
[Sponsors] 
May 8, 2008, 13:06 
Dear Foamers
I have a littl

#1 
New Member
Valerio Novaresio
Join Date: Mar 2009
Location: Polonghera, Cuneo, Italy
Posts: 27
Rep Power: 9 
Dear Foamers
I have a little question about the passive scalar transport. I molelled a mixture of N2 and O2 like a carrier flow and the concentration like a passive scalar. I have this boundary condition:  A pressure inlet where I know the concentrations  A first O2 (only) outlet where I know the mass flow rate  A second outlet (N2 + O2) where I know the mass flow rate but not the concentration. At inlet always is ok > I define pression and concentration At the second outlet always is ok > I define velocity (concentration is calculated) At the fisrt inlet ??? > I define velocity but I don't know wath kind of boundary condition I have to assign for the concentration. I suppose N2 density and O2 density are the same, so the fluid density and the fluid properties are constant and the concentration is completly indipendent from the flow (only use U to solve the transport equation). My solver is a modified version of icoFoam (icoFoam + passive scalar transport equation for the O2 concentration). Can someone help me?
__________________
...The best way to acquire new knowledge is to share it... 

May 13, 2008, 10:30 
I have resolved my problem. I

#2 
New Member
Valerio Novaresio
Join Date: Mar 2009
Location: Polonghera, Cuneo, Italy
Posts: 27
Rep Power: 9 
I have resolved my problem. I have assigned the flux at the oxigen oultet.
If someone have the same problem contact me...
__________________
...The best way to acquire new knowledge is to share it... 

May 13, 2008, 10:50 
Hi Valerio
if possible, ple

#3 
Senior Member
Join Date: Mar 2009
Posts: 248
Rep Power: 10 
Hi Valerio
if possible, please provide an email address in your profile so that others users could contact you with request on similar problems. With Best Regards Jaswinder 

May 14, 2008, 09:40 
Thanks Valerio
Jaswi

#4 
Senior Member
Join Date: Mar 2009
Posts: 248
Rep Power: 10 
Thanks Valerio
Jaswi 

August 6, 2008, 08:57 
In my diploma thesis I simulat

#5 
New Member
Apanasevich, Pavel
Join Date: Mar 2009
Location: Bremen, Germany
Posts: 2
Rep Power: 0 
In my diploma thesis I simulate the mixing process in a Tshaped
> micromixer (width 200?m, height 100?m). The flow is laminar > (steadystate) thus I am using the simpleFoam solver and I've added the > scalar transport equation > > fvm::ddt(C) + fvm::div (phi,C) –fvm::laplacian(DC,C) > > in the solver in order to solve the species equation and calculate the > concentration field in the mixer. > > The scalar is released at the inlet 2 (C=1), and at the inlet 1 (C=0, > dimensionless) there is no scalar. The boundary condition for the > velocity is a parabolic velocity profile (Umax = 3.29m/s at the Inlet 1 > und 3.29 m/s at the Inlet 2). At the outlet I am using zeroGradient for > velocity und fixedValue (0) for p (pressure). The cells size is 4?m  > 4?m  4?m (hexcells). > > The problem is the following: the calculated concentration must be > between 0 and 1 but I receive values from 0.16 until 1.16. > > I've tried the following steps: > > 1) div (phi,U) Gauss limitedLinearV 1.0; > div (phi,C) Gauss limitedLinear 1.0; > laplacian (DC,C) Gauss linear corrected; > Result: C = 0.153 – 1.08, but the physical sense of mixing is not > correct (compared to simulation results using CFDACE+ and experimental > results) > 2) div (phi,U) Gauss linear;UpwindV Gauss; > div (phi,C) Gauss Gamma01 1 Gauss; > laplacian (DC,C) Gauss linear limited .0; > Result: C = 0.17 – 1.07, the physical sense of mixing is better than > 1) but is not correct too. > > 3) div (phi,U) Gauss linearUpwindV Gauss; > div (phi,C) Gauss linearUpwind Gauss; > laplacian (DC,C) Gauss linear corrected;> > Result: C = 0.157 – 1.16, the physical sense of mixing is *correct* > (compared to simulation results using CFDACE+ and experimental results) > but C is not between 1 and 0 > > *fvSolution file for all cases*: > > … > > C PBiCG > > { tolerance 1e06; > > relTol 0; > > preconditioner DILU; > > }; > > … > > RelaxationFactors > > P 0.3; > > U 0.7; > > C 0.7; > > … > > *fvSchemes:* > > … > > fluxRequiment > > { default no; > > P; > > C; (here I've tried with and without C à I cannot see any difference) > > How can I improve my results from approach #3, so that my concentration > is in the boundaries between 1 and 0? I would appreciate any advice 

