courseshub.world · Lives in Mathematics and Physics

G. I. Taylor

Sir Geoffrey Ingram Taylor

A course in two strands: the life of George Boole's grandson, a Cambridge physicist who flew, sailed and measured everything he theorized, and the physics of rotating fluids, turbulence, dislocations, blast waves, interfacial instabilities and slow viscous flow that he founded.

Born 7 March 1886, London Died 27 June 1975, Cambridge Taylor vortices 1923 Level advanced undergraduate → graduate
Taylor vortices, in a cut through the axis. When the inner cylinder spins fast enough, the gap fills with stacked rings of counter-rotating cells, each about as tall as the gap is wide.
Lesson 00

How to use this course

Geoffrey Ingram Taylor, known to everyone as G. I., spent nearly his whole working life in Cambridge, mostly without teaching duties, and published some 250 papers across fluid mechanics, solid mechanics, meteorology and oceanography. His method was distinctive. He chose a physical question, often prompted by something he had seen at sea, in the air or in a war, built a simple apparatus to look at it, and then found the mathematical model that matched what he saw. Many of his results carry his name: Taylor vortices, the Taylor–Proudman theorem, Taylor dispersion, the Taylor microscale, the Rayleigh–Taylor instability, the Saffman–Taylor fingers, the Taylor cone.

Part I traces his formation as the grandson of George Boole, a Cambridge mathematician turned meteorologist, and a wartime pilot. Part II presents his main contributions in rough chronological order. Part III covers the Second World War, including his work on the atomic bomb, and his long and productive retirement.

Prerequisites for Part II
  • Vector calculus, ordinary and partial differential equations, separation of variables.
  • The Euler and Navier–Stokes equations, vorticity, and Bernoulli's equation at the level of a first fluids course.
  • Elementary probability: means, variances, correlation functions.
  • For Lesson 06, linear elasticity (shear modulus) and the idea of a crystal lattice.
  • For Lesson 10, electrostatics in a conductor and Legendre functions.

Each technical lesson opens with a paragraph for the general reader, then gives precise statements, derivations and exercises with folded solutions. Many exercises are back-of-the-envelope estimates in Taylor's own style: physical reasoning, dimensional analysis, and a number at the end.

Reference

Timeline

1886Born 7 March in St John's Wood, London, son of the artist Edward Ingram Taylor and Margaret Boole, daughter of George Boole.
1899–1905University College School, London.
1905Scholarship to Trinity College, Cambridge.
1907–08Twenty-second wrangler in Part I of the Mathematical Tripos (1907); first-class honours in Part II of the Natural Sciences Tripos (1908).
1909Interference fringes with feeble light, his first paper. Work on shock waves wins a Smith's Prize.
1910Prize fellowship at Trinity.
1911Schuster Reader in Dynamical Meteorology at Cambridge.
1913Meteorologist aboard the Scotia on the North Atlantic ice patrol set up after the loss of the Titanic.
1914–18Royal Aircraft Factory, Farnborough. Pilot's certificate (1915); parachute jumps.
1915Eddy motion in the atmosphere; Adams Prize for an essay on turbulent motion in fluids.
1919Fellow of the Royal Society. Returns to Trinity as fellow and lecturer in mathematics.
1921Diffusion by continuous movements.
1923Royal Society Yarrow Research Professor, at the Cavendish Laboratory, until 1952. Taylor–Couette stability paper; experiments on rotating fluids; Bakerian Lecture.
1925Marries Grace Stephanie Frances Ravenhill on 15 August.
1933Royal Medal of the Royal Society.
1934Dislocation theory of plastic deformation, independently of Egon Orowan and Michael Polanyi.
1935Statistical theory of turbulence.
1936Royal Institution Christmas Lectures on ships; one of them is the first Christmas Lecture televised by the BBC.
1938The spectrum of turbulence: the frozen-turbulence hypothesis.
1939–45Consultant on blast waves, underwater explosions and the effects of bombs on structures.
1944Knighted; Copley Medal.
1944–45Visits Los Alamos with the British mission; witnesses the Trinity test on 16 July 1945.
1946US Medal for Merit.
1950Papers on the intense blast wave and on the instability of accelerated interfaces.
1951Analysis of the swimming of microscopic organisms.
1952Retires from the Yarrow professorship; keeps working at the Cavendish for twenty years.
1953Dispersion of soluble matter in a tube (Taylor dispersion).
1958Viscous fingering, with Philip Saffman.
1964Disintegration of water drops in an electric field: the Taylor cone.
1967Death of his wife Stephanie.
1969Order of Merit.
1972Severe stroke ends his research.
1975Dies 27 June at his home in Cambridge, aged 89.
Part I · Formation
Lesson 01

London and the Booles, 1886–1905

Geoffrey Ingram Taylor was born on 7 March 1886 in St John's Wood, London. His father, Edward Ingram Taylor, was an artist who painted landscapes and flowers and designed decorative interiors for ocean liners. His mother, Margaret Boole, was the second daughter of the logician George Boole and of Mary Everest Boole, a writer on the teaching of mathematics. Several of Margaret's sisters were remarkable. Alicia Boole Stott found the regular polytopes of four-dimensional space without formal training in mathematics; Ethel Lilian Voynich wrote the novel The Gadfly. Geoffrey had a younger brother, Julius.

Geoffrey went to a school in Hampstead and in 1899 entered University College School in London, where his interest in science grew. The sea and the wind would later supply many of his scientific problems.

Lesson 02

Trinity, feeble light and the ice patrol, 1905–1914

In 1905 Taylor won a scholarship to Trinity College, Cambridge. He read mathematics, hearing lectures by Alfred North Whitehead, Edmund Whittaker and G. H. Hardy, and was twenty-second wrangler in Part I of the Mathematical Tripos in 1907. He then switched to physics and took first-class honours in Part II of the Natural Sciences Tripos in 1908.

Interference with feeble light

His first research project came from J. J. Thomson, who wondered whether interference fringes would survive if light were so weak that only a few quanta of energy were in the apparatus at once. Taylor photographed the diffraction pattern of a needle with a gas flame dimmed by smoked glass screens, using exposures of up to several months. The fringes were as sharp as with strong light. His short 1909 paper was the first experiment of its kind; with hindsight it shows that interference is a property of each photon, not of many photons interacting. Taylor did not pursue quantum physics further.

Shock waves and meteorology

His second piece of work was theoretical. Building on nineteenth-century work, he analysed the structure of a weak shock wave, showing how viscosity and heat conduction give it a definite thickness. It won him a Smith's Prize and, in 1910, a prize fellowship at Trinity. In 1911 he was appointed to the new Schuster Readership in Dynamical Meteorology.

