tag:forum.featool.com,2006:forum-74Nabble - Basic Use2024-03-29T04:58:02ZQuestions on <i>basic use</i> of the <a href="https://www.featool.com" target="_blank" rel="nofollow" link="external">FEATool Multiphysics</a> and <a href="https://www.cfdtool.com" target="_top" rel="nofollow" link="external">CFDTool</a> toolboxes, and questions of the type <i>"how can I do ..."</i>.
<br/><br/>Questions from licensed users, and users who have answered forum questions and/or submitted showcase and model examples will be prioritized for developer support.
<br/>tag:forum.featool.com,2006:post-1625Re: Use of saved MATLAB file2024-03-16T16:49:48Z2024-03-16T16:49:48ZPrecise Simulation
The easiest way is to first start the FEATool toolbox GUI, and then leave it open in the background.
<br/><br/>Alternatively, you can manually add the searchpaths to the running Matlab instance.
<br/><br/><pre>
addpath(genpath('path_to_toolbox_folder'))
</pre><br/>where "path_to_toolbox_folder" is the <b>App Path:</b> shown when you select "System Info..." from the "Help" menu in the toolbox GUI. If you want to make this permanent, you can use the <a href="https://www.mathworks.com/help/matlab/ref/savepath.html" target="_top" rel="nofollow" link="external">savepath</a> command.
tag:forum.featool.com,2006:post-1624Use of saved MATLAB file2024-03-15T14:06:39Z2024-03-15T14:06:39Zarnar
Greetings,
<br/><br/>I saved a model I made in FEATool as a matlab file, I wanted to open it in matlab to see if I could code some things manually, to see total deformation etc. I was unable to run the script because it didn't understand these functions that were being referenced, like addphys, or any of them.
<br/><br/>What to do here?
<br/>Thanks,
<br/>Arnar.
tag:forum.featool.com,2006:post-1607Calculation of deflection in a cantilever beam with a single load ?2024-01-25T13:17:38Z2024-01-25T13:17:38Zsvthuesen
Hello, I cant get the same results as when doing a calculation?
<br/><br/>Calculation of deflection in a cantilever beam with a single load.
<br/><br/><br/>U=(F*l^3)/(3*E*I)
<br/><br/>I do a 3d model, after selecting linear elasticity first.
<br/><br/>I Just tried a flat piece of steel, 2x10x200mm, 10N for example, i cant get the same results ?
<br/><br/>Any hints, am I using the wrong module or?, I just downloaded the program, so new..
<br/><br/>
tag:forum.featool.com,2006:post-1606Re: Time-dependent solution2024-01-19T06:24:51Z2024-01-19T06:24:51ZLarry Scipioni
Hi, thank you for the input. As the radiative term is significant in this case, I will continue with the time-dependent solver. Boundary conditions are correct, as not all materials have the same emissivity.
tag:forum.featool.com,2006:post-1605Re: Time-dependent solution2024-01-19T01:58:32Z2024-01-19T01:58:32ZPrecise Simulation
Thank you for attaching a model file. With the default settings, the stationary solver does not converge likely due to the nonlinear radiative term ~T^4, so the solution can not be expected to be correct.
<br/><br/>One can try to tune the solver setting by decreasing the nonlinear relaxation parameter and increasing the number of iterations. Or slowly increasing the nonlinear term and using the previously computed solution as initial guess. Also please check if all you boundary coefficients are correct, as some have the coefficient 5E-8 and others 1.5E-8.
tag:forum.featool.com,2006:post-1604Re: Time-dependent solution2024-01-17T06:26:55Z2024-01-17T06:26:55ZLarry Scipioni
<a href="http://forum.featool.com/file/n1604/test2.fea" target="_top" rel="nofollow" link="external">test2.fea</a><br/><br/>Hi, here is a model that shows very different behavior if the solution is requested as time-dependent vs. Stationary. The former produces a reasonable-looking result, while the latter is non-sensical. The system is a coating on a substrate, with the coating being heated and the substrate clamped on the edge, thus held at a fixed temperature on a ring.
