Reynolds, Osborne (1842–1912), engineer, was born 23 August 1842 in Belfast, son of the Rev. Osborne Reynolds and Jane Reynolds (née Hickman). He came from a clerical family: his father, grandfather, and great-grandfather were rectors of Debach, Suffolk. His father was thirteenth wrangler (ranking in the mathematical tripos at Cambridge University) in 1837 and subsequently fellow of Queens’ College, Cambridge, principal of Belfast Collegiate School, headmaster of Dedham Grammar School, Essex, and finally, in his turn, rector of Debach.
Reynolds's early education was by his father, first at Dedham and afterwards privately. In 1861, at the age of 19, he entered the workshop of Edward Hayes, mechanical engineer, of Stony Stratford, in order (as Hayes expressed it) ‘to learn in the shortest time possible how work should be done, and, as far as time would permit, to be made a working mechanic before going to Cambridge to work for honours’. In October 1863 he was admitted to Queens' College, Cambridge, to study for the mathematical tripos. The entry requirements included a pass in Greek achieved by Reynolds through ‘the obstinate labour of a few weeks’ to reach the standard of the ‘previous’ examination. He graduated in 1867 as seventh wrangler and was immediately elected to a fellowship of Queens’ College.
Reynolds left Cambridge to enter the offices of Lawson & Mansergh, civil engineers in London, but just one year later, in 1868, at the age of 26, he was appointed to the newly established chair of engineering at Owens College, which later became the Victoria University of Manchester. He occupied this chair for thirty-seven years, retiring in 1905. This was almost the first chair of engineering in England. That distinction probably lies with King's College, London, where William Hosking was appointed in 1840 at the same time as Lewis Gordon became regius professor of civil engineering and mechanics at the University of Glasgow. In Ireland the first chair of civil engineering was established at TCD in 1842, while chairs of civil engineering were established at the queen's colleges in Belfast, Cork, and Galway in 1849. The selectors for the Owens College chair were highly successful men, distinguished in the practice of business and engineering in the Manchester area, and their selection of such a young and relatively inexperienced engineer seems remarkable. Reynolds's subsequent career proved their choice to be inspired.
Reynolds was of the view that engineering students required a strong scientific training. The course of instruction which he arranged for his students was noteworthy for the thoroughness and completeness of the theoretical groundwork. He was of the opinion that engineering, from the student viewpoint, was a unified whole, requiring the same fundamental training irrespective of the nature of the specialisation to come afterwards in practice. He was equally concerned with the practical aspects of engineering, and established and developed the famous Whitworth engineering laboratories. Several of the more important appliances in these laboratories, such as the triple-expansion engines and the hydraulic brakes, were specially designed by Reynolds for study by students and for research, and contained many novel features.
There are two aspects to Reynolds's scientific work. As an engineering professor he addressed some major practical issues of his time. These included ship propulsion, pumps, turbines, models of rivers and estuaries, cavitation, condensation of steam, thermodynamics of gas flow, rolling friction, and lubrication. But he was also concerned with understanding the fundamental scientific principles underlying engineering processes, and hence he developed fundamental theory in a number of areas of the mechanical sciences. Two examples are presented here as illustrations. Many others might have been similarly selected.
Reynolds conducted experiments of fluid flow in long glass tubes. He was able to demonstrate (in terms of modern notation, not used by Reynolds) that the transition to turbulence of flow in a pipe occurs at a critical value of what is now called ‘the Reynolds number’. The critical value of the Reynolds number (for transition to turbulence of pipe flow) is approximately 2,000. Turbulence is an extremely important theoretical and technological problem, since the presence of turbulence increases resistance to motion; it augments heat transfer rates and general diffusion properties of fluids and gases; it creates noise both directly and through forced vibrations of adjacent structures. Reynolds provided insight into turbulent behaviour in a simple experimental situation; research on turbulent behaviour continues unabated to the present, since turbulence normally occurs in complicated geometries and in a variety of environments.
From the middle of the nineteenth century, industrial advance saw the development and operation of a vast range of machines such as lathes, drills, mechanical harvesters, threshing machines, sewing machines, typewriters, road carriages, railway engines and carriages, which depended for their efficient operation on the lubrication of their moving parts. This technology of lubrication, friction, and wear is called tribology. There was concern in industry at the weakness in design of bearings, evidenced by failure in operation. This exposed the lack of understanding of the physical basis of effective lubrication. Reynolds sought to establish a hydrodynamic model for the thin film of lubricant in journal bearings which would yield pressure distributions in agreement with experiments. In this he was successful. From his model he identified an equation (now called the ‘Reynolds equation’) which offers understanding of the underlying scientific basis for the effective operation of gas and fluid bearings. Research on and development of thin film lubrication devices continued to be vigorously active at the start of the twenty-first century.
Osborne Reynolds married first (1868) Charlotte, daughter of Dr Chadwick of Leeds, but unfortunately she died a year later; there was one son from this marriage, who died in 1879. He married secondly (1881) Annie Charlotte, daughter of the Rev. H. Wilkinson, rector of Otley, Suffolk; they had three sons and a daughter. One of the sons graduated in engineering at Manchester in 1908 and later held the Vulcan and Osborne Reynolds fellowships. Failing health caused Reynolds to retire in 1905. His retirement years were spent in Watchet, Somerset, where he died on 21 February 1912. A portrait (1904) by the Hon. John Collier is at Manchester University.