After the Titanic sank in April 1912, the British government sent the ship Scotia to the North Atlantic in 1913 to watch for icebergs, and Taylor sailed as its meteorologist. He flew kites and balloons carrying instruments to measure temperature, humidity and wind at different heights above the cold sea. The data showed how heat and water vapour were carried up from the surface by turbulent eddies. His analysis, Eddy motion in the atmosphere (1915), estimated eddy diffusivities from measured profiles, and his essay on turbulent motion in fluids won the Adams Prize of 1915 (Lesson 04).

Lesson 03

Farnborough and the Cavendish, 1914–1925

When war broke out in 1914, Taylor joined the group of Cambridge scientists working at the Royal Aircraft Factory in Farnborough. He studied the stresses in propeller shafts, and with A. A. Griffith turned Ludwig Prandtl's membrane analogy for torsion into a practical soap-film method of measurement. This work led to his later interest in the plasticity of metals. He studied the stability of parachutes and the pressure distribution on wings. To understand aircraft he learned to fly, gaining his pilot's certificate in 1915, and made parachute jumps himself.

In 1919 he returned to Trinity as fellow and lecturer in mathematics and was elected a Fellow of the Royal Society. Ernest Rutherford, the new Cavendish Professor, gave him space for experiments in the Cavendish Laboratory. Teaching did not suit him, and in 1923 the Royal Society appointed him its Yarrow Research Professor, a post with no teaching duties that he held at the Cavendish until 1952. The same year produced two of his finest papers, on rotating fluids and on the stability of flow between cylinders (Lesson 05), and he gave the Royal Society's Bakerian Lecture.

On 15 August 1925 he married Stephanie Ravenhill, a schoolteacher. They had no children. Together they sailed long distances in small boats, including a voyage to the Lofoten Islands of Norway, and in 1929, after a Pacific science congress, they explored the interior of Borneo. Sailing also produced an invention: in the 1930s Taylor designed the CQR plough anchor, which holds far better than traditional anchors for its weight and is still made today.

Part II · The physics
Lesson 04

Turbulent diffusion

For the general reader. Smoke from a chimney spreads far faster than molecules alone could carry it, because turbulent eddies tear the plume apart and mix it with clean air. Taylor's first great theoretical paper, in 1921, asked how far a single particle wanders in a turbulent flow. His answer used only one statistical function, the correlation of the particle's velocity with itself at different times. It explained why spreading is fast and ballistic at first and then slows to a random walk.

Goals
  • Define the Lagrangian velocity autocorrelation and integral time scale.
  • Prove Taylor's theorem on the mean square displacement.
  • Derive the short-time and long-time limits and the eddy diffusivity.

Eddy diffusivity

From his Scotia data, Taylor modelled the turbulent flux of heat as if it were molecular conduction with a much larger diffusivity, \(\overline{w'T'}=-K\,\partial\bar T/\partial z\). Unlike a molecular diffusivity, \(K\) is a property of the flow, not of the fluid. The 1921 paper explained where such a diffusivity comes from.

Diffusion by continuous movements (1921)

Let a marked fluid particle start at the origin and have velocity \(v(t)\) in one direction, so that its displacement is \(X(t)=\int_0^tv(t')\,dt'\). Suppose the turbulence is statistically stationary and homogeneous, with \(\overline{v}=0\), \(\overline{v^2}=u'^2\), and Lagrangian autocorrelation

\[ R(\tau)=\frac{\overline{v(t)\,v(t+\tau)}}{u'^2},\qquad R(0)=1,\qquad T_L=\int_0^\infty R(\tau)\,d\tau. \]
Taylor's theorem (1921)

Under these assumptions,

\[ \frac{d}{dt}\overline{X^2}=2u'^2\int_0^tR(\tau)\,d\tau,\qquad \overline{X^2}(t)=2u'^2\int_0^t(t-\tau)\,R(\tau)\,d\tau. \]

Hence \(\overline{X^2}\approx u'^2t^2\) for \(t\ll T_L\), and \(\overline{X^2}\approx2u'^2T_L\,t\) for \(t\gg T_L\) when \(T_L\) is finite. At long times the spreading is diffusive with eddy diffusivity \(K=u'^2T_L\).

Proof. \(\frac{d}{dt}\overline{X^2}=2\overline{X\,v(t)}=2\int_0^t\overline{v(t')v(t)}\,dt'=2u'^2\int_0^tR(t-t')\,dt'\), using stationarity. Substitute \(\tau=t-t'\). Integrating once more and exchanging the order of integration gives the second formula. The limits follow from \(R\approx1\) for small \(\tau\) and from \(\int_0^tR\to T_L\).

The theorem needs no equation of motion, only stationarity. It anticipated results that later became standard in the theory of stationary random processes, and it connects to Einstein's 1905 relation between Brownian displacement and diffusion.

Exercise 4.1For \(R(\tau)=e^{-\tau/T}\), find \(\overline{X^2}(t)\) exactly and check both limits.

Show solution
\(\overline{X^2}=2u'^2\int_0^t(t-\tau)e^{-\tau/T}d\tau=2u'^2T\big[t-T(1-e^{-t/T})\big]\). For small \(t\), \(1-e^{-t/T}\approx t/T-t^2/(2T^2)\), so the bracket is \(t^2/(2T)\) and \(\overline{X^2}\approx u'^2t^2\). For large \(t\) the bracket is \(t-T\), so \(\overline{X^2}\approx2u'^2T(t-T)\), diffusive with \(K=u'^2T\).

Exercise 4.2In the atmospheric surface layer on a windy day, \(u'\approx0.5\) m/s and \(T_L\approx20\) s. Estimate the eddy diffusivity and the spread of a smoke plume one hour after release. Compare \(K\) with the molecular diffusivity of smoke particles in air, about \(10^{-9}\) m²/s.

Show solution
\(K=u'^2T_L=0.25\times20=5\) m²/s. After 3600 s, \(t\gg T_L\), so the r.m.s. displacement is \(\sqrt{2Kt}=\sqrt{36000}\approx190\) m. Molecular diffusion would spread the plume by \(\sqrt{2\times10^{-9}\times3600}\approx3\) mm. Turbulence is faster by a factor of \(5\times10^9\) in diffusivity.

Exercise 4.3Suppose \(\int_0^\infty R(\tau)\,d\tau=0\), as in a fluid with a restoring force (for example a particle in a wave field). What happens to \(\overline{X^2}\) at large \(t\)?

Show solution
Then \(d\overline{X^2}/dt\to0\) and \(\overline{X^2}\) tends to the finite limit \(-2u'^2\int_0^\infty\tau R(\tau)\,d\tau\), which is positive for such correlations. The particle oscillates without wandering away: there is no long-time diffusion. Finite non-zero \(T_L\) is the condition for an eddy diffusivity to exist.
Lesson 05

Rotating fluids and Taylor vortices

For the general reader. Rotation makes fluids behave strangely. In a spinning tank of water, a small object pushed slowly along the bottom drags a whole column of fluid above it, as if the water had become rigid along the axis. And when liquid fills the gap between two cylinders and the inner one spins fast enough, the smooth flow breaks into a stack of doughnut-shaped vortices. Taylor showed both effects in 1923, and in the second case he did something new: he predicted the exact speed at which the instability starts and confirmed it by experiment.

