How to stop a simulation at a specific time?

Jalouis · July 14, 2023, 09:48

Hi I am new to Autodesk CFD, and I have a few basic questions regarding the procedure. The problem statement is as such:

"An object is heated for about 300 seconds, and is water cooled constantly. After the inital 300 seconds, the heat flux is 0, and the object will be water cooled only for another 300 seconds. Determine the temperatures of the object parts after the first 300 seconds, and after the second 300 seconds."

For this, I am using a piecewise linear time curve to have the heat flux load for the first 300 seconds, and then 0 heat flux for the second 300 seconds. What I am a little confused about is how to set the simulation as such, that the simulation stops exactly at 600 second mark. I understand the need to use Transient settings instead of steady state, but I don't know how to configure the time step size, stop time and inner iterations etc.

Can someone help me with this? I would also like to know if it is necessary to have an external volume; in my simulation the object must be kept in vacuum.

Apologies if a similar question and solution already exists.

LuckyTran · July 14, 2023, 11:21

inner iterations, enough of converge every time-step, usually a number like 10
stop time, 600s, the actual answer to your question
timestep, small enough for accuracy but large enough that you don't lose your mind. The finer the mesh, the smaller this number needs to be for stability reasons. Usually it is a small number like 0.001s unless you have an extremely coarse mesh.

July 14, 2023, 09:48	How to stop a simulation at a specific time?	#1
Jalouis New Member Louis Jamie Join Date: Jul 2023 Posts: 1 Rep Power: 0	Hi I am new to Autodesk CFD, and I have a few basic questions regarding the procedure. The problem statement is as such: "An object is heated for about 300 seconds, and is water cooled constantly. After the inital 300 seconds, the heat flux is 0, and the object will be water cooled only for another 300 seconds. Determine the temperatures of the object parts after the first 300 seconds, and after the second 300 seconds." For this, I am using a piecewise linear time curve to have the heat flux load for the first 300 seconds, and then 0 heat flux for the second 300 seconds. What I am a little confused about is how to set the simulation as such, that the simulation stops exactly at 600 second mark. I understand the need to use Transient settings instead of steady state, but I don't know how to configure the time step size, stop time and inner iterations etc. Can someone help me with this? I would also like to know if it is necessary to have an external volume; in my simulation the object must be kept in vacuum. Apologies if a similar question and solution already exists.

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July 14, 2023, 11:21		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,677 Rep Power: 66	inner iterations, enough of converge every time-step, usually a number like 10 stop time, 600s, the actual answer to your question timestep, small enough for accuracy but large enough that you don't lose your mind. The finer the mesh, the smaller this number needs to be for stability reasons. Usually it is a small number like 0.001s unless you have an extremely coarse mesh.