non constant PDE toolbox coefficients with second order derivatives.

1 次查看（过去 30 天）
Kaveh Gharibi
Kaveh Gharibi 2017-6-11
评论： Kaveh Gharibi 2017-6-15
I need to specify coefficients in PDE tool box. My coefficients are related to the second derivatives not first derivatives. Can I use state.uyy and state.uxx and state.uxy as second derivatives? You can see the code here. Thank you so much.
function amatrix = acoefminsurf(region,state)
n1 = 16;
nr = numel(region.x);
amatrix = zeros(n1,nr);
normrev=-(sqrt( state.uyy(4,:).^2+state.uxx(4,:).^2-2*state.uxy(4,:).^2 ) );
amatrix(2,:) = normrev;
amatrix(7,:) = normrev;
amatrix(12,:) = normrev;

请先登录，再回答此问题。

采纳的回答

Alan Weiss
Alan Weiss 2017-6-13
No, the state structure does not support uxx or uyy, as documented.
I suppose that you might try to increase the number of variables in your equation, such as making a system [u,v] and having v = ux so that uxx = vx. But I make no guarantees that you can really do this successfully. You would have to come up with coefficients and boundary conditions for the system.
Good luck,
Alan Weiss
MATLAB mathematical toolbox documentation
  3 个评论
显示 1更早的评论
Ravi Kumar
Ravi Kumar 2017-6-14
Could you share your script, and necessary data, for the nonlinear system of PDEs that did not converge?
Kaveh Gharibi
Kaveh Gharibi 2017-6-15
I figured it out. My C matrix was wrong. Pay attention when converting the problem to Matlab divergence format.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Geometry and Mesh 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by