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How to apply confining pressure to cylinder

Asked by Lou Jichao

Dear all,
How could I do, if I want to apply radial confining pressure to side.
I have mesh a cylinder using gmsh. And The radius is 10 in the XY plane. The center of the circle is (0，0，0). And the High is 5 along Z axis. And I want to apply radial confining pressure with 100kpa to the cylinder side. I have express the cylinder side using this:
"bound=whereNegative(100-x[0]*x[0]-x[1]*x[1])"
But I don't know how to set the radial confining pressure in the Nbc of PDE. Could you give me some help or suggestions.
Thank you very much in advance for your help or suggestions.
Regards,
Lou Jichao

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Lutz Gross
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Lutz Gross (l-gross) said : 		#1

I assume you want to have the boundary condition

sigma.n= sigma'.n - p*n =- p_surface*n

where n is the surface nornal and p_surface is the confining pressure?

Do you use an unstructured mesh and are all surface elements part of the mesh?

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Lou Jichao (ljc-1) said : 		#2

Dear Lutz Gross:
Yes, i want to have that boundary condition and I use an unstructured mesh, all surface elements are part of mesh.
Regards,
Lou jichao

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Best Lutz Gross (l-gross) said : 		#3

Try:

x=FunctionOnBoundary(domain).getX()
m=whereZero(x[2]-inf(x[2]))+whereZero(x[2]-sup(x[2]))
pde.setValue(y = - p_surface*domain.getNormal()*(1-m))

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Lou Jichao (ljc-1) said : 		#4

Thanks Lutz Gross, that solved my question.