# Questions tagged [boundary-conditions]

For questions regarding the choice and/or appropriateness of conditions necessary to model a particular phenomenon with a partial differential equations.

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### Solving Stokes flow with walls using Oseen tensor

Introduction I've developed a code to solve for generalised, incompressible 2D Stokes flow $\eta \nabla^2 \mathbf{v} - \nabla p + \mathbf{S} = 0$ $\nabla . \mathbf{v} = 0$ where $\mathbf{S}$ can ...
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### Problem in Discretizing Convection-Diffusion-Reaction equation

I'm trying to solve the Convection-Diffusion-Reaction (CDR) equation on a rectangular domain, using cylindrical coordinates and Finite Difference Methods (FDM) (this approximates a flow reactor). ...
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### Dirichlet boundary condition for sparse matrix - Solving Ax=b only for free nodes?

I am solving Biot equation with sparse matrix in MATLAB. I have no problem with global sparse matrices assembly, but when I assign Dirichlet boundary condition, it is so slow. From this topic, How to ...
291 views

### Understanding Neumann BC

I understand what Neumann BC means physically and how to imply them. However, I am not able to perfectly understand it the way it is represented mathematically as $\partial u / \partial n$ where $n$ ...
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### Marker and Cell Method (MAC) - STOKES FLOW - boundaries?

please can you help me with my problem with Stokes flow written using Marker and cell method (MAC)? I need only to solve the eq. of continuity + momentum eq. for a given condition (steady state). I ...
347 views

### Boundary conditions in conforming Galerkin method for biharmonic equation

I am trying to solve simple scalar biharmonic equation using bubnov-galerkin finite element method. I am using $H^2$ conforming basis functions. I was wondering that if anyone can give me some ...
151 views

### Imposing symmetry plane boundary condtition

I want to impose symmetry plane boundary condition for a solid mechanics problem. I googled around and found out that in many places people say to "forbid displacemnts out of symmentry plane and ...