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Material Property Specification for Natural Convection of Air

I'm trying to model Natural Convection between Heated aluminum block and air, the results I obtained are in contrary to buoyancy induced flow (the hot air is moving down). For additional Information I have checked Thermal Flow, specified gravitational force (-9.8 om y direction) and disabled turbulence.

It would be really helpful if anyone could advice me about how to proceed from here. Also could you please give me an insight about Air-ideal Gas in material library?

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HyperMesh CFD

v2022

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acupro

What are the boundary conditions on the model? Maybe post a new image with BCs indicated - along with the .inp in order to match that with the image. Generally a domain like in the image is useful. Use an inlet at the bottom with a small velocity - like 0.01 m/s and room temp, and outflow at the top. The contraction (slip BC) to the exit helps to prevent reverse flow.

Most basic approach would be to use Boussinesq density - function of temperature only.

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acupro

Jagan

aAnd could you please let me know how to change transparency of the model like yours?

1.prt.inp

acupro

aAnd could you please let me know how to change transparency of the model like yours?

If you use the stagnation pressure BC, you'll also need to activate hydrostatic pressure, with a defined origin for that hydrostatic pressure. This makes the pressure consistent with the weight of the fluid column. If you leave them all in one set, that's OK. If you separate them into separate BC sets, make sure you use the same origin for each of them. (I don't see the stagnation pressure BC in the .inp you provided.) Also - if you have inlets/outlets, you shouldn't use that Fixed Pressure BC.

The image was actually generated in a different software package.

Ovando_RBB

Hi there,

One thing that has worked for me while analyzing oil cooled electrical transformers is to define as walls all the boundaries around the assembly where the buoyancy takes effect. You just need to make sure that the Boussinesq approximation is being taken into account during the solving (variable mass density with temperature, gravitational effects activated).

Also, make sure that the volume of air is at least 5 to 10 times longer than the height of the aluminum block you are trying to heat to properly capture the plume of the free convection.

Hope this comment helps!