Download Some reminiscences from the Fluid Dynamics Side

Fifty Years of DAMTP: Some Reminiscences from the Fluid Dynamics Side.
DAMTP was founded exactly 50 years ago, and more than 700 PhD s have been nurtured within its walls
over that period. They form a wonderfully talented worldwide network, and I think DAMTP can take
credit for having launched so many on their brilliant subsequent careers, some in University teaching and
research, but many also in applications of research in the wider outside world.
Of course, we have to admit that mathematics, pure and applied, did exist in Cambridge before 1959!
Indeed 750 years of it, ever since those disaffected scholars from Oxford made the trek towards these
Eastern fens; I’m sure there were one or two mathematician, or at least arithmeticians, among them. We
certainly had the three-hundred year tradition of the Lucasian chair to live up to, from Isaac Barrow and
his incomparable protégé Isaac Newton through to the great succession of Stokes, Larmor and Dirac that
had spanned more than a century from 1850 on. Dirac was a legend in 1959, but was also something of a
recluse, and disinclined for any leadership role. The drive to establish a University Department
undoubtedly came from George Batchelor, who had held a Lecturership in the Faculty of Mathematics
since 1948. George had built up a substantial research group in fluid mechanics during the 1950s; the
problem was, there was nowhere to put them except in a scattering of rooms in the old Cavendish
Laboratory made available by courtesy of the Physics Department. George developed a vision of a
Department of Applied Mathematics and Theoretical Physics with its own building where Research
Students, Lecturers, and Senior Visitors could meet and interact on a daily basis. We take this so much
for granted now that it’s hard to believe there was ever a time when the need was not recognized.
So the Department was duly established in 1959 in a set of rooms in Free School Lane – or at any rate,
that’s where the fluid mechanics group was housed, and where I was based for the next five years first as
a research student under Batchelor’s watchful eye, then as an Assistant Lecturer. We gave all our lectures
in the Arts School in Bene’t Street, so Free School Lane was a very convenient location. Also we had a
coffee room, which doubled as a library, and this was of the greatest importance: it was where lively
discussions took place on a daily basis involving all the lecturers and research students in a very friendly
atmosphere. I remember our revered Lucasian Professor, Stephen Hawking, arriving as a new research
student in 1962, in a black velvet jacket and floppy bow tie, and making an immediate impact!
In 1963, it became known that Cambridge University Press was going to move to new premises in South
Cambridge, and that its 19th century Print House and warehouse on Silver Street, behind the Pitt Press
building, were therefore to become vacant. Batchelor leapt at this opportunity and put in a bid for the
Print House, which after due process in the Old Schools, was granted. At about the same time, the
neighbouring warehouse was allocated to our sister department DPMMS, about to be established in 1964.
We always considered that we had the better part of the bargain!
George roped me in to liaise with Estate Management on the conversion of the Print House for
departmental use. This took a full year, and we began our move from Free School Lane in 1964. In his
characteristically frugal style, George insisted that we didn’t need the help of professionals for this move,
and he roped in all the research students to carry the desks and other furnishings down Botolph Lane and
across Trumpington Street to our new premises. The Old Press building was actually technically
condemned, and Estate Management estimated that it was good for only 5 years’ occupation. In the
event, we occupied it for 38 years, and gradually extended our occupancy as the Department expanded,
finally taking over even the Syndics Building on the South side of the complex. The ground floor
Common Room in the main building played a central socializing role, providing the coffee tables and the
felt-tip pens whereby new, and often outlandish, physical and mathematical ideas could be developed.
Batchelor’s appointment as Head of Department in 1959 was for five years, but the rules envisaged the
possibility of reappointment. In the event, he was reappointed four times, serving as Head of Department
until, in 1983, he was induced to accept an offer from the General Board, an offer “that he couldn’t
refuse”, to take early retirement at the age of 63. This was during the Thatcher era of great financial
stringency. It was a serious situation for me personally, as I found myself in line to succeed him in this
arduous role.
