Buoyancy initialisation problems

GHylands · May 1, 2009, 18:23

Hello,

I am simulating free surface fluid sloshing in a moving rectangular tank with air and water present. Buoyancy is active with -9.81 set in the Y direction and the standard free surface model is selected. When I view the results of the simulation, the water and fuel do not begin as two distinct layers at the beginning as expected but instead dispersed everywhere in the tank and then slowly settle over the first few timesteps.

Does anyone know how to set-up the run so that water is on the bottom layer and air is on the top layer at the beginning of the run as they would be in their undisturbed state ?

Much appreciated,
Greg

stumpy · May 1, 2009, 22:26

The Volume Fraction field needs to be initialized correctly. The air phase should be initialized to something like
step(y/1[m])
and the water phase to
1 - step(y/1[m])

GHylands · May 2, 2009, 09:58

Thank you very much, the initialisation settings now start the simulation as expected.

May 1, 2009, 18:23	Buoyancy initialisation problems	#1
GHylands New Member Greg Hylands Join Date: May 2009 Posts: 4 Rep Power: 16	Hello, I am simulating free surface fluid sloshing in a moving rectangular tank with air and water present. Buoyancy is active with -9.81 set in the Y direction and the standard free surface model is selected. When I view the results of the simulation, the water and fuel do not begin as two distinct layers at the beginning as expected but instead dispersed everywhere in the tank and then slowly settle over the first few timesteps. Does anyone know how to set-up the run so that water is on the bottom layer and air is on the top layer at the beginning of the run as they would be in their undisturbed state ? Much appreciated, Greg

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May 1, 2009, 22:26		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	The Volume Fraction field needs to be initialized correctly. The air phase should be initialized to something like step(y/1[m]) and the water phase to 1 - step(y/1[m])

May 2, 2009, 09:58		#3
GHylands New Member Greg Hylands Join Date: May 2009 Posts: 4 Rep Power: 16	Thank you very much, the initialisation settings now start the simulation as expected.