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Old   February 29, 2016, 05:28
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Hey Chriss,

thats for the feedback. The reason for that is simple,... during the weekend I reorganized my page and checked my servers traffic. I found that there are (as always) some asia server that produces a lot of traffic on my homepage that I want to avoid. The last year I set the IP´s to my blacklist but they change. To overcome that, I added the login section - hopefully to avoid this. I think I will also make this for the tutorial cases.

Of course, the login is for free and no data are shared.
At least some nice effect, I really know who downloaded the stuff and if I make some modifications, I can write all peoples an e-mail about the changes.

I know - register and login - is always annoying but at the moment I did not find another solution. Hope it is okay for you. I think it maight be worth (;
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Old   February 29, 2016, 05:35
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Have you tried a Captcha-based method? Just throwing this into the room, as I feel that requiring a login might keep many users from downloading the documents. Alternatively publishing on the wiki might also be an option.
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Old   February 29, 2016, 05:57
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Good hint,

I will check out if the plugin can handle that or if there is some other plugin available (:

I agree with you, that it maight be possible that people do not download it if you have to login.

I keep you up to date but the next days I have other stuff to do. So at least its like that.
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Old   February 29, 2016, 07:47
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Maybe today evening I will find time to change it. The registration will be for free then, to update everybody who want to be informed about news (:
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Old   March 1, 2016, 03:54
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Hey all,

yesterday I changed it for free-download again. I would be very happy (anyway), if you register because I am also interested in who is using my stuff. Also everybody who register freely will be updated if new tutorials, publications are available or if file will be renewed.

Feedback is welcomed.
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Old   March 3, 2016, 10:49
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Paper / Articel what ever we want to name it ... is now available on researchgate too.

Cheers
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Old   May 1, 2016, 06:04
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Hi, Tobias!
I had a look at the document and made a few comments inside it. I am not sure if all (and the one you use specifically) pdf readers/editors can display them correctly, though. If you you have any issues with them please let me know and I'll do my best to fix the problem somehow.
The revised document is here: https://drive.google.com/open?id=0Bz...jdRUWJsbGdWazQ.
My suggestion to you for future work is to include derivation of turbulence modelling equestions (k-e, k-w,...) in your text.
And I do appreciate you giving me some credits in the acknowledgement part.
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Old   May 1, 2016, 15:11
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Dear Zeppo,

I will check out your PDF. The implementation of turbulence models could be done (of course) but was not the aim goal in that work because k-epsilon etc. are only models based on assumptions with time, convection, diffusion terms plus other terms (modelling terms). Well, if I will have time, I will do it. I also should explain what it mean to make an average. I did this very nice in my masterthesis with nice graphics. This should also be included to be more clear.

To your checks.

  • First, thanks for reading
  • Second, thanks for doing some corrections
  • If I think the corrections should be done, I will set you into the acknowledgement (of course)
The next two weeks I will not have time for checking the PDF. For you as a hint... Linux -> Okular.
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Old   May 1, 2016, 15:20
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Just one question. Can you please sent me your complete name + titles etc. I will replace it (nickname is not so nice as I realized now).

In addition, okular shows me your corrections like that (attachment). Is that correct? Otherwise let me know which one I should use.

Many thanks in advance (with your corrections the stuff will improve; if you wish some special words in the acknowledgement - let me know - PM).
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Old   May 1, 2016, 17:31
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I used Foxit Reader to add annotations to your text. The page you refer to should look like this
foxit.jpg
Those little popup windows contain corrections and additional notes. You can either install Foxit Reader (available on Windows, Linux, Mac) or try to find a button, checkbox or whatever it is in Okular to make the popups show.
From time to time I need to see all the governing equations as a whole in one place. You text could possibly become this place.
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Old   May 2, 2016, 02:49
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Hey,

yesterday I got something wrong (I was too tired):
Quote:
And I do appreciate you giving me some credits in the acknowledgement part.
I thought you want to get some acknowledgement (: Today I realized that you are already in my acknowledgement. Many thanks to your corrections (very helpful and smart that you checked it, just checked a few lines). I will correct my paper as soon as possible (as I told, maybe next week) and will use your pdf viewer if Okular can not show the comments.
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Old   May 2, 2016, 14:22
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Dear all,

I found time to check Sergei 's correction. Very good remarks and I also found a few important errors. I will make a summary of the changes and will publish it as fast as I can.