<br/>Thoughts? I get the feeling that the way I define the objects or even the order I add them to the model affects the result. But I am not able to tell if I am doing something wrong in my setup.
tag:forum.featool.com,2006:post-1603Re: Time-dependent solution2024-01-15T14:00:46Z2024-01-15T14:00:46ZLarry Scipioni
I cannot post the geometry, as it is proprietary. I can try to make a simplified version and see if it exhibits the same error.
tag:forum.featool.com,2006:post-1599Re: Time-dependent solution2024-01-06T02:16:01Z2024-01-06T02:16:01ZPrecise Simulation
Thank you for trying the software. With such a general description it would be impossible to say what could be an issue. Could you attach the model file either to the forum post or using a cloud file transfer service if it is too big?
tag:forum.featool.com,2006:post-1598Time-dependent solution2024-01-04T13:28:11Z2024-01-04T13:28:11ZLarry Scipioni
I have a fairly simple heat transfer model, in 3D. When I model it with time dependence it seems to provide a reasonable-looking solution. However, if I model it as stationary it won't solve. Postprocessing plot shows the one surface I input at fixed temperature, and the rest of the volume shows no temperature solution (just transparent).
<br/>I don't need a time-dependent solution. I have a feeling it is something to do with the boundary conditions. Any ideas?
tag:forum.featool.com,2006:post-1587Re: How to solve turbulent flow problem with FEA2023-11-26T17:38:10Z2023-11-26T17:38:10ZPrecise Simulation
It seems you have tried to use the built-in solver, please follow the example in this tutorial to learn how to use the OpenFOAM external solver:
<br/><br/><a href="https://featool.com/doc/Fluid_Dynamics_09_turbulent_flow1" target="_top" rel="nofollow" link="external">https://featool.com/doc/Fluid_Dynamics_09_turbulent_flow1</a>
tag:forum.featool.com,2006:post-1585How to solve turbulent flow problem with FEA2023-11-25T01:04:37Z2023-11-25T01:04:37Zyuri
When I tried to solve the turbulence model using OpenFoam, I ran into the problem as shown in the image below<img src="http://forum.featool.com/file/n1585/%E5%B1%8F%E5%B9%95%E6%88%AA%E5%9B%BE_2023-11-25_160213.png" border="0"/>
tag:forum.featool.com,2006:post-1532How to enter a simple equation in the custom equation form2023-09-07T18:52:13Z2023-09-07T18:52:13ZSecretModeller
Hello, I have some super basic doubt, hopefully.
<br/><br/>I want to solve two simple equations. These are for a 3D problem.
<br/><br/>In summary it is Divergence of H = J and Divergence of E = dB/dt.
<br/><br/>What's the proper way to specific this in 3D using the notation in FEA?
<br/><br/>
tag:forum.featool.com,2006:post-1531Re: How to obtain the Poisson equation as used by FEATool?2023-09-07T00:40:02Z2023-09-07T00:40:02Zmsandink
Hello,
<br/><br/>Since my last response I have learned a lot about FEM formulations of equations. Even so, the time derivative in the Helmholtz equation continues to elude both me and my RA. Please, either reference the derivation you used for the Helmholtz/Poisson equation or explain why the time derivative presents in your usage of the Helmholtz equation. I'm using your (very robust) software for my thesis. There's an excellent chance the modeling I've done in your program will be published, and time is running out very quickly to understand exactly what's being done here to produce such compelling results. Any light you could shed would be much appreciated.
tag:forum.featool.com,2006:post-1529Re: How to obtain the Poisson equation as used by FEATool?2023-08-24T10:14:18Z2023-08-24T10:14:18Zmsandink
Hi,
<br/><br/>Thanks for the prompter than expected response! I know that the Helmholtz equation and Poisson's equation are both standard PDEs, but I don't recognize them in the state they are presented. Both equations have a time derivative included, whereas the standard formulations of the equations do not. I don't see in the Poisson's equation section of the documentation where there is any time derivative. or where the FEM formulation of Poisson's equation has to do with what's presented in the documentation. It appears to be more akin to the diffusion equation, which is related to the heat equation, as opposed to the wave equation.
