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October 31, 2008, 06:50 
Hello,
I try to simulate th

#1 
New Member
Samuel Vogel
Join Date: Mar 2009
Posts: 20
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Hello,
I try to simulate the injection of water into a pipe flow. Therefor I took the dieselFoam tutorials case. I updated the Mesh and boundary files to my geometry with inflow and outflow and I replaced the injector position and the injection direction. This where the only changes I made. But I get a growing Evaporation Continuity Error from the beginning of the simulation. Is this related to the mesh resolution? What would be a good mesh resolution? Thanks Sammy 

October 31, 2008, 07:18 
The Evaporation Continuity err

#2 
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Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
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The Evaporation Continuity error assumes closed boundaries and does not account for the inflow/outflow. Neither does it account for liquid mass going out through the open boundaries.
It has survived since the implementation days where I had it to make sure the evaporated mass was accounted for in the PISO. In fact it could be removed now, since Im sure it works as it should. 

October 31, 2008, 07:33 
Thanks, but even when I close

#3 
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Samuel Vogel
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Thanks, but even when I close my pipe by putting zeroGradient BC on the outlet and inlet, the Evaporation Continuity Error grows. What could be the reason for this?
Thanks, Sammy 

October 31, 2008, 07:36 
zeroGradient is not closing th

#4 
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Niklas Nordin
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zeroGradient is not closing the pipe.
fixedValue uniform (0 0 0) on velocity is closing the pipe. 

December 1, 2008, 08:02 
Hello,
I still have problem

#5 
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Samuel Vogel
Join Date: Mar 2009
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Hello,
I still have problems with the mass balance. I simulate a simple pipe flow with inlet and outlet and I inject a constant amount of mass per time unit. when I calculate the mass of the evaporated outflow I don't get the injected mass per time. The pipe is long enough for complete evaporation of the liquid, there are no parcels leaving the geometry. The simulation is runnig long enough for a quasisteadystate situation. The outflow amount of the evaporated, injected C7H16 doesn't change with time. I calculate the whole mass flow at the outlet. Then I take this number for calculating the mass flow at the outlet of C7H16 by using the concentration in the C7H16 volScalarField at the outlet. I use the filter 'integrated variables' at the outlet. My questions: Is the dieselFoam solver suitable to solve such problems with injection in a flow (open system)? What could be my mistake? What is the unit of the species in the O2 / N2 / C7H16 volScalarField? Is it kg / kg or mol / mol. Both are leading to wrong numbers... Thanks Sammy 

December 1, 2008, 08:45 
Turn off injection.
Do you st

#6 
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Niklas Nordin
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Turn off injection.
Do you still have problem with mass balance? Try to increase the accuracy of the pressure equation. N 

December 4, 2008, 09:24 
Hi,
When I sompute the mass

#7 
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Samuel Vogel
Join Date: Mar 2009
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Hi,
When I sompute the massflow at the outlet I get the exact result of the added injected massflow plus the mass flow in the pipe. But the integrated massfraction of the injected speciest at the outlet is different. Where can I increase the accuracy of the pressure equation? Shall I use underrelaxation factors? 

December 18, 2008, 09:32 
Hi Niklas,
I have still the

#8 
New Member
Samuel Vogel
Join Date: Mar 2009
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Hi Niklas,
I have still the problem with wrong mass fraction at the outlet. I changed the geomtrys to a simple channel with a cube mesh. I inject C7H16 in a slow flow (1 m/s). When I look at the phi Field at the outlet, there is the added massflow of the injected mass and the mass in the channel flow. But when I look integrate over the C7H16 Field at the outlet, I get a massfraction of about 0.5. The massflow through the channel is about 1.39 e4 kg /s and the injected mass is constant at 1.0 e5 kg/s. So the correct concentration should be around 0.067 . What could be the reason for this behaviour of the C7H16 massflowpeofile? As air flow I use a pure N2 flow. My BCs are: k, epsilon, T, N2, YDefault: at the inlet: fixedValue at the wall and the outlet: zeroGradient U: at the inlet: fixedValue at the wall (0 0 0) at the outlet: zeroGradient spray: empty p: st the inlet and wall: zerogradient at the outlet: fixedValue I am wondering about the correct phiField at the outlet and the wrong mass fraction in the C7H16 File! Could you help me? Thanks Sammy PS: I put nCorrectors to 5, but the Problem is still there! 

December 18, 2008, 11:09 
Can u mail me the case so I ca

#9 
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Niklas Nordin
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Can u mail me the case so I can look at it myself.
pls dont mail it to my scania mail since I am on vacation. use my private address niklas dot nordin at nequam dot se 

January 26, 2010, 10:47 

#10 
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Dear sir,
After running a case using th dieselFoam solver, the evaporation continuity error has been steadily rising. From reading the above, can it be that I have misdefined my BC's. I assumed to spray a liquid into a highpressure closed cell. My BC's are defined as zerogradients. Thanks in advance for your time and expertise, Graham 

May 7, 2010, 17:40 
dieselFoam

#11 
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N. A.
Join Date: May 2010
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From where can you get the tutorials for dieselFoam? Is there a weblink where you can download the rest of the tutorials from?


December 26, 2010, 20:21 
vapor penetration

#12 
Member
amin
Join Date: May 2009
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hello dears
I have a question about ploting vapor penetration versus time in openfoam, how can I do it? how did you calculate vapor penetration in your numerical results? how much vapor mass fraction did you select if you used this method to plot vapor penetration? is it possible to explain more about how to plot vapor penetration by means of a numerical code like openFoam? regards 

December 27, 2010, 08:42 

#13 
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The vapor penetration can be determined through the gaseous mass fraction of the fuel (heptane?) you are injecting. Using paraview these fields can be visualized and exported for dataprocessing per time instance. You will need some kind of treshold criterion though. I used a Virtual Schlieren (matlab routine I could send you) technique to compare simulated vapor penetration results with experiments.
Pieter 

December 27, 2010, 18:55 
reply

#14 
Member
amin
Join Date: May 2009
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Hello Dear Pieter;
thank you for your reply, I sent a private massage to you including my email adress and my questions. regard Last edited by az1362f; December 27, 2010 at 19:21. 

December 30, 2010, 11:50 

#15 
Member
amin
Join Date: May 2009
Posts: 59
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Hello Dear Pieter;
thank you for your reply, I sent a private massage to you including my email adress and my questions. please send it for me. regard 

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