Serendipity in the development of demonstration experiments

Abstract

Some experiments drawn from granular mechanics, fluid mechanics and heat and mass transfer are described. These experiments demonstrate the following aspects: (i) the deformation of a dense assembly of particles such as sand leads to an increase in the porosity, (ii) the stress field in a static bed of granular material is non-hydrostatic, (iii) the motion of an hour-glass in a sealed cylinder filled with water is affected by wall friction, (iv) when a syringe containing salt water is lowered into a cylinder filled with fresh water, oscillatory flow is observed due to a convective instability, (v) the 'drinking duck' (a toy) works better when water is replaced by a more volatile liquid such as methanol. It is also shown that the accidental use of variations from the published procedures leads to interesting results.