Osborne Reynolds - Fluid Mechanics

Fluid Mechanics

Reynolds most famously studied the conditions in which the flow of fluid in pipes transitioned from laminar flow to turbulent flow. From these experiments came the dimensionless Reynolds number for dynamic similarity — the ratio of inertial forces to viscous forces. 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.

His publications in fluid dynamics began in the early 1870s. His final theoretical model published in the mid 1890s is still the standard mathematical framework used today. Examples of titles from his more groundbreaking reports:

Improvements in Apparatus for Obtaining Motive Power from Fluids and also for Raising or Forcing Fluids. (1875)

An experimental investigation of the circumstances which determine whether the motion of water in parallel channels shall be direct or sinuous and of the law of resistance in parallel channels. (1883)

On the dynamical theory of incompressible viscous fluids and the determination of the criterion. (1895)

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. Reynolds himself had a number of papers concerning ship design published in Transactions of the Institution of Naval Architects.