# continuity residual problem

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July 1, 2013, 05:35
continuity residual problem
#1
Senior Member

Saeed
Join Date: Jan 2013
Posts: 177
Rep Power: 4
HI.

I am modeling channel with two inlet (water+air) with velocity inlet for inlets and pressure outlet for outlet boundary.
But in solving, i am trying for 2000 iteration and more but continuity residual does not cross down of continuity criteria ( 0.001) and solving is keeping and not stop.
Can you help me?
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Last edited by flow_CH; July 19, 2013 at 02:41.

 July 19, 2013, 02:41 #2 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 4 please help

 July 19, 2013, 06:24 #3 New Member   ishan verma Join Date: May 2012 Posts: 1 Rep Power: 0 are you using any urf for density? Just set it to 1

 July 19, 2013, 06:28 #4 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 4 No. I am not using urf.The density for air and water is constant.

 July 22, 2013, 06:04 #5 Senior Member   Paritosh Vasava Join Date: Oct 2012 Location: Lappeenranta, Finland Posts: 545 Rep Power: 12 You can try refining your mesh. Also increase the order of discretization.

 July 22, 2013, 12:08 #6 Member   Join Date: Nov 2011 Posts: 81 Rep Power: 5 It may be that there's absolutely nothing wrong with your simulation. The values of the residuals is scaled with the residuals at the start of the calculation. If your initial guess was particularly good then residuals won't drop so much but still you will have a physically valid result. If residuals are stable for a long number of iterations and other physical parameters of interest in your simulation (in your case maybe the pressure drop across the pipe could be one) are stable too and the results do not show anything clearly wrong then I guess you can consider your simulation correct.

 July 23, 2013, 02:46 #7 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,098 Rep Power: 19 To gain insight if robbofleas statment applies to your case, you can switch your simulation to double precision. Then the residuals should drop further.

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