<br/><br/>Both me and my research advisor have spent a long while trying to figure it out, to no avail. Any light you can shed would be greatly appreciated.
tag:forum.featool.com,2006:post-1524Re: How to obtain the Poisson equation as used by FEATool?2023-08-20T15:54:12Z2023-08-20T15:54:12ZPrecise Simulation
How do you mean "to figure out how this equation is obtained"? These are standard PDEs
<br/><br/><a href="https://en.wikipedia.org/wiki/Poisson%27s_equation" target="_top" rel="nofollow" link="external">https://en.wikipedia.org/wiki/Poisson%27s_equation</a><br/><a href="https://en.wikipedia.org/wiki/Helmholtz_equation" target="_top" rel="nofollow" link="external">https://en.wikipedia.org/wiki/Helmholtz_equation</a>
tag:forum.featool.com,2006:post-1520How to obtain the Poisson equation as used by FEATool?2023-08-17T11:21:06Z2023-08-17T11:21:06Zmsandink
Hello,
<br/><br/>I am new to modeling and simulation in general and am trying to find the modes of an acoustic resonator including dissipative effects and thermal conductivity. I am using the Poisson equation as given in FEATool by
<br/><br/>dts_poi*p' - d_poi*(px_x + py_y + pz_z) = f_poi
<br/><br/>with dts_poi as the time scaling coefficient, d_poi as the diffusion term, and f_poi the source term, set to 0. I have tried at length to figure out how this equation is obtained, or even the Helmholtz equation as provided in the "Resonance Frequencies of a Room" tutorial, given by
<br/><br/>u' - (ux_x + uy_y + uz_z) = 1.
<br/><br/>Neither one seems like a standard variational construction of the equation. I get the modes predicted but don't understand why. So how can one obtain these equations from the standard (nabla)^2 * f = x?
tag:forum.featool.com,2006:post-1508Moment as a face load2023-07-25T08:21:13Z2023-07-25T08:21:13ZPaul23
Hi! I'm testing Featool for the first time.
<br/>In the Boundary Settings, in the Linear Elasticity condition, how can I set a moment as a face load?
<br/>
tag:forum.featool.com,2006:post-1483Re: Is it possible to have athermal analysis of a board inside a box?2023-06-08T03:03:54Z2023-06-08T03:03:54ZPrecise Simulation
<blockquote class="quote dark-border-color"><div class="quote light-border-color">
<div class="quote-author" style="font-weight: bold;">federicoma wrote</div>
<div class="quote-message">question: Is it possible to have a thermal analysis of an electronic board inside a box?
<br/><br/>details: I have a .step file of the lower shell of the box, and a .step file of upper shell of the box, I have a .step file of an electronic board, I have this problems:
<br/>- how can I put the electronic board in the correct position inside the lower shell and, the same question, how can I close the box putting the upper shell in the right position?
<br/>- Once I successfully complete the first step, will it be possible to edit the thermal properties of the electronic board inside the box? Will I be able to check the temperature of the components?
<br/><br/>I didn't find an example of something inside a box, with a thermal conduction/convection sistuation inside the box different from the thermal convection outside the box, do you have an example to suggest?
</div>
</div></blockquote>
Technically, yes it should be possible to perform this kind of simulation. In practice it typically depends how complex your geometry and resulting mesh if it will be possible. Please have a look at some of the heat transfer tutorials.
<br/><br/>Regarding positioning, you can move your geometry objects with the transform geometry object button.
