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May Lim September 29, 1998 10:23

Computational Modelling of Vortex Separators
Hi! I am very new to CFD. I have been working on the computational modelling of fluid flow and flocs behaviour in vortex separator (also know as fluidsep, hydronamic separator and swirl concentrator) using the Fluent cfd software packages for about 6 months.

I am looking at gaining more information on the following : * modelling of swirling flow * modelling of solid particle flow * modelling of flocs behaviour in a shear field using cfd.

If there is anyone who can recommend good references (books, journal papers etc) or tips on the above topics, I would appreciate it very much.

I would also like to get in contact with person involved in similar research. Thanks ! :)

Fabien Coppens September 30, 1998 08:14

Re: Computational Modelling of Vortex Separators

I did my PhD research on DNS and LES of aircraft trailing vortices. I concentrated in particular on vortex modeling and hydrodynamic stability. Feel free to get in touch with me through my e-mail address if you want some specific information.

Richard Hathway September 30, 1998 15:14

Re: Computational Modelling of Vortex Separators
Hi May Lim!

I have been searching for info about cyclone separation for a couple of weeks now.

I recently bought a Dyson Cyclone vaccum cleaner here in the UK.

The design of this machine seems very interesting - especially the "air cyclone" separator.

I have scanned the Internet looking for information on air cyclones - but I have not found much which explains how they work.

However I have just found this website ... you all seem to be fluid dynamics "gurus"!

I wonder if you could do me a very great favour and answer a couple of technical questions:

1. What is the air pressure profile and air velocity profile in an air cyclone separator? (I believe that air pressure is inversely proportional to velocity. Does this mean that the air pressure at the fast/narrow end of the cyclone cone is in fact very low?)

2. If I drilled a hole in the wall of the narrow end of the cyclone cone, would the dust (and air??) fly OUT OF the cone .... or would air come INTO the cone because of the lower internal air pressure? (I am having problems visualising the environment inside the cyclone!)

I hope that you, or any other "visitor" here, can help with these questions ... I don't want to drill holes in my vacuum cleaner to see what happens!

Thanks very much indeed for your help with this unusual request!

kindest regards,

Richard Hathway


John C. Chien September 30, 1998 16:48

Re: Computational Modelling of Vortex Separators
The principle is similar to that of a tornado, where the slow moving outer flow ( moving in tangential direction) is being drawn into the core and removed from the top (in the axial direction). Due to the conservation law of tangential momentum ( mass * tangential velocity = constant ), the tangential velocity increases as the radius is reduced ( the flow moves closer to the core). Along a streamline, the pressure drops as the energy of the fluid entering the device is being converted into kinetic energy ( 0.5 * rho * velocity * velocity ).

John C. Chien September 30, 1998 16:59

Re: Computational Modelling of Vortex Separators
Correction: the conservation of the tangential momentum is (mass * radius * tangential velocity = constant ). sorry for the typo.

Hyun S. Lee October 1, 1998 00:27

Re: Computational Modelling of Vortex Separators
Hi everyone!

Here are useful technical papers about cyclone separators:

##Analytical modelling

G. Ramanchandran, D. Leith, J. Dirgo and H. Feldman "Cyclone Optimization Based on a New Empirical

Model for Pressure Drop", Aerosol Science and Technology 15:135-148(1991)

##CFD related

F. Boysan, W.H. Ayers and J. Swithenbank " A Fundamental Mathematical Modelling approach to Cyclone Design" Trans. IChemE, Vol 60,222-230(1982)

W.D. Griffths and F. Boysan " Computational Fluid Dynamics(CFD) and Empirical Modelling of the Performance of a Number of Cyclone Samplers", J. Aerosol Sci. Vol 27, No.2, 281-304(1996)

Good luck! and if u want more information please E-mail me.

Rob Harwood November 13, 1998 13:36

Re: Computational Modelling of Vortex Separators
I have recently completed a 3 year study funded by EPSRC which used Fluent to investigate the flow pattern and particle retention efficiency performance of CSO structures including hydrodynamic separators. The work also included experimental validation of the numerical predictions. Early results of this work were presented in the proceedings of the 7th Int. Conf on Urban Storm Drainage held in Hannover, Germany in September 1996. Several further papers are currently being written. Other people using CFD to model hydrodynamic separators include N. Tyack at the University of Hertfordshire. Hydro International, the manufacturers of the Stormking are also investigating its performance using CFD. Hope this info is useful.

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