Goals
  • Derive the Taylor–Proudman theorem and explain Taylor columns.
  • State Rayleigh's criterion for rotating flows.
  • Understand Taylor's linear stability result for Couette flow and the Taylor number.

The Taylor–Proudman theorem

In a frame rotating with angular velocity \(\boldsymbol\Omega\), the momentum equation of an incompressible fluid is

\[ \frac{\partial\mathbf u}{\partial t}+(\mathbf u\cdot\nabla)\mathbf u+2\boldsymbol\Omega\times\mathbf u=-\frac1\rho\nabla P+\nu\nabla^2\mathbf u, \]

where \(P\) includes the centrifugal potential. When the flow is slow compared with the rotation (small Rossby number \(U/\Omega L\)), steady, and nearly inviscid (small Ekman number \(\nu/\Omega L^2\)), only the Coriolis and pressure terms remain.

Taylor–Proudman theorem (Proudman 1916, Taylor 1917–23)

If \(2\boldsymbol\Omega\times\mathbf u=-\nabla P/\rho\) and \(\nabla\cdot\mathbf u=0\), with \(\boldsymbol\Omega\) constant, then

\[ (\boldsymbol\Omega\cdot\nabla)\,\mathbf u=0: \]

the velocity does not vary along the rotation axis.

Proof. Take the curl: \(\nabla\times(\boldsymbol\Omega\times\mathbf u)=\boldsymbol\Omega(\nabla\cdot\mathbf u)-(\boldsymbol\Omega\cdot\nabla)\mathbf u=-(\boldsymbol\Omega\cdot\nabla)\mathbf u\), while the curl of a gradient vanishes. Taylor tested it by towing a small cylinder slowly across the bottom of a rotating tank. Dye showed that the fluid above the cylinder, all the way to the free surface, moved around it as if it were a solid extension of the obstacle: a Taylor column. Such columns appear above seamounts in the ocean and in laboratory models of planetary atmospheres.

Stability of Couette flow (1923)

Fluid between cylinders of radii \(r_1<r_2\) rotating at \(\Omega_1,\Omega_2\) has the exact circular solution

\[ v_\theta(r)=Ar+\frac Br,\qquad A=\frac{\Omega_2r_2^2-\Omega_1r_1^2}{r_2^2-r_1^2},\qquad B=\frac{(\Omega_1-\Omega_2)r_1^2r_2^2}{r_2^2-r_1^2}. \]
Rayleigh's criterion (1916)

An inviscid circular flow \(v_\theta(r)\) is stable to axisymmetric disturbances if and only if the square of the circulation, \((rv_\theta)^2\), does not decrease anywhere outward.

The reason is an exchange argument: swapping two rings of fluid conserves their angular momentum, and the kinetic energy rises if \((rv_\theta)^2\) increases outward. For Couette flow with the outer cylinder at rest, the circulation decreases outward, so the inviscid flow is unstable. Viscosity delays the instability. Taylor solved the linearized viscous problem for axisymmetric disturbances proportional to \(\cos(kz)\,e^{\sigma t}\), found the boundary \(\sigma=0\), and built an apparatus precise enough to test it.

Taylor's stability result (1923), narrow gap

Let \(d=r_2-r_1\ll r_1\) and the outer cylinder be at rest. Define the Taylor number \(\mathrm{Ta}=\Omega_1^2r_1d^3/\nu^2\). Circular Couette flow is stable for \(\mathrm{Ta}<\mathrm{Ta}_c\approx1.7\times10^3\). At onset it is replaced by steady axisymmetric toroidal vortices of axial wavelength \(\approx2d\), alternately rotating in opposite senses. When both cylinders rotate in the same sense, the critical inner speed rises, and the flow is stable whenever \(r_2^2\Omega_2>r_1^2\Omega_1\), in agreement with Rayleigh.

Taylor's apparatus confirmed the predicted onset speeds and cell sizes over a range of \(\Omega_2/\Omega_1\), including counter-rotating cylinders. It was the first quantitative confirmation of a hydrodynamic stability calculation and of the no-slip condition in such a setting. Taylor–Couette flow has since become a model system for the transition to turbulence.

Exercise 5.1Show that for Couette flow \(rv_\theta=Ar^2+B\), and that Rayleigh's criterion holds throughout the gap if and only if \(\Omega_2r_2^2\ge\Omega_1r_1^2\) (cylinders rotating in the same sense).

Show solution
\(\frac{d}{dr}(rv_\theta)^2=2(rv_\theta)\cdot2Ar\). With both cylinders rotating in the same sense \(rv_\theta>0\) in the gap, so the derivative is non-negative exactly when \(A\ge0\), that is \(\Omega_2r_2^2\ge\Omega_1r_1^2\). With the outer cylinder at rest, \(A<0\): inviscid instability.

Exercise 5.2Water (\(\nu=10^{-6}\) m²/s) fills a gap \(d=5\) mm around an inner cylinder of radius 5 cm; the outer cylinder is fixed. At what rotation rate do Taylor vortices appear? How tall is each cell?

Show solution
\(\Omega_1=\sqrt{1700\,\nu^2/(r_1d^3)}=\sqrt{1700\times10^{-12}/(0.05\times1.25\times10^{-7})}\approx0.52\) rad/s, about 5 revolutions per minute. The wavelength is about \(2d=1\) cm, so each cell is about 5 mm tall, as tall as the gap is wide. The hero figure shows this pattern.

Exercise 5.3Prove the Taylor–Proudman theorem by a second route: write \(\boldsymbol\Omega=\Omega\hat{\mathbf z}\) and show directly from the component equations that \(u\) and \(v\) are independent of \(z\), and then that \(\partial w/\partial z=0\).

Show solution
The components are \(-2\Omega v=-P_x/\rho\), \(2\Omega u=-P_y/\rho\), \(0=-P_z/\rho\). The third gives \(P=P(x,y)\), so \(u=-P_y/(2\Omega\rho)\) and \(v=P_x/(2\Omega\rho)\) do not depend on \(z\). Also \(u_x+v_y=(-P_{yx}+P_{xy})/(2\Omega\rho)=0\), so continuity gives \(w_z=0\). The horizontal flow is geostrophic and non-divergent.
Lesson 06

Dislocations and plastic flow

For the general reader. A perfect crystal should be enormously strong: to shear it, whole planes of atoms would have to slide over each other at once. Real metals yield at stresses thousands of times lower. In 1934 Taylor, and independently Egon Orowan and Michael Polanyi, explained the paradox. Crystals contain line defects, called dislocations, that let one row of atoms slip at a time, like moving a rug by pushing a ruck along it. Taylor also explained why metals harden as they are deformed: the dislocations multiply and get in each other's way.