<br/><br/>
tag:forum.featool.com,2006:post-1482Is it possible to have athermal analysis of a board inside a box?2023-06-05T23:44:15Z2023-06-05T23:44:15Zfedericoma
Hi, I'm a new forum member, I'm evaluating FEATool, thanks for your attention.
<br/>question: Is it possible to have a thermal analysis of an electronic board inside a box?
<br/><br/>details: I have a .step file of the lower shell of the box, and a .step file of upper shell of the box, I have a .step file of an electronic board, I have this problems:
<br/>- how can I put the electronic board in the correct position inside the lower shell and, the same question, how can I close the box putting the upper shell in the right position?
<br/>- Once I successfully complete the first step, will it be possible to edit the thermal properties of the electronic board inside the box? Will I be able to check the temperature of the components?
<br/><br/>I didn't find an example of something inside a box, with a thermal conduction/convection sistuation inside the box different from the thermal convection outside the box, do you have an example to suggest?
<br/><br/><br/>
tag:forum.featool.com,2006:post-1476Re: Setting up units for Convection-Diffusion2023-05-25T15:58:49Z2023-05-25T15:58:49ZPrecise Simulation
<blockquote class="quote dark-border-color"><div class="quote light-border-color">
<div class="quote-author" style="font-weight: bold;">Noah wrote</div>
<div class="quote-message">I understand that the Toolbox generally does not assume units, but it surely has to assume a unit of time?
</div>
</div></blockquote>
Hi, thanks for trying the toolbox.
<br/><br/>How and in what unit you interpret <i>d/dt</i> is entirely up to you (and what other units you have chosen). But the general recommendation is to stick to a unit system (for example SI) to make it simple. For the convection-diffusion physics mode you would for example typically use the following SI units:
<br/><br/><pre>
Concentration, c [mol/m3]
Diffusion coefficient, D [m2/s]
Reaction rate, R [mol/(m3/s)]
Velocities u, v, w [m/s]
Boundary flux, N [mol/(m2/s)]
</pre><br/>But you could just as well substitute the time unit <i>s</i> to minutes if you like, as long as it is consistent.
tag:forum.featool.com,2006:post-1475Setting up units for Convection-Diffusion2023-05-24T10:55:50Z2023-05-24T10:55:50ZNoah
I am trying to set up a simple 2D convection-diffusion problem where oxygen diffuses from a small cirlce into a larger circle. The larger circle (which represents brain tissue) is consuming oxygen at a certain rate.
<br/><br/>My boundary condition for O2 concentration in the small circle is in mL / L. What should be my units for the reaction rate, R, in the large circle? I understand that the Toolbox generally does not assume units, but it surely has to assume a unit of time? Should I use mL / L / second, mL / L / minute, etc.?
tag:forum.featool.com,2006:post-1428Re: OpenFoam installation error2023-04-04T03:47:12Z2023-04-04T03:47:12ZPrecise Simulation
Could you also please share your Configuration (Select "System Info..." from the "Help" menu)?
tag:forum.featool.com,2006:post-1426OpenFoam installation error2023-03-31T05:54:47Z2023-03-31T05:54:47ZKRYSTAL
Hello experts,
<br/>I'm a newbie trying FEATool for the first time and I'm having trouble calling the solver.
<br/>When I was trying this case <a href="https://www.featool.com/model-showcase/06_Multiphysics_09_multi_simulation1/.I" target="_top" rel="nofollow" link="external">https://www.featool.com/model-showcase/06_Multiphysics_09_multi_simulation1/.I</a> have a problem trying to call openfoam to solve as follows.
<br/><br/>OpenFoam Error:
<br/>Could not find any OpenFOAM installations.
