{"id":45863,"date":"2021-07-12T16:23:48","date_gmt":"2021-07-12T16:23:48","guid":{"rendered":"https:\/\/www.simscale.com\/?page_id=45863"},"modified":"2025-07-17T15:43:25","modified_gmt":"2025-07-17T15:43:25","slug":"incompressible-lbm","status":"publish","type":"page","link":"https:\/\/www.simscale.com\/docs\/analysis-types\/incompressible-lbm\/","title":{"rendered":"Incompressible LBM (Lattice Boltzmann Method) Analysis"},"content":{"rendered":"\n

The Incompressible LBM<\/strong> analysis type is used to run large transient external aerodynamics simulations when the Mach number is < 0.3 and where the geometry usually involves large domains.<\/p>\n\n\n\n\n\n\n

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Figure 1: Transient aerodynamics simulation over ‘Gangnam District’ with velocity magnitude contours using Incompressible (LBM) analysis<\/figcaption><\/figure>\n<\/div>\n\n\n

It is a GPU-based solver using the lattice Boltzmann method (LBM), developed by Numeric Systems GmbH, Pacefish\u00ae\\(^1\\). It has the ability to run on multiple GPUs in parallel giving highly accurate results for transient simulations at running times reduced from weeks and days to hours and minutes.<\/p>\n\n\n\n

Within SimScale, one can effortlessly set up an incompressible LBM simulation with the steps described below.<\/p>\n\n\n\n

Creating an Incompressible LBM Analysis<\/h2>\n\n\n\n

To create an Incompressible (LBM)<\/em> analysis, first, select the desired geometry and click on ‘Create Simulation’<\/strong>:<\/p>\n\n\n

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Figure 2: Steps to create a simulation in SimScale. Click on ‘Create Simulation’<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

Next, a window with a list of several analysis types supported in SimScale will be displayed:<\/p>\n\n\n\n

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Figure 3: Select ‘Incompressible (LBM)’<\/strong> <\/em>analysis type from the tree above and click on ‘Create Simulation’<\/strong> at the bottom.<\/figcaption><\/figure>\n\n\n\n
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<\/i>Specialized analysis type<\/p>\n <\/div>\n

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Incompressible (LBM)<\/em> is a specialized analysis type restricted to users with a paid plan. For more details please visit our product & pricing page<\/a> or contact sales.
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Choose ‘Incompressible (LBM)’<\/strong> analysis type and click on ‘Create Simulation’<\/strong>. This will lead to the Workbench with the following simulation tree and the respective settings:<\/p>\n\n\n

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Figure 4: Simulation tree for incompressible LBM analysis in SimScale Workbench<\/figcaption><\/figure>\n<\/div>\n\n
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Figure 4: Simulation tree for incompressible LBM analysis in SimScale Workbench<\/figcaption><\/figure>\n<\/div>\n\n\n

Global Settings<\/h2>\n\n\n\n

To access the global settings, click on ‘Incompressible (LBM)’<\/strong> in the simulation tree. Here you can define the turbulence model that needs to be applied for the simulation. A choice between RANS, LES, and DES turbulence models is available. <\/p>\n\n\n\n

Detailed information about each of these turbulence models can be found here<\/a>.<\/p>\n\n\n\n

Geometry<\/h2>\n\n\n\n

The Geometry <\/em>section allows you to view and select the CAD model required for the simulation. It is important that the CAD model is well prepared to avoid any meshing or simulation-related errors. Find more details on CAD preparation and upload here<\/a>.<\/p>\n\n\n\n

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<\/i>Did you know?<\/p>\n <\/div>\n

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While uploading your CAD model for LBM or wind comfort simulations it is recommended to toggle on\u00a0‘Optimize for LBM \/ PWC’<\/strong>.<\/p>

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Figure 5:\u00a0Optimize for LBM\/PWC<\/em>\u00a0upload option for CAD model is recommended wile performing LBM simulations in SimScale.<\/figcaption><\/figure>

This option allows you to import a *.stl file that is optimized for the incompressible LBM and wind comfort analysis types. It leaves out complex import steps like sewing and cleanup that are not required by the LBM solver and therefore also allows to import big and complex models fast.<\/p><\/p>\n <\/div>\n<\/div>\n\n\n\n

External Flow Domain<\/h2>\n\n\n\n

Here you can define the cuboidal flow domain that acts as a virtual wind tunnel to perform the fluid flow simulation. You need to define the following parameters:<\/p>\n\n\n\n