Ever wondered why water splays when it hits the sink before heading down the plughole? This everyday household occurrence, which has baffled engineers for centuries, has finally been explained by an Indian-origin researcher at the University of Cambridge.
The phenomenon, known as a hydraulic jump, was documented first by famous inventor and painter Leonardo da Vinci in the 1500’s.
Hydraulic jumps are harmless in our household sinks but they can cause violent waves, turbulence, and whirlpools in deeper water, said Rajesh Bhagat, a Ph.D. student at St John’s College, the University of Cambridge in the UK. Since the 1820s scientists have believed that hydraulic jumps occur partly as a result of the gravitational pull.
However, the latest study published in the Journal of Fluid Mechanics has disproved this longstanding theory.
Bhagat fired jets of water upwards and sideways onto flat surfaces and witnessed exactly the same hydraulic jumps as those when the water flowed downwards. He suspected they could all be affected by the same factors – surface tension and viscosity.
By altering these attributes of the water he was able to accurately predict the size of the hydraulic jumps.
This was regardless of which direction the water was moving – debunking the 200-year-old gravitational theory as the cause of a kitchen sink type hydraulic jump.