By the mid nineteenth century fundamental advances were coming on
several fronts. The physician Jean Poiseuille (1799–1869) had accurately
measured flow in capillary tubes for multiple fluids, while in Germany
Gotthilf Hagen (1797–1884) had differentiated between laminar and turbulent
flow in pipes. In England, Lord Osborn Reynolds (1842–1912) continued
that work and developed the dimensionless number that bears his name.
The late nineteenth century was notable for the expansion of fluid theory
by Irish and English scientists and engineers, including in addition to
Reynolds and Stokes, William Thomson, Lord Kelvin (1824–1907), William
Strutt, Lord Rayleigh (1842–1919), and Sir Horace Lamb (1849–1934).
These individuals investigated a large number of problems including dimensional
analysis, irrotational flow, vortex motion, cavitation, and waves. In a
broader sense their work also explored the links between fluid mechanics,
thermodynamics, and heat transfer.