# discrete phase Boundary condition

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 April 13, 2004, 03:22 discrete phase Boundary condition #1 prasanth Guest   Posts: n/a 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

 April 13, 2004, 09:01 Re: discrete phase Boundary condition #2 David Guest   Posts: n/a 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

 April 13, 2004, 09:53 Re: discrete phase Boundary condition #3 prasanth Guest   Posts: n/a 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

 April 13, 2004, 10:16 Re: discrete phase Boundary condition #4 prasanth Guest   Posts: n/a Also I want to know what we have to specify for mean mixture fraction and variance>?? thanks in advance prasanth

 April 13, 2004, 21:23 Re: discrete phase Boundary condition #5 danel Guest   Posts: n/a I think trap means incomplete,escape means particle flow with fluid out of boundary

 April 14, 2004, 01:04 Re: discrete phase Boundary condition #6 prasanth Guest   Posts: n/a 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

 April 14, 2004, 02:53 Re: discrete phase Boundary condition #7 danel Guest   Posts: n/a I am sorry,I dcannot reply this question.In my cases particles come in with fluid.

 April 14, 2004, 02:56 Re: discrete phase Boundary condition #8 danel Guest   Posts: n/a I think in fluent6.1'Tutorial 13: Using the Non-Premixed Combustion Model may give you some help.

 April 14, 2004, 04:28 Re: discrete phase Boundary condition #9 prasanth Guest   Posts: n/a They also doing same thing as yours. thank you sir

 April 14, 2004, 07:02 Re: discrete phase Boundary condition #10 David Guest   Posts: n/a 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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