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 fpingqian November 25, 2004 20:51

Two way coupling in DPM

 Rob Hart November 26, 2004 07:17

Re: Two way coupling in DPM

If your particles all have the same mass, then the number concentration is proportional to the mass concentration, and you could write a simple custom field function.

As for the whole collision thing, I think it's probably possible, but it's gonna be a serious piece of work. The trick will be locating when collisions occur, particularly if the size of the particle is small compared to the size it can move in any given time step, and/or the frequency of collisions is high.

Good luck

Rob

 Jan Rusås November 27, 2004 21:30

Re: Two way coupling in DPM

"inlet solid mass loading is 0.0533,and the solid volume fraction is 2.36e-5" You dont neccesary have a two-way coupling at those conditions. The mass loading is actually not very high, it is in the upper range of one way coupling or lower range of two-way. The coupling also depends on the Stokes number, i.e. the the particle response time (depends on the density of your particles, diameter, viscosity, etc.) and a global time scale. I do not understand why you multiply the drag with a factor ...., why is it neccesary? Regards Jan

 fpingqian November 28, 2004 23:47

Re: Two way coupling in DPM

Thanks for your answering my questions. To Rob Unfortunately in my simulation, particles have Rosin-Rommler distribution, so I don¡¯t know how to deal with this. In addition, as for collision, I only consider particles collision between the current cell and its adjacent ones, and each cell has one or two particles, because I use the numerical particles (i.e. one numerical particle stands for many particles). My question is that how I can get the particles¡¯ information which is in the adjacent current cell. Hope you can give me some advice, thanks very much. To Jan I know as for my question, sometimes one-way coupling is enough, but I want to extend the range of my question, so I have to use the two-way coupling. Elghobashi (1994) has mapped the interaction between particles and turbulence by means of two characteristic dimensionless quantities, viz. the volume fraction of particles, and the ratio of the particle response or relaxation time, and the Kolmogorov time scale. When the volume fraction of particles is 2.36e-5, the momentum transfer from the particles is large enough to alter the turbulence structure, so I have to consider the two-way coupling. After considering the two-way coupling, the velocity of gas phase should be damped, although the turbulence intensity may be not change. I don¡¯t know why my simulation has not this result. Why do I multiply the drag with a factor much bigger than 1? I think I can view the individual numerical particles as parcels and enhance the influence of the particles on the gas flow field by means of this method. Maybe not right, welcome you give me some advice. Thanks in advance. Best regards to you, fpingqian

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