Goals
  • Estimate the theoretical shear strength of a perfect crystal.
  • Relate plastic strain rate to dislocation density and velocity.
  • Use Taylor's hardening law \(\tau\propto Gb\sqrt\rho\).

The strength paradox

Shearing two planes of atoms with spacing \(h\) and atomic period \(b\) through a displacement \(x\), the stress is periodic in \(x\). Approximating it by \(\tau=\tau_{\max}\sin(2\pi x/b)\) and matching Hooke's law \(\tau=Gx/h\) at small \(x\) gives Frenkel's estimate (1926)

\[ \tau_{\max}=\frac{Gb}{2\pi h}\approx\frac G{2\pi}. \]

For copper this is several gigapascals; single crystals yield near one megapascal.

Taylor's 1934 theory

Taylor's dislocation is a line along which the crystal on one side has slipped by one lattice vector \(\mathbf b\) (the Burgers vector) relative to the other. Moving the line across the slip plane shears the crystal by \(b\), but at any moment only atoms near the line are displaced, so a small stress suffices. Counting the dislocations crossing a region gives Orowan's relation, and Taylor's model of interacting dislocations gives the hardening law.

Kinematics and hardening (Orowan, Taylor 1934)

If mobile dislocations of density \(\rho_m\) (line length per unit volume) move with mean speed \(\bar v\), the plastic shear strain rate is

\[ \dot\gamma=\rho_m\,b\,\bar v. \]

If a crystal contains dislocations of total density \(\rho\), the flow stress needed to move dislocations past the stress fields of their neighbours, spaced about \(\rho^{-1/2}\) apart, is

\[ \tau=\alpha\,G\,b\,\sqrt\rho,\qquad \alpha\approx0.2\text{–}0.5. \]

Sketch. The shear stress at distance \(r\) from a straight dislocation is of order \(Gb/(2\pi r)\). To force a dislocation past a neighbour at the typical spacing \(r\sim\rho^{-1/2}\) requires a stress of that order, \(\tau\sim Gb\sqrt\rho\). Since deformation multiplies dislocations, \(\rho\) and hence \(\tau\) rise with strain: work hardening. In 1938 Taylor extended the analysis to polycrystals. Requiring each grain to deform with the overall strain, using five independent slip systems, he found that the tensile yield stress is \(M\) times the critical resolved shear stress of a single crystal, with \(M\approx3.1\) for randomly oriented face-centred cubic metals (the Taylor factor; later refined to 3.06).

Exercise 6.1For copper, \(G=48\) GPa and \(b=0.256\) nm. Compute Frenkel's \(\tau_{\max}\) and the Taylor flow stress for an annealed crystal (\(\rho=10^{10}\) m⁻²) and a heavily worked one (\(\rho=10^{14}\) m⁻²), with \(\alpha=0.3\).

Show solution
\(\tau_{\max}\approx48/(2\pi)\approx7.6\) GPa. Taylor: \(0.3\times48\times10^9\times0.256\times10^{-9}=3.69\) N/m, times \(\sqrt\rho\). For \(\rho=10^{10}\): \(3.69\times10^5\) Pa \(\approx0.37\) MPa. For \(10^{14}\): \(3.69\times10^7\) Pa \(\approx37\) MPa. With \(M=3.06\) the polycrystal tensile yield stress of the worked metal is about 110 MPa, the right order for cold-drawn copper. All values lie far below the theoretical strength.

Exercise 6.2A bar is strained in shear at \(\dot\gamma=10^{-3}\) s⁻¹. With \(\rho_m=10^{12}\) m⁻² and \(b=0.25\) nm, how fast do the dislocations move on average?

Show solution
\(\bar v=\dot\gamma/(\rho_mb)=10^{-3}/(10^{12}\times2.5\times10^{-10})=4\times10^{-6}\) m/s, a few micrometres per second. Slow, steady deformation of a whole bar is produced by many dislocations creeping a short way.
Lesson 07

The statistical theory of turbulence

For the general reader. A turbulent velocity record looks random. Taylor proposed in 1935 to stop trying to follow individual eddies and to describe turbulence by averages: how strongly the velocity at one point is correlated with the velocity nearby, and how the energy is spread over eddies of different sizes. He introduced the simplest case, turbulence that looks the same in every direction, and gave the tools that experimenters still use to analyse wind-tunnel data.

Goals
  • Define homogeneous isotropic turbulence and the correlation function \(f(r)\).
  • Define the Taylor microscale and relate it to dissipation.
  • Use the frozen-turbulence hypothesis to convert time records into spatial spectra.

Isotropic turbulence (1935)

Turbulence is homogeneous if its statistics do not depend on position, and isotropic if they are also unchanged by rotations and reflections. Grid turbulence in a wind tunnel, made by blowing air through a mesh, approximates this well. For such flows, the longitudinal correlation

\[ f(r)=\frac{\overline{u_1(\mathbf x)\,u_1(\mathbf x+r\mathbf e_1)}}{u'^2} \]

is a single function that determines the whole two-point correlation tensor (as shown later by Theodore von Kármán and Leslie Howarth). Taylor defined two length scales from it: the integral scale \(L=\int_0^\infty f\,dr\), the size of the energy-containing eddies, and the microscale \(\lambda\), from the curvature of \(f\) at the origin.

Taylor microscale and dissipation (1935)

Write \(f(r)=1-\dfrac{r^2}{2\lambda^2}+O(r^4)\). Then \(\overline{(\partial u_1/\partial x_1)^2}=u'^2/\lambda^2\), and in isotropic turbulence the rate of dissipation of kinetic energy per unit mass is

\[ \varepsilon=15\,\nu\,\frac{u'^2}{\lambda^2}. \]

Taylor also argued that at high Reynolds number \(\varepsilon\) is set by the large eddies, \(\varepsilon\approx A\,u'^3/L\) with \(A\) of order one, independent of the viscosity.

The first statement is a Taylor expansion of the correlation; the factor 15 comes from expressing all nine velocity gradients \(\overline{(\partial u_i/\partial x_j)^2}\) through the single longitudinal one using isotropy. The second statement is the cornerstone of later theory. Combined, they show that \(\lambda/L\) shrinks like \(\mathrm{Re}^{-1/2}\), so the eddies that dissipate energy are much smaller than those that contain it. Andrey Kolmogorov's theory of 1941 grew from this observation.

