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S. S. Mudathir July 15, 2002 10:36

I canít believe that nobody doesn't know the answe
 
Many days I sent a message in the board to ask about the adopted turbulence model in ALGOR FEA 12.04 but unfortunately I received no answer till now. May be this is not strange but the strange thing is that I sent ALGOR FEA customer services the same question and received no answer till now!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!

calm down July 15, 2002 11:32

not everyone works on the weekend
 
Your post was on Saturday 7/13, and ALGOR responded to you on Monday 7/15? Wouldn't that be the start of their normal business hours?

Unless they have a 24/7 customer service line, their response was pretty good.

Jongdae Kim July 15, 2002 12:28

Re: I canít believe that nobody doesn't know the a
 
Hi, Mr. Mudathir,

As far as I know that most of the users of this forum are biginers on CFD. As for me, I didn't know what is finite volume method when I started my PhD program. Now I spent four years for CFD and now I roughly understand on my thesis topic. My background was structural analysis.

This 'Main Forum' is for general discussions of CFD field. You can find very general and fundamental discussions as well cutting-edge topics. CFD-ONLINE also provides other forums for those who use commercial packages such as FLUENT, PHOENICS, etc.

During my study I got advices from this web-site. So I'd like to contribute myself whatever it is small. But most of the questions are difficult to make answer becuase CFD is very wide field and some questions are very specific. Only for a few questions, I can join the discussions.

Your question is not easy to answer for me. The reasons are at first, I didn't know that ALGOR has the ability to solve turbulent flow. And secondly, until now not so many people use this web-site (this is my opinion. I want almost all the CFD people in the world to use this web-site), you have not yet received the answer. Please ask your friends and other CFD people to used this site.

I used ALGOR for structural analysis only very long time ago. But if you don't mind getting my humble opinion, I'd like to suggest that please read the manual of ALGOR and run some sample problems provided by the package. There maybe several kinds of turbulence models such as zero equation model, one-eqaution model, two-equation model, etc.

Flow analysis, especially turbulent flow around bluff bodies, is totally different from the analysis of the behavior of structures. The viewpoint is different. One is Eulerian, the other is Lagrangian, generally speaking. Number of degree of freedom are also vere different. Without knowing you problem exactly, not easy to answer. If your problem is incompressible, turbulent flow around fixd bluff body, we can discuss more.

Other suggestion. If you want to solve flow itself, why don't you use FLUENT, CFX, STAR-CD, etc. These are oriented only flow analysis.

Kim.

mukkarum July 16, 2002 03:52

Re: I canít believe that nobody doesn't know the a
 
Hi, i want to know about turbulence model. How many turbulence models are there and their definitions please tell me.

Jongdae Kim July 16, 2002 10:58

Re: I canít believe that nobody doesn't know the a
 
I found from ALGOR-website. This FEA software has "mesh adaptive subgrid scaled turbulence model". This is just like other algebraic eddy viscosity models uses a turbulent or eddy viscosity proportional to the quantity.

I also tried to find different kinds of turbulence model but failed. If you have manual of this software, you may find other models.

Kim.

S. S. Mudathir July 16, 2002 15:25

Re: I canít believe that nobody doesn't know the a
 
Dear Mr. Jongdae Kim Hi, I really don't know what to say but I think it is a must to say thank you. I will tell you the further details when I overcome this problem.

S. S. Mudathir

mukkarum July 16, 2002 22:56

Re: I canít believe that nobody doesn't know the a
 
what we mean by turbulence model what property a turbulence model have and what is the meaning of k-epsolon model. I am working on Francis Turbine which model should i use, and in the last i couldn't get leterature on Francis Turbine can you guide me about books, papers or websites from where i can get knowledge.

Li Yang July 17, 2002 05:34

Re: I canít believe that nobody doesn't know the a
 
David C. Wilcox's book: Turbulence Modeling for CFD.

S. S. Mudathir July 17, 2002 06:37

Re: mukkarum inquiry about turbulence models
 
Dear mukkarum, It is not easy to get an answer about turbulence models in such a little place, but you have to get on of the books dedicated for turbulence, cause the understanding of these models come from the derivations of Reynolds stress after assuming that the velocities in the spatial coordinates consist of two values a mean value and another which change withwith time according to many factors. Having this assumption subsitituted in the NAVIER STOCKES equation, new nonlinear terms appear and it is very complex or maybe even impossible to solve the equation with these new terms. Due to this serval approximation the the reynolds stresses were tried and lead to what is know now as turbulence models

mukkarum July 17, 2002 23:48

Tensor,cavitation,Francis Turbine
 
I want to know about Tensor. it defination and types. I am studing "Introduction TO Computational Fluid Dynamics by Versteeg and Malalasakra". Chapter three of this book consist material about turbulence model. Do you know the name of other books which will be helpful for me to understand turbulence modelling, and also guide me about good website relatted to turbulence modelling, Francis Turbine and Cavitation.Thanks

michael malin July 18, 2002 06:21

Re: Tensor,cavitation,Francis Turbine
 
A very good introductory book on turbulence modelling is:

W.Rodi: "Turbulence models and their application in hydraulics - a state of the art review",International Association for Hydraulic Research, Delft, 3rd edition 1993, Balkema.

It is very well written and easy to understand, but the application examples are obviously for hydraulics not turbomachinery.

A more detailed and comprehensive description of turbulence modelling can be found in David Wilcox's excellent book 'turbulence modeling for CFD'( see http://www.dcwindustries.com/books/0963605151.htm)


mukkarum July 18, 2002 23:14

Re: Tensor,cavitation,Francis Turbine
 
Can we download research papers on CFD ,Turbulence Modeling, Grid Generation, Tensor from net

mukkarum July 19, 2002 00:07

Re: Tensor,cavitation,Francis Turbine
 
I am very happy that i got both two books from my university Library. I am going to study them and contevt you soon. Thanks

mukkarum July 24, 2002 04:48

Re: Tensor,cavitation,Francis Turbine
 
I got the sentence from w. Rodi's book TURBULENCE MODELS AND THEIR APPLICATION IN HYDRAULICS that " eddy viscosity proportional to a velocity characterizing the fluctuation motion and to a typical lenth of this motion which prandlt called mixing length" i want to know what is the meaning of velocity characterizing and typical length and mixing length.


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