Introduction to transport equations - Part 1

[@FANDEFOLKLORE80]

I've followed all your tutorials in order until this one and I think that they are great. Thank you.

[@geronimo1007]

Clever tutorial. Good idea to merge geometry definition and configuration files of two different cases. It demonstrates what the individual files are for and how modelers usually start setting up new cases.

[@akshaymani1182]

Thanks for this wonderful tutorial showing the difference between convection and diffusion through a simple openFoam simulation.

[@taox1018]

Hello, thank you for the video. Is just when you type the command in the bottom the scream it usually covered by video progress bar.

[@StudySessionYT]

Is there any large incentive to working in just the terminals all the time as opposed to just navigating in the folders menu and right clicking and opening from a terminal there when necessary?

[@OpenFOAMJozsefNagy]

You can choose to work only in the terminal. With time it is much faster.

[@siamakbagherian2728]

use this command instead of copying 10 times: for i in {1..10}; do cp -r transport_baseCase transport_baseCase_$i; done

[@elarabibabas6928]

Sir , i hope you can see my comment. I am currently using the openfoam v10 , the version of 2022 (it is recommended that i download the newest version) and i didnt have a problem until this tutorial. I have done everything you did (copied the files , deleted what was unnecessary) and i executed first blockMesh. Everything went well. Then i did execute the setFields . Execution was ok , it appeared everything that appeared to your screen too. I checked the file of T at the 0 directory , and for the -0.5 to 0.5 , the value of T was indeed one. So i guess everything was ok. Then i even created the dummy file foam.foam , even though i think it is not needed that much (please share your opinion on this topic) and launched paraview. In paraview , i had of course to uncheck the box of skip zero value and the the mesh appeared. But , unfortunately , there was not any 0 values. The whole mesh had the value of 1, as i could see from the legend down right. I dont know what i am doing wrong , honestly , and its a shame i cant run the simulation as i want to realize every step before moving on. Of course , this question is addressing every member of the CFD community that is currently watching the video. Thank you in advance.

[@OpenFOAMJozsefNagy]

Please use the version v2206 from openfoam.com. v10's compatibility is very bad. There are too many syntax changes. We all knew, that is is going to come, but as far as I can judge the time has come and people have to decide which version to use.

[@GUERREROPEDRO]

Hi Nagy. First, I wanted to thank you for the excellent material shared. I have a doubt for the simple diffusion case. If I wanted the temperature / concentration / etc. travel for the left side, with a different diffusion coefficient than for the right side in the same mesh, how should I program this case and what files should I modify? Greetings and thanks!!

[@OpenFOAMJozsefNagy]

Diffusion is a uniform phenomenon and not directional.

[@idreeskhan1629]

Nice, could you explain how to use dimensionless equation's in OpenFoam?

[@sungbaelee818]

Hello sir, paraview foam.foam & doesn't seem to work but paraFoam works! I don't understand because I don't know how OpenFOAM works yet... Do you have any idea about this? It works though...I'm happy now :) Thank you so much for your very instructive videos again !

[@sungbaelee818]

Oh I think I found the reason... maybe .foam changed to .OpenFOAM I made foam.OpenFOAM and I did paraview foam.OpenFOAM and it works!

[@OpenFOAMJozsefNagy]

I am glad it works. I am happy to help.

[@ironsimonx4221]

Very nice tutorials so far! Do I see it right that scalarTransportFoam.C is not the same in openFOAM v7 ? Where can I get the one you used from somewhere? Thank you a lot.

[@OpenFOAMJozsefNagy]

This was version 2.3

[@rishisharma9112]

hi @József Nagy, i am working on CFD simulation of a ceiling fan, can you tell me where i can get MRFsimpleFoam tutorials? I enjoyed the videos, can you suggest me more sources to learn openFoam. Thanks

[@OpenFOAMJozsefNagy]

I will post a video on exactly in the next couple of weeks, please stay tuned!

[@alovyachowdhury9143]

Hey, I wanted to do some simulations of ceiling fans myself (it gets so hot here in Bangladesh I wanted to see how effective the fans really are). Did you make any progress in this area?

[@shivamgupta9967]

Sir, Can we say by looking into the create Fields of any solver, we can know what boundary conditions like U, T and P are required. As in the current solver there were U and T in the solver which were the same in 0 folder.

[@OpenFOAMJozsefNagy]

No, in general not. In an already working tutorial yes. But if there is a modification, you have to change the dictionary as well.

[@kyleqwert]

Hello Sir, I am using version 11 in openfoam, I would like to ask on where to place the codes for diffusion coefficients (DT), Is it on the physicalProperties (file) since there is no transportProperties for the version 11? Thank you.

[@OpenFOAMJozsefNagy]

The .org version is not compatible anymore. Please use v2306 from openfoam.com.

