Zhenyu, can you tell us what happens if you remove the h_elem term in your
penalty formulation ? Usually, we just set the penalty to a very large
number, and do not involve the mesh size in setting it. See example 3:
http://libmesh.github.io/examples/introduction_ex3.html
On Tue, Mar 17, 2015 at 8:09 AM, Zhang <zyzh...@nuaa.edu.cn> wrote:
> Dear Libmesher,
>
> I tried to write an incompressible Naiver-Stokes solver based Libmesh.
> Following features includes:
> coupled pressure-velocity method
> TransientNonlinearImplicitSystem used with
> compute_jacobian(..) and compute_residual(..) run separatedly
> Lid-driven cavity case for initial tests
> BDF1 time marching
> QUAD4 element,
> vel_order=2, pres-order=1, both LAGRANGE elements
> Pressure pinned at node_id=0
>
> I tried DirichletBoundary class to impose the velocity BC, the code runs
> OK.
>
> Now the problem is :
> I coded myself the common penalty method for term
> \int_{\Gamma_D}dt*\gamma/h*u*v,
> and applied the forms in boundary integral part of jacobian function
> Jxw_face[qp_face]*dt*penalty/h_elem*phi_face_[j][qp_face]
> *phi_face_[i][qp_face]
> and
> Jxw_face[qp_face]*dt*penalty/h_elem*phi_face_[i][qp_face] *(u-u_bc)
> at counterparts of residual function
> the results show the boundary velocity not fully applied ,esp. at the side
> walls near
> the two top corners. Actually there are nonzero u normal to the local side
> wall.
> So I wonder anybody here will kindly show me some hints.
>
> Furthermore, I tried applied the weak Dirichlet conditions by add futher
> boundary integrals like
> dt\int_{\partial\Omega} (-\mu\nabla \vec{ u}+pII)\cdot \vec{n}\cdot\vec{v}
> +
> dt\int_{\partial\Omega} (-\mu\nabla \vec{ v}+qII)\cdot \vec{n}\cdot\vec{u}
> at left and
> dt\int_{\partial\Omega} (-\mu\nabla \vec{ v}+qII)\cdot
> \vec{n}\cdot\vec{u_bc}
>
> The case is even worse.
>
> I also attached the code, and I am looking forward to any suggestions.
> Many thanks.
>
> Zhenyu
>
>
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--
Vikram Garg
Postdoctoral Associate
Predictive Engineering and Computational Science (PECOS)
The University of Texas at Austin
http://web.mit.edu/vikramvg/www/
http://vikramvgarg.wordpress.com/
http://www.runforindia.org/runners/vikramg
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Dive into the World of Parallel Programming The Go Parallel Website, sponsored
by Intel and developed in partnership with Slashdot Media, is your hub for all
things parallel software development, from weekly thought leadership blogs to
news, videos, case studies, tutorials and more. Take a look and join the
conversation now. http://goparallel.sourceforge.net/
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