Kelvin Helmholtz Instability problem

May 30, 2008, 12:29

Hi, I build a KHI model : 4m by 10m rectangular mesh with 50K cells, two layers (the light one above the heavy ) . I use a VOF model and I perturbate the interface between the two layers with a sin function. The problem is that when I run the model, the bottom layer is moving out of the mesh. I use boundary conditions of: velocity inlet (on the left) and pressure outlet (on the right). I normally patch the bottom layer to the phase 2 . I tried to patch the top layer but it didn't help much. How do I keep both of the layers in the mesh?

Thanks

Nadav

adr_adr · July 10, 2009, 11:44

Hi,

I try to simulate the KH instability by two fluids with different properties (density & velocity) in a 2D domain. I have used a patch file to give the initial conditions. I have got some different instabilities playing with the densities & velocities of the fluids.

Though, I have a doubt.

Is gravity necessary to lead the instability? Our code was intended for high speed for aircraft & gravity is not included. As a consequence, I did not obtained yet the "cat's eye" shape of instability.

Thanks for any advice.

Andrea.

May 30, 2008, 12:29	Kelvin Helmholtz Instability problem	#1
nadav wetzler Guest Posts: n/a	Hi, I build a KHI model : 4m by 10m rectangular mesh with 50K cells, two layers (the light one above the heavy ) . I use a VOF model and I perturbate the interface between the two layers with a sin function. The problem is that when I run the model, the bottom layer is moving out of the mesh. I use boundary conditions of: velocity inlet (on the left) and pressure outlet (on the right). I normally patch the bottom layer to the phase 2 . I tried to patch the top layer but it didn't help much. How do I keep both of the layers in the mesh? Thanks Nadav

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July 10, 2009, 11:44		#2
adr_adr New Member Andrea Da Ronch Join Date: Jul 2009 Posts: 1 Rep Power: 0	Hi, I try to simulate the KH instability by two fluids with different properties (density & velocity) in a 2D domain. I have used a patch file to give the initial conditions. I have got some different instabilities playing with the densities & velocities of the fluids. Though, I have a doubt. Is gravity necessary to lead the instability? Our code was intended for high speed for aircraft & gravity is not included. As a consequence, I did not obtained yet the "cat's eye" shape of instability. Thanks for any advice. Andrea.