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radial velocity to velocity vector input

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I am trying to simulate a drug release pattern from biodegradible polymer implants in a brain. I am using 3D Convection and Diffusion model (transient) and I would like to input radial velocity of the fluid in a brain subdomain. Because I can only use cartesian coordinates in COMSOL, I would like to change radial velocity (v_r) to velocity vectors (u, v, w). How can I change that? (There is no v_theta and v_phi.)

1 Reply Last Post 2010年1月6日 GMT-5 17:42
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2010年1月6日 GMT-5 17:42
Hi

you can change your variables, but by default the spherical coordinates are not implemented as is. You must write out the formulas yourself.

Depending on what exactly you need you can sometimes get around with a coordinate frame or WP change, there is an example somewhere about applying torsional loads (cylindrical coordinates) in the Structural Module doc.

And take a look at the KB and try "spherical" in the search there are a few topics/ explanations there too

As well examples in the model gallery

Hope this helps
Good luck
Ivar
Hi you can change your variables, but by default the spherical coordinates are not implemented as is. You must write out the formulas yourself. Depending on what exactly you need you can sometimes get around with a coordinate frame or WP change, there is an example somewhere about applying torsional loads (cylindrical coordinates) in the Structural Module doc. And take a look at the KB and try "spherical" in the search there are a few topics/ explanations there too As well examples in the model gallery Hope this helps Good luck Ivar

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