| Author | Message | ||
     oliver groening (gol127) New member Username: gol127 Post Number: 1 Registered: 05-2008 |
Hi everybody, I am quite new to FlexPDE and I have a problem with exporting eigenvalues (the lambda's)of a mode analysis. E.g. in the drumhead.pde example. Can any one help me? All the best Oliver | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 1125 Registered: 06-2003 |
1) Eigenvalues are always automatically exported to a text file named <problem_name>.eig (that is, the name of your script file with "pde" replaced by "eig"). See "Eigenvalue Summary" in the Help Index. 2) If you want more control over the format of the output, you can define a SUMMARY plot with REPORTS involving LAMBDA. See for example "Samples | Eigenvalues | 3d_Plate.pde". This SUMMARY page can be exported to a file using the EXPORT FILE="filename". | ||
| Muhammad Noaman ul Haq (mnhaq) New member Username: mnhaq Post Number: 1 Registered: 06-2008 |
Hi everyone, I am new to the Flex Pde I would be happy if anyone could inform me how to handle Neuman and Drichlet that is mixed boundry conditions in Finite difference(Central)technique | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 1133 Registered: 06-2003 |
Since FlexPDE does not use the finite difference method, I am a little unclear about the focus of your question. In the normal sense of "mixed" boundary conditions, in FlexPDE you would simply declare a Natural() BC on part of your boundary and Value() on another part. If you mean a Robin (combined) BC, dn(u)+au=b, then use Natural(u)=b-a*u. | ||
| abbasali Member Username: abbasali Post Number: 6 Registered: 04-2010 |
Hi dear Dr. Nelson I am a mathematics student and I have derived some abstract mathematics result about an eigenvalue problem. A simple form of this problem is as follows TITLE 'nonlinear eigenvalue problem' select modes=1 ERRLIM =.001 VARIABLES u DEFINITIONS v r1=3 r=10 e1=3 e2=0 k1=1* USTEP(r1-(x-e1)^2-(y-e1)^2 ) k2=1*USTEP(10-(x-e2)^2-(y-e2)^2 ) EQUATIONS Div(grad(u))-v*u=(-k1*lambda*u)-((k2-k1)*(lambda^2)*u) BOUNDARIES REGION 1 'blob1' { the outter blob } v=.7 START(r+e1,0) VALUE(u)=0 ARC(CENTER=e1,e1) ANGLE=360 REGION 2 'blob2' { the embedded blob } v=.1 START(r1+e2,0) ARC(CENTER=e2,e2) ANGLE=360 PLOTS surface(u) painted SUMMARY REPORT(INTEGRAL(u^2,'blob2')) REPORT(INTEGRAL((k2-k1)*u^2,'blob1')) report(lambda) END I would like to know is this type of equations which depends linearly on the eigenparameter in a subset of the domain and quadratically elsewhere , after some simplifications, models any physical phenomenon? regards. | ||
| mgnelson Moderator Username: mgnelson Post Number: 216 Registered: 07-2007 |
See http://www.pdesolutions.com/discus/messages/4/2294 |