<br/>Plesse install the precompiled Native- windows/mingw OpenFOAM distribution
<br/><a href="https://deve1op" target="_top" rel="nofollow" link="external">https://deve1op</a>. openfoam. com/Deve1opment/openfoam/-/wikis/precomp1ed/windows to the default installation location, for example C: \Users \%USERNAME%\AppData\Roaming\ESI-0penCFD\OpenF0AM\v2112
<br/><br/>Actually,I am using a win10 desktop computer, I downloaded FEATool as a separate software on the Windows system.I tried downloading the native-Windows version of OpenFoam(<a href="https://dl.openfoam.com/source/latest/OpenFOAM-windows-mingw.exe" target="_top" rel="nofollow" link="external">https://dl.openfoam.com/source/latest/OpenFOAM-windows-mingw.exe</a>). However, I have encountered the above problems and have not been able to solve them.
<br/><br/>The following is my installation path:
<br/>FEATool download path:D:\Program Files\Precise Simulation\FEATool_Multiphysics
<br/>Matlab runtime download path:D:\Program Files
<br/>Openfoam download path:C:\Users\DZKD\AppData\Roaming\ESI-OpenCFD\OpenFOAM\v2212
<br/><br/>I will be very grateful if you can solve my doubts,thanks.
<br/>Krystal
tag:forum.featool.com,2006:post-1417Re: plotting output vs time Or pass variable to Matlab2023-03-18T00:42:23Z2023-03-18T00:42:23ZPrecise Simulation
Thank for trying the toolbox, from the GUI you have the "Post > Animate" menu option in the which allows you to create animations with for example velocity vectors. If you want to plot curves as a function of time for certain point(s) the best option is to export the "fea" data and use the "evalexpr" function to evaluate the expression for your desired times (for example as done in the ex_navierstokes5 m-script example but for error checking instead of visualization)
<br/><br/><a href="https://www.featool.com/doc/evalexpr_8m" target="_top" rel="nofollow" link="external">https://www.featool.com/doc/evalexpr_8m</a><br/><br/><a href="https://www.featool.com/doc/ex__navierstokes5_8m" target="_top" rel="nofollow" link="external">https://www.featool.com/doc/ex__navierstokes5_8m</a>
tag:forum.featool.com,2006:post-1416plotting output vs time Or pass variable to Matlab2023-03-17T19:22:00Z2023-03-18T00:43:20Zjohnchandler
sorry, edited the post instead of posting a reply. (Question was how to visualize velocity as a function of time).
tag:forum.featool.com,2006:post-1369Re: Boundary Conditions for The Navier-Stokes Equations2022-12-26T12:46:15Z2022-12-26T12:46:15ZOzgulilhan
Thank you for reply, I will try to define a custom equation and boundary condition.
<br/><br/>
tag:forum.featool.com,2006:post-1368Re: Boundary Conditions for The Navier-Stokes Equations2022-12-25T01:54:16Z2022-12-25T01:54:16ZPrecise Simulation
<blockquote class="quote dark-border-color"><div class="quote light-border-color">
<div class="quote-author" style="font-weight: bold;">Ozgulilhan wrote</div>
<div class="quote-message">Thank you for your fast reply. I don't want to use no-slip, Symmetry/Slip, outflow, neutral outflow and inlet boundary conditions. How can I describe a new boundary condition in the GUI?
</div>
</div></blockquote>
Unfortunately, there currently is no functionality to re-define or change boundary conditions in the GUI.
<br/><br/><blockquote class="quote dark-border-color"><div class="quote light-border-color">
<div class="quote-author" style="font-weight: bold;">Ozgulilhan wrote</div>
<div class="quote-message">I tried to describe a new boundary condition in the m-files. Firstly, I set fea.phys.ns.bdr.sel as follows ...
</div>
</div></blockquote>
It is also not possible to re-define boundary conditions using the physics modes (you can only use the defined ones).
<br/><br/>The physics modes (here the Navier-Stokes physics mode defined in "fea.phys.ns") are used by the "parsephys" function to calculate the global (monolithic) weak equation and boundary contributions, that is the "fea.eqn" and "fea.bdr" are determined from the physics modes with the parsephys call.
