Understanding Top to Bottom Couplings for 2D shell elements (Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal)

In the Mesh Collector dialog box, if you create either a Thin Shell or Null Shell type 2D mesh collector using the Top and Bottom option from the Radiation list in the Thermo-Optical Properties group, you can use the Top to Bottom Couplings option to control how the software treats the top and bottom sides of the element.

The Create Top and Bottom as Two-Layer Shells option controls whether the software creates a thermal resistance between the top and bottom of the shell element.

• If you select Create Top and Bottom as Two-Layer Shells check box, the thermal solver creates a null shell element behind the main element with the specified bottom thermo-optical properties. The thermal solver accounts for conduction or radiation between the main and null elements. The null elements do not conduct in plane. The two layers do not model physical layers, but rather model detailed through plane conduction. For each element in the mesh, each of the two layers provides a calculation point for the thermal solver. This allows it to calculate two different temperatures, one for the top and one for the bottom, of each element. Top to bottom couplings model conductive and radiative fluxes through the thickness of the element. Thermal loads and fluxes applied to one side are transferred to the other side based on the coupling value you define. Note: If you select this option, you can use the options in the Account for list to control the type of heat transfer that takes place between the top and bottom sides of the element. See the 2D Mesh Collector dialog box (Thermal/Flow/SST/ESC) for more information.

• If you deselect Create Top and Bottom as Two-Layer Shells check box, the software models conduction in only two dimensions. Each element has a single temperature value with no distinction between top and bottom sides.

One common use of the Create Top and Bottom as Two-Layer Shells option is to model multi-layer insulation (MLI). In this situation, the top element layer models the in-plane conduction through the structure or panel and the bottom layer models the outer MLI surface. A radiative coupling between the top and bottom layers, with an effective emissivity value, models the insulating effects of the MLI.

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Understanding Top to Bottom Couplings for 2D shell elements (Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal), Simcenter 3D 2021.1 Series

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