This article describes the workflow and settings/considerations to Setup an ANSYS CFX CFD project in stand-alone mode on the Nimbix cloud.
To access ANSYS CFX on the Nimbix cloud, the following steps are required:
1. Select the desired ANSYS Fluids release from the Compute dashboard.
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:
2. A splash window will open. Select the CFX option for interactive mode, as shown below:
3. The Cloud setup screen opens and here you must choose some of your settings by clicking on the Tabs on the top of the window (General, Optional, etc) one tab at a time.
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 a single CPU, others will have better graphics and therefore higher cost, etc).
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 to default in this case):
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 with traceability of your running jobs. For example, My_CFX_Project):
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
The “Elastic_File” 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 Performance_SSD vault is strongly recommended. The Performance_SSD vault can be found in the drop-down under “Select Vault” tab (NOTE: requires subscription and extra monthly payment to have access to Performance_SSD vault).
Before submitting your job for running, you can preview your settings under the Preview Submission tab.
Start your Nimbix job by selecting/pressing on the SUBMIT button.
After ANSYS Workbench Platform has been successfully launched, you should be able to see the ANSYS Workbench in the preview and can access the window by clicking on it (you can see details on the number of nodes, some information regarding memory, etc):
After clicking "OK" on the ANSYS feedback survey participation window, ANSYS CFX modules are available for use:
Set your working directory to your chosen directory for this project by clicking on the "Browse" option to the "Working Directory" text box and navigating to the location you want to store your data (click "Choose" to accept the location) or by typing that location in the "Working Directory" text box:
NOTE: Setting up the appropriate working directory will allow you to conveniently save and organize your data in the same folder without having to navigate to it every time you save.
ANSYS CFX Setup and Solution On the Nimbix Cloud
CFX – PRE: Model setup (materials, boundary conditions, initial conditions, analysis type)
1. Click on CFX-Pre to New Case in order to start a new case from scratch (will use a General case for this article but you can choose several options presented to you by CFX-Pro):
- General Case: For general purpose CFD analysis (uses all features of CFX-Pre)
- Turbomachinery: specialized mode to quickly set up turbomachinery simulations (compressors or turbines)
- Quick Setup: provides fewer model options and is suitable for simple physics setup
- Library Template: enables a CCL physics definition to be imported for use with an existing mesh.
2. Set-up your case (in this article, a Fluent Mesh/Input file was used to illustrate flow over an isothermal obstacle with ¼ symmetry)
NOTE: ANSYS Mesh in Workbench can be used to generate the CFX input file. Use Named Sections to define the walls, inlet/outlet, etc. Upon Exiting ANSYS Mesh to Export to Fluent Input File (several options are available such as ANSYS Mesh, cmdb, and .dsdb extensions, ICEM CFD such as .cfx and .msh extensions, Fluent Input files .msh extension, CNGS files, and other options)
3. Save your Case file and define your Run before exiting CFX-Pre. After the case is completed/setup and the analysis type is properly defined to fit your needs, right-mouse-click on Simulation Controls to Start Solver to Define Run
Note: Write the input file for the solver, and you can quit the CFX-Pre. You can run (if you use solver defaults – serial) the solver from the CFX-Pre without writing the input file.
4. Write the "Solver Input File" (see below) in the current working directory (by checking the Quit CFX-Pre box you will automatically quit the CFX-Pre module and start the CFX-Solver Manager):
CFX – Solver Manager: Option setup and solving the CFD model that was Setup in CFX-Pre
1. Define the run mode and initial values using the CFX-Solver Manager dialog window:
NOTE: There are several considerations that you need to be aware of when defining your Run
- Ensure the Solver Input File is correct (browse to the appropriate file/location if needed using the "Open" button on the right side of the text box)
- Type of Run
- Full: runs the partitioner if applicable, and then runs the solver (default option – to solve your model)
- Partitioner only: used for parallel runs only and does not run the solver
- Run Mode
- Serial: model is solved as one process on one computer
- Intel MPI Local Parallel: local parallel run mode for one node/computer (multiple threads/cores) only
- Intel MPI Distributed Parallel: network parallel for multiple nodes/computers with multiple threads/cores
- For a local parallel run, specify the number of partitions. This value is the number of separate processes that will be executed during solve
For a distributed parallel run, specify the number of partitions assigned to each host.
PARTITION NOTE: In order to determine the "optimal" number of partitions for the CFX solver, check the number of cores/threads you have in your CPU (for serial/local machines). Then in the "Partitions" tab, enter a number equal with either number_of_cores - 1 or number_of_cores - 2 (do not use all cores/threads to starve your computer of computing power). For Network parallel or local parallel, you can use the same principle using the number of cores that you selected during the cloud setup (you can use up to the total number of cores for the "Partitions" tab, keeping in mind that, for network parallel, the "Partitions" tab specified the number of partitions for each host/node).
NOTE: In NIMBIX cloud, for large problems that use "Intel MPI Distributed Parallel" run mode, delete the default host (using the "Remove Host" button) and add the hosts assigned to your job by clicking the "Insert Host" button and selecting the two hosts in the pop-up window.
Click "Close" when finished and add the partitions for each host (see the note above):
2. Start the Run (solve your CFD model), inspect your residuals, and monitor the job by pressing "Start Run" button in the CFX-Solver Manager.
NOTE: You can start CFD-Post and shut down the solver manager once the solution is finished, and the solver completed the Run. Inspect the workspace for any error messages and proceed with post-processing.
NOTE: You can also monitor your CPU utilization and memory usage (an important metric that you can track while analyzing large models). Click on the Detailed Metrics button.
CFD-POST: Post Process your results using CFD – Post
Plot desired results in the planes of interest (temperature contours, velocity plots, streamlines, clipping planes, pressure drops, etc.)