Running unsteady simulation from start

Shamoon Jamshed · December 6, 2025, 12:50

Hello experts

I wanted to know that I want to do unsteady simulation. I am not sure that do I have to start the simulation from scratch and run directly unsteady simulation or I should run a steady simulation then switch to unsteady after (say) 200 iterations? Please guide in this regard.

Regards

SJ

MKuhn · December 9, 2025, 10:07

That depends on your physics. What are the conditions at the beginning of your simulation (in reality)? Normally it is better to have full established flow field with a steady state solution. Than switch to transient and change the boundary conditions.

Shamoon Jamshed · December 9, 2025, 10:42

yes, you are right. Actually its a simulation of a bullet case. Exp data is available but I want to run transient to compute damping and dynamics lift and drag coefficients.

December 6, 2025, 12:50	Running unsteady simulation from start	#1
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Islamabad Posts: 415 Rep Power: 20	Hello experts I wanted to know that I want to do unsteady simulation. I am not sure that do I have to start the simulation from scratch and run directly unsteady simulation or I should run a steady simulation then switch to unsteady after (say) 200 iterations? Please guide in this regard. Regards SJ

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December 9, 2025, 10:07		#2
MKuhn Senior Member Moritz Kuhn Join Date: Apr 2010 Location: Germany, Dresden Posts: 246 Rep Power: 18	That depends on your physics. What are the conditions at the beginning of your simulation (in reality)? Normally it is better to have full established flow field with a steady state solution. Than switch to transient and change the boundary conditions.

December 9, 2025, 10:42		#3
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Islamabad Posts: 415 Rep Power: 20	yes, you are right. Actually its a simulation of a bullet case. Exp data is available but I want to run transient to compute damping and dynamics lift and drag coefficients.