A means of solving ordinary and partial differential equations. The domain of the problem is broken up into elements, and the solution in each element is expanded in a basis of functions. The Finite Element Method lends itself well to adaptive refinement, irregular geometry, and good error ...

learn more… | top users | synonyms (1)

3
votes
0answers
12 views

How to project a vector into the H(div) space (in the context of finite elements)?

Say I have a simple elliptic PDE: $$ -\nabla\cdot(K\nabla p) = f \;\;\;\text{in}\;\Omega $$ with the appropriate boundary conditions. I solve for $p$ using a FEM (a discontinuous Galerkin method to ...
0
votes
0answers
18 views

Abaqus changing the orientation [on hold]

in Abaqus, *ORIENTATION,NAME=RECT,SYSTEM=RECTANGULAR 1.0, 0.0, 0.0, 1.0, 1.0, 0.0,0.0,0.0,0.0 **** i would like to change the orientation of the composite ...
1
vote
0answers
33 views

Determining Youngs Modulus of defined material in FEA (ABAQUS)

I am quite new to FEA but need to determine if I am performing my simulations correctly. I have a cube of material with defined elastic properties (Youngs Modulus and poison ratio). I perform a ...
4
votes
1answer
82 views

How to avoid negative values of numerical solution of transport equation using FEM scheme?

The transport equation is actually an advection-diffussion-reaction equation, which has the form as $$\frac{\partial C}{\partial t} + v_1 \frac{\partial C}{\partial x} + v_2 \frac{\partial ...
1
vote
1answer
46 views

Reaction-Diffusion problem A->B, solving for B

I need to solve a Reaction-Diffusion using Finite Elements, piecewise linear elements. In this problem, a reaction $A \rightarrow B$, with rate law $ r_A = - k_A \cdot u_A $, takes part, where $u_i$ ...
1
vote
0answers
40 views

Can variational formulations be solved using series solutions?

What I specifically mean is, given some functional $F\left[\mathbf{x}\right]$ which is stationary with respect to $\dot{\mathbf{x}}=f(\mathbf{x})$ and some boundary or initial conditions, can one ...
3
votes
1answer
52 views

Solving pure Neumann problem enforcing B.C. with Lagrange Multiplier

I want to solve the Laplace Equation with pure Neumann B.C. using Finite Element Method: $- \Delta u = f \ $ in $ \ \Omega $ $- \partial u/\partial n = g \ $ on $ \ \Gamma = \partial \Omega$ With ...
2
votes
1answer
69 views

Best preconditioner for mixed-poisson problem (RT0 elements)

For a very large mixed-poisson problem with lowest order Raviart-Thomas elements (RT0), I plan on using an iterative solver. However, this kind of problem is not positive-definite (saddle point ...
5
votes
2answers
136 views

How do hexahedral FEM meshes improve approximation quality per degree of freedom, compared to tetrahredal meshes?

From the deal.II FAQ : ...quadrilaterals and hexahedra typically provide a significantly better approximation quality than triangular meshes with the same number of degrees of freedom; you ...
1
vote
1answer
137 views

Step-wise finite element formulations: can this be done?

Given the functional: $$ F[\mathbf{x}]=\frac{1}{2}[\mathbf{x}^{\text{T}} * D(\mathbf{x})]-\frac{1}{2}[\mathbf{x}^{\text{T}} * \mathbf{Ax}]-\frac{1}{2}\mathbf{x}^{\text{T}}(0)\mathbf{x}(t) $$ Where ...
9
votes
3answers
150 views

Finite elements on manifold

I'd like to solve some PDEs on manifolds, say for example an elliptic equation on a sphere. Where do I start? I'd like to find something that use preexisting code/libraries in 2d , nothing so fancy ...
4
votes
1answer
160 views

Why are functional representations of systems important in numerical applications?

I tried asking a similar question in SE.Physics, and I got some information regarding the abstract side of this, but I figured I should post here to get more complete information about the numerical ...
3
votes
0answers
47 views

Creating FEM mesh for image region — what is the most suitable shape function?

