).

UNDER PREVIEW SUBMISSION TAB

1. Before submitting your job for running, you can preview your settings under the PREVIEW SUBMISSION tab to check the batch session inputs.

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Once you submitted your job, batch mode is running as shown in the image below (warning: image may be different than shown):

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NOTE: The results are saved in your data folder as shown above (note the results file for post-processing).

2. Monitor your CPU utilization (Click “Detailed Job Metrics” to see the utilization of your nodes during Solve):

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NOTE: The CPU utilization time refreshes every 30 seconds. For distributed problems, all nodes will be displayed along with CPU utilization per node (warning: image may be different than shown here).

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3. Post-process your results. Use the output file saved in the “data” folder (new COMSOL session)

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4. Save and Exit once post-processing is completed.

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