<br/><br/><pre>
fea.phys.ns = ... % select eqations coefficents and boundary conditions
fea = parsephys(fea); % > defines fea.eqn.(...) / fea.bdr.(...) from fea.phys.(...)
% assemble and solve using definitions in fea.eqn./fea.bdr
</pre><br/>So if you want to define custom boundary conditions (or equations) you would change/modify the fea.bdr (or fea.eqn). For boundary conditions fea.bdr.d prescribes dirichlet coefficients and fea.bdr.n the Neumann/flux condition (if a Dirichlet condition is not prescribed). See the following page for definition of the boundary struct
<br/><br/><a href="https://www.featool.com/doc/feastruct#bdr_struct" target="_top" rel="nofollow" link="external">https://www.featool.com/doc/feastruct#bdr_struct</a><br/><br/>
tag:forum.featool.com,2006:post-1367Re: Boundary Conditions for The Navier-Stokes Equations2022-12-22T03:03:57Z2022-12-22T03:03:57ZOzgulilhan
Thank you for your fast reply. I don't want to use no-slip, Symmetry/Slip, outflow, neutral outflow and inlet boundary conditions. How can I describe a new boundary condition in the GUI?
<br/><br/>I tried to describe a new boundary condition in the m-files. Firstly, I set fea.phys.ns.bdr.sel as follows,
<br/><br/>fea.phys.ns.bdr.sel = [ 1, 5, 1, 1, 2, 1, 4, 1, 1, 1 ];
<br/><br/>and then for the second boundary I used symmetry/slip boundary condition, so that I get now for second boundary,
<br/><br/>'bs_ns', 'n&.u = 0, -n.(-pI + mu(grad u+grad uT)).t = 0', 'Symmetry/slip', [], { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, [], { 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip', 'solve_hook_bdrslip';
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
<br/> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } };
<br/>
<br/>The boundary condition I want to describe is similar to the symmetry boundary condition. When I changed the " -n.(-pI + mu(grad u+grad uT)).t = 0", the solutions did not change. What can I do?
<br/><br/>Thanks..
<br/><br/><br/><br/>
tag:forum.featool.com,2006:post-1366Re: what is parameter Fx Fy2022-12-21T03:30:10Z2022-12-21T03:30:10ZPrecise Simulation
If you press in the [<b>?</b>] button in the lower right corner you will be directed to the equation specifications in the documentation. Alternatively, you can press the [<b>edit</b>] button and see how the equations and coefficients defined by the physics mode. Hovering a few seconds over a coefficent edit field also shows a tooltip with a description.
<br/><br/><img src="http://forum.featool.com/file/n1366/featool_multiphysics_documentation_help.jpg" border="0" alt="FEATool Multiphysics Help button"/><br/><br/><img src="http://forum.featool.com/file/n1366/FEATool_Multiphysics_hoover_tooltip.jpg" border="0"/>
tag:forum.featool.com,2006:post-1365Re: Boundary Conditions for The Navier-Stokes Equations2022-12-21T03:25:15Z2022-12-21T03:25:15ZPrecise Simulation
b><blockquote class="quote dark-border-color"><div class="quote light-border-color">
<div class="quote-author" style="font-weight: bold;">Ozgulilhan wrote</div>
<div class="quote-message">How can change the boundary conditions on m-files?
</div>
</div></blockquote>
In general I would first suggest to change it in the GUI, and save as m-file. Then you can compare and see the syntax (what has changed).