The spectrum and frozen turbulence (1938)

A hot-wire probe at a fixed point records \(u(t)\). To get the spatial structure, Taylor proposed that if the turbulent fluctuations are small compared with the mean speed \(U\), the pattern of eddies is carried past the probe nearly unchanged:

\[ \frac{\partial}{\partial t}\approx-U\frac{\partial}{\partial x},\qquad k=\frac{2\pi f}{U}. \]

He showed that the one-dimensional spectrum of \(u_1\), measured as a function of frequency, is the Fourier transform of the correlation \(f\), so that the spectrum and the correlation contain the same information. The frozen-turbulence hypothesis is used in nearly every experimental study of turbulence and of atmospheric wind.

Exercise 7.1Combine \(\varepsilon=15\nu u'^2/\lambda^2\) and \(\varepsilon=u'^3/L\) to show \(\lambda/L=\sqrt{15}\,\mathrm{Re}_L^{-1/2}\), with \(\mathrm{Re}_L=u'L/\nu\). Evaluate for grid turbulence with \(u'=0.5\) m/s, \(L=2\) cm in air.

Show solution
Equating, \(15\nu/\lambda^2=u'/L\), so \(\lambda^2=15\nu L/u'\) and \(\lambda/L=\sqrt{15\nu/(u'L)}=\sqrt{15}\,\mathrm{Re}_L^{-1/2}\). With \(\nu=1.5\times10^{-5}\): \(\mathrm{Re}_L=0.5\times0.02/1.5\times10^{-5}\approx667\), so \(\lambda/L\approx3.87/25.8\approx0.15\), \(\lambda\approx3\) mm.

Exercise 7.2A hot wire in a wind tunnel at \(U=10\) m/s records a spectral peak at 50 Hz and measurable energy up to 5 kHz. What eddy sizes do these correspond to? When does the frozen-turbulence hypothesis fail?

Show solution
Wavelength \(U/f\): 20 cm at 50 Hz and 2 mm at 5 kHz. The hypothesis requires the eddies to change little while they pass the probe, so it needs \(u'\ll U\). It fails in jets and wakes with large turbulence intensity, near walls where the convection speed varies with height, and in flows with no mean velocity.

Exercise 7.3Check that \(f(r)=e^{-r/L}\) has integral scale \(L\), but no finite microscale. Why is such a correlation unphysical for a viscous fluid at small \(r\)?

Show solution
\(\int_0^\infty e^{-r/L}dr=L\). But \(f'(0)=-1/L\neq0\), so \(f\) has a corner at the origin and no quadratic expansion; \(\lambda=0\) and \(\varepsilon=15\nu u'^2/\lambda^2\) would be infinite. In a viscous fluid the velocity is smooth on scales below the dissipation scale, so \(f\) must be even and twice differentiable at \(r=0\). An exponential can only model the correlation at scales well above \(\lambda\).
Lesson 08

Blast waves and accelerated interfaces

For the general reader. During the Second World War Taylor was asked what happens when a very large amount of energy is released in a very small space. He found that the expanding fireball and shock follow a simple law: the radius grows as the two-fifths power of time, with a constant fixed by the energy. When photographs of the first atomic test were released in 1947, he used the law to estimate the yield, a figure that was still secret. In the same years he showed why the boundary between a heavy and a light fluid becomes unstable when the light fluid pushes the heavy one, a question that mattered for the implosion bomb and now matters for fusion and supernovae.

Goals
  • Derive the blast-wave radius law by dimensional analysis.
  • Estimate the yield of an explosion from a photograph.
  • Derive the Rayleigh–Taylor growth rate, with and without surface tension.

The intense point explosion

Energy \(E\) is released at a point in air of density \(\rho_0\). Once the shock is strong, the pressure behind it is so large that the ambient pressure is irrelevant. The only parameters are \(E\), \(\rho_0\), the time \(t\) and the dimensionless ratio \(\gamma\) of specific heats.

Taylor's blast-wave law (1941, published 1950)

For a strong spherical blast from an instantaneous point release of energy \(E\),

\[ R(t)=S(\gamma)\left(\frac{E\,t^2}{\rho_0}\right)^{1/5}, \]

and the flow behind the shock is self-similar, a function of \(r/R(t)\) only. Taylor solved the resulting ordinary differential equations numerically and found \(S\approx1.033\) for \(\gamma=1.4\). The same solution was found independently by John von Neumann and by Leonid Sedov, who obtained it in closed form.

The only combination of \(E\) (kg m² s⁻²), \(\rho_0\) (kg m⁻³) and \(t\) (s) with the dimension of length is \((Et^2/\rho_0)^{1/5}\), which fixes the law up to the constant. In 1950 Taylor published both his wartime theory and a comparison with the photographs of the Trinity test. Plotting \(\log R\) against \(\log t\) gave a straight line of slope 2/5, and his yield estimates were close to the true value of about 20 kilotons.

The Rayleigh–Taylor instability (1950)

A layer of heavy fluid resting on light fluid under gravity is unstable, as Rayleigh had noted in 1883. Taylor observed that an acceleration acts in the same way: in the accelerated frame it is equivalent to gravity. An interface is unstable when it is accelerated in the direction from the light fluid toward the heavy one. D. J. Lewis confirmed it in experiments published alongside Taylor's paper, in which a liquid layer was driven downward by compressed air faster than free fall.

Rayleigh–Taylor growth rate

Let fluid of density \(\rho_2\) lie above fluid of density \(\rho_1<\rho_2\) in an effective gravity \(g\), with interfacial tension \(\gamma\). A small sinusoidal disturbance of the interface, of wavenumber \(k\), grows like \(e^{\sigma t}\) with

\[ \sigma^2=\mathcal A\,g\,k-\frac{\gamma k^3}{\rho_1+\rho_2},\qquad \mathcal A=\frac{\rho_2-\rho_1}{\rho_2+\rho_1}, \]

the Atwood number. Waves shorter than \(2\pi/k_c\), with \(k_c=\sqrt{(\rho_2-\rho_1)g/\gamma}\), are stabilized.

Derivation. Take irrotational flow on each side with potentials \(\phi_j\propto e^{\mp k z}\cos kx\,e^{\sigma t}\), decaying away from the interface \(z=\eta=\eta_0\cos kx\,e^{\sigma t}\). Kinematic conditions give \(\partial_z\phi_j=\sigma\eta\). The linearized Bernoulli equation on each side, \(\rho_j(\partial_t\phi_j+g\eta)+p_j=\text{const}\), and the pressure jump \(p_1-p_2=-\gamma\eta_{xx}=\gamma k^2\eta\) combine to give the dispersion relation. With \(\rho_1>\rho_2\) (stable layering) the same formula gives oscillating gravity–capillary waves.

Exercise 8.1A photograph taken \(t=25\) ms after a nuclear detonation shows a fireball of radius about 140 m. Estimate the yield in kilotons of TNT (\(1\) kt \(=4.18\times10^{12}\) J), taking \(\rho_0=1.25\) kg/m³ and \(S=1.033\).

