# Confuse on initial condition and velocity profile v(0)=0

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 September 17, 2015, 08:38 Confuse on initial condition and velocity profile v(0)=0 #1 Member     kiwi Join Date: Mar 2012 Location: South East Asia Posts: 53 Rep Power: 5 Dear all, I am confused on the role of initial condition in the transient laminar flow practice and hope someone can explain to me. e.g. if I have definite my initial velocity as the maximum flow rate of my entire velocity profile, such as v= 0.5m/s which I have the respective pressure magnitude which I achieved through the steady solution. when I input my velocity profile as inlet profile of a tube, I start with v(0)=0, may I know which one fluent solver will use as its starting point for the iterations for better convergence? I am quite worried about initial condition. as it looks to me that if it start with v(0)=0.5m/s, then what if my v(0.01)=0.1m/s, shouldn't it a big problem for solver to converge from 0.5 to 0.1m/s? hope someone can explain it to me. thank you.

 September 18, 2015, 11:21 #2 Senior Member   Lucky Tran Join Date: Apr 2011 Location: Orlando, FL USA Posts: 762 Rep Power: 13 The initial conditions apply only to the interior cells. The boundary conditions are also imposed on the boundaries. So for interior cells the initial velocities would be the initial conditions. For boundary faces, the initial velocities would be taken from your boundary conditions. fruitkiwi likes this.

September 19, 2015, 00:26
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kiwi
Join Date: Mar 2012
Location: South East Asia
Posts: 53
Rep Power: 5
Quote:
 Originally Posted by LuckyTran The initial conditions apply only to the interior cells. The boundary conditions are also imposed on the boundaries. So for interior cells the initial velocities would be the initial conditions. For boundary faces, the initial velocities would be taken from your boundary conditions.
Thanks for your help. it make things clear for me.

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