I wish to create a FEM mesh to solve an inverse elasticity problem, for an irregular domain. This domain is given by a medical image, so it is discretised and each square on the grid has one scalar ...
0
votes
0answers
28 views

Resources for viscous behavior in simple FEM

I am working on a simple explicit-integration lumped-mass elastic FEM code which implements CST+DKT triangles (plate+shell) and constant-strain tetrahedra ...
2
votes
1answer
69 views

Effect of banded matrix on error

It is necessary for me to solve a Poisson problem with a numerical method on a square domain with two types of triangular mesh: uniform triangular mesh (using uniform distribution nodes on square) and ...
9
votes
2answers
99 views

Finite elements $W^{1,\infty}$ error estimates

Are there finite element method setups that provide error estimates in the $W^{1,\infty}$ norm (i.e., bounds on $\|u'_h - u'\|_\infty$)? Which families of elements can be used for implementing them? ...
0
votes
1answer
50 views

Solving Initial Value problem ignoring the time-derivative

I am looking at a heat initial value problem \begin{align} \frac{\partial u}{\partial t}-\nabla^2u = f\quad&\text{in}\quad \Omega\times(0,T)\\ u = g \quad&\text{on}\quad ...
3
votes
2answers
136 views

Initial Value Problem using Finite Element

I am trying to implement a FEM solver for the following initial value problem \begin{align} \frac{\partial u}{\partial t} - \nabla^2 u &= f\quad \text{ in } \Omega\times (0,T)\\ u &= g\quad ...
1
vote
0answers
59 views

Thin plate stiffness: analytical formula to validate FEM model

I tried to compute analitically the stiffness of a cantilever thin plate (shown in picture). The plate is also homogeneous and isotropic. The aim is to compare the result I obtain with the result I ...
0
votes
1answer
131 views

How to solve Energy Balance equation by numerical method

Good Day I am new to heat transfer technique please give me some suggestion on solving energy balance equation $$a \frac{\partial T_p}{\partial t}=\frac{\partial}{\partial x}\left(b\frac{\partial ...
2
votes
2answers
96 views

Model of heat sink problem with fan

I am trying to solve this problem using advection-diffusion model and finite element method for the solution, due to the complex geometry. Basically the problem i'm trying to solve using OpenFOAM is ...
5
votes
1answer
102 views

Effect of subdomain topologies on overlapping additive Schwarz?

Is there a reference on the effect of subdomain topology on performance of the overlapping additive Schwarz method for (high order) finite elements? For example, taking subdomains to be vertex ...
3
votes
2answers
172 views

Projecting Finite Element solution onto new mesh

I am implementing a finite element solver in MATLAB and I have the following problem. Let's say I have a mesh $\mathcal{T}_1$ with triangular elements on a rectangular domain ...
0
votes
1answer
76 views

Importing results of FEM analysis into Matlab

I need to import in Matlab the results (like time histories of diplacement or frequency response at a specific point) obtained from a FEM analysis in Nastran. At the moment I ask Nastran to save the ...
4
votes
2answers
221 views

P versus Q elements

I am currently developing a project that uses finite elements for multi-dimensional PDEs and I'm still wondering if I will use P elements (triangles in 2D and tetra in 3D) or Q elements (squares in 2D ...
0
votes
2answers
78 views

Structural FEM analysis: transiet response vs frequency response

I am running 2 simulations on a cantilever plate in Nastran: one is a transient analysis (time domain) and the other one is a frequency response analysis. The transient analysis computes the response ...
3
votes
0answers
80 views

Is it possible to predict the null space of a structure from contributing elements null spaces?

I am trying to solve an almost incompressible problem with heterogeneous properties by domain decomposition. Solution with CG converges slowly or divergerces completely. My problem becomes ...
2
votes
2answers
185 views

Why does FEM usually formulate the problems in reference configuration?

I'm with the background of computer engineering and generally use FEM for graphics simulation. As far as I know, FEM formulation is usually expressed with respect to the reference configuration, i.e., ...
1
vote
2answers
74 views

How to determine the support/influence domain for irregularly distributed nodes in the Element-Free Galekin Method?

EDIT (26-12-14):In the Belytschko's EFG code, the domain of influence for uniform distributed node can be calculated using the code below; my question is how to calculate xspac and yspac when the ...
0
votes
1answer
229 views

Alternatives to Comsol Multiphysics

This might be a question better suited for the Software Recommendations side of S.E., however I do believe that people who frequent this part of S.E. are more likely to be able to answer this ...
2
votes
2answers
159 views

FEM for a nonlinear parabolic PDE

I'm looking to numerically compute the solution to $$ k(x,u) \partial_t u - \Delta u = f \quad\quad\text{ in } \Omega \times [0,T]$$ where $k$ is a continuous but nonlinear (in $u$) real-valued ...
0
votes
1answer
68 views

What is Mesh Independence Report?

