All Questions
35 questions with no upvoted or accepted answers
3
votes
0
answers
53
views
Datasets for inverse heat transfer problems
I was wondering if there is an available, real-life known inverse heat transfer problem dataset to benchmark oneselfs algorithm, as in MNIST for deep learning. Talking about... (well in this case I ...
- 191
3
votes
0
answers
100
views
Is there any book about fundamental FEM theory using similar terminology as Comsol MultiPhysics?
I am considering to solve complexed PDE systems, like in this post, using Comsol MultiPhysics. The PDEs are different from the General Form provided by Comsol. The Weak Form module may be worth a ...
- 31
3
votes
0
answers
108
views
Correct approach for thermal finite element simulation of layered assembly
I would like to optimise the heat transfer on a PCB. Several dies are on the top and cooling air is going through the fins in heat sink on the bottom. The assembly consists of several layers like ...
- 570
3
votes
0
answers
135
views
Strain propagation from surface to bulk in COMSOL
I am trying to simulate strain propagation from the surface into the bulk. I have a rectangular semiconductor block (~2 μm thick) on top of which metal gates (~25 nm thick) are deposited as seen in ...
- 31
2
votes
0
answers
114
views
Efficient heat diffusion implementation with varying coefficients
I have the following heat diffusion equation:
\begin{alignat}{3}
\partial_t u(t, \vec{x}) &= g(\vec{x})\Delta u(t,\vec{x}), &\quad& \vec{x} \in\Omega, \, t\in(0,\infty],\\
\partial_n u(t,\...
- 2,892
2
votes
0
answers
113
views
Conceptual doubt regarding 2D conjugate heat transfer modelling (COMSOL and Mathemtica)
I have been dealing with some conceptual flaws in my understanding of modelling, which I will elaborate herein. I am modelling conjugate heat transfer of a reciprocating fluid, which flows with ...
- 41
2
votes
0
answers
92
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How to accelerate the computing of implicit finite difference method for heat conduction between two solids
Edit on May 3rd: I have found the problem. Because the difference of between $k_1$ and $k_2$ is huge, a very small time step need to be chosen so that the right green part can "feel" the ...
- 21
2
votes
0
answers
294
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Rosenthal equation for multi track
Rosenthal's equation lets one calculate the temperature profile of a moving point heat source analytically for thin and thick plates. For simplicity I use the equation for thick plates defined as:
$$T-...
- 840
2
votes
0
answers
150
views
switching boundary conditions to simulate a reciprocating flow in COMSOL
This is a re-posted question which was poorly defined earlier
I have been trying to simulate reciprocating flow of a convective fluid through a heated channel in COMSOL-Multiphysics. The schematic of ...
- 41
2
votes
0
answers
3k
views
COMSOL - Implementing Perfectly Matched Layers (3D)
If there are any COMSOL gurus here, I want to simulate a 3D RF system infinite in 1 direction. I realize I need to use PML's, but am unsure how to configure them. it seems that simply scaling them by ...
- 21
2
votes
1
answer
448
views
Derivatives over a Finite Element mesh
I have a data extracted from Comsol on some node points and I know the coordinates of each node.
Does anyone know how Comsol calculate the partial derivative from the values at each node and also ...
- 23
1
vote
1
answer
256
views
Coupled Partial Differential Equations
I'm trying to solve the following system of coupled differential equations, the two-temperature model for $e$ = electrons and $l$ = lattice.
$$
\rho_{e}C_{p,e}\frac{\partial T_{e}}{\partial t} = k_{e}\...
- 11
1
vote
0
answers
50
views
How can I apply a mixed boundary condition to a multi-material heat transfer problem using Crank-Nicolson?
I am working on a mixed material model for a melting material and need to enforce both a Dirichlet and Neumann type condition at the interface. Subject to an external surface heat flux at the top of ...
- 11
1
vote
0
answers
41
views
What is the physical quantities in the equations for linear elasitc materials in a frequency study in comsol
I am using comsol to model a linear elastic materials and perform a frequency domain study. I try to understand the equations it provided but all symbols are not explained. For example,
How should or ...
- 111
1
vote
0
answers
115
views
Accuracy of the Crank-Nicolson method for non-linear, inhomogeneous heat equation
I am currently coding a solution to the following PDE:
$\frac{\partial T }{\partial t} =\frac{\partial}{\partial \theta}(A(\theta ,\phi )\frac{\partial T }{\partial \theta}) +\frac{\partial }{\partial ...
- 11
1
vote
0
answers
111
views
Weird "oscillatory" modes appearing in FEM simulations
I am using COMSOL to solve a mathematical model involving thermoelectric hydrodynamic (TEMHD) flow. I am running a very large parameter sweep and using the solutions obtained to make some plots. ...
- 111
1
vote
0
answers
456
views
Incorporating radiation boundary condition at the edge in finite difference
I am trying to solve the 2-d heat equation on a rectangle using finite difference method. I am confused as to how to incorporate non linear radiation boundary condition at the edge.
