Researchers carry out tests in bid to develop quiet appliances

The immediate applications will be for the next generation of vacuum cleaners and fans, but the research also has the potential to improve the development of silent helicopter intakes, industrial refrigerators, jet engines and wind turbines.

The first of two planned projects focuses on the aeroacoustics of cyclone separators — complex 3D flows that swirl about a central column of fluid in line with the axis of rotation.

‘The core itself becomes unstable beyond a certain velocity of operation and when this happens the core starts precessing — the thing starts wobbling — and the frequency at which this wobbles is the frequency of the noise,’ said Dr Anurag Agarwal, project lead and lecturer in aeroacoustics at Cambridge. ’This is a large source of noise and we’d like to understand the physics of this.’

Some of the planned experiments will involve building a simplified model of a cyclone separator in water, then using dye injectors within a Perspex tunnel to gather data.