I am investigating into the flow in microchannels with bends. I have already applied no slip boundary conditions and now moving to Slip boundary conditions.
From what I understand in Ansys you need to enter Shear stresses. But how do you go about calculating the shear stresses? Which equations are used?
ps. I am a newbie to Fluent so would appreciated your help.
Thanks in advance.
Slip wall (zero shear stress). Simply in the wall panel do the following:
1- Click on specified shear.
2- Make sure the value of x, y and z components of shear stress are zeros.
The shear stress Fluent asks you to enter is the tengential component of the constraint tensor in the fluid at the wall. So if you set an imposed shear stress BC at your wall and impose a null stress you should get a sliping wall (that is, the action from the wall on your flow will only be directed along the normal to the wall).
If you want to impose another (non zero) value of shear stress at the wall...Well, that's unusual, I've never met such a situation where you know your stress in advance so I can''t help.
As well as you know the slip condition is defined as wall boundary condition. So at first you should choose wall boundary condition then at left bottom of page you can change default setting " no-slip" to other options.
I use CFX in my investigations but as far I understood you need to apply the Shear Stress Transport that is a turbulence model. The Wall Shear Stres is obtained in the results - this is a tangent stress generated on the wall of the channel. It's very important parameter in blood flow simulations.
Slip wall (zero shear stress). Simply in the wall panel do the following:
1- Click on specified shear.
2- Make sure the value of x, y and z components of shear stress are zeros.
You must go to the documentation of fluent and search for the WSS equation that is implemented into the program.
The slip condition has a main relation as follow
u=B du/dn
n is the normal vector.You can introduce the slip condition with using UDF or inserting a number for shear stress.
I tried to calculate the shear stress (non zero value) but some of the equations needed to calculate it arent really clear on ansys document. So I have decided to do the UDF for the slip condition. Thank you very much for your replies guys! Appreciate it!
Can anybody help me on the udf of the wall slip boundary condition writting? I will really appreciate it.
hi Aroshi Vaz
I have the same problem
how do you write the UDF for this problem?
please help...
thanks
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