Pressure drop in a channel using VOF

Agad15 · April 20, 2014, 01:49

I am a new user to FLUENT. I am trying to calculate the pressure drop between parallel plates (3D) using Viscous-laminar model, but the result what I am getting is wrong whereas if I use VOF model calculating pressure drop its showing a right answer. Where am I doing mistake? Please help me.

And also I want to hook slip wall BC to VOF model. Does anyone has udf for slip wall?

Thanks in advance.

shk12345 · April 21, 2014, 10:55

Quote:

Originally Posted by Agad15

I am a new user to FLUENT. I am trying to calculate the pressure drop between parallel plates (3D) using Viscous-laminar model (Are you using the single phase or multiphase model), but the result what I am getting is wrong whereas if I use VOF model calculating pressure drop its showing a right answer. Where am I doing mistake? Please help me.

And also I want to hook slip wall BC to VOF model. Does anyone has udf for slip wall?

Thanks in advance.

If you are using the Eulerian Eulerian Model you may to use various forces inside the model to get your desired results.
For slip wall you may specify the slip velocity at the wall. In wall on the second tab from the right there is a option of choosing no slip or some slip.
You can alppy the constant slip at the wall there.

Hope this help

shk

Agad15 · April 21, 2014, 11:53

Hi,

Thanks for the reply.

I am using Multiphase-VOF model to calculate the pressure drop. Its working fine . I want to impose alternative slip and no slip condition at the bottom wall, for that I need udf. Is udf in VOF is different from other models?

Also if I want to use Viscous-Laminar model to calculate the pressure drop between parallel plates with water as a working fluid, will it work? For me its not working

(I mean the pressure drop what I am getting is wrong).

Shall I provide some more details?

shk12345 · April 21, 2014, 12:11

Quote:

Originally Posted by Agad15

Hi,

Thanks for the reply.

I am using Multiphase-VOF model to calculate the pressure drop. Its working fine . I want to impose alternative slip and no slip condition at the bottom wall, for that I need udf. Is udf in VOF is different from other models?

Also if I want to use Viscous-Laminar model to calculate the pressure drop between parallel plates with water as a working fluid, will it work? For me its not working

(I mean the pressure drop what I am getting is wrong).

Shall I provide some more details?

VOF model works with water and air. You may also have to use air otherwise use single phase models which are less computational extensive.
There is no need to use udf for slip BC if your slip is constant. Just specefy a constant slip at the wall. The udf for multiphase models are different. You may have to add some additional features to make it work.
For laminar model it should work, just try to increase the order of discretization equations to higher order to second or quick to visualise the better results.

Hope that helps
shk

Agad15 · April 25, 2014, 02:10

Thank you. Even laminar model is working fine.

In my model (flow between parallel plates), the bottom plate has some array of rectangular pillars and flat on top plate. I applied wall boundary condition on both the top and bottom plates. Theoretically the pressure drop should be less when compared to "when both the top and bottom walls are flat". Experimentally also verified that pressure drop is less. But on contrary, in simulations pressured drop is coming more and I observed wall shear stresses are very high on pillars which is leading to high pressure drop. I want to know why? Can u help me?

April 20, 2014, 01:49	Pressure drop in a channel using VOF	#1
Agad15 New Member Anvesh Join Date: Jan 2014 Posts: 25 Rep Power: 12	I am a new user to FLUENT. I am trying to calculate the pressure drop between parallel plates (3D) using Viscous-laminar model, but the result what I am getting is wrong whereas if I use VOF model calculating pressure drop its showing a right answer. Where am I doing mistake? Please help me. And also I want to hook slip wall BC to VOF model. Does anyone has udf for slip wall? Thanks in advance.

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April 21, 2014, 11:53		#3
Agad15 New Member Anvesh Join Date: Jan 2014 Posts: 25 Rep Power: 12	Hi, Thanks for the reply. I am using Multiphase-VOF model to calculate the pressure drop. Its working fine . I want to impose alternative slip and no slip condition at the bottom wall, for that I need udf. Is udf in VOF is different from other models? Also if I want to use Viscous-Laminar model to calculate the pressure drop between parallel plates with water as a working fluid, will it work? For me its not working (I mean the pressure drop what I am getting is wrong). Shall I provide some more details?

April 25, 2014, 02:10		#5
Agad15 New Member Anvesh Join Date: Jan 2014 Posts: 25 Rep Power: 12	Thank you. Even laminar model is working fine. In my model (flow between parallel plates), the bottom plate has some array of rectangular pillars and flat on top plate. I applied wall boundary condition on both the top and bottom plates. Theoretically the pressure drop should be less when compared to "when both the top and bottom walls are flat". Experimentally also verified that pressure drop is less. But on contrary, in simulations pressured drop is coming more and I observed wall shear stresses are very high on pillars which is leading to high pressure drop. I want to know why? Can u help me?