An English engineer and physicist, best known for his work in the fields of hydraulics and hydrodynamics, Reynolds was born in Belfast on Aug. 23, 1842. Gaining early workshop experience and graduating at Queens College Cambridge in 1867, he became the first professor of engineering in the Owens College, Manchester in 1868. He was elected a Fellow of the Royal Society in 1877 and a Royal Medallist in 1888.
Reynolds' studies of condensation and the transfer of heat between solids and fluids brought about radical revision in boiler and condenser design, while his work on turbine pumps laid the foundation of their rapid development. A fundamentalist among engineers, he formulated the theory of lubrication (1886), and in his classical paper on the law of resistance in parallel channels (1883) investigated the transition from smooth, or laminar, to turbulent flow, later (1889) developing the mathematical framework which became standard in turbulence work.
His name is perpetuated in the "Reynolds Number", which provides a criterion for dynamic similarity and hence for correct modelling in many fluid flow experiments.
Among his other work was the explanation of the radiometer and an early absolute determination of the mechanical equivalent of heat. Reynolds retired in 1905 and died at Watchet, Somerset, on Feb. 21, 1912.