Changes in large and small time-step

Natali_Beginner · May 7, 2013, 16:06

Hello Everyone,
I have a fundamental question.
Is that true that we should expect a change inside the flow happens earlier with a larger time-step size?
I am simulating a transient problem. However, I am using 2 different time-step sizes, 0.00001 s and 0.01 s. But, the changes in the the flow characteristics are exactly the same.
Why that happens?
Thanks,
Natali

Jim87 · May 7, 2013, 16:45

I don't know if it's a generell procedure, but sometimes smaller time steps are helpfull to start the simulation. In some cases it is necessary two get down with ones time steps in order to start the simulation and don't get trouble with the residuals.

Natali_Beginner · May 7, 2013, 16:50

Quote:

Originally Posted by Jim87

I don't know if it's a generell procedure, but sometimes smaller time steps are helpfull to start the simulation. In some cases it is necessary two get down with ones time steps in order to start the simulation and don't get trouble with the residuals.

Thanks,
You know, I start simulation with a small time-step.
Then I have to change something.
I tested this change by a large and small time-step size.
However, the changes are exactly the same. that is completely odd.

May 7, 2013, 16:06	Changes in large and small time-step	#1
Natali_Beginner New Member Natali Join Date: Apr 2013 Posts: 21 Rep Power: 13	Hello Everyone, I have a fundamental question. Is that true that we should expect a change inside the flow happens earlier with a larger time-step size? I am simulating a transient problem. However, I am using 2 different time-step sizes, 0.00001 s and 0.01 s. But, the changes in the the flow characteristics are exactly the same. Why that happens? Thanks, Natali

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May 7, 2013, 16:45		#2
Jim87 Member Stephan Langenberg Join Date: Sep 2011 Location: Germany Posts: 73 Rep Power: 14	I don't know if it's a generell procedure, but sometimes smaller time steps are helpfull to start the simulation. In some cases it is necessary two get down with ones time steps in order to start the simulation and don't get trouble with the residuals.