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Derivative of Normal on a Surface

Posted 2013年9月26日 GMT-4 13:36 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 2015年5月31日 GMT-4 03:56
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Hello John Austin

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Ling-Feng Lu
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Posted: 9 years ago 2015年5月31日 GMT-4 03:56
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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