The son of a lawyer, David Allan Spence was born in Auckland, New Zealand in 1926.
After his education at Kings' College, Auckland, and the University of Auckland he moved to Clare College, Cambridge, taking a doctorate in engineering in 1952. He then joined the scientific staff of the Royal Aircraft Establishment at Farnborough.
For many purposes, the flow of air or fluid past a solid body may be treated by splitting the fluid into a "boundary layer" close to the body, where turbulence and viscosity are important, and the rest. Such boundary layers are critical in the design of aircraft wings, because they determine the lifting force and the drag or resistance. What happens at the trailing edge is particularly important.
Spence worked particularly on the "jet flap", which is used to eject a thin jet of air at the trailing edge. This enabled performance to be enhanced by increasing lift and decreasing drag. Spence also worked on propagation of shockwaves and how such waves are weakened by viscosity, questions of great importance for supersonic flight.
In 1964 he joined the engineering department at Oxford, becoming a Fellow of Lincoln. He remained in Oxford for the best part of 20 years, before being appointed a Professor of Mathematics at Imperial College London, where he had special responsibility for teaching maths to engineering and science students.
His research interests were stimulated by his many visits to universities in Australia, New Zealand and the US, especially Cornell and the California Institute of Technology.
After his successful use of complex analysis and asymptotics in aerodynamics and the mechanics of solids, Spence showed his versatility by applying them to geophysics. The motivation here was better to understand magma flow beneath the Earth's surface and how it behaves in the presence of fractures -- which is crucially important in the study of volcanic eruptions. Further work concerned the use of injected water to enhance oil recovery from a well, which is important for energy conservation of depleting reserves in areas such as the North Sea.
He was a Fellow of the Royal Aeronautical Society, and of the Institute of Mathematics and its Applications and was a member of the London Mathematical Society. However, he had a variety of intellectual interests beyond mathematical and engineering research, particularly in political history and the law.
David Spence was a quiet, thoughtful and kindly man with a great love for and pride in his family. In his younger days he was keen on golf and on strenuous walking in mountainous regions. After his retirement, in 1991, he remained very active mathematically and scientifically, despite a long illness.
He is survived by his wife, Isobel, and their two sons and two daughters.
Professor D. A. Spence, mathematician, was born on January 3, 1926. He died on September 7, 2003, aged 77.
Copyright © The Times, 2003