# reversed flow and divergence

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 April 7, 2009, 15:24 reversed flow and divergence #1 New Member   Howard Join Date: Mar 2009 Posts: 5 Rep Power: 9 Hi, I have following message: reversed flow in 80 faces on pressure-outlet 4. Error: divergence detected in AMG solver: x-momentum Error Object: () Can I get help, how can I solve it? Thanks HW

 April 8, 2009, 05:05 #2 New Member   Tenar Join Date: Apr 2009 Posts: 3 Rep Power: 9 Hi Howard, first of all i recommend you to increase your maximum limits as much as possible(solve>controls>limits) (i think your face number-which reversed flow problem occurs- is controllable.) Moreover you can start fmg initilization by solve>initialize>fmg initilization. FMG initilization provides better convergence. If problem continues i recommend you to check your grid if your skewness is high. But i hope you dont need it Ciaooo Tenar alimoh1987 likes this.

 April 8, 2009, 11:12 #3 New Member   Howard Join Date: Mar 2009 Posts: 5 Rep Power: 9 Hi, Tenar, maximum limits of 1e+20 is allowable. I cannot find menu FMG initilization in solve>initialize>fmg initilization. Can you tell me how to get this menu? My skewness is high, how can I fix it? Thanks HW PS here is my grid check ------------------- Grid Check Domain Extents: x-coordinate: min (m) = 9.288283e-015, max (m) = 3.139997e+000 y-coordinate: min (m) = 8.000000e+000, max (m) = 1.000000e+001 z-coordinate: min (m) = -1.570000e+000, max (m) = 1.570000e+000 Volume statistics: minimum volume (m3): 6.394585e-008 maximum volume (m3): 1.183709e-002 total volume (m3): 9.413165e+000 Face area statistics: minimum face area (m2): 1.300699e-004 maximum face area (m2): 1.211852e-001 ............... ---------------------

 April 9, 2009, 01:31 #5 New Member   Howard Join Date: Mar 2009 Posts: 5 Rep Power: 9 Hi, Tenar, My case is for mixture (two phase), unsteady, So computer show me: --------------------------- /solve/initialize> fmg-initialization FMG initialization is not available with the unsteady solver. ------------------------------- If you like, please send your email address to me: mechflo@gmail.com so I can send email to you. Thanks HW

 April 25, 2009, 23:46 #6 New Member   irineupetri Join Date: Mar 2009 Posts: 7 Rep Power: 9 The message "reversed flow" can to cause a problem on the convergence, for take off this message, you should put in the comand line [solve/set/flow-warnings?/no] + enter or [solve] + enter [set] + enter [flow-warnings?] + enter [no] + enter

 August 10, 2010, 00:24 #7 Senior Member   Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 9 Hello I have following querries regarding FMG initialization. I will be grateful for your kind look at these: 1. When I run Fmg initialization without starting any iterations then it gives me the following error: /solve/initialize> fmg-initialization invalid command [fmg-initialization] Please specify. Why it is so. As its prime function is to give the initial solution so isn't it should be specified before iterations? 2. When FMG initialization is complete I get the following message: FMG: Initialize flow for Segregated solution.. . end It means that FMG initialization has been done and after this I dont need to change the initial values from solve...> initialize. And I only have to iterate now? 3. I am using multiphase flow DPM. But first i think i should run FMG initialization without DPM and then introduce DPM later(making it single phase in order to for FMG initialization to run). Is it possible. Please help me. I will be grateful Mohsin

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