Show solution
\(E=\rho_0R^5/(S^5t^2)=1.25\times(140)^5/(1.18\times6.25\times10^{-4})\). Since \(140^5=5.38\times10^{10}\), \(E\approx1.25\times5.38\times10^{10}/7.35\times10^{-4}\approx9.1\times10^{13}\) J, about 22 kt. Because \(E\propto R^5\), a 10% error in the radius gives a 60% error in the yield; Taylor used many frames to fit the line.

Exercise 8.2Show that the shock speed is \(\dot R=\tfrac25R/t\), and estimate it at the moment of Exercise 8.1. Why must the shock eventually stop following the law?

Show solution
\(R\propto t^{2/5}\) gives \(\dot R=\tfrac25R/t=0.4\times140/0.025=2240\) m/s, about Mach 6.5. The law assumes a strong shock, with post-shock pressure far above ambient. As \(R\) grows, the pressure falls like \(E/R^3\); when it nears atmospheric pressure the shock weakens into a sound wave, and the counterpressure can no longer be neglected.

Exercise 8.3A glass of water is turned upside down with its mouth covered by a card, which is then removed. For water and air (\(\gamma=0.072\) N/m), find the wavelength below which surface tension stabilizes the interface. Why does the water fall out of a wide glass but stay in a narrow straw?

Show solution
\(\lambda_c=2\pi/k_c=2\pi\sqrt{\gamma/(\Delta\rho\,g)}\approx2\pi\sqrt{0.072/(999\times9.81)}\approx1.7\) cm. In a glass several centimetres wide, unstable wavelengths fit across the mouth, and the interface breaks up into fingers of falling water and rising bubbles. In a straw a few millimetres wide, no unstable wave fits, and the water stays in place.
Lesson 09

Slow viscous flow

For the general reader. After he retired, Taylor turned to flows so slow or so small that inertia does not matter: bacteria and sperm swimming, dye spreading along a narrow tube, oil being pushed out of rock by water. In this world motion is reversible and intuition from everyday life fails. Taylor made films and demonstrations of it that are still shown to students, and found three results that each started a field.

Goals
  • Understand the swimming of a waving sheet at low Reynolds number.
  • Derive the Taylor dispersion coefficient for Poiseuille flow.
  • Derive the Saffman–Taylor instability of a displacement front in a Hele-Shaw cell.

Swimming (1951)

At very small Reynolds number the Stokes equations \(\mu\nabla^2\mathbf u=\nabla p\), \(\nabla\cdot\mathbf u=0\) hold. They have no time derivative, so a swimmer that runs through a sequence of shapes and then reverses it returns to its starting point. Taylor asked how a microorganism can swim at all, and modelled it as an infinite sheet carrying a travelling wave, \(y=b\sin(kx-\omega t)\).

Taylor's swimming sheet (1951)

To second order in the amplitude, an inextensible sheet carrying a transverse wave \(y=b\sin(kx-\omega t)\) in a viscous fluid swims with speed

\[ U=\tfrac12\,\omega k\,b^2 \]

in the direction opposite to that of the wave.

The speed is second order in \(b\) because reversing the sign of \(b\) gives the same motion shifted by half a wavelength, so \(U\) must be even in \(b\).

Taylor dispersion (1953)

Solute injected into a liquid flowing slowly through a narrow tube spreads along it far faster than molecular diffusion allows, yet far more slowly than the velocity differences across the tube would suggest. Taylor showed that the two effects combine.

Taylor dispersion (1953; Aris 1956)

For Poiseuille flow of mean speed \(U\) in a tube of radius \(a\), with molecular diffusivity \(D\), after times long compared with \(a^2/D\) the cross-sectionally averaged concentration \(\bar c\) obeys, in a frame moving with speed \(U\),

\[ \frac{\partial\bar c}{\partial t}=D_{\text{eff}}\frac{\partial^2\bar c}{\partial x^2},\qquad D_{\text{eff}}=D+\frac{a^2U^2}{48D}. \]

The striking feature is that \(D_{\text{eff}}\) grows as \(D\) decreases. Shear stretches the solute along the tube; radial diffusion samples fast and slow streamlines and so limits the stretching. The faster the radial diffusion, the less the spreading. Taylor used the result to measure molecular diffusivities, and it underlies the analysis of chromatography and of solute transport in blood vessels and rivers.

Viscous fingering (1958)

In a Hele-Shaw cell, two glass plates a small distance \(b\) apart, the gap-averaged velocity obeys Darcy's law \(\mathbf u=-\frac{b^2}{12\mu}\nabla p\), the same law as flow in porous rock. Taylor and Philip Saffman studied what happens when one fluid displaces another.

Saffman–Taylor instability (1958)

A plane front at which fluid of viscosity \(\mu_1\) displaces fluid of viscosity \(\mu_2\) at speed \(U\) is unstable if \(\mu_1<\mu_2\). With interfacial tension \(\gamma\) and no gravity, a perturbation of wavenumber \(k\) grows at rate

\[ \sigma=\frac{k}{\mu_1+\mu_2}\Big[(\mu_2-\mu_1)U-\frac{b^2\gamma k^2}{12}\Big]. \]

A less viscous fluid pushing a more viscous one forms fingers, which compete until, in a channel, one finger of about half the channel width remains. The instability limits the recovery of oil by water flooding, and the selection of the finger width became a celebrated problem of pattern formation in the 1980s.

Exercise 9.1Derive \(D_{\text{eff}}-D=a^2U^2/(48D)\). Use the velocity relative to the mean, \(u'=U(1-2r^2/a^2)\), and the quasi-steady balance \(D\,\frac1r\frac{\partial}{\partial r}\big(r\frac{\partial c'}{\partial r}\big)=u'\,\frac{\partial\bar c}{\partial x}\) for the concentration deviation \(c'(r)\).

Show solution
Integrate twice: \(r\,\partial_rc'=\frac{U\bar c_x}{D}\big(\tfrac{r^2}{2}-\tfrac{r^4}{2a^2}\big)\), so \(c'=\frac{U\bar c_x}{D}\big(\tfrac{r^2}{4}-\tfrac{r^4}{8a^2}\big)+\text{const}\). The extra axial flux is the average of \(u'c'\) over the section. The constant drops out because \(u'\) has zero mean. Then \(\overline{u'c'}=\frac{2}{a^2}\int_0^aU(1-\tfrac{2r^2}{a^2})\frac{U\bar c_x}{D}\big(\tfrac{r^2}4-\tfrac{r^4}{8a^2}\big)r\,dr=-\frac{a^2U^2}{48D}\bar c_x\). A flux \(-K\bar c_x\) is diffusion with \(K=a^2U^2/(48D)\).

Exercise 9.2Water carries a dye (\(D=10^{-9}\) m²/s) at \(U=1\) mm/s through a capillary of radius 0.5 mm. Compute \(D_{\text{eff}}\) and the time after which Taylor's result applies.

