Modeling flow surface obstructions

The Embedded Flow Surface With Obstructions and Boundary Flow Surface With Obstructions types let you model convection and drag caused by small objects that obstruct the flow near a Flow Surface.

For example, you can use these types to model thin surfaces with many attached components convecting to a surrounding fluid, such as printed circuit board assemblies.

A Flow Surface obstruction has the following characteristics:

• It convects from the top of the obstruction only. The convection on the portion of the flow surface that is hidden by the obstruction is suppressed.

• It produces drag on the fluid and suppresses drag on the hidden portion of the flow surface.

Modeling the obstructions

The geometry of the obstructions must be visible in your idealized part. In general, you should use simple geometry to model the obstructions, such as cubes or cylinders.

Meshing the obstructions

The flow solver calculates drag and convection with the assumption that the obstruction faces are parallel to the Flow Surface, and that they represent the maximum height of the obstruction. For accuracy, when you mesh the obstructions, the elements should be parallel to the primary surface at a distance that represents the height of the obstruction. The solver ignores any unmeshed obstruction faces.

The obstruction elements do not need to align with the 3D flow mesh. To model conduction between the elements on the obstruction and the Flow Surface, you must define a Thermal Coupling.

Note:

You can select a face that is not meshed in a Flow Surface simulation object when you select the Rotating/Translating Surface in Shear check box.

How do I

Create a flow surface

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Understanding flow surfaces

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Modeling semi-permeable surfaces

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Modeling flow surface obstructions, Simcenter 3D 2021.1 Series

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