[itsme_kit]

Hi

In Fluent, can anyone explain the effects of following combinations?

a) stationary wall+nonzero shear stress
b) stationary wall+zero shear stress
c) moving wall +nonzero shear stress
d) moving wall + zero shear stress

Thanks in advance

[pakk]

Maybe you should explain what confuses you, otherwise you will probably not get an answer you can use...

[itsme_kit]

Originally Posted by pakk

Maybe you should explain what confuses you, otherwise you will probably not get an answer you can use...

Hi PAKK

Hi

As far as I know, free slip condition is based on zero shear stress and stationary wall. So the velocity at wall is subjected to the velocity of cell next to the wall

How about in case of moving wall and zero shear stress? I guess the velocity of moving wall will determine the velocity of cell next to the wall

Is it right?

[macfly]

Hi Ke,

Have you read the User's Guide 15.0 Section 6.3.14.Wall Boundary Conditions? It will answer your questions.

[itsme_kit]

Originally Posted by macfly

Hi Ke,

Have you read the User's Guide 15.0 Section 6.3.14.Wall Boundary Conditions? It will answer your questions.

Hi Francois

This is the information copied from user guide

The no-slip condition is the default, and it indicates that the fluid sticks to the wall and moves with the
same velocity as the wall, if it is moving. The specified shear and Marangoni stress boundary conditions
are useful in modeling situations in which the shear stress (rather than the motion of the fluid) is known.
Examples of such situations are applied shear stress, slip wall (zero shear stress), and free surface conditions
(zero shear stress or shear stress dependent on surface tension gradient).

I can understand moving wall or stationary wall with no slip condition

However, in the rest of information about specified shear stress, the motion of wall is not clearly explained

[macfly]

Imho, I think there is nothing to be 'explained'. If you have a non-slip moving wall, just click 'Moving Wall' and define its speed. If you have a slip non-moving or moving wall, specify shear with 0 values. If you have a moving wall with some specified shear, you have to know what values to enter for specified shear (if you don't know, time to go read some papers), Fluent can't predict boundary conditions for you.

[itsme_kit]

Originally Posted by macfly

Imho, I think there is nothing to be 'explained'. If you have a non-slip moving wall, just click 'Moving Wall' and define its speed. If you have a slip non-moving or moving wall, specify shear with 0 values. If you have a moving wall with some specified shear, you have to know what values to enter for specified shear, Fluent can't predict boundary conditions for you.

In case of moving wall with no slip condition, the velocity of moving wall is the same as the velocity of the cell next to the wall

How about the case of moving wall with zero shear stress, has it the same effect as moving wall with no slip condition?

Also, I'm not sure what gonna happen if moving wall plus a specified shear stress

In case of stationary wall with zero shear stress, is the velocity of fluid uniform along the wall?

In case of stationary wall with specified shear stress, is the fluid profile gonna be parabolic like stationary wall with no slip condition?

Sorry for my lots of words, I just want to clarify them

[macfly]

The best way to answer all your questions is to build a simple 2D flow model, try every options and analyze the results. I would go with a fine mesh that can capture the boundary layer (10-20 cells).