Defining friction between wall and fluid

maccheese · June 6, 2018, 12:43

Hi guys,

my simulation contains walls which move in an environment which is filled with two different phases.

When I edit the properties of the wall "shear condition", the default setting is always "no slip". However, I would like to define a certain amount of friction between the wall and the surrounding fluids. So how do I do that?

Has the function "specifying shear stress" anything to do with it?

Ansys manuel says the following:

"In addition to the no-slip wall that is the default for viscous flows, you can model a slip wall by specifying zero or non-zero shear. For non-zero shear, the shear to be specified is the shear at the wall by the fluid."

So what I do with this function, is basically defining a certain value of shear stress which is present between the wall and the surrounding fluid?

I am a little bit confused at this point..

Thanks in advance for any insights on this!

LuckyTran · June 6, 2018, 15:33

Yes you specify the shear. What is the confusion? The benefit of having things written down in text is that you can always go back to reread it.

maccheese · June 7, 2018, 15:48

Hi LuckyTran,

my simulation has two different phases in it. So wouldn´t I have to define two different shear stresses for the phases in order to define the frictional interaction between fluid 1 and fluid 2 and my wall?

Or is the kind of the fluid which is surrounding the wall completely irrelevant, as the chosen shear stress would be used for any wall/fluid interaction, no matter which fluid is in contact with the wall?

June 6, 2018, 12:43	Defining friction between wall and fluid	#1
maccheese New Member Join Date: Mar 2018 Posts: 24 Rep Power: 9	Hi guys, my simulation contains walls which move in an environment which is filled with two different phases. When I edit the properties of the wall "shear condition", the default setting is always "no slip". However, I would like to define a certain amount of friction between the wall and the surrounding fluids. So how do I do that? Has the function "specifying shear stress" anything to do with it? Ansys manuel says the following: "In addition to the no-slip wall that is the default for viscous flows, you can model a slip wall by specifying zero or non-zero shear. For non-zero shear, the shear to be specified is the shear at the wall by the fluid." So what I do with this function, is basically defining a certain value of shear stress which is present between the wall and the surrounding fluid? I am a little bit confused at this point.. Thanks in advance for any insights on this!

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June 6, 2018, 15:33		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,845 Rep Power: 68	Yes you specify the shear. What is the confusion? The benefit of having things written down in text is that you can always go back to reread it.

June 7, 2018, 15:48		#3
maccheese New Member Join Date: Mar 2018 Posts: 24 Rep Power: 9	Hi LuckyTran, my simulation has two different phases in it. So wouldn´t I have to define two different shear stresses for the phases in order to define the frictional interaction between fluid 1 and fluid 2 and my wall? Or is the kind of the fluid which is surrounding the wall completely irrelevant, as the chosen shear stress would be used for any wall/fluid interaction, no matter which fluid is in contact with the wall?