$-k\frac{\partial ...
- 19
1
vote
0
answers
46
views
Fitting a multivariate PDE (using Java)
I'm doing simulations of 2 coupled PDE's with Comsol Multiphysics. I want to fit some data (using the Application method, whose language is Java) to those simulations.
In order to answer my question ...
- 171
1
vote
0
answers
582
views
Changing geometry scale breaks simulation
I'm trying to find the capacitance matrix for a small array of metal boxes in air using Comsol 5.4. The geometry presented here is a simple geometry that recreates the problem I'm experiencing.
...
- 111
1
vote
0
answers
424
views
How to simulate water, falling under gravity, and impinging on a curved surface, which is kept/present in a domain, containing air?
TL;DR: How do I simulate a hole, at the bottom of a (full) water tank?
I am attempting to simulate water, flowing out of a hole/slit, at the bottom of a tank (Water Domain) (under the influence of ...
- 111
1
vote
0
answers
953
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Methods and tools to solve the two-temperature model (TTM)
I would like to model heat diffusion at the gold / water interface after excitation of the metal surface by an ultrafast laser pulse (ca. 80 fs).
An appropriate model to start with would be the "two ...
- 21
1
vote
0
answers
2k
views
3D visualization of the results of a 2D simulation in COMSOL
Considering that COMSOL forum is dead and CFD-online is not responsive, I'm gonna try asking my question here:
I have done a 2D simulation in COMSOL multiphysics. I have two independent variables x ...
- 147
1
vote
0
answers
71
views
Computing dilogarithm
I'm measuring the integral of a quantity which, mathematically, requires the computation of a dilogarithm function.
$$\operatorname{Li}_2(be^{ax})$$
where $b$ and $a$ (are real and) can be positive ...
- 183
1
vote
0
answers
212
views
BTCS-like method for heat conduction in unstructured triangular grid
I want to write a simple simulation for heat conduction in a unstructured triangular mesh.
I already made it work for a structured rectangular grid with the ADI method, but now I need more complex ...
- 23
1
vote
0
answers
114
views
Representing a 3D system in 2D (Electromagnetic modelling)
Ok so I'm a complete beginner in computational modelling (I use analytical methods of physics typically) but I would like to model an anisotropic, aperiodic (but not random) finite array of metallic ...
- 201
1
vote
0
answers
4k
views
Stationary solution converge but time dependent doesn't
I've coupled a COMSOL model for fluid dynamics with a very simple pde that model the transport of humidity in air.
When I solve it for the stationary case, the solution converge easily, but when I ...
1
vote
0
answers
65
views
Can I use RANS to see the effect of mixed convection?
my question is: can I use a RANS simulation to see the effect of mixed/natural convection?
Actually I have also a second question: I would like to do this in Comsol multiphysics, but it seems that it ...
0
votes
0
answers
35
views
Help Understanding the Weak Equation for Fully Developed Flow (Inlet) in COMSOL
I'm working on a simulation in COMSOL Multiphysics and trying to understand the Fully Developed Flow (Inlet) boundary condition. The documentation mentions:
The Fully Developed Flow boundary condition ...
0
votes
0
answers
28
views
Combining Study Steps with Multiple Geometries in COMSOL
Currently, I am using COMSOL to first solve an eigenmode problem in a simple element and subsequently extracting the displacement from the surface of said element and the results from the eigenmode-...
- 1
0
votes
0
answers
128
views
Heat Equation for fast source with FiPy
I'm trying to solve the following differential equation with FiPy, basically laser irradiation on a surface
$$
\rho_{s}C_{p,s}\frac{\partial T}{\partial t} = k_{s}\frac{\partial^{2}T}{\partial x^{2}} +...
- 11
0
votes
0
answers
38
views
Thermo Hydraulic Mechanical modeling of energy wall slab in Comsol multiphysics
I am currently working on a complex simulation project involving an energy wall slab, and I need assistance in accurately modeling and validating it using COMSOL Multiphysics. Here are the details of ...
0
votes
0
answers
41
views
Fermi level determination
Is there a semiconductor physics module in COMSOL which correctly describes the Fermi level position for any bandgap system ( especially under different doping concentration)?? If not what is solving ...
- 1
0
votes
0
answers
54
views
Why does COMSOL treat a well as a rectangular cube?
I'm trying to learn COMSOL for a graduate research project and am struggling through a flow and transport in 3D tutorial. As such I'm walking through my boundary conditions and trying to figure out if ...
0
votes
0
answers
336
views
COMSOL Circularl polarization
I'm having some problems trying to implement circularly polarized light in COMSOL Muliphysics.
For a isotropic homogenous media, I've obtained without problems the TE and TM reflectance curves. ...
0
votes
0
answers
112
views
Simulating flow in a branched pipe
I am trying to simulate 1D advection and convection of a solute in the following blood vessel segment.
I would like to know if this system can be simulated in COMSOL or MATLAB.
I have used pdepe ...
- 433