3 - Separation and Time-Dependent Flows

Summary

Introduction and key concepts

Fluid mechanics is fortunate to have fundamental equations and pioneering contributions that are primarily due to Sir Isaac Newton (1643–1727), Gottfried W. Leibniz (1646–1716), Leonhard Euler (1707–1783), John Bernoulli (1667–1748), Daniel Bernoulli (1700–1782), Jean le Rond d’Alembert (1717–1783), Joseph-Louis Lagrange (1736–1813), Pierre Simon de Laplace (1749–1827), Barré de Saint Venant (1797–1886), James A. Froude 1818–1894), Sir William Thomson (Lord Kelvin) (1824–1907), Sir George G. Stokes (1819–1903), Herman L. F. von Helmholtz (1821–1894), Ernst Mach (1838–1916), Claude Navier (1785–1836), John William Strutt (Lord Rayleigh) (1842–1919), Arnold J. W. Sommerfeld (1868–1951), Ludwig Prandtl (1875–1953), G. I. Taylor (1886–1975), among many others.

Although our understanding of the fundamental concepts of fluid mechanics is sound, the applications are in a continual state of flux. In the years to come, either the laws of physics of turbulence will be discovered or delegated to heuristic reasoning, meticulous observations and measurements, physical and numerical simulations, and rigorous analyses.

Batchelor (1967) stated, “One of the most important problems of fluid mechanics is to determine the properties of the flow due to moving bodies of simple shape, over the entire range of values of Re, and more especially for the large values of Re corresponding to bodies of ordinary size moving through air and water.” The advances in fluid mechanics over the past 50 years have only enhanced the importance of the problem.