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How to Apply Pessure on Normal Direction of Boundary

0 votes

Usually, to apply the pressure P boundary condition, the pressure P is decomposed into x, y, z directions as Px, Py, Pz. Now I have a curvy boundary to apply pressure. In this case, the normal direction of the boundary need to be calculated by use: n=FacetNormal(mesh).

But I can't use P*n to define the traction boundary conditions for defining Px, Py, Pz.

Anyone knows how to define a pressure boundary condition which is normal to the boundary.

asked May 12, 2014 by wmy32552316wmy FEniCS Novice (230 points)

There was a thread about a year ago on Stack Exchange:
http://scicomp.stackexchange.com/questions/7123/fenics-separate-boundary-conditions-in-normal-and-tangential-direction-of-mesh

commented May 12, 2014 by timm FEniCS User (2,100 points)

Pressure is a scalar and doesn't have direction. Do you want to apply a traction that is normal to the surface?

Which equation are you solving?

commented Oct 7, 2015 by Garth N. Wells FEniCS Expert (35,930 points)

1 Answer

0 votes 
T = Expression(('p*x[0]/R', 'p*x[1]/R'), t=10000., R = R)

thus, the surface integral in variational formular:

L = inner(T, v)*ds

in which $p$ is the pressure imposed on the boundary of a circle of radius $R$. Tell me if you need sample code (linear elasticity).

answered Oct 7, 2015 by newuser FEniCS Novice (650 points)
edited Oct 9, 2015 by newuser

But what if the boundary is not circular?

commented May 7, 2017 by linyx FEniCS Novice (210 points)
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