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Energy equation convergence acusolve (thermal analysis - natural convection)

User: "Sebastian Yang"
Altair Community Member
Updated by Sebastian Yang

Hi all,

 

I am having a tough time trying to reach convergence regarding temperature residuals in a 3D natural convection problem. It consists of a box cointaining an hole in the middle which releases heat flux per unit area into the fluid.

image

The BCs are:

Fixed temp on the outer wall.

Heat flux on the walls of the square hole.

 

The solver settings are:

Boussinesq density model

laminar flow

relaxation factor 0.2

 

 

My questions are:

1. Are there separate relaxation factors for each one of the residuals (velocity, pressure, temperature) ? I only see 1 global relaxation factor.

2. How can I check the regions with bad convergence? In this post,

https://community.altair.com/community?id=community_question&sys_id=88b600ba1b2bd0908017dc61ec4bcbf1

ydigit explains that there is an option of outputting advanced varaiables. ¿How can I do that and how do I visualize the "bad" regions?

3. Any recommendation on large models? I can get convergence in a small model of size 0.1 m x 0.1 m, where residuals of temperature are <1e-3. However, I have a model of 1.5 m x 1 m size, I can not afford putting the same element size I used in the small model and the temperature residuals I am getting are around 0.1 after testing various mesh densities. On the other hand, Is it possible or is it a usual practice to do similarity analysis?

Thank you

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