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DieselFoam Spray Evaporation Continuity Error

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Old   October 31, 2008, 06:50
Default Hello, I try to simulate th
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Samuel Vogel
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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
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Old   October 31, 2008, 07:18
Default The Evaporation Continuity err
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Niklas Nordin
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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.
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Old   October 31, 2008, 07:33
Default Thanks, but even when I close
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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
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Old   October 31, 2008, 07:36
Default zeroGradient is not closing th
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zeroGradient is not closing the pipe.

fixedValue uniform (0 0 0) on velocity is closing the pipe.
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Old   December 1, 2008, 08:02
Default Hello, I still have problem
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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 quasi-steady-state 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
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Old   December 1, 2008, 08:45
Default Turn off injection. Do you st
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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
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Old   December 4, 2008, 09:24
Default Hi, When I sompute the mass
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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?
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Old   December 18, 2008, 09:32
Default Hi Niklas, I have still the
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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 e-4 kg /s and the injected mass is constant at 1.0 e-5 kg/s. So the correct concentration should be around 0.067 . What could be the reason for this behaviour of the C7H16 mass-flow-peofile? 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 phi-Field 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!
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Old   December 18, 2008, 11:09
Default Can u mail me the case so I ca
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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
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Old   January 26, 2010, 10:47
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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
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Old   May 7, 2010, 17:40
Default dieselFoam
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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?
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Old   December 26, 2010, 20:21
Default vapor penetration
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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
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Old   December 27, 2010, 08:42
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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
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Old   December 27, 2010, 18:55
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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.
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Old   December 30, 2010, 11:50
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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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