<br/><br/>However, in this case you need to specifically change <b>fea.phys.ns.bdr.sel</b><br/><br/><pre>
fea.phys.ns.bdr.sel = [ 1, 1, 5, 1 ];
</pre><br/>so that
<br/><br/><pre>
fea.phys.ns.bdr.sel(index_to_boundary) = boundary_condition_type
</pre><br/>here boundaries 1, 2, and 4 are of boundary type 1 (no-slip), and bound 3 is slip (type 5). The boundary type is as given here <a href="https://www.featool.com/doc/physics#phys_ns__bc" target="_top" rel="nofollow" link="external">https://www.featool.com/doc/physics#phys_ns__bc</a> and in the dropdown box in the GUI.
tag:forum.featool.com,2006:post-1364Boundary Conditions for The Navier-Stokes Equations2022-12-20T14:05:01Z2022-12-20T14:05:01ZOzgulilhan
Hi,
<br/><br/>I try to solve 3D Navier-Stokes Equations. I set the model using the FEATool and export it as m-files on MATLAB. I want to change the symmetry/slip boundary conditions on m-files. I tried to change the symmetry/slip boundary condition, but the solutions did not change. How can change the boundary conditions on m-files?
<br/><br/>Thanks.
tag:forum.featool.com,2006:post-1363what is parameter Fx Fy2022-12-13T21:56:11Z2022-12-13T21:56:11ZRyu
<img src="http://forum.featool.com/file/n1363/%EA%B7%B8%EB%A6%BC1.png" border="0"/><br/>what is parameter Fx, Fy, ρ In Featool plane stress equation
tag:forum.featool.com,2006:post-1360Re: Problem in modeling a simple heat loss through convection2022-11-26T19:26:07Z2022-11-26T19:26:07ZPrecise Simulation
Unless you are absolutely sure, the solution should (easily) converge to a stable solution, the answer usually is that it is a difficult non-linear problem, possibly also that no stable solution exists. The workflow for highly non-linear problems is usually:
<br/><br/>- Increase the non-linear relaxation parameters and maximum number of non-linear steps in the solver settings
<br/>- Perform multiple restarted solver steps, while in each step restarting using the old/previous solution and increasing the parameters leading to the non-linearity little by little
<br/>- Switch to a time dependent solver
tag:forum.featool.com,2006:post-1355Problem in modeling a simple heat loss through convection2022-11-24T02:50:57Z2022-11-24T02:50:57Zhamid
Hi mates, <br>
I'm trying to make a very simple model for a pin losing heat through free convection to an environment. To account to for the buoyancy force, I have used the term "<b>alpha*g*rho_air*(T-Tamb)</b>" (taken from a sample by FEATool). <br>
For boundary conditions, I have used <b>Temperature </b> and <b>Pressure </b> for the vertical wall against warm plate. <br>
For the top part I have used "<b>Natural outflow</b>" with "<b>convective heat flux</b>" and for the bottom part I have tried "<b>convective heat flux</b>" and "<b>Insulation</b>" with "<b>Wall no slip</b>" and "<b>Natural out flow</b>". <br>
Neither of these conditions give me a stable answer. Anybody has any idea what's going wrong here? I have uploaded the file here as well. <a href="http://forum.featool.com/file/n1355/pin_2D.fea" target="_top" rel="nofollow" link="external">pin_2D.fea</a> <br>
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Thanks for your help beforehand. <br>
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PS: In the samples of FEATool for convection inside a box, I replaced the above-mentioned term with Pr.Ra for the Fy and it totally changed the results and velocity profile, but at least the model could converge.
tag:forum.featool.com,2006:post-1354Re: evaluation of the diffusion term at each grid point2022-11-23T05:05:30Z2022-11-23T18:48:08ZPrecise Simulation
The total (diffusive + convective) flux is in general defined as "-d_cd*(cx+cy)+(u_cd+v_cd)*c" for a typical 2D convection diffusion physics mode, and can be plotted just by enterin this expression in the GUI, or using the "postplot" function, or evaluated in grid (or general) point using the "evalexpr" function (which is essentially what the postplot function uses).
<br/><br/>Hard to give specific advice with the information provided, could you include the actual code/functions to generate the plot?