Sedimentation Tank Baffle

Bmolaie · March 3, 2014, 02:25

I'm trying to model a rectangular sedimentation tank, but baffles seems to have no effect on the model, I tried to use the baffle option and also I tried to define it as a solid object... should I consider any specific considerations?!

JBurnham · March 12, 2014, 22:08

The mosikely reason the baffles aren't affecting the flow is that they may not be defined correctly. Baffles must be defined with one (1) "definition" (X-plane coordinate, for example), and then limiters can be added to cut the baffle down to the correct size (y-min, y-max, z-min, z-max, for example, if the definition is an x-coordinate). If you rotate the baffle, it is rotated around the origin, so rotated baffles are easiest to define about the origin and then translate them to their final location. Preprocess the simulation before you run it: view the output to check if the baffles are correctly defined and placed.

Bmolaie · March 16, 2014, 07:28

thanks

I also have some confusion about the inflow and outflow... I did a laminar model but the inlet and outlet volume rate are not the same... is there any option in the software that I could determine that?! (I need height of the water to stay constant but I could only assign the height in initial conditions

)

JBurnham · March 19, 2014, 22:26

If you don't want to predict the shape of the free surface, then set "no sharp interface" option. All cells will be filled with fluid. Put the z-max boundary condition at the fluid "surface" and set it to Symmetry type, or put a solid component over the free surface and set the friction coefficient = 0 for free-slip.

If inflow still does not equal outflow, check that you are not losing fluid through cracks in your geometry, that the mesh cells are as close to cubes as possible, that the boundary conditions are correct, and that the simulation runs long enough to reach steady state.

Good luck.

March 3, 2014, 02:25	Sedimentation Tank Baffle	#1
Bmolaie New Member Baharan Molaie Join Date: Feb 2014 Posts: 6 Rep Power: 12	I'm trying to model a rectangular sedimentation tank, but baffles seems to have no effect on the model, I tried to use the baffle option and also I tried to define it as a solid object... should I consider any specific considerations?!

March 16, 2014, 07:28		#3
Bmolaie New Member Baharan Molaie Join Date: Feb 2014 Posts: 6 Rep Power: 12	thanks I also have some confusion about the inflow and outflow... I did a laminar model but the inlet and outlet volume rate are not the same... is there any option in the software that I could determine that?! (I need height of the water to stay constant but I could only assign the height in initial conditions)

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March 12, 2014, 22:08		#2
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	The mosikely reason the baffles aren't affecting the flow is that they may not be defined correctly. Baffles must be defined with one (1) "definition" (X-plane coordinate, for example), and then limiters can be added to cut the baffle down to the correct size (y-min, y-max, z-min, z-max, for example, if the definition is an x-coordinate). If you rotate the baffle, it is rotated around the origin, so rotated baffles are easiest to define about the origin and then translate them to their final location. Preprocess the simulation before you run it: view the output to check if the baffles are correctly defined and placed.

March 19, 2014, 22:26		#4
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	If you don't want to predict the shape of the free surface, then set "no sharp interface" option. All cells will be filled with fluid. Put the z-max boundary condition at the fluid "surface" and set it to Symmetry type, or put a solid component over the free surface and set the friction coefficient = 0 for free-slip. If inflow still does not equal outflow, check that you are not losing fluid through cracks in your geometry, that the mesh cells are as close to cubes as possible, that the boundary conditions are correct, and that the simulation runs long enough to reach steady state. Good luck.