Hello, everyone,

Currently, I am using FLUENT to solve a cyclone problem (the cyclone is the same as Fraser:"Computational and experimental investigations in a cyclone dust separator", Pros Instn Mech Engrs Vol 211 Part E,1997. The turbulence model i uesed is RSM and RNG k-eps, the inlet velocity is 7.5m/s. But the maximum swirl veloity is only 5~6m/s compared with the experience 13m/s is very small. Could you give me an adivce and tell me why i can't get the correct result.

Best regards

Grid is too coarse?

The grid is : about 40 in the r-direction , 40 in the the-direction and 60 in the z-direction. I think the grid is very fine.

Just wsome wild guesses, have you checked; -Are you using higher order differencing schemes -Have you checked your Y+ -How do you treat the outlet from the cyclone, what kind out boundary conditions are you using and are they valid

try to change the values for K and eps., in your intial values and boundry conditions. then look for the false time step !

Hi, I am a new CFD user and till now I have not dived to the zoon of running multiphase flow or advanced turbulence models. I am also not FLUENT user. In the partial fulfillment in required for master degree I am making a comparison study between ALGOR FEA and PHOENICS for a simple flow. At the beginning I found that the results were fluctuation and relatively far from reality and experimental results although the problem I was handling is considered as theoretically solvable by means of analytical methods. I tried to change the grid specifications and found the result changing extremely within the grid dimensions. Due to this I ran a computer experiment by changing the grid specification and then plot the results against the grid dimension. The resulting curve gave me a good indication about the best grid dimensions setting. When I used this setting excellent results were obtained. I think you have to check what is the most suitable grid specification for your case and may be you will get good results. Very glad if this modest contribution could help S. S. Mudathir.

Dear Wang,

In my PhD dissertation, I´ve been doing LES of a hydrocyclone without air core and the results are quite satisfactory. There are some things you should bear in mind though: 1. this flow is anisotropic, and I´m not sure if the RNG k-eps would work fine, 2. normally, higher order schemes are necessary, even if you´re using RSM. I´ve come across papers showing good results for cyclone flow using the RSM and QUICK scheme. By the way, did you get the Rankine vortex for the swirl velocity?

Best regards,

Francisco.

P.S. For a glance at my preliminary results, visit my homepage: www.geocities.com/chicao99br