[@kyleqwert]

@@OpenFOAMJozsefNagyNoted Sir, thank you.

[@Dmplivemail]

What's the difference between set the control on runTime or on timeStep? I'm still confused about the meaning of deltaT.

[@philosopher2425]

"What's the difference between set the control on runTime or on timeStep?" Setting writeControl to runTime will lead to result files being written after consecutive time intervals defined by writeInterval, whereas the option writeControl -> timeStep means that results will be written after the number of time steps, again defined by the parameter writeInterval. So for example writing 10 equidistant result files for a 1 second simulation (endTime -> 1) could be achieved by either setting writeControl to runTime and concurrently writeControl to 0.1. OpenFOAM writes a file every 0.1 seconds. The second option would be, to set writeControl to timeStep and simultaneously writeInterval to 1. Since your simulation timeStep is defined by deltaT and you would like to write 10 result files, deltaT has to be equal to 0.1 in this case. That means in the first case deltaT has no influence on how frequent result files are being generated, in the second case it does. "I'm still confused about the meaning of deltaT." The time step of your simulation defines the temporal discretization of the partial differential equation underlying the physical problem at hand. The equation itself is continuous in time and space, since it describes the real physical world. Its computational representation in contrast has to be discretized (described and solved at particular instances of time and space), because computers have limited accuracy. The step size that governs the temporal evolution of your solving process is called the time step.

[@ashhadali14]

I am using openfoam7 but in the pizDaily folder in constant folder there is no Polymesh file in my case, what should i do?

[@OpenFOAMJozsefNagy]

blockMesh

[@wardreams7378]

Sir , can u tell a source from where i can learn how to transfer mesh in openFoam?

[@OpenFOAMJozsefNagy]

Transfer mesh from where to where?

[@malinidasgupta8419]

Hi Nagy, Í have followed the video to make the necessary changes. But when I create the blockmesh , I again get the error --> FOAM FATAL ERROR: Failed writing polyMesh. From function int main(int, char**) in file blockMesh.C at line 336. What can I do here?

[@OpenFOAMJozsefNagy]

Do you have writing access, where your case is located?

[@malinidasgupta8419]

I use sudo for this

[@OpenFOAMJozsefNagy]

That might not work. Copy your case to a location, where you have writing and reading permission.

[@vishwamohan2512]

@@OpenFOAMJozsefNagy Thank you sir worked!!!

[@elmou4186]

Hi i followed all Steps i made the Mesh and runed Simulation and opened paraview and i can see the mesh lines but i cant select neither T or U there is only solidcolor please help

[@OpenFOAMJozsefNagy]

Uncheck "skip zero time" in paraview.

[@elmou4186]

@@OpenFOAMJozsefNagy thank you so much

[@OpenFOAMJozsefNagy]

​@@elmou4186 I am glad to help

[@joaoantoniomagalhaes1273]

@@OpenFOAMJozsefNagy thank you so much! I was so lost in this part, thanks Jozsef!

[@yaowang1712]

direct after 'setFields' without 'scalerTransportfoam' you can see the Temperatur in paraview, but why can i only see Solid color? i can not choose T. or U to have a check.

[@jackelinecornelsen5206]

The same happens with me, I believe could be the version of OpenFOAM.

[@yaowang1712]

@@jackelinecornelsen5206 i have solved it, just uncheck "skip zero time"

[@StudySessionYT]

@@yaowang1712 Thank you!

[@jinlaizhang312]

How do I copy the previous line of code?

[@OpenFOAMJozsefNagy]

ctrl+shift+c in the command line.

[@stock9291]

Hello, I have a question about transport equation (it's a link to an image): s21.postimg.org/ip54v24hj/transport_Eq.jpg I am from a university in Croatia and since our professors insist on Fluent because OpenFOAM is too complicated, I had decided to go for OpenFOAM in my free time and I did not regret. I'm following your tutorials which are great and which have helped me a lot. I even made an icoFoam case of my own, not physically meaningful, but it works!

[@OpenFOAMJozsefNagy]

stock9291 T is the passive scalar, and phi is the flux through the cell face i.e. the velocity U interpolated onto the surface. Take a look at what the actual intergral form looks like and then you will see, why you use the flux.

[@stock9291]

József Nagy Thanks, that's about what I thought.

[@wardreams7378]

sir, how to use 0.orig file

[@OpenFOAMJozsefNagy]

I am sorry, but I don't exactly understand the question. 0.orig is a folder. There you have the backup files of the files located in 0.

[@wardreams7378]

sir, i copied 0.orig and made 0 folder on applyinG blockMesh it Gave error fileName::stripInvalid() called for invalid fileName 0

[@OpenFOAMJozsefNagy]

It might be the probem, that your case directory or the path leading to it might have a space in it. Maybe it is called "Case 1". Just rename the folder to "Case1"