#### Applied mathematician and teacher who did significant work on high-speed aerodynamics and plasma theory

Leslie Woods was an applied mathematician of considerable repute in a number of fields, and one who contributed much to the academic life of several universities throughout the British Commonwealth.

Leslie Colin Woods was born in New Zealand in 1922 and went to Seddon Memorial Technical College, Auckland. His university education was interrupted by the Second World War, and his first degree was taken, literally, on the wing while he was serving as a commissioned officer in the RNZAF as a fighter pilot in the Pacific.

After the war he took a degree in mechanical engineering, and a Rhodes scholarship took him to Oxford, where he completed a DPhil in engineering science and a BA in mathematics. He joined the newly formed New Zealand Defence Scientific Corps in 1951 and spent the next three years on secondment at the National Physical Laboratory working on high-speed aerodynamics.

It was a time of rapid development in the field, with many of the world's most distinguished workers at the NPL. His own contributions while there and subsequently at the universities of Sydney and of New South Wales are contained in a considerable textbook

*The Theory of Subsonic Plane Flow.*Appointed professor at New South Wales in 1956, he soon became involved in the academic development of the university, while at the same time, thanks to contact with the work at Lucas Heights, he became interested in neutron transport.

While on leave at Harwell in 1960 he met for the first time the problems of low-frequency wave propagation in plasmas, and soon established a reputation by treating problems with realistic boundary conditions and complexity of collision processes so that comparison could be made directly with the experimental work in progress.

This interest led to a continuing association when the Culham Laboratory was established, while he found an academic base in Oxford, first in the department of engineering science and, from 1964 onwards, in the Mathematical Institute.

He was elected professor of mathematics, with particular reference to plasma theory, in 1970. During this period he was a frequent visitor to such universities as Monash, Berkeley, MIT, Austin, Maryland, Haifa, Witwatersrand, Cornell and Canterbury, building up fruitful collaboration with colleagues around the world.

His early training as a mechanical engineer, coupled with his mathematical sensitivity, led to a longstanding dissatisfaction with the concept of entropy as traditionally presented.

This finally found its resolution in a book

*The Thermodynamics of Fluid Systems*(1975), in which the importance of timescales was made clear. He was much concerned about the formulation of problems and particularly that in a physical situation the physics should be preserved rather than looking for mathematical simplicity -- the art of modelling was how he usually referred to it.

He was active in encouraging scientific publication both on behalf of the Oxford University Press and as a founder editor of the

*Journal of the Institute of Mathematics and its Applications*.

A large number of scientists throughout the world have been encouraged at some time by his comments and interest.

Woods retired in 1990 but continued to be active up to the time of his death. His textbooks

*Kinetic Theory of Magneto Plasmas*and

*Thermodynamic Inequalities in Gases and Magneto Plasmas*were published in 1993 and 1996. His style was generally held to be provocative and was well summed up in an autobiography,

*Against the Tide*, published in 2000.

Woods was married three times. Two of the five daughters of his first marriage predeceased him.

Professor Leslie Woods, mathematician, was born on December 6, 1922. He died on April 15, 2007, aged 84

15 May 2007 © The Times