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January 5, 2013, 05:13 

#21  
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sqing
Join Date: Sep 2012
Location: Dalian
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Quote:
I am also simulating a case using the rhoPimpleFoam solver, RAS turbulence model. In my casewalljet flow, I set the inlet velocity as fixed value. However, I don't know how to set the the outlet condition for velocity and inlet/outlet condition for pressure. I wander that how do you set these condition in your case? Regards, Sunxing 

January 11, 2013, 13:01 

#22 
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Suranga Dharmarathne
Join Date: Jan 2011
Location: TX, USA
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Hi Sunxing,
You can use zeroGradient BC or inletOutlet BC for U at the outlet. For p you can use zeroGradient at the inlet and fixedvalue at the outlet. I am also a new member so please double check my suggestions. If any senior members can support/oppose my comment that would be really appreciated. BR, Suranga. 

January 11, 2013, 21:09 

#23 
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sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
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Hi Suranga,
Thanks for your reply. I have already tested this condition that you have suggested, however it has turned out to be a bad setting. regards, Sunxing 

May 26, 2013, 03:55 

#24  
Member
Join Date: Aug 2011
Posts: 89
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Hello,
at the moment I have some problems with one simulation. k and epsilon have very high values at the wall. I think that there is something wrong with the wall function. But I am not familiar with this topic. I read this sentence here in the discussion. Quote:
Are there any literature explaining the wall function model used in OF in k epsilonmodel? Sorry for this simple question, but I am very confused at the moment and I am not very good in C++. Thanks for your help Idefix 

June 6, 2013, 10:32 

#25 
New Member
ali
Join Date: Feb 2012
Posts: 8
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hi, I have a difficulty with discretization of source terms of k and epsilon. for example we have (du/dy)**2 in the k source term. my code is on FVM and explicit. Please guide me through.


June 7, 2013, 03:15 

#26 
Senior Member
Join Date: Mar 2010
Location: Germany
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Please don't hijack other threads! What have you done so far and which discretization scheme are your trying to employ? What's your intention  writing an own solver?
Have a look at the book "Essential Computational Fluid Dynamics" by Oleg Zikanov. It covers the basics of FVM discretization pretty thoroughly. Many other CFD books do as well. cutter 

June 7, 2013, 03:24 

#27  
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ali
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Quote:


August 20, 2013, 13:05 
regarding boundary conditions for omega

#28 
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payal
Join Date: Aug 2013
Location: banglore
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helo
I am relatively new in OF and would be grateful if some one can help me please. I am trying to set up a case using rhopimplefoam solver and the kOmegaSST model but I have difficulties defining the boundary conditions for omega. frankly speaking i dont have any clue about omega BC"S. in my case i have inlet , axis , upperwall, outlet so hw to define BC's for that ? 

July 13, 2017, 13:37 

#29 
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Joseph O'Neill
Join Date: May 2017
Posts: 5
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Hi All!
I would like to possibly revive this thread as I have a few questions regarding setting up k and omega for the SST model. I am simulating moderate flow over a bumpy airfoil (Re =300,000) and I have calculated values for both k and omega based on a length scale of 7 percent of my chord length (ie 0.07*0.201768 meters) and an initial guess of turbulence intensity of 1%. I know most literature says for moderate flows to use 15% but I am unsure of how to adequately guess where I fall within that range. The values I calculated with this become k = 0.083622 and omega = 37.38255. (1) Should these values be initialized as the "internalField uniform" values or as the value uniform for the inlet? (2) I have an inlet outlet condition with the inletValue uniform set to 0 for both k and omega so if there is any reverse or inlet flow in theory there should be little or no effect on my flow traveling over my airfoil if there is any reverse or back flow appearing(please forgive me if I misunderstand how the inletOutlet type works...I am relatively new with OpenFOAM). With a zero gradient at the outlet, would these be proper BC's to set? Any help at all would be appreciated! Thanks, Joe 

February 7, 2018, 18:47 
Regarding the Reynold's number in Rotational wall velocity

#30 
New Member
Anand
Join Date: Nov 2017
Posts: 3
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Hello Everyone
I'm using this code for running my Rotating wall, bump { type rotatingWallVelocity; origin (958.85 1755.17 0); axis (0 0 1); omega constant 230.3834; //rad per sec using 13200 deg/s=2200 rpm value; In this what will be the reynold's number. and how to change the reynold's number if I want to ? Thanks in Advance Any reply will be helpful 

July 22, 2019, 11:25 

#31 
New Member
igne
Join Date: Jul 2019
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What if I use my initial velocity and calculate k and epsilon values?


March 5, 2021, 10:32 
values of K, omega

#32 
Member
Deutschland
Join Date: Sep 2020
Posts: 69
Rep Power: 5 
Hey,
I am simulating a kayak for velocity 4.5 and 5.5 m/s and I am using Komega SST. I found the formulas for finding the values as shown in the image. I am not an expert in CFD. I am getting really high value for omega. I don't know if I am making any mistakes consept. But when I try these formula on some on the examples cases, I am not getting the correct answer length 5.19 Following are the values Code:
Re = 23355000 I = 0.0191 k = 0.0111 L/sqr(Re) = 1.073e3 l =4.29e4 omega =488 can some one help? thanks in advance vava10 

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