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-   -   Time step, Number of time step, Maxximum Iterations per time step (http://www.cfd-online.com/Forums/fluent/90658-time-step-number-time-step-maxximum-iterations-per-time-step.html)

sandisk July 18, 2011 02:57

Time step, Number of time step, Maxximum Iterations per time step
 
Hi,
I am performing transient simulation of slurry flow in horizontal pipe, ( am new to CFD). I understand that slurry flow is best simulated in unsteady state. I am using mixture model and my sand conc varies from 0-10 %. However, I am not sure how to specify the time step size and number of time step.. My length of the pipe is 21 ft and I have discretized it into 750 points, so each cell length in z direction is 0.33 inches or 0.027 feet. My velocity of flow is 12 ft/sec. So , should I be giving time step as 0.027/12 = 0.00231 sec or abt 1/3rd of this value. Also, i read that time step size is set in such a way that the simulation converges within 5-7 iterations for each step. So i can leave the max iterations per time step at default values. But I dont know what criterion should be used for Number of time steps. Any help would be appreciated.


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