Learning Forum

[suraj9735]

Why my solution converge in one iteration in fluent? I am solving only for energy equation.

[Konstantine Kourbatski]

depending on the initial temperature field, it may happen the convergence criterion for scaled residuals is already satisfied during the first iteration. This doesn't necessarily mean the solution is converged. For solution to be declared converged, three conditions must be satisfied:

1) residuals drop below a specified threshold,

2) global balance of mass and heat is achieved: report - fluxes. The imbalance must be < 1% of the smallest flux through a boundary

3) monitors of interest are not changing from iteration to iteration

In your case, either reduce the convergence criterion, say, by an order of magnitude, or simply set the convergence criterion to none and iterate until 2) and 3) are satisfied 

[seeta gunti]

You turn off the residuals and continue the run. Please follow the instruction given by Kourbat.

Regards,

Seeta

[seeta gunti]

Hello,

If you got the solution, please make this thread as resolved.

Thanks,

Seeta

 

[suraj9735]

Thanks for replying me..!

I strange to see the solution converged in 2 iterations (in initialization only). So I curious to know how can I predict that particular model is going to converge in following no. of iteration.

BTW, I compare my model solution of Fluent with " steady state thermal analysis" of ANSYS Mechanical. And I found a similar result. But there is some difference.

Mechanical result

 

Fluent result

 

I use total power 120 W. Heat flux report shows -116.3293 W. still there is missing 4W. My model has only solid and try to solve energy equation. Could you please recommend me what method in Fluent is suitable for this model?

2) I can also solve this model in Mechanical but I try to solve in Fluent because I think it has the more advanced function that will help me in further modelling  to control the temperature of this model.

[Keyur Kanade]

If it has only solids, please go head with mechanical. 

[suraj9735]

I don't know how to work with command in Ansys Mechanical, That is why I am using Fluent because I know something about UDF and trying to write source udf.

[seeta gunti]

Hi Suraj,

Can you check all the positive and -ve values and calculate and compare with Net value.

[suraj9735]

Thanks guys. I use "none" setting for residuals convergence and let it to converge till what I want. And it works!

Thanks again