Re: [femm] discontinuities in stress tensor mask in thin air

As I understand from Dave's description of the technique, the mesh density serves as a type of permeability in the solution of the differential (Laplaces?) equation which sets the level contours, the gradient of which becomes the weighting function for the volume integral carried out in the air over the divergence of the stress tensor. The abrupt change in permeability between regions of different mesh density leads to abrupt changes in the "mask". Regions of higher density will have a greater percentage of the level contours.

But how about your force values? Were they more realistic, smoother, etc.?

Jim

>From: "mikeshonle"

>Reply-To: femm@xxxxxxxxxxxxxxx

>To: femm@xxxxxxxxxxxxxxx

>Subject: [femm] discontinuities in stress tensor mask in thin air

>Date: Sat, 08 Mar 2003 04:26:39 -0000

>Hi, I'm trying to increase accuracy by having different regions (all

>of type 'air') have different mesh spacings (starting at .005 and

>then increasing by about 10% at each concentric region). However,

>when I compute the force and then plot the stress tensor mask, the

>lines abrubtly change direction at the boundry. I'm working on a

>problem with two magnets, and I'm selecting one and doing the 'Force

>via Wweighted Stress Tensor'. Is there something I'm doing wrong or

>any other ideas or suggestions? I'm using version 3.3a3. And what's

>a good practical upper limit on the number of mesh nodes? I seem to

>start running into problems at around 350,000. Also, I would like to

>thank Mr. Meeker for this excellent program.

>Thanks in advance,

>-Mike