the initial condition for transient simulation

junc · August 21, 2012, 23:33

hi, everyone.
i am modeling a ducted fan in cfx. And i'd like to run a transient analysis using the steady state simulation as an initial guess. however, it's very hard to reach convergence in the steady state simulation, and the RMS Residual Level of velocity is about 2.2*10^-4.
Can i use this steady condition as the initial guess for the transient simulation?
thanks, any help would be appreciated!

pavitran · August 21, 2012, 23:57

Check for the mass and momentum imbalances, if they are ok then you can use the result as initial conditon for transient simulation. You can have an additional check by monitoring some integral quantity like torque.

If the problem which your simulating is inherently transient in nature, then the residuals would be oscillating and achieving convergence criteria would be difficult.

All the best

junc · August 22, 2012, 07:13

thank you for your reply, i will check that.

August 21, 2012, 23:33	the initial condition for transient simulation	#1
junc New Member su yunde Join Date: Aug 2012 Location: China Posts: 16 Rep Power: 14	hi, everyone. i am modeling a ducted fan in cfx. And i'd like to run a transient analysis using the steady state simulation as an initial guess. however, it's very hard to reach convergence in the steady state simulation, and the RMS Residual Level of velocity is about 2.2*10^-4. Can i use this steady condition as the initial guess for the transient simulation? thanks, any help would be appreciated!

August 21, 2012, 23:57	Hi	#2
pavitran Member Dynampally Pavitran Join Date: Mar 2010 Location: India Posts: 74 Rep Power: 16	Check for the mass and momentum imbalances, if they are ok then you can use the result as initial conditon for transient simulation. You can have an additional check by monitoring some integral quantity like torque. If the problem which your simulating is inherently transient in nature, then the residuals would be oscillating and achieving convergence criteria would be difficult. All the best junc likes this.

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August 22, 2012, 07:13		#3
junc New Member su yunde Join Date: Aug 2012 Location: China Posts: 16 Rep Power: 14	thank you for your reply, i will check that.