|
[Sponsors] |
How do I compute the normal vector to a surface with FEM |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
July 30, 2009, 09:00 |
How do I compute the normal vector to a surface with FEM
|
#1 |
New Member
Join Date: Apr 2009
Posts: 17
Rep Power: 17 |
I am trying to compute the normal vector to an inclined plate with the FEM.
Based on theory, the normal vector is given by n=(-dz/dx,0,1) This is the normal to the top surface. There is no variation in the y-direction. Consider it as a 2D geometry. The plate has length L, and height H, and it is inclined with a slope equal to PHI, so that it's bottom right corner is located at (a,0) and it's top left corner is located at (b,1). If I use the FEM to compute the dz/dx derivative, I will find that it is equal to zero. Does this make sense? The only way to compute a non-zero value for the dz/dx derivative is to solve the problem where the domain was originally a rectangular which deformed to the one I have now. Is this the only way to compute the normal vector with FEM? |
|
July 31, 2009, 06:10 |
|
#2 |
New Member
Join Date: Apr 2009
Posts: 17
Rep Power: 17 |
I am trying to calculate the normal on the outer surface of a circle. The circle lies in the y-z plane.
I compute the value of the derivative dz/dy (which is equal to (y-y0)/(z-z0), if the equation for the circle is (z-z0)^2+(y-y0)^2=R^2 ), and there is no good agreement between FEM and theory. Any ideas why this is happening? |
|
July 31, 2009, 07:37 |
|
#3 |
New Member
Join Date: Apr 2009
Posts: 17
Rep Power: 17 |
My mistake, I can not compute the normal vectors because both x and z are independent variables.
|
|
July 31, 2009, 08:59 |
|
#4 |
New Member
Join Date: Apr 2009
Posts: 17
Rep Power: 17 |
So, how do I calculate the normal vectors in a moving boundary domain.
If we assume that x=f(X,Z) and z=h(X,Z) taking the derivative of dx/dZ will give me the rate of deformation. But, we need to compute quantities such as dx/dz. Does anybody has any idea about how to compute the normal vectors with FEM? |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
How to get the surface normal vector | ohrmond | CFX | 3 | February 1, 2018 06:45 |
[Gmsh] Error : Self intersecting surface mesh, computing intersections & Error : Impossible | velan | OpenFOAM Meshing & Mesh Conversion | 3 | October 22, 2015 12:05 |
[Gmsh] Problem with Gmsh | nishant_hull | OpenFOAM Meshing & Mesh Conversion | 23 | August 5, 2015 03:09 |
NACA0012 geometry/design software needed | Franny | Main CFD Forum | 13 | July 7, 2007 16:57 |
CFX4.3 -build analysis form | Chie Min | CFX | 5 | July 13, 2001 00:19 |