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-   -   Brake Rotor Thermal Calculation in STAR-CD- Urgent (http://www.cfd-online.com/Forums/cd-adapco/55447-brake-rotor-thermal-calculation-star-cd-urgent.html)

ps June 20, 2006 01:47

Brake Rotor Thermal Calculation in STAR-CD- Urgent
 
I am a fluent user and have a small query regarding the solving procedure of a problem In STAR-CD which involves fluid flow over the solid and the conduction within the solid (for ex: thermal calculations of the brake rotor, which involves flow over the brake rotor and the heat conduction with in the brake rotor)

In Fluent, for this problem, first we simulate the flow over the brake rotor and find the convective heat transfer coefficients. Then we deactivate the fluid volume (fluid domain around the brake rotor) and make only the solid volume (rotor solid) active. Then we run only the energy equation with in the solid by using the convection values obtained from the fluid flow simulation. By deactivating the fluid volume, which is not needed while solving for the conduction within the solid rotor, we can save CPU time.

Is this possible in STAR-CD. Can we deactivate the fluid volume and make only the solid volume activate in STAR-CD, which is possible in Fluent.

In Fluent, if we want, we can toggle of the Flow and can run only the Energy equation, which helps in saving the CPU Time. Is this option available in STAR-CD

Please let me know whether these options are available in STAR-CD. If these options are not available, then when is the best possible way in STAR-CD to solve the above problem by saving the CPU run time?

Your immediate response/help in this regard is highly appreciated.

Thanking You


steve June 20, 2006 02:54

Re: Brake Rotor Thermal Calculation in STAR-CD- Ur
 
It is possible in STAR-CD to freeze the flow/turbulence field and solver for temperature only.

I am not sure why you would really want to do this since the expensive part of the calculation ,especially when you do radiation is not the temperature, it is the flow.

One thing that is important is to check that the solid URF for temperature is set correctly. I have done a few calculations myself and have now started using STAR-CCM+ v2 for such a calculations I have to increase the solid temperature URF from 0.9 to some value close to one (or 1 if I have a perfect grid). STAR-CD 3.26 has a solid shell URF of 1.0 and this ensures that the solid converges in temperature fast.

I hope this helps.

William Blake June 21, 2006 07:31

Re: Brake Rotor Thermal Calculation in STAR-CD- Ur
 
There is a good reason to go this way. First calculate the flow steady state and after this use the frozen flow field for a transient temperature calculation with large timesteps.


STAR-USER June 27, 2006 04:18

Unsteady Solid Condution solving in STAR-CD
 
Hi All!

I have a small query regarding the Solid conduction problem solution in STAR-CD. This is an unsteady problem and my aim is to find the temperature variation of that solid with time by dissipating the heat by convection. I enter the heat trainsfer coefficients values.

Please let me know how to calculate the time step in solid conduction problems, where as we calculate the time step based on CFL in case of a fluid. I have to simulate for a long time. can I enter the big time steps and any condition to be validated like CFL in case of fluids.

Is there any care to be taken in relaxation factors and any other text interface commands to be enterred in this condution problem in STAR-CD.

Your help in this regard is highly appreciated


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