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Parameters in create boundary layers in HW CFD 2022?

User: "James Lewis"
Altair Community Member
Updated by 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.

image

 

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!

image

 

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    User: "acupro"
    Altair Employee
    Updated by 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.

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    Very clear and helpful.

    Thank you!

     
    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    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!

    User: "acupro"
    Altair Employee
    Updated by acupro

    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).

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    image

     
    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    image

     
    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

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

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    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!