# convective flux exceeded stability limit!

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 January 10, 2019, 03:43 convective flux exceeded stability limit! #1 New Member   Ebrahim Hamid Join Date: Jan 2019 Posts: 4 Rep Power: 6 Dear Flow3D users; I run simulation with General Moving Objects option, after few seconds I get this message " convective flux exceeded stability limit" then the software start to re-estimate very long time to solve the problem. Suddenly the simulation ends and it dos not reach to the end of the time that I need. Your help is highly appreciated.

 February 19, 2019, 13:03 #2 Senior Member   Adwaith Gupta Join Date: Dec 2015 Location: India, USA Posts: 124 Blog Entries: 1 Rep Power: 9 Try setting up an initial time step (in numerics tab) much smaller than the time step you see in the simulation manager at t=0.

 June 27, 2020, 18:12 #3 New Member   Jose Ramos Join Date: Jun 2020 Posts: 1 Rep Power: 0 Use Solver Text Output to Diagnose Errors 1. Locate the Warnings & Errors button above the runtime plots. It means warnings are present. 2. After the meshblock mismatch errors discussed in There is one warning, which is displayed below. Solver Messages: convective flux exceeded stability limit at t= 3.0009E-02 cycle= 1 iter= 51 delt= 3.0009E-02 mesh block 4 restarting cycle with smaller time step maximum failure ratio = 2.26944E+00 is in x-coordinate direction at cell ( 82, 34, 17) mesh block 4 3. The meaning is as follows: a. At t = 0.03 seconds, a packet of fluid tried to move more than one cell at a time. The packet probably accelerated unexpectedly, which is why the solver didn’t predict the velocity of the packet. The stability limit is the requirement that fluid packets only move one cell per time step. The solver takes care of the problem by restarting the time step with a smaller dt. b. The error occurred in Mesh Block 4, the conforming block. c. The offending cell number is i, j, k = 82, 34, 17. Remember that i,j,k values are block-specific, while x,y,z values are global. d. The problematic fluid packet was moving in the x-direction. In the next step you will find the problem cell and identify why the problem occured. 4. Use the small X in the upper right corner of the dialog to close the Warnings & Errors. 5. Scroll up through the text output displayed below the plots and find the same warning. Notice that the cell location and mesh block are not given in this summary. 6. Select Diagnostics > Solver Errors from the menu at the top of the screen: the same information is displayed. Some errors report additional information to the Solver Errors file, so it should always be checked. http://docshare02.docshare.tips/file.../272471970.pdf Page 7 of 13 M.Nazrin likes this.

 Tags flow 3d, mov