# residual

 Register Blogs Members List Search Today's Posts Mark Forums Read

 September 1, 2013, 01:02 residual #1 New Member   Join Date: Jul 2013 Posts: 6 Rep Power: 6 Sponsored Links Dear All Have a nice day Please find attached file, Results obtained after 715 iteration. As can be seen, the residual curve for some equation is above 1 (about 100). If the residual graph is higher than 1, what can be concluded? Does the model have a problem?residual.JPG

 September 1, 2013, 12:08 #2 New Member   Deepak Bansal Join Date: Jul 2013 Posts: 9 Rep Power: 6 go to monitor option and go to normalization and instead auto u put as off..after that u check that its less than 1 or not.........if not less than 1 it means problem in ur set up.............

 September 2, 2013, 03:08 #3 Member   Roman Join Date: Mar 2011 Posts: 46 Rep Power: 8 Actually, I don't think that this looks bad at all. It looks like your values converges well, what you should look out for are sudden "spikes" in your residuals that can push your solution in a divergence state. Also, taken from manual: "In general, use normalized residuals to monitor the behavior of the solvers at each iteration to make sure that the solution is converging toward the machine precision. If the simulation is steady state, the convergence is displayed over the total number of iterations. If the solution is time-dependent, make sure that convergence occurs within each time-step."

 September 2, 2013, 06:20 #4 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,510 Rep Power: 25 If this is a transient simulation, decrease the time step size and increase the number of iterations per time step. akhshik likes this.

 September 7, 2013, 10:40 #5 New Member   Join Date: Jul 2013 Posts: 6 Rep Power: 6 Dear all, thank you for your help

 January 29, 2014, 09:46 Problem with residuals -- Sudden jump #6 New Member   Aditya Join Date: May 2013 Location: Munich Germany Posts: 29 Rep Power: 6 Hello all I have been experiencing similar problem. The thing is .. I have sudden jumps in the residual especially for Tdr ... ! Also Tdr residual(normalization off) starts at 100 and decreases to 0.1 in 10 iterations and then every 40-50 iterations it jumps to 100 again and then starts decreasing for next 40-50 iterations and then again jumps to 100 ... this continues ... !! Rest all residuals are smooth and keep reducing ... in the order of 1e-5 or so .. ! only Tdr is oscillating above 1 or so .. ! I cannot figure out what is going on ... if there is mistake in my problem set up ... it would be very helpful if some one can give me some hints what could be wrong . Thank you in advance Aditya

 February 6, 2014, 20:39 #7 Senior Member   Join Date: Nov 2010 Location: USA Posts: 898 Rep Power: 13 Typically this occurs with an incorrect near-wall spacing or with incorrect inlet/initial turbulence values.

 March 11, 2014, 13:15 #8 New Member   Join Date: May 2012 Posts: 2 Rep Power: 0 you can try to reduce the Under relaxation factor (URF) of turbulence solver to 0.5 or 0.4.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Artex85 OpenFOAM Running, Solving & CFD 11 February 16, 2017 14:40 mbay101 OpenFOAM Running, Solving & CFD 13 December 28, 2013 14:12 hfs OpenFOAM Running, Solving & CFD 3 October 29, 2013 09:35 sivakumar OpenFOAM Running, Solving & CFD 7 March 17, 2013 07:37 jonmec OpenFOAM Running, Solving & CFD 3 July 28, 2011 05:24