Ramping Boundary Condition for Steady FSI Simulation

ashtonJ · August 20, 2012, 23:32

Dear all,

I am doing steady FSI modelling in an artery model.

I know how to ramp the pressure boundary condition for transient FSI case; however, I don't know how to ramp the pressure boundary condition for steady FSI.

In transient modelling, because the pressure is dependent on time, so the time can be used as an independent variable to ramp the boundary condition like below

P=12*10*t*step((0.1-t))+12*step((t-0.1))

Although for steady flow there is not any independent variable to be used for ramping.

I would be too pleased if any could help me.

Regards,
AshtonJ

Lance · August 21, 2012, 03:25

Do a transient simulation first and use the results as input for your steady simulation?

ashtonJ · August 21, 2012, 04:13

Thank you. To be honest, I cannot understand what you mean!

Just letting you know that first I need to run steady case then use the steady case results as the initial condition for transient case. I’ve had difficulty in converging the steady case with applied boundary condition, so I am trying to ramp the boundary condition to see if it helps.

Regards,
AshtonJ

Lance · August 21, 2012, 04:18

I see. I thought you wanted to do a steady FSI.

If you are going to ramp up your BCs you need to to a transient analysis to reach a steady-state from where you can continue with your "real" BCs. Then just use the last results from the ramping transient analysis as initial condition.

August 20, 2012, 23:32	Ramping Boundary Condition for Steady FSI Simulation	#1
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 17	Dear all, I am doing steady FSI modelling in an artery model. I know how to ramp the pressure boundary condition for transient FSI case; however, I don't know how to ramp the pressure boundary condition for steady FSI. In transient modelling, because the pressure is dependent on time, so the time can be used as an independent variable to ramp the boundary condition like below P=1210tstep((0.1-t))+12step((t-0.1)) Although for steady flow there is not any independent variable to be used for ramping. I would be too pleased if any could help me. Regards, AshtonJ

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August 21, 2012, 03:25		#2
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	Do a transient simulation first and use the results as input for your steady simulation?

August 21, 2012, 04:13		#3
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 17	Thank you. To be honest, I cannot understand what you mean! Just letting you know that first I need to run steady case then use the steady case results as the initial condition for transient case. I’ve had difficulty in converging the steady case with applied boundary condition, so I am trying to ramp the boundary condition to see if it helps. Regards, AshtonJ

August 21, 2012, 04:18		#4
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	I see. I thought you wanted to do a steady FSI. If you are going to ramp up your BCs you need to to a transient analysis to reach a steady-state from where you can continue with your "real" BCs. Then just use the last results from the ramping transient analysis as initial condition.