# Unexpected Behavior of fluidized bed

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 April 5, 2020, 04:33 Unexpected Behavior of fluidized bed #1 New Member   Chanon Bunsaksit Join Date: Mar 2020 Posts: 3 Rep Power: 6 Hello I simulated the psuedo 2D fluidized bed reactor with CFD-DEM model. When I simulate the high gas velocity, the particles are clogged on the outlet reactor where I set discrete phase BC Type is "reflect" and no fall to the bottom of rector until the divergent calculation is appeared. However, I have completely result when I get the low gas velocity. How can I solve this problem when I want to simulate the high velocity where the geometry of the reactor can't change the dimension. Thank you Chanon

 April 6, 2020, 08:23 Reflect #2 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36 If the outlet is acting like a wall for particles and the momentum of continuous fluid is high enough to push those to the outlet, then this is the expected behavior. You have to compare the drag force, based on the drag formulation you are using, against the weight of the particle. If the drag is high, particle will rise up and hit the outlet. Of course, weight of each particle could be same but drag is not, but if it is quite high for few of the particles, then most likely, it is more than weight for almost each of the particle. ChanonB likes this. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

 April 11, 2020, 13:43 #3 New Member   Chanon Bunsaksit Join Date: Mar 2020 Posts: 3 Rep Power: 6 Thank you for your answer. I have a question for velocity. I want to create the packed bed of 200 micron particle. Due to a large number of particle, I will generate the injection which a parcel, 2.5 mm diameter, has 2000 particles for each parcel. I find the velocity based on minimum fluidized velocity by archimedes number. I want to know what the diameter which I use to calculate, particle diameter or parcel diameter? thank you Chanon

 April 11, 2020, 15:25 Diameter #4 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36 Fluent will do all the calculations based on the diameter specified by the user in the injection. Do note that parcel diameter should not be representing an equivalent diameter calculated using volume or mass of all represented particles. Parcel's diameter should be same as particle diameter. User should also do all the calculations based on the actual (particle) diameter. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

 Tags cfd-dem, dem, fluidized beds