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How to prescribe both the dependent variable and its derivative at boundary?

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Hi there,

I am trying to solve a set of differential equations, defined at x belongs to [0,1] as

L1[u1(x),u2(x),u3(x)]=0,

L2[u1(x),u2(x),u3(x)]=0,

L3[u1(x),u2(x),u3(x)]=0, as well as,

u1(0)=0, u2(0)=0, u1(1)=0, u2(1)=0, u3(1)=0, u3x(0)=0, u3x(1)=0, B[u3(0)]=0, where

L1,L2,L3 and B are derivative operators. The first 7 are enforced boundary conditions, while the last is a natural boundary condition.

The "Weak Form PDE" interface is employed. The enforced boundary conditions, viz., u1(0)=0, u2(0)=0, u1(1)=0, u2(1)=0, u3(1)=0, are prescribed by Dirichlet boundary condition.

****I don't know how to prescribe the rest two enforced boundary condtions,u3x(0)=0 and u3x(1)=0.

Any suggestion is most welcomed.

Best HC


1 Reply Last Post 5 juin 2021, 21:50 UTC−4

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Posted: 3 years ago 5 juin 2021, 21:50 UTC−4

I tried to use boundary flux/source, like https://ftp.bmp.ovh/imgs/2021/06/3abed9d297275d5d.png

However, in the view of the solution, the boundary condition u3x(1)=0 is not enforced.

I tried to use boundary flux/source, like ![https://ftp.bmp.ovh/imgs/2021/06/3abed9d297275d5d.png](http://) However, in the view of the solution, the boundary condition u3x(1)=0 is not enforced.

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