January 16, 2009, 05:35 
Hi,
Im using simpleFoam and

#6 
New Member
Nicolai Heilskov
Join Date: Mar 2009
Location: Kgs. Lyngby, Denmark
Posts: 2
Rep Power: 0 
Hi,
Im using simpleFoam and want to include transport of a passive scalar. How and were shall I add the scalar transport equation. Do I need to add any thing else? Any advice is appreciated. 

January 16, 2009, 05:37 
Hi,
Im using simpleFoam and

#7 
New Member
Nicolai Heilskov
Join Date: Mar 2009
Location: Kgs. Lyngby, Denmark
Posts: 2
Rep Power: 0 
Hi,
Im using simpleFoam and want to include transport of a passive scalar. How and were shall I add the scalar transport equation. Do I need to add any thing else? Any advice is appreciated. 

January 16, 2009, 14:33 
Hi All,
I am using coupled

#8 
Senior Member
Vishal Nandigana
Join Date: Mar 2009
Location: Champaign, Illinois, U.S.A
Posts: 208
Rep Power: 10 
Hi All,
I am using coupled Transport equations... I would like to add flux boundary condition at the walls of my geometry (which is square channel). This is the equation i would like to add... D1*grad(C1)  K1*C1*grad(Phi) = 0 D1*grad(C2)  K1*C2*grad(Phi) = 0 where C1 C2 and Phi are concentrations and potential respectively which I have obtained from solving my transport equation and poison equation (for Phi)...These equations are coupled... I solved them using simple boundary conditions but I would like to solve them using the above mentioned flux boundary condition.. can anyone help me out with regard to this... Thanks Regards Vishal 

June 26, 2009, 04:59 

#9 
New Member
Join Date: Mar 2009
Posts: 7
Rep Power: 9 
hi, Andy, could you give me some suggestion on how to use passive scalar method in fluent? I'm fresh hand for this method, totally have no mean for it. I appriciate for your help.
Last edited by Susan YU; June 26, 2009 at 05:05. Reason: post wrong place, but cannot delete 

September 6, 2012, 06:52 
ScalarTransportFoam with a nonconstant DT

#10 
New Member

Dear Friends,
I want to solve a very simple scalar transport problem(Heat transfer). The main issue is that the Diffusion Coefficient(DT) is not constant and is a function of z(in 1D) and grad(T).In fact DT should represent the effects of stability(Richardson Number) in the heat transfer model.(see the link: http://dl.dropbox.com/u/93154655/HeatTransfer1D.pdf). I defined the necessary fields but it seems that this solver doesn't work with a nonconstant DT?!! Does anybody have an idea about it? Thanks in advance. 

May 5, 2016, 13:31 

#11  
Member
anonymous
Join Date: Mar 2016
Location: Canada
Posts: 91
Rep Power: 2 
Quote:


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Passive scalar initial condition  Adam  CDadapco  1  May 13, 2008 17:23 
Passive Scalar  Andy R  FLUENT  0  January 10, 2007 15:49 
passive scalar boundaries  ultrich  CDadapco  0  July 12, 2005 11:20 
starwatch & passive scalar  isidro  CDadapco  1  June 24, 2005 23:59 
Mixing of a passive scalar  Maged Ismail  FLUENT  0  June 10, 2005 09:09 