Osborne Reynolds (23.08.1842- 21.02.1912) was an English physicist and engineer and a Fellow of the Royal Society (1877). He was born in Belfast. He graduated from the University of Cambridge (1867). In 1868-1905 he was professor at the University of Manchester.
His research was in mechanics, hydrodynamics, heat, electricity, magnetism and astrophysics, but chiefly in the theory of turbulence, the theory of dynamic similarity in the flow of a viscous liquid, and the theory of lubrication. He contributed to the laws of the flow of water in pipes. In 1883 he established that the transition from laminar to turbulent flow occurs when a dimensionless quantity exceeds a certain critical value (the Reynolds number). He developed (1886) the hydrodynamic theory of lubrication. He determined the mechanical equivalent of heat and designed a number of turbines and centrifugal pumps. He studied the phenomenon of cavitation. He gave a theory of the radiometer.
The Royal Medal (1884).