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Osborne Reynolds

Osborne Reynolds (23 August 1842–21 February 1912) was a British fluid dynamics engineer. He was born in Belfast, Ireland and died in Watchet in Somerset, England. He graduated from Cambridge University in 1867 after studying mathematics. In 1868 he became a professor of engineering at Owens College in Manchester (a predecessor of the Victoria University of Manchester, merged with the UMIST in 2004 to become the University of Manchester), and was only the second to hold this role in England. He retired in 1905.

Reynolds famously studied the conditions in which the flow of fluid in pipes transitioned from laminar to turbulent. From these experiments came the dimensionless Reynolds number for dynamic similarity—the ratio of inertial forces to viscous forces. In 1877 he was elected a fellow of the Royal Society, and in 1888 he won the Royal Medal.

Reynolds also proposed what is now known as Reynolds-averaging of turbulent flows, where quantities such as velocity are expressed as the sum of mean and fluctuating components. Such averaging allows for 'bulk' description of turbulent flow, for example using the Reynolds-averaged Navier-Stokes equations.

Reynolds' contributions to fluid mechanics were not lost on ship designers ("naval architects"). The ability to make a small scale model of a ship, and extract useful predictive data with respect to a full size ship, depends directly on the experimentalist applying Reynolds' turbulence principles to friction drag computations, along with a proper application of William Froude's theories of gravity wave energy and propagation.

A crater on Mars is named in his honour and the Reynolds Building at the University of Manchester is named after him.

The following achievements are attributed to, or named in honour of, Osborne Reynolds:

• Reynolds number
• Reynolds transport theorem
• Reynolds decomposition
• Reynolds stresses
• Reynolds-averaged Navier-Stokes equations
• Reynolds' dilatancy

• O'Connor, John J., and Edmund F. Robertson. "Osborne Reynolds". MacTutor History of Mathematics archive.
• Osborne Reynolds- Scientist, Engineer, Pioneer - University of Manchester