James Lighthill (1924–98)

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Obituary and go on studying them!” And so he did. James Lighthill (1924–98) It was through this total immersion that a new realm of scientific endeavour was Applied mathematician defined, explored and revealed to the fluid dynamics community. ORIAL and fluid dynamicist In biofluiddynamics, Lighthill ICT Fluid dynamics developed and has contributed equally to our understanding continued to thrive through its of the flight of birds and of insects, topics UNIVERSAL P applicability to fields of great practical for which his mastery of aerodynamics8 was importance. Dominant among these, well adapted. His appointment as provost during the first half of this century, was of University College London (1979–89) aerodynamics, which grew from an did nothing to diminish his formidable embryonic understanding of boundary- research output. Again, his interaction layer theory, flow instability, and subsonic with zoologists was of key importance. and supersonic flow. Since about 1960, the One such collaboration stands out — that dynamics of ocean and atmosphere, with with Torkel Weis-Fogh, a successor of its intricate interplay of wave-motion and James Gray at Cambridge — which led to turbulence, has emerged as a field of elucidation of the mechanism of lift- comparable vitality. And since about 1970, production in small hovering insects. This the fluid dynamics of biological systems is the clap–fling–sweep sequence by which has developed as a field of immense circulation round each wing, and so lift, is challenge now ripe for rapid growth. generated by an essentially inviscid James Lighthill’s meteoric career was mechanism. Thus does the chalcid wasp characterized by pioneering contributions Encarsia formosa achieve a lift coefficient in each of these areas. His work was based jet engines whose noise output could be greater than that of any man-made flying on classical techniques of applied reduced to tolerable levels. Lighthill machine. mathematics, but his style involved achieved worldwide recognition Lighthill was knighted in 1971, exactly strenuous efforts to interpret the for this seminal work, and at the age halfway through his long research career. mathematics, however complex, in terms of 29 was elected a fellow of the Royal He was in great demand as a plenary of fundamental physics. It was this aim, so Society. lecturer at international meetings, and he successfully achieved, that gave his papers From 1959 to 1964, Lighthill served as would invariably rise to such occasions their renowned lucidity and impact. director of the Royal Aircraft with gusto. His style was magisterial and Michael James Lighthill was educated at Establishment at Farnborough, he would present his material with total Winchester College and Trinity College, Hampshire. Despite the burdens of this authority and little respect for any Cambridge, where he read mathematics post, he retained close contact with the constraint of time. His lectures conveyed a for the accelerated two-year wartime wider research community, and indeed passionate commitment to his subject, and degree, graduating in 1943. His inclination published papers in both geophysical and rapier thrusts abound. Thus, for example, was to undertake research in pure biological fluid dynamics, a foretaste of the in 1962 when the magnetohydrodynamic mathematics, but wartime imperatives interests that were to become his main bandwagon was in full swing: “It needs dictated otherwise, and he moved directly preoccupation. These interests were given categorically to be reaffirmed that the to the National Physical Laboratory to lease through his appointment in 1964 to a continuum mechanics of a fluid innocent work on supersonic aerodynamics. There Royal Society professorship at Imperial of electric current has as vital and exciting he worked with ferocious intensity. Elected College, London, and his subsequent a present and future as any other branch of to a research fellowship at Trinity College appointment in 1969 as Lucasian Professor physical science”. Lighthill’s own work in 1945, he was attracted in the following of Mathematics at Cambridge, a post he testified to the enduring truth of this year to the University of Manchester held for the next decade. statement. by Sydney Goldstein, where he His great work during this period was Sir James Lighthill died on 17 July, at remained until 1959; he succeeded concerned with waves in fluids the age of 74, having almost completed a Goldstein as Beyer Professor of Applied (particularly fluids in rotation, as in the swim, in choppy seas, around the island of Mathematics in 1950 at the exceptionally geophysical context) and also, most Sark in the English Channel, a feat that he early age of 26. notably, with the subject that he named had first accomplished 25 years earlier. He By that time, the hazard of noise from ‘biofluiddynamics’. Lighthill’s interest in was a compulsive island circumnatator, jet aircraft was already recognized, and it this topic had been stimulated much and his major source of pride in this was here that Lighthill made what many earlier by the Cambridge zoologist Sir respect was to have swum around will consider his greatest contribution. In James Gray; but it was only through his Stromboli while it was erupting. Not for two papers, published in 1952 and 1954, he survey article, “Hydrodynamics of Aquatic him the timid security of the seashore; he laid the foundations for all subsequent Animal Propulsion”, published in 1969, died as he had lived, with style and work on the subject. Recognizing that the that the field really opened up. Lighthill bravado. He is survived by his wife Nancy turbulence in a high-speed jet is equivalent himself emphasized the need for an Dumaresq, to whom he was married for 53 to a distribution of quadrupole sources, interdisciplinary approach: “… if I was to years, and by one son and four daughters. Lighthill was able to calculate the intensity help in classifying the hydrodynamics of Keith Moffatt (an eighth-power law) and directional aquatic animal locomotion I must talk to Keith Moffatt is at the Isaac Newton Institute for distribution of the radiated sound field. An zoologists and go on talking to them; read Mathematical Sciences, 20 Clarkson Road, understanding of this mechanism of noise their works and go on reading them; study Cambridge CB3 0EH, UK. production was essential to the design of their collections (in museums and aquaria) e-mail: [email protected]