non constant PDE toolbox coefficients with second order derivatives.

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Kaveh Gharibi 2017-6-11

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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;

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Answer 1

Alan Weiss 2017-6-13

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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

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