Saline sinks in fresh water in the same way that heat rises in air (albeit upside-down). Small-scale 'salt bath' laboratory experiments allow us to isolate, visualise and investigate all sorts of fluid dynamical phenomena - from localised jets of hot air to whole-building ventilation flows to sandstorms more than a kilometre in height - anything where differences in temperature (and therefore density) are involved.
During 2015, Andy worked with the University of Cambridge and Dyson on an experimental project to better understand how to efficiently heat and cool our indoor spaces. By projecting jets of dyed saline into fresh water, he was able to model the jets of hot or cool air produced by fan heaters or cooling devices, and to explore how best to provide personalised comfort, whilst minimising energy use.
Zooming out to the level of a whole building, the salt bath technique can also be used to model natural ventilation flows. In this case, inputs of saline represent the heat generated by people and equipment within the building, as well as solar gains. The newly constructed James Dyson building, at the Cambridge University Engineering Department, will be naturally ventilated and Andy has designed a series of experiments to model the system.