How to correct the error in specifycoefficient

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Boni_Pl 2019-6-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/467524-how-to-correct-the-error-in-specifycoefficient

评论： Ravi Kumar 2019-6-18

My function is

function c=ccoef(nodes,elements,~,~,~,~)
N=1;
nr=size(elements,2);
c=zeros(N,nr);
c(1,:)=1/3/(0.02+0.01*20)*ones(1,nr);
a=[];
for i=1:size(nodes,2)    
    if nodes(1,i)>-0.1 && nodes(1,i)<0.1 && nodes(2,i)<=-5 
        a=[a i];
    end
end
[~,col]=find(elements==a(1));
% b=1/3./(0.02+0.01*20);
 
c(:,col(1))=1/3./(0.3+0.01*20);
specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

Error in command window is

Error in pde.PDEModel/specifyCoefficients (line 139)
        coef = pde.CoefficientAssignment(coefcont,argsToPass{:});
Error in fem (line 14)
specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

How to correct this error

kindly help me

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Boni_Pl 2019-6-18

The equation is

ccoef is the D(r).

model=createpde();

g = @circleg;

geometryFromEdges(model,g);

figure,

pdegplot(model,'EdgeLabels','on')

specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

generateMesh(model,'Hmax',0.75);

figure,

pdeplot(model);

Ravi Kumar 2019-6-18

Coefficient functions should use region and state, which contain coordinates and solution values, respectively, to compute the coefficient. You don't need to deal with elements and nodes as you are doing. Refer to simple examples in the documentation page: https://www.mathworks.com/help/pde/ug/pde.pdemodel.specifycoefficients.html

Also, it looks like you are modeling axisymmetric problem, correct? If so, you need to modify the setup a bit as PDE Toolbox uses Cartesian coordinates.

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