Panta rhei — “everything flows.” The phrase is attached to the Greek philosopher Heraclitus, and it is a good motto for this book. Water and air are the most familiar things in the world, yet the science of how they move took more than two thousand years to build, and it is still unfinished. Along the way, the study of flow shaped how people thought about the heavens, about energy, about machines and war, and about the water that sustains cities and farms.
This short web textbook tells that story for students of civil engineering, hydraulics and hydrology. It is not a replacement for a textbook of fluid mechanics. Instead, it answers questions that a textbook usually leaves out: Who first wrote down the equations you use, why they were interested in the problem, and what was happening around them when they did it.
Why read a history of fluid mechanics?¶
Equations have authors and contexts. Bernoulli’s equation, the Navier–Stokes equations, the Reynolds number, Darcy’s law and the unit hydrograph were each the answer to a practical or philosophical problem of their time: supplying water to a city, aiming a cannon, building a faster ship, flying, or forecasting the weather. Knowing the problem makes the equation easier to understand and to remember.
Theory and practice have often been apart. For two centuries, mathematicians produced an elegant “hydrodynamics” that could not predict the drag on a ship, while engineers built a practical “hydraulics” from experiments and empirical coefficients. Much of the history in this book is the story of how the two were finally reconnected, through the concepts of similarity, viscosity, the boundary layer and turbulence.
Science and society flow together. Fluid mechanics grew up alongside revolutions in astronomy, politics and industry. The word revolution itself began as a term for the turning of the heavens. Steam engines, artillery, telegraph cables, aircraft, rockets and computers all fed problems into the science of flow, and the science fed answers back. Wars and emigrations moved people and ideas from one country to another.
Water science is part of the same story. Hydrology grew from the same roots: the measurement of rainfall and river flow, the water balance, and the physics of evaporation and seepage. The last chapter traces that history up to the present.
How this book is organized¶
| Page | Period | Main questions |
|---|---|---|
| Timeline | All periods | What happened when? |
| 1 Before the Scientific Revolution | Antiquity – 1500s | How did ancient and medieval engineers move water without a theory of flow? |
| 2 The Scientific Revolution | 1580s – 1720s | How did experiments on air and water, and the debate over Descartes’s vortices, lead to Newton’s Principia? |
| 3 The Enlightenment and analytical hydrodynamics | 1720s – 1790s | How did the Bernoullis, Euler, d’Alembert and Lagrange turn flow into mathematics, and why did it fail to predict drag? |
| 4 The industrial age and engineering hydraulics | 1790s – 1880s | How did the French Revolution, steam power and thermodynamics, ships and canals produce the Navier–Stokes equations and engineering hydraulics? |
| 5 Turbulence and boundary layers | 1880s – 1940s | How did Reynolds, Prandtl, von Kármán, Taylor and Kolmogorov reconcile theory and experiment? |
| 6 War, flight and computing | 1890s – today | How did aviation, two world wars, rockets and computers transform fluid mechanics? |
| 7 A history of hydrology | Antiquity – today | How did the water cycle become a quantitative science? |
| 8 Who lived when | All periods | Which of these people were alive at the same time? |
Each chapter ends with a short list of further reading. Equations are included where they help to explain an idea; you can skip them and still follow the story.
A note on sources¶
The narrative draws on standard histories of hydraulics, hydrodynamics, aerodynamics and hydrology, listed at the end of each chapter. Its approach of reading the history of fluid mechanics alongside political, industrial and intellectual revolutions owes much to Min Tae-gi’s Panta Rhei (판타 레이: 혁명과 낭만의 유체 과학사, ScienceBooks, 2022), a Korean book that tells the history of fluid science from Leonardo da Vinci’s vortex drawings to modern rocketry. Readers of Korean are encouraged to read it alongside this text.
Dates are given in the Common Era unless marked BCE. Where historians disagree about a date or an attribution, the text says so.
Further reading¶
Rouse, H., & Ince, S. (1957). History of Hydraulics. Iowa Institute of Hydraulic Research.
Darrigol, O. (2005). Worlds of Flow: A History of Hydrodynamics from the Bernoullis to Prandtl. Oxford University Press.
Anderson, J. D. (1997). A History of Aerodynamics and Its Impact on Flying Machines. Cambridge University Press.
Biswas, A. K. (1970). History of Hydrology. North-Holland.
Min, T. (2022). Panta Rhei: 혁명과 낭만의 유체 과학사 (in Korean). ScienceBooks.