I am performing analysis on chassis (Static Structural) and for optimization purpose i am asked to generate MESH-INDEPENDENCE REPORT,of which i have no idea. I have tried going through research papers ...
1
vote
1answer
107 views

Solve steady state reaction-diffusion/Helmholtz equation numerically

I am solving a problem of the form: $\dfrac{\partial u(x,y,t)}{\partial t} = \nabla^2 u(x,y,t) - f(x,y,t)u(x,y,t) - \kappa(x,y,t)$ At the moment, I am solving this at each time step by assuming a ...
1
vote
3answers
121 views

Solve diffusion equation with linear source term

I would like to solve numerically the diffusion equation, where the sink term depends linearly on the field, and there is field-independent sink: $\frac{\partial^2 u(x)}{\partial x^2} =f(x)u(x) - ...
4
votes
4answers
207 views

Motivation behind Galerkin method

I have a question about Galerkin method. I don't understand why the Galerkin method weights the residual by the shape functions and sets it equal to zero. I want to know what is reason of this. Why we ...
2
votes
1answer
226 views

Finite Element integration with tensor notation

While I was studying discontinuous finite element methods I found an integration of a Navier Stokes equation using tensorial notation. The equation is the following: $\mathbf{\bar {u}}_{t} + ...
4
votes
4answers
252 views

Need a simple mesh format (for FEA) and a tool to generate the mesh

I want to write a 2D FEA code for my course project and I need to import a mesh (2d, simple quad/tri) on a simple geometry such as a L shaped plate or with a square/circular hole in it, something like ...
5
votes
1answer
132 views

Are additional penalty terms necessary to solve elliptic PDE's with DG-FEM?

After a cursory glance at several references to discontinuous galerkin finite element methods for the elliptic poisson PDE, i notice that all of them emphasize using penalty methods where an ...
5
votes
1answer
238 views

On the completeness of the Periodic Table of Finite Elements

In a recent SIAM News article, there is a long article describing a systematic organization of the finite elements, aptly dubbed the Periodic Table of Finite Elements. Its really quite fascinating to ...
3
votes
0answers
181 views

Poisson equation with pure Neumann boundary conditions (using FEM)

I am trying to derive the correct variational form for the Poisson equation with pure Neumann boundary conditions, and an additional contraint $\int_{\Omega} u \, {\rm d} x = 0$, as described in this ...
1
vote
0answers
117 views

Galerkin FEM: Handling Dirichlet boundary condition with quadratic basis function

Consider a simple BVP: $-u_{xx} = f$ with $u(1) = g$ and $-u_x(0) = H$. Following Hughes' notation for Galerkin FEM, the variational function space $V$ is defined first using basis $\{N_A(x)\}$, $A = ...
1
vote
0answers
84 views

Splitting Operator

I have a problem with this finite element formulation. After applied a Splitting Operator $Q=\hat{Q} + \tilde{Q}$ I do not know how to procede. I need to obtain the solution of the following finite ...
3
votes
1answer
201 views

When should a geometric stiffness matrix for truss elements include axial terms?

Bathe's Finite Element Procedures shows the "nonlinear strain stiffness matrix" for a 2D truss element as $$ \frac {^tP} {L_0 + \Delta L} \left[ \begin{array}{ccc} 1 & 0 & -1 & 0 \\ 0 ...
3
votes
2answers
361 views

Programming Finite Element Methods in C++

I am trying to develop a library for finite element methods in C++ and for that I am looking at the data structures for meshes. Based on what I've read up on fenics and deal.ii, the general ...
2
votes
0answers
54 views

Mixed DG for Poisson with mixed BC's

I am trying to find a good reference on a proper weak formulation for mixed DG (Raviart Thomas and DG) formulation for a Poisson equation with mixed boundary conditions. Can anyone suggest a good ...
1
vote
1answer
44 views

Transparent boundary conditions for finite element simulation of TDSE

I have implemented a version of Visscher's method for numerically solving the TDSE (A fast explicit algorithm for the time-dependent Schrödinger equation) (also described in Are there simple ways to ...
3
votes
2answers
165 views

Do I need to impose boundary conditions in the Jacobian matrix?

In the framework of Finite Element Method, when the Newton method is used, we solve $J(x^k) \delta x = -f(x^k)$, and the increment $\delta x$ would not change some entries from $x^k$ related to ...
1
vote
1answer
39 views

Modifying finite difference solution to Schrodinger eqn to account for fermion/boson effects

I have been playing with an implementation of Visscher's explicit method for solving the time dependent Schrodinger equation (Are there simple ways to numerically solve the time-dependent ...
8
votes
2answers
112 views

Method to quantify geometric difference of two dissimilar meshes

I am looking for a method or algorithm to produce a value that describes how different two meshes are geometrically but that have different topologies. An example would be some CAD data that has had ...
0
votes
1answer
93 views

Buckling reference using the FEM

I want to analyze buckling in a composite using the FEM. So far I have studied this references Zdenek P Bazant, Luigi Cedolin. Stability of Structures: Elastic, Inelastic, Fracture and Damage ...