Show solution
\(a^2U^2/(48D)=(2.5\times10^{-7})(10^{-6})/(4.8\times10^{-8})\approx5.2\times10^{-6}\) m²/s, about 5000 times the molecular value. The result needs \(t\gg a^2/D=250\) s, a few minutes.

Exercise 9.3Water (\(\mu_1=10^{-3}\) Pa·s) displaces oil (\(\mu_2=0.1\) Pa·s) at \(U=1\) mm/s in a Hele-Shaw cell with \(b=1\) mm and \(\gamma=0.03\) N/m. Find the shortest unstable wavelength and the wavelength that grows fastest.

Show solution
\(\sigma=0\) at \(k_c=\sqrt{12U(\mu_2-\mu_1)/(b^2\gamma)}=\sqrt{12\times10^{-3}\times0.099/(10^{-6}\times0.03)}\approx199\) m⁻¹, so \(\lambda_c\approx3.2\) cm. Maximizing \(\sigma\propto k(\Delta\mu U-b^2\gamma k^2/12)\) gives \(k_m=k_c/\sqrt3\), so \(\lambda_m\approx5.5\) cm. In a cell 10 cm wide only one or two fingers fit.

Exercise 9.4A spermatozoon's flagellum has wavelength 50 μm, amplitude 5 μm and beat frequency 30 Hz. Using the swimming-sheet formula as a rough guide, estimate its speed and compare it with the wave speed.

Show solution
\(k=2\pi/50\) μm⁻¹, \(\omega=2\pi\times30\) s⁻¹. \(U=\tfrac12\omega kb^2=\tfrac12(188.5)(0.1257\ \mu\text{m}^{-1})(25\ \mu\text{m}^2)\approx296\) μm/s. The wave speed is \(\omega/k=1500\) μm/s, so the swimmer moves at about one fifth of it. Real flagella are slender filaments, not sheets; slender-body theory, developed after Taylor, reduces the estimate by a modest factor.
Lesson 10

Electrified drops and the Taylor cone

For the general reader. In his late seventies Taylor took up a question from meteorology: what happens to raindrops in the strong electric fields of a thunderstorm? He found that a drop of conducting liquid stretches in a field, and that above a critical field its ends become sharp cones that shoot out fine jets. He showed that the cone has a universal angle, the same for every liquid. The Taylor cone is now the working heart of electrospray, the technique that lets mass spectrometers weigh large proteins, and of electrospinning and some spacecraft thrusters.

Goals
  • Balance electric stress against surface tension on a conical surface.
  • Show that the potential must vary like \(r^{1/2}\).
  • Find the Taylor angle from the zero of a Legendre function.

Balancing stresses

The surface of a perfect conductor is an equipotential, and the electric field \(E\) just outside it pulls the surface outward with stress \(\tfrac12\varepsilon_0E^2\). Surface tension \(\gamma\) pulls inward with pressure \(\gamma\kappa\), where \(\kappa\) is the mean curvature (sum of principal curvatures). For a cone of half-angle \(\alpha\), one principal curvature vanishes and the other, at distance \(r\) from the apex, is \(\cot\alpha/r\). Balance at every \(r\) requires \(E^2\propto1/r\), so \(E\propto r^{-1/2}\) and the potential varies like \(r^{1/2}\).

The Taylor cone (1964)

A conical equipotential surface of a conducting liquid can be in static equilibrium between electric stress and surface tension only if the potential outside it has the form \(\phi=\phi_0+C\,r^{1/2}P_{1/2}(\cos\theta)\), where \(\theta\) is measured from the axis outside the cone and \(P_{1/2}\) is the Legendre function of degree \(\tfrac12\). The cone surface is then the zero \(\theta_0\approx130.7^\circ\) of \(P_{1/2}(\cos\theta)\), so the liquid cone has half-angle

\[ \alpha=180^\circ-\theta_0\approx49.3^\circ. \]

The angle does not depend on the liquid, the field strength or the scale.

Sketch. Laplace's equation in spherical coordinates with axial symmetry admits separated solutions \(r^\nu P_\nu(\cos\theta)\). The stress balance forces \(\nu=\tfrac12\). The function \(P_{1/2}(\cos\theta)\) is regular on the axis \(\theta=0\) and has exactly one zero in \((0,\pi)\), at \(\theta_0\approx130.71^\circ\). Taylor verified the angle by photographing cones formed on drops and soap films between electrodes. Real cones emit a thin jet from their tips, which breaks into charged droplets: this is the cone-jet mode of electrospray. John Fenn's development of electrospray ionization for large biomolecules earned a share of the 2002 Nobel Prize in Chemistry.

Exercise 10.1Show that \(\phi=r^\nu F(\theta)\) satisfies Laplace's equation in axisymmetric spherical coordinates if and only if \(F\) satisfies Legendre's equation of degree \(\nu\), and explain why \(\nu=\tfrac12\) is forced by the stress balance.

Show solution
\(\nabla^2\phi=\frac1{r^2}\partial_r(r^2\partial_r\phi)+\frac{1}{r^2\sin\theta}\partial_\theta(\sin\theta\,\partial_\theta\phi)\). The radial part gives \(\nu(\nu+1)r^{\nu-2}F\), so \(\frac1{\sin\theta}(\sin\theta F')'+\nu(\nu+1)F=0\), Legendre's equation. The field is \(|\nabla\phi|\propto r^{\nu-1}\), so the electric stress is \(\propto r^{2\nu-2}\). Surface tension on a cone gives \(\gamma\cot\alpha/r\propto r^{-1}\). Equality for all \(r\) requires \(2\nu-2=-1\), \(\nu=\tfrac12\).

Exercise 10.2For water (\(\gamma=0.072\) N/m) on a Taylor cone, find the electric field at \(r=10\) μm from the apex. Compare with the breakdown field of air, about \(3\times10^6\) V/m. What does this suggest?

Show solution
\(\tfrac12\varepsilon_0E^2=\gamma\cot\alpha/r\) with \(\cot49.3^\circ\approx0.86\): \(E=\sqrt{2\times0.072\times0.86/(8.85\times10^{-12}\times10^{-5})}\approx3.7\times10^7\) V/m, about ten times the breakdown field. Close to the apex the field becomes large enough to ionize air and, more importantly, the static cone cannot persist: in practice the tip emits a jet and the true field there is limited by the charge carried away.
Part III · Life and legacy
Lesson 11

War and Los Alamos, 1939–1945

Through the 1930s Taylor's work had turned increasingly to solids and to turbulence. His correspondence with Ludwig Prandtl, mostly on turbulence, ran from 1923 to 1938. In letters of 1938 and 1939 to Taylor and his wife, Prandtl defended Nazi policy toward the Jews (see Prandtl's course, Lesson 11).

