Error convective flux exceeded stability limit??

sajad.mojatahedi · April 22, 2024, 11:22

Hello, dear experts
I am simulating scouring around the spur dike , unfortunately , I get an error with the convective flux exceeded stability limit. To solve this problem, I had to reduce the (initial time step) value from the (numerics) menu to (0.00001), of course, this increased the simulation time. Do you think it will cause problems in the validation process? And will the accuracy of the simulation results be a problem?

MSM1985 · April 24, 2024, 02:03

Hi. If the said error has caused stoppage of your simulation run, then it needs to be addressed. Usually as first step, it is the initial conditions which you need to be set carefully to address this error. Otherwise the solution you gave above also works but shall slower the simulation.

sajad.mojatahedi · April 24, 2024, 15:53

What do you mean by initial conditions? Is the section (t=0) in the software?

MSM1985 · April 25, 2024, 01:27

The logical initial condition will be that one which nearly describes the actual physical condition. That either might be a gradual raising fluid level or an initial guess of constant water level, however this will be best judged by the modeler for the problem he is solving.

koful · May 29, 2024, 05:27

You can consider to limit the maximum time step size also. Did you check your mesh size? If aI rememember correct, It should be 10 times bigger that the sediment grain diameter. Documentation can give more information.
Also, for the initial conditions, If your bed is not dry at the beginning of the simulation, you should enter your inlet velocity to the initial velocity section and you should give fluid elevation.

April 22, 2024, 11:22	Error convective flux exceeded stability limit??	#1
sajad.mojatahedi New Member sajad mojtahedi Join Date: Dec 2023 Posts: 21 Rep Power: 3	Hello, dear experts I am simulating scouring around the spur dike , unfortunately , I get an error with the convective flux exceeded stability limit. To solve this problem, I had to reduce the (initial time step) value from the (numerics) menu to (0.00001), of course, this increased the simulation time. Do you think it will cause problems in the validation process? And will the accuracy of the simulation results be a problem? Ashit Barun likes this.

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April 24, 2024, 02:03		#2
MSM1985 Member Sehroosh Join Date: Apr 2019 Location: Pakistan Posts: 60 Rep Power: 7	Hi. If the said error has caused stoppage of your simulation run, then it needs to be addressed. Usually as first step, it is the initial conditions which you need to be set carefully to address this error. Otherwise the solution you gave above also works but shall slower the simulation.

April 25, 2024, 01:27		#4
MSM1985 Member Sehroosh Join Date: Apr 2019 Location: Pakistan Posts: 60 Rep Power: 7	The logical initial condition will be that one which nearly describes the actual physical condition. That either might be a gradual raising fluid level or an initial guess of constant water level, however this will be best judged by the modeler for the problem he is solving.

May 29, 2024, 05:27		#5
koful Member Join Date: Jun 2014 Location: Turkey Posts: 58 Rep Power: 12	You can consider to limit the maximum time step size also. Did you check your mesh size? If aI rememember correct, It should be 10 times bigger that the sediment grain diameter. Documentation can give more information. Also, for the initial conditions, If your bed is not dry at the beginning of the simulation, you should enter your inlet velocity to the initial velocity section and you should give fluid elevation.