Thanks again for this really nice correction!!!
Now the paper get even better.
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Last edited by Tobi; May 2, 2016 at 17:41.
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Old   May 2, 2016, 17:19
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Dear all,

I uploaded the new version to my server and research gate. I saw that I already have more than 250 downloads. Due to that and Sergei 's sentence:

Quote:
From time to time I need to see all the governing equations as a whole in one place. You text could possibly become this place.
I will extend the turbulence section:
  • Derive the RANS equations (show how we get the fluctuations and mean terms and how they can be eliminated or remain -> term that has to be modelled)
  • Introducing turbulence models and the assumption we make (energy cascade etc.)
  • k-epsilon
  • k-omega
  • These two models I want to use at least. Other models can be included in the feature
  • Due to the fact that I have (at the moment) limited time (also do video-recording of equations -> youtube and other stuff), it could take a while but as you know I will do it as fast as I can
Thanks for reading + feedback, my fruits should be yours! (The open-source thought).

Have a nice time and if you want to be more up-to-date about my work, you can register freely on my website. Cheers.
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Old   May 3, 2016, 04:48
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Hi Tobias,

First of all nice paper and nice work !

I have one comment about your equation 2.2 when you write the mass balance. The proper way should be to consider the difference of mass between a time t and a time t + Dt :

mass at t + DT = mass at t + what's going in during Dt - what's going out during Dt

It's what you already did but with a few more terms before ending up with drho/dt. You went a bit fast here.

Cheers,

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Old   May 3, 2016, 05:49
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Hey,

thanks for the replay. I will change it because I already did this in my teaching (if you mean this one here) --> Minute 18 please: https://www.youtube.com/watch?v=hwhZfLhEYws

I will change this too.
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Old   May 11, 2016, 04:17
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Hello Tobi,

thank you for the nice document. Two typos:

- S-9: Incompressible
- S-36: Applying

And maybe you could explain in detail, how you get eq. 7.2, especially what the indices i and j mean.

Thanks again,

Kate
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Old   May 11, 2016, 07:53
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Hey Kate,

the last two days I was working on the derivation of eqn. 7.2 (:
So you can look forward to see that.

Thanks for the typos.
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Last edited by Tobi; May 11, 2016 at 16:51. Reason: Time changed
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Old   May 12, 2016, 18:50
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Dear all,

Just an update for you. Today I finished the chapter of the Reynolds-Averaging method and derived the mass conservation, momentum equations and the general conservation equation using the averaging method in a straight forward way.

I demonstrated how we get the additional terms (turbulent scalar flux or if we talk about the momentum equations, the Reynolds-stresses).

In addition I found again a few typos in equations.

The next step is to derive turbulence models (i think at the beginning I will derive k-eps and k-omega plus maybe the sst).

If you want to be more up to date, feel free to register on my homepage.
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Old   May 18, 2016, 06:50
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Tobi this is solid work, thanks a lot for clarifying things esp. with respect to the way the equations are implemented in OpenFOAM. My C++ is still bad enough that I get lost in the code, so having all the relevant code pieces (as well as all the equations) in one place is extremely helpful.
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Old   May 18, 2016, 10:32
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Hi,

thanks for the feedback.
At the moment I am deriving the RANS equations (incompressible) + turbulence model k/epsilon but I also want to derive the equations for compressible flows. The problem, it is getting even worse and complex (Reynolds time-averaging + density-weighted ...)

So the new update will include a lot of new things:

  • Correct some mistakes (in general)
  • Include the handling of the time derivative as differences first
  • Turbulence modeling
    • Introduce to Reynolds-Averaging methods (time-average, ensemble, ...)
    • Time-Averaging operations on linear, nonlinear terms and constants
    • Derivation of incompressible Reynolds time-averaged mass conservation
    • Derivation of compressible Reynolds time-averaged mass conservation (to show why we get more trouble here)
    • Derivation of incompressible Reynolds time-averaged momentum equation
    • Introducing turbulent Reynolds stress tensor
    • Comparison of Reynolds stress tensor and Cauchy stress tensor (especially to show the modified pressure we use in OpenFOAM p', important to know in some cases)
    • Introducing to the Boussinesq approximation
    • Introducing the eddy viscosity
    • Derivation of the Reynolds-Stress equation to derive the turbulent kinetic energy equation
    • Derivation of the kinetic energy equation of the turbulence
    • Derivation of the dissipation guy
  • Introducing the Favre averaging concept
  • Derivation of compressible mass conservation using Favre
  • Derivation of momentum equation using Favre
  • Derivation of energy equation using Favre
  • And terrible non-ending story
For OpenFOAM I will put the derivation of DIVDEVRHOREFF to the appendix and do it again for Version 3.0.
Furthermore I will put the PIMPLE expression (that I published in the WIKI) into the guy.


You see - a lot of things to do. Problem ... always tired and for the derivations you have to be very concentrated (and furthermore for me things are also some times new to me). The good thing, I understand more and more.

For example (in RANS), using a modified turbulence model where a pressure term is included have to be derived again or you should be sure that this kind of model uses the modified pressure field p' = p + 2k rho, otherwise you should rebuild a new pressure field...


Sofar
Finally - I am not doing new things because I also just look into the literature. It is not possible to sum up all things (see Wilcox, beautiful book).
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