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Derivative of Normal on a Surface

Posted 26.09.2013, 13:36 GMT-4 Fluid & Heat, Computational Fluid Dynamics (CFD), Geometry, Studies & Solvers Version 4.3a 1 Reply

John Austin
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Hello. Any help would be greatly appreciated. I am trying to calculate the mean curvature on a boundary. To do this, I am trying to calculate the dot product of the surface gradient operator and the normal vector. Thus, I need to take derivates like d(nr,r). However, whenever I do this, I only get zeros. Does anyone know how to implement these derivatives?

Another question would be, how do you take the derivative of something with respect to arc length, such as dn/ds?

Thanks in advance!
John
1 Reply Last Post 31.05.2015, 03:56 GMT-4
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Hello John Austin

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Ling-Feng Lu
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Posted: 9 years ago 31.05.2015, 03:56 GMT-4
I got an answer from COMSOL support. There is no direct way to implement derivative with respect to r or arc length s. You need to transform the derivative w.r.t x,y,z coordinates. E.g. dn/ds=tx*dn/dx+ty*dn/dy.
hope this help you
I got an answer from COMSOL support. There is no direct way to implement derivative with respect to r or arc length s. You need to transform the derivative w.r.t x,y,z coordinates. E.g. dn/ds=tx*dn/dx+ty*dn/dy. hope this help you

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