When George was first reappointed in 1964, this was vigorously contested by Fred Hoyle, Plumian
Professor of Astronomy and Experimental Philosophy, who had succeeded Harold Jeffreys in this Chair
in 1958. Batchelor was by that time a Reader, although soon after, he was elected to the newly
established Chair of Applied Mathematics. An informal vote within the Department came out clearly in
favour of Batchelor, and that was that! Fred Hoyle gave his own version of events in his autobiography;
it is therefore no secret that he moved out of the Department in a fit of pique, and thereafter devoted his
energy, and his genius, to establishing the Institute of Theoretical Astronomy, now the Institute of
Astronomy, on Madingley Road; this took three years to accomplish. Cambridge Astrophysics and
Cosmology were thus split down the middle; nevertheless they continued to flourish within DAMTP, as
they do to this day, under the inspiration of our Lucasian Professor.
Meanwhile, Harold Jeffreys had no such problems adapting to the ethos of DAMTP; he came quite
regularly to the Common Room for his coffee until well into his 90s, usually wearing shorts and having
cycled from his home on Huntingdon Road.
The Common Room was important, but equally important for the fluid dynamics group was the fluid
mechanics laboratory in the basement where theories could be tested out against small-scale experiments.
One of the earliest experiments was the ‘tilting tank’ experiment of Steve Thorpe, demonstrating the
Kelvin-Helmholtz instability in a shear flow. The photograph that Steve took of this instability has been
reproduced in Van Dyke’s famous Album of Fluid Mechanics, and is one of the best known images of our
subject. We had a photographic dark-room attached to the lab, beautifully designed by my research
student Juri Toomre, where all the photographic processing for the lab was carried out for many years.
When Dirac retired in 1969, James Lighthill was elected to the Lucasian Chair, which he occupied till
1978, when he moved to become Provost of University College London. Stephen Hawking succeeded
him and completes a magnificent tenure of thirty years in this Chair in one week’s time.
I look back on the 1970s as the decade of Lighthill in DAMTP. His was a flamboyant presence, and a
great inspiration. Who can forget his seminar on the flight of the chalcid wasp Encarsia Formosa, which
he mimicked with such enthusiasm that he appeared to float above the podium? … or his account of his
swim round the volcanic island Stromboli while it was erupting? His great passion was swimming round
islands, and he carried this to the ultimate extreme with his nine-hour swim round the island of Sark in the
Channel Islands at the age of 74; he died while still in the water through failure of the mitral valve in his
heart, which had a weakness of which he had been unaware. This event had all the flavour of a Greek
tragedy: Lighthill was our Icarus who had flown too close to the sun!
I have written elsewhere of certain parallels between Batchelor and Lighthill on the one hand, and their
19th century counterparts, Stokes and Kelvin, on the other. In character, Batchelor and Lighthill could not
have been more different; yet they both had a passionate interest in fluid mechanics that transcended their
temperamental divergences, and ensured a decade of great achievement for both them and their research
groups throughout the ’70s. We were privileged to have such giants of the subject in our midst!
Three years after Batchelor’s retirement in 1983, we were allowed to advertise the vacant Chair of
Applied Mathematics. We were then lucky enough to attract David Crighton from Leeds who was duly
elected in 1986. This turned out to be an inspired appointment. David took over from me as Head of
Department in 1991, and served us brilliantly in this capacity till his tragically early death from cancer at
the age of 58 in the millennium year 2000. This was just 2 weeks after the death of George Batchelor; it
was indeed a traumatic time for the Department, and a sombre watershed, just as we were beginning the
move to our new premises.
During the 1990s, the Department had continued to expand under David’s direction, and the pressure on
accommodation, particularly for the growing number of research students and post-docs and the many
visitors to the department, became intolerable. At the same time, the Isaac Newton Institute for
Mathematical Sciences, which had been founded in 1991 as an initiative originating in DAMTP, was
running an exciting sequence of visitor research programmes, and a seven-acre site alongside the Newton
Institute was available for development. This combination of circumstances was irresistible, and plans
were soon afoot to establish our new Centre for Mathematical Sciences, in which both DAMTP and
DPMMS were at last to be reunited. There was a huge fund-raising campaign to make this historic move
possible. This Jubilee celebration gives us the opportunity to again thank our great benefactors for their
wonderful generosity to Cambridge mathematics. It is this generosity that enabled the realization and
completion of Ted Cullinan’s spectacular architectural design, that will provide a home and a springboard
for Cambridge mathematical sciences for centuries to come.
Keith Moffatt
September 2009