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Old   April 13, 2004, 03:22
Default discrete phase Boundary condition
  #1
prasanth
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hai

In my problem for non-premixed combustion, I am sending coal by using "release from surfaces" option and taking coal inlet as the surface....now, what boundary condition shall I give for coal inlet in boundary conditions panel..."only coal is sent throught the coal inlet"///

air is coming from other inlet....

waiting for a kind response

Prasanth
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Old   April 13, 2004, 09:01
Default Re: discrete phase Boundary condition
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David
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hi,

from my point of view you can use mass flow inlet as a boundary condition for coal.

let me know if this helps

regards

David
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Old   April 13, 2004, 09:53
Default Re: discrete phase Boundary condition
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prasanth
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hai

Thanks for your kind reply. I have given mass flow condition itself. I want to know which is reasonable: 'trap' or 'escape'.

thanks and regards
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Old   April 13, 2004, 10:16
Default Re: discrete phase Boundary condition
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prasanth
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Also I want to know what we have to specify for mean mixture fraction and variance>??

thanks in advance prasanth
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Old   April 13, 2004, 21:23
Default Re: discrete phase Boundary condition
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danel
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I think trap means incomplete,escape means particle flow with fluid out of boundary
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Old   April 14, 2004, 01:04
Default Re: discrete phase Boundary condition
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prasanth
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Hello Sir

Thanx for your reply. But still we are having doubt with it. whether escape mode escapes out all the particles when it approaches the inlet/outlet boundary? If we don't want the particle to escape through some inlet/outlet, what type we have to select: "escape" or "trap"? when will we use the other mode "wall jet" (application?)?

In defining discrete phase, we will specify velocity and flow rate for coal; is it needed to specify the mass flow rate at the mass flow inlet B C at coal-inlet?

* In our case, at coal inlet,only coal goes into the chamber, not along with air. Air comes through other inlet.

Regards Prasanth
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Old   April 14, 2004, 02:53
Default Re: discrete phase Boundary condition
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danel
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I am sorry,I dcannot reply this question.In my cases particles come in with fluid.
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Old   April 14, 2004, 02:56
Default Re: discrete phase Boundary condition
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danel
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I think in fluent6.1'Tutorial 13: Using the Non-Premixed Combustion Model may give you some help.
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Old   April 14, 2004, 04:28
Default Re: discrete phase Boundary condition
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prasanth
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They also doing same thing as yours.

thank you sir
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Old   April 14, 2004, 07:02
Default Re: discrete phase Boundary condition
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David
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hi,

this is what FLuent's manual says:

``trap'' terminates the trajectory calculations and records the fate of the particle as ``trapped''. In the case of evaporating droplets, their entire mass instantaneously passes into the vapor phase and enters the cell adjacent to the boundary

``reflect'' rebounds the particle off the boundary in question with a change in its momentum as defined by the coefficient of restitution

``escape'' reports the particle as having ``escaped'' when it encounters the boundary in question. Trajectory calculations are terminated

``wall-jet'' means that the direction and velocity of the droplet particles are given by the resulting momentum flux, which is a function of the impingement angle, $\phi$, and Weber number.

I didn't know wall jet. I think it is a new BC included into DPM in fluent.

FLUENT assumes the following boundary conditions:

* ``reflect'' at wall, symmetry, and axis boundaries, with both coefficients of restitution equal to 1.0

* ``escape'' at all flow boundaries (pressure and velocity inlets, pressure outlets, etc.)

* ``interior'' at all internal boundaries (radiator, porous jump, etc.)

I hope this helps

regards

David
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