Normal/tangential BC in 3D for vector variable

General discussions about how to formulate a script for FlexPDE.

Normal/tangential BC in 3D for vector variable

Postby jabberwocky on Thu Jul 12, 2018 8:19 am

Hi. How to set BC in 3D for vector variable when I need the component normal to the cylidrical surface to be fixed (value(u)=0) and free BC for tangential component (load(u)=0). I use FlexPDE6
Thank you in advance.
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Re: Normal/tangential BC in 3D for vector variable

Postby moderator on Thu Jul 12, 2018 1:05 pm

Declaring a variable to be a VECTOR quantity is really just a user convenience. Ultimately, the components are treated as individual scalar variables.
If you declare a Variable, say U=VECTOR(a,b), then a and b are the components of the vector U.
You can declare a boundary condition for the VECTOR, such as VALUE(U)=VECTOR(ux,uy), or you can declare the boundary conditions of the components individually, as VALUE(a)=a0, NATURAL(b)=0.
note:
NATURAL(.)=0 is the default, so except as a termination of an earlier BC, you need not declare NATURAL(.)=0.
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