From 1939 Taylor worked as a consultant on the physics of explosions for several British ministries and committees. He analysed the propagation of blast waves in air and of shock waves and gas bubbles in underwater explosions, the response of plates and structures to blast, and the penetration of armour. Early in 1941 he wrote the analysis of the very intense point explosion summarized in Lesson 08; it circulated to the Civil Defence Research Committee of the Ministry of Home Security in June of that year. He was knighted and received the Copley Medal of the Royal Society in 1944.

In 1944 and 1945 he visited Los Alamos as a member of the British mission to the Manhattan Project. His expertise on the instability of accelerated interfaces bore directly on the implosion design of the plutonium bomb, in which a heavy shell is driven inward by explosives. He was among the observers of the Trinity test in New Mexico on 16 July 1945. He was elected to the US National Academy of Sciences in 1945 and received the US Medal for Merit in 1946. In 1950, after the Trinity photographs had been released, he published his blast-wave analysis with the yield estimate that, in effect, revealed a classified number from public data.

DiscussionTaylor's 1950 estimate of the Trinity yield used only published photographs and dimensional analysis. What does this episode say about secrecy in physics? Compare it with other cases where a classified result could be reconstructed from public information.

Lesson 12

The long afternoon, 1945–1975

Taylor retired from the Yarrow professorship in 1952 but kept his room and workshop at the Cavendish and worked for another twenty years. In 1959 George Batchelor founded the Department of Applied Mathematics and Theoretical Physics at Cambridge, and Taylor's presence helped make Cambridge a world centre of fluid mechanics. His style of work became famous: simple apparatus, often built by his own hands, followed by an elegant analysis. In the 1960s he appeared in the American series of educational films on fluid mechanics, demonstrating low-Reynolds-number flows himself.

His doctoral students and younger collaborators included George Batchelor, Albert Green, Rosa Morris, Philip Drazin, Francis Bretherton, Stewart Turner and Philip Saffman. Batchelor edited his collected scientific papers in four volumes (1958–71) and later wrote his biography. Among Taylor's many honours were the Royal Medal (1933), the Copley Medal (1944), the De Morgan Medal of the London Mathematical Society (1956), the Timoshenko Medal (1958), the Franklin Medal (1962) and the Order of Merit (1969). In 1972 he received the SIAM Theodore von Kármán Prize.

Stephanie Taylor died in 1967. Taylor continued to publish into his eighties, including six papers on electrohydrodynamics between 1964 and 1969. A severe stroke in 1972 ended his research. He died at his home, Farmfield, on Huntingdon Road in Cambridge, on 27 June 1975, aged 89.

Legacy

  • Fluid mechanics: Taylor–Couette flow and Taylor columns in rotating fluids; turbulent diffusion, the statistical theory of turbulence, the microscale and the frozen-turbulence hypothesis; the Rayleigh–Taylor and Saffman–Taylor instabilities; the intense blast wave; Taylor dispersion; swimming at low Reynolds number.
  • Solid mechanics: dislocations, Taylor hardening and the Taylor factor for polycrystals; the Taylor impact test for dynamic yield strength.
  • Geophysics and engineering: eddy diffusion in the atmosphere and ocean, tidal friction in shallow seas, the CQR anchor, parachute design.
  • Method: a model for how to combine simple experiments, scaling arguments and exact solutions. The G. I. Taylor Medal of the Society of Engineering Science honours this approach.

Final projectChoose one result from Part II. Design a tabletop experiment to test it with materials costing under fifty euros, predict the outcome with the formulas of the lesson, and explain which approximation is most likely to cause a discrepancy. Taylor would have expected you to build it.

Reference

Sources and further reading

Biography and history

  1. J. J. O'Connor and E. F. Robertson, Geoffrey Ingram Taylor, MacTutor History of Mathematics.
  2. G. K. Batchelor, Taylor, Sir Geoffrey Ingram, Dictionary of National Biography (via MacTutor).
  3. G. I. Taylor, Wikipedia (honours, doctoral students).
  4. Trinity College Cambridge, Papers of Sir Geoffrey Taylor; correspondence with L. Prandtl.
  5. G. K. Batchelor, The Life and Legacy of G. I. Taylor, Cambridge University Press, 1996.
  6. G. K. Batchelor, Geoffrey Ingram Taylor, Biographical Memoirs of Fellows of the Royal Society 22 (1976).
  7. M. Eckert, Ludwig Prandtl: A Life for Fluid Mechanics and Aeronautical Research, Springer, 2019 (the Prandtl–Taylor letters).

Physics

  1. G. I. Taylor, Interference fringes with feeble light, Proc. Camb. Phil. Soc. 15 (1909).
  2. G. I. Taylor, Eddy motion in the atmosphere, Phil. Trans. R. Soc. A 215 (1915).
  3. G. I. Taylor, Diffusion by continuous movements, Proc. London Math. Soc. 20 (1921).
  4. G. I. Taylor, Stability of a viscous liquid contained between two rotating cylinders, Phil. Trans. R. Soc. A 223 (1923).
  5. G. I. Taylor, Experiments on the motion of solid bodies in rotating fluids, Proc. R. Soc. A 104 (1923).
  6. G. I. Taylor, The mechanism of plastic deformation of crystals, Proc. R. Soc. A 145 (1934).
  7. G. I. Taylor, Statistical theory of turbulence, parts I–IV, Proc. R. Soc. A 151 (1935); The spectrum of turbulence, Proc. R. Soc. A 164 (1938).
  8. G. I. Taylor, The formation of a blast wave by a very intense explosion, I and II, Proc. R. Soc. A 201 (1950).
  9. G. I. Taylor, The instability of liquid surfaces when accelerated in a direction perpendicular to their planes, Proc. R. Soc. A 201 (1950).
  10. G. I. Taylor, Analysis of the swimming of microscopic organisms, Proc. R. Soc. A 209 (1951).
  11. G. I. Taylor, Dispersion of soluble matter in solvent flowing slowly through a tube, Proc. R. Soc. A 219 (1953).
  12. P. G. Saffman and G. I. Taylor, The penetration of a fluid into a porous medium or Hele-Shaw cell containing a more viscous liquid, Proc. R. Soc. A 245 (1958).
  13. G. I. Taylor, Disintegration of water drops in an electric field, Proc. R. Soc. A 280 (1964).
  14. G. K. Batchelor (ed.), The Scientific Papers of Sir Geoffrey Ingram Taylor, 4 vols., Cambridge University Press, 1958–71.
  15. G. K. Batchelor, The Theory of Homogeneous Turbulence, Cambridge University Press, 1953.
  16. P. G. Drazin and W. H. Reid, Hydrodynamic Stability, 2nd ed., Cambridge University Press, 2004 (Rayleigh criterion, Taylor–Couette and Rayleigh–Taylor problems).