Parameters in create boundary layers in HW CFD 2022?

James Lewis

Hi experts,

 

I'm creating boundary layer in HW CFD.

And I don't know all the parameter in Create Boundary Layer dialog below.

 

I tried to find information in Help.

But it's not detailed enough for me to understand.

Anyone please can help me know where could I find some more information about this.

 

Many thanks!

 

acupro

First there are different ways to define the first layer height - the height of the first layer in the boundary layer column, or the distance from the wall to the first node.  I find Constant and Fraction of Surface Mesh Size most useful.

Then there are different ways to define the growth ratio - how the thickness of the layers expand as layers are added - and the number of layers to create using the boundary layer meshing.  Match outer layer attempts of have the last layer in the boundary layer column be the same size as the interior tet element.

James Lewis

Very clear and helpful.

Thank you!

 

James Lewis

acupro_21778 said:

First there are different ways to define the first layer height - the height of the first layer in the boundary layer column, or the distance from the wall to the first node.  I find Constant and Fraction of Surface Mesh Size most useful.

Then there are different ways to define the growth ratio - how the thickness of the layers expand as layers are added - and the number of layers to create using the boundary layer meshing.  Match outer layer attempts of have the last layer in the boundary layer column be the same size as the interior tet element.

I have question about the value 0.8 of final layer height/base ratio, how it is estimated.

And what is the differences between termination policy truncate and squeeze?

Thank you!

acupro

James Lewis said:

I have question about the value 0.8 of final layer height/base ratio, how it is estimated.

And what is the differences between termination policy truncate and squeeze?

Thank you!

That height/base ratio is based off the surface triangle size (the base) and the thickness of that particular layer (the height), to avoid tall-skinny elements.  Once that is reached, the layers are either truncated (no additional layers are grown) or they are squeezed (additional layers are grown, but the height is not increased).

James Lewis

 

James Lewis

 

James Lewis

I find documents about this issue, hope it'll be helpfull!

James Lewis

acupro_21778 said:

That height/base ratio is based off the surface triangle size (the base) and the thickness of that particular layer (the height), to avoid tall-skinny elements.  Once that is reached, the layers are either truncated (no additional layers are grown) or they are squeezed (additional layers are grown, but the height is not increased).

Thanks you, I got it!