sprayFoam flow and mixture formation

azborals · February 14, 2013, 05:57

Hallo everyone,

I tried to calculate a case with inlet flow in a cyinder and injection (constant mesh, no piston moving). Therefore I used sprayFoam. I forced a velocity at the outlet and the inlet is zero gradient. At first the result looked really good, but later the iteration became very small because the velocity in one cell at the inlet surface rose to 800 m/s. I tried to run diffrent cases --> but always the same. I thought it could be a mesh problem, so I did checkMesh --> Mesh OK

can anybody help me!

vainilreb · February 14, 2013, 06:45

Hey,

how does the temperature in your domain behave before the time step decrease occurs? I've encountered severe problems with temperature divergence, pressure divergence, very high velocities and thus very small time steps followed by a crash of the simulation - I fixed this by deactivating time step adjustment and setting a fixed timestep.

Best regards,

Robert

azborals · February 14, 2013, 09:25

>>Hey,

how does the temperature in your domain behave before the time step decrease occurs? I've encountered severe problems with temperature divergence, pressure divergence, very high velocities and thus very small time steps followed by a crash of the simulation - I fixed this by deactivating time step adjustment and setting a fixed timestep.

Best regards,

Robert
<<

Hey,

the temperature was okay. Now, I fixed the time step adjustment too --> the temperature increased to 1.4e41. If I run a case with a simple box, one surface is inlet and an other is outlet --> it works. But in the special case I use a complex geometry (cyclinder and intake manifold of a combustion engine --> stl). Do you have an idea?

Best regards,

André

niklas · February 14, 2013, 10:00

zero gradient velocity inlet condition!!!

you will never get that working.

try instead to specify the velocity at the inlet

February 14, 2013, 05:57	sprayFoam flow and mixture formation	#1
azborals New Member André Zboralski Join Date: Jan 2013 Posts: 11 Rep Power: 13	Hallo everyone, I tried to calculate a case with inlet flow in a cyinder and injection (constant mesh, no piston moving). Therefore I used sprayFoam. I forced a velocity at the outlet and the inlet is zero gradient. At first the result looked really good, but later the iteration became very small because the velocity in one cell at the inlet surface rose to 800 m/s. I tried to run diffrent cases --> but always the same. I thought it could be a mesh problem, so I did checkMesh --> Mesh OK can anybody help me!

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February 14, 2013, 06:45		#2
vainilreb Member Robert Join Date: Aug 2012 Location: Berlin Posts: 74 Rep Power: 13	Hey, how does the temperature in your domain behave before the time step decrease occurs? I've encountered severe problems with temperature divergence, pressure divergence, very high velocities and thus very small time steps followed by a crash of the simulation - I fixed this by deactivating time step adjustment and setting a fixed timestep. Best regards, Robert

February 14, 2013, 09:25		#3
azborals New Member André Zboralski Join Date: Jan 2013 Posts: 11 Rep Power: 13	>>Hey, how does the temperature in your domain behave before the time step decrease occurs? I've encountered severe problems with temperature divergence, pressure divergence, very high velocities and thus very small time steps followed by a crash of the simulation - I fixed this by deactivating time step adjustment and setting a fixed timestep. Best regards, Robert << Hey, the temperature was okay. Now, I fixed the time step adjustment too --> the temperature increased to 1.4e41. If I run a case with a simple box, one surface is inlet and an other is outlet --> it works. But in the special case I use a complex geometry (cyclinder and intake manifold of a combustion engine --> stl). Do you have an idea? Best regards, André

February 14, 2013, 10:00		#4
niklas Super Moderator Niklas Nordin Join Date: Mar 2009 Location: Stockholm, Sweden Posts: 693 Rep Power: 29	zero gradient velocity inlet condition!!! you will never get that working. try instead to specify the velocity at the inlet