Time step in Transient simulation

sandisk · February 2, 2011, 17:31

how should we calculate time step in case of transient simulations ? I am simulating slurry flow (water and sand) in pipes ? Has anyone done simulation of slurry flow ? Had some queries ? Thnx.

ComputerGuy · February 2, 2011, 21:56

In transient simulations, the time step is set, not calculated. A rule of thumb is that if your transient simulations are converging in 5-7 time steps (after the initial few, which may take slightly more), your time step is small enough.

Two phase (solid-liquid, solid-vapor) transport of granular solids can definitely be modeled in Fluent. The appropriate drag law is important, as is the characterization of the type (mono-disperse, poly-disperse) of particles you're flowing.

ComputerGuy

sandisk · February 3, 2011, 00:55

Thanks for the reply. I am trying to simulate water sand slurry using Eulerian and Mixture model. Do we have to patch the initial sand fraction before iterating ? I am trying both the models.

February 2, 2011, 17:31	Time step in Transient simulation	#1
sandisk New Member sunny Join Date: Jan 2011 Posts: 29 Rep Power: 15	how should we calculate time step in case of transient simulations ? I am simulating slurry flow (water and sand) in pipes ? Has anyone done simulation of slurry flow ? Had some queries ? Thnx.

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February 2, 2011, 21:56		#2
ComputerGuy Senior Member Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 16	In transient simulations, the time step is set, not calculated. A rule of thumb is that if your transient simulations are converging in 5-7 time steps (after the initial few, which may take slightly more), your time step is small enough. Two phase (solid-liquid, solid-vapor) transport of granular solids can definitely be modeled in Fluent. The appropriate drag law is important, as is the characterization of the type (mono-disperse, poly-disperse) of particles you're flowing. ComputerGuy

February 3, 2011, 00:55		#3
sandisk New Member sunny Join Date: Jan 2011 Posts: 29 Rep Power: 15	Thanks for the reply. I am trying to simulate water sand slurry using Eulerian and Mixture model. Do we have to patch the initial sand fraction before iterating ? I am trying both the models.