The last 10 years has seen an unprecedented change in the domestic vacuum cleaner market in the United Kingdom, thanks to the pioneering Dual Cyclone™ vacuum cleaner designs of James Dyson. His company, set up in 1993, has grown to encompass over $250M of the British vacuum cleaner market over the last seven years, due to its radical double cyclone designs. These designs make use of a classic conical internal cyclone (for small particles) and a cylindrical external cyclone (for big particles). Operated in series, the dual cyclones both filter and collect different diameters of household dirt. Dyson claims that the cyclones maintain a 100 percent suction rate 100 percent of the time. This revolutionary technology has become a best seller in the UK and has even glamorized the household chore of vacuuming for the first time in 50 years!

A Dyson DC05 cyclonic vacuum cleaner with superimposed FLUENT CFD dirt particle pathlines

The Dyson Dual Cyclone technology can process up to 30 liters of air per second and remove particles smaller than a thousandth of a millimeter in diameter. The dusty air first enters the outer cyclone through a tangential inlet, which causes the air and dust to spin rapidly. The centrifugal force generated by this rotation causes the dust particles, which are much denser than air, to be thrown out of the airflow towards the wall. The airflow then passes through a perforated shroud into the inner cyclone. Together, the outer cyclone and the shroud remove all but very fine particles from the flow. The inner cyclone also has a tangential inlet to spin the air and generate a large centrifugal force. Dust particles are subjected to forces of more than 100,000 times the strength of gravity, so even the finest particles accelerate rapidly toward the wall. Near the wall, the air flows downward into the hopper where the dust is collected. Near the cyclone center, clean air flows upward and escapes through a chimney-like tube.

From a fluid flow point of view, Dual Cyclone vacuum cleaners cover some very complex flow phenomena, including highly turbulent swirling flow, complex flow passageways, large discrete phase particles of various shapes and texture, and time varying effects. To model these phenomena correctly within realistic industrial time frames requires a highly robust, efficient, and accurate CFD code. This fact was recognized by Dyson in 1997 when it sought to license FLUENT. FLUENT was the first CFD code to offer Dyson the flexibility of fully unstructured meshes without compromising accuracy in highly swirling flow conditions. Dyson continues to expand its product offerings and it hopes to use Fluent's CFD codes to solve many other complex flowfields.

To view an animation of the Dyson DC05 vacuum cleaner, point your browser to: www.dyson.com/technology/page2.asp

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