| Author | Message | ||
     Iyad (ihijazi) Junior Member Username: ihijazi Post Number: 3 Registered: 09-2005 |
Thanks Robert, Does NATURAL(U)= 0 in Cylinrical Coordinates, CYLINDER('Z','R'), means du/dz = 0 or du/dr = 0 ? | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 483 Registered: 06-2003 |
Neither. If you read the documentation I referenced in response to your last post, you will see that the NATURAL() boundary condition defines the value of the surface terms arising from integrating the PDE by parts. Because of this definition, the meaning of NATURAL depends on the way you pose your PDE. In a heat equation div(-k*grad(Temp)), it means the outward normal heat flux across the boundary. In displacement equations as usually posed, it means surface-normal stress. This definition of NATURAL is valid in any geometry. |