Transient & Steady state velocity profile

TheMightySpartan · September 22, 2018, 15:52

Hello,

Im doing simulation of flow in pipe and my velocity profile (developed) is different for transient at different time steps in transient analysis.

The steady state analysis appears to be inline with the pipe velocity profile development theory however the transient analyiss at the lower time steps is very skinny in the near wall region and of near uniform velocity profile in the core.

The pipe is straight of length 10D and the diameter is 4 inches with water at 2 m/s.

Is this correct?

Thank you.

LuckyTran · September 24, 2018, 16:29

Probably just a matter of settings. Play with your time-step size and number of iterations per time-step to make sure that the solution is well-converged at each time-step before moving on to the next time-step.

Duke711 · September 24, 2018, 20:38

It is not necessarily advisable to solve a steady state case with a transient solver. Depending on the steady state case, it will be takes a long time to equilibrium state. Especially if there are small time steps size and thus many time steps are required.

-> You need more time steps.

September 22, 2018, 15:52	Transient & Steady state velocity profile	#1
TheMightySpartan New Member Join Date: Oct 2017 Posts: 25 Rep Power: 8	Hello, Im doing simulation of flow in pipe and my velocity profile (developed) is different for transient at different time steps in transient analysis. The steady state analysis appears to be inline with the pipe velocity profile development theory however the transient analyiss at the lower time steps is very skinny in the near wall region and of near uniform velocity profile in the core. The pipe is straight of length 10D and the diameter is 4 inches with water at 2 m/s. Is this correct? Thank you. Last edited by TheMightySpartan; September 22, 2018 at 16:00. Reason: Added photo

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September 24, 2018, 16:29		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Probably just a matter of settings. Play with your time-step size and number of iterations per time-step to make sure that the solution is well-converged at each time-step before moving on to the next time-step.

September 24, 2018, 20:38		#3
Duke711 Member Join Date: Dec 2016 Posts: 44 Rep Power: 9	It is not necessarily advisable to solve a steady state case with a transient solver. Depending on the steady state case, it will be takes a long time to equilibrium state. Especially if there are small time steps size and thus many time steps are required. -> You need more time steps.