Professor Leslie Howarth

Leslie Howarth, mathematician: born 23 May 1911; Berry-Ramsey Research Fellow, King's College, Cambridge 1936-45; Lecturer in Mathematics, Cambridge University 1936-49; Fellow, St John's College, Cambridge 1945-49; Professor of Applied Mathematics, Bristol University 1949-64, Henry Overton Willis Professor 1964-76 (Emeritus); FRS 1950; OBE 1955; married 1934 Eva Priestley (two sons); died Maldon, Essex 22 September 2001.

In 1949 Leslie Howarth went to Bristol University as Professor of Applied Mathematics. He promptly used his experience to start the strong research group in fluid mechanics at Bristol that thrives to this day.

He brought Keith Stewartson from Cambridge at once and soon attracted Bill Chester from Manchester, following these with many other successful appointments at Bristol. In 1950 Howarth was elected to the fellowship of the Royal Society, in 1951 he won the Adams Prize, and in 1953 Modern Developments in Fluid Dynamics: high speed flow was published for the Aeronautical Research Council under his editorship. For volume viii of the Handbuch der Physik (1959) he wrote the article "Laminar Boundary Layers": an influential, lucid and comprehensive review of boundary-layer theory up to the impact the theory received from singular-perturbation theory in the 1960s.

Howarth was a courteous, modest, kind and generous man of high integrity, given to saying whatever circumstances called for, but seldom more. He cared as much for the personal welfare of his staff and students as for their academic prowess, and he would always put the affairs of others before his own research.

The administrative duties of a professor, before the days of personal chairs, were unavoidable and consumed the time of such a conscientious man, who felt that it was his duty to attend (and fully brief himself for) every meeting to which he was invited, whether an Aeronautical Research Council committee or a civil service promotions board in London, or a faculty meeting in Bristol. But he found the energy to do this without its distracting him from developing the applied mathematics group in Bristol into one of the strongest in Britain.

In 1962 Howarth invited the British Theoretical Mechanics Colloquium, that is the annual meeting of British applied mathematicians, to meet in Bristol. To set up a bank account for the Colloquium, he went with the treasurer, Derek Moore, a young lecturer, to see a bank manager. The manager seemed to eye them suspiciously, but eventually agreed to set up the account. On leaving the bank, Howarth said that he felt that the manager was surprisingly unfriendly over such a routine matter. Moore offered no explanation, omitting to mention that the previous week the same manager in the same office had refused to lend him the money to buy a high-powered motor bicycle. Of course, the Colloquium was carefully planned and was a success, bringing in a record number of participants.

Leslie Howarth was born in 1911 and, a very bright boy, entered Accrington Grammar School, then went on to Manchester University, where he graduated in mathematics under the influence of Sydney Goldstein. As was not uncommon in the 1930s, graduates of provincial universities would take another degree at Cambridge. It so happened that at this time Goldstein moved from Manchester to Cambridge, so it was no surprise that Howarth entered Gonville and Caius College at Cambridge in 1931 and took Part II of the Mathematical Tripos in 1933.

He was taken on by Goldstein as a research student, won the Smith's Prize in 1935 and got his PhD in 1936, for the theory of flow past a cylinder. He became a Fellow of King's College and a Lecturer in Mathematics at Cambridge University in 1936.

This was a time when rapid improvements in aeroplane designs were called for, and Howarth was one of an élite of applied mathematicians working on the theory underpinning aerodynamics. It was a golden age for research in boundary-layer theory, a key to the drag of a stream of fluid on a body, such as air on a wing. Howarth followed the papers based on his PhD work with a sequence of papers that have become classics, pushing forward the understanding of boundary layers on bodies.

One paper, then at the frontier of research, involved some lengthy laborious computations with hand operation of the primitive mechanical calculators of the day; although today it would be an easy exercise for an afternoon's work on a PC by a research student, it took Howarth, with his wife's help, months – but they got it right. Goldstein naturally recruited Howarth to contribute to a book, Modern Developments in Fluid Dynamics, he was editing; the book, published in 1938, soon became a landmark in the literature of fluid mechanics.

Howarth spent 1937-38 on leave at the California Institute of Technology, and branched out into another topic, also related to the drag on a body – turbulence. With Professor Theodor von Karman, he wrote a paper on what has come to be called the Karman-Howarth relation; the paper remains to this day one of the few enduring papers in the notoriously difficult topic of turbulence. It seems that Howarth was the last British survivor of this golden age of research before the Second World War.

The advent of the war led to Howarth's service at the External Ballistics Department Ordnance Board from 1939 to 1942 and the Armament Research Department, 1942-45. He worked on the theory of the aerodynamics and dynamics of external ballistics and on the design and analysis of experimental trials. For this secret work and later work for the scientific civil service he was appointed OBE in 1955.

Howarth returned to his lectureship at Cambridge in 1945, transferring to a fellowship at St John's College. He was joined by George Batchelor in setting up the research group in fluid mechanics, a communicating group rather than a few lone individual researchers. In 1948 they started the fluids seminars on Friday afternoons that continue to this day.

At Bristol, he was Dean of the Faculty of Science from 1957 to 1960. In 1964 he became the Henry Overton Wills Professor of Mathematics and Head of the Department of Mathematics. He retired in 1976, living quietly with his wife in Henleaze, a suburb of Bristol, until 1997, when they moved to a residential home in Essex.

Philip Drazin and John Shepherdson