Fritz Ursell

Fritz Joseph Ursell (born April 28, 1923 in Düsseldorf ; † May 12, 2012 in Manchester ) was a German-British applied mathematician who dealt with hydrodynamics .

Life

Ursell, whose father Siegfried Ursell was a pediatrician, attended the Comenius-Gymnasium in Düsseldorf-Oberkassel and came to Great Britain in 1937 as a young Jewish refugee from the National Socialists (his parents and sister also followed). He attended Clifton College and Marlborough College and studied from 1941 with a talented scholarship mathematics at Trinity College of Cambridge University with a bachelor's degree in 1943 and then worked for the British Admiralty to problems of wave forecasts in a team under the chemist and oceanographer George Deacon (1906-1984). The work was of importance to the landing companies in Normandy and the Pacific.

In 1947 he went to the University of Manchester as a Post Doctoral Fellow of ICI (without ever receiving a doctorate). In the same year he received a fellowship from Trinity College, Cambridge, but asked for a three-year delay to stay in Manchester for the time being. In 1950 he became a lecturer in Cambridge. There he also met the hydrodynamicist GI Taylor .

In 1951 he was in the USA, where he met Richard Courant and Kurt Friedrichs in New York and Garrett Birkhoff at Harvard University . In 1957/58 he was with Arthur Ippen at the Massachusetts Institute of Technology . From 1961 he taught again at the University of Manchester as Beyer Professor of Applied Mathematics. In 1990 he retired.

In addition to various problems relating to water waves and their interaction with structures (such as obstacles or hulls), he also published on asymptotic developments in analysis and theoretical acoustics.

In 1959 he married Katharina Renate Zander, whom he had met in New York and with whom he had two daughters.

Ursell number

The Ursell number in the nonlinear theory of surface waves under the influence of gravity is named after him:

${\ displaystyle U = {\ frac {\ lambda ^ {2} \, H} {h ^ {3}}} = {\ frac {H} {h}} {({\ frac {\ lambda} {h} })} ^ {2}}$

with the wave height (difference between the wave valley and the wave crest), the mean water depth and the wave length. Except for a constant of the order of magnitude, it shows the ratio of the leading and the next leading term in the Stokes expansion (according to George Gabriel Stokes ) of the surface displacement and is an indication of whether linear wave theory (for long waves and ) or a non-linear wave equation are used must (like the Korteweg-de-Vries equation or the Boussinesq equation ). ${\ displaystyle H}$ ${\ displaystyle h}$ ${\ displaystyle \ lambda}$ ${\ displaystyle {\ frac {1} {100}}}$ ${\ displaystyle \ lambda >> h}$ ${\ displaystyle U << 100}$

Honors

In 1972 he became a Fellow of the Royal Society .

Fonts

The effect of a fixed vertical barrier on surface waves in deep water, Math. Proc. Cambridge Phil. Soc., Vol. 43, 1947, pp. 374-382
with Norman Frederick Barber: The Generation and Propagation of Ocean Waves and Swell. I. Wave Periods and Velocities, Philosophical Transactions of the Royal Society A, Volume 240, 1948, pp. 527-560
Surface waves on deep water in the presence of a submerged circular cylinder, 2 parts, Math. Proc. Cambridge Phil. Soc., Vol. 46, 1950, pp. 141-152, 153-158
Trapping modes in the theory of surface waves, Math. Proc. Cambridge Phil. Soc., Vol. 47, 1951, pp. 347-358
Edge waves on a sloping beach, Proc. Roy. Soc. A, Vol. 214, 1952, pp. 79-97
The long-wave paradox in the theory of gravity waves, Math. Proc. Cambridge Phil. Soc., Vol. 49, 1953, pp. 685-694
On Kelvin's ship wave pattern, J. Fluid Mech., Vol. 8, 1960, pp. 418-431
The transmission of surface waves under surface obstacles, Math. Proc. Cambridge Phil. Soc., Vol. 57, 1961, pp. 638-668
The decay of free motion of a floating body, J. Fluid Mech., Vol. 19, 1964, pp. 305-319
On the rigorous foundation of short-wave asymptotics, Math. Proc. Cambridge Phil. Soc., Vol. 62, 1966, pp. 227-244
Ship Hydrodynamics, Water Waves, and Asymptotics: Collected Papers of F. Ursell, 1946-1992. Advanced Series on Fluid Mechanics. World Scientific, 2 volumes, 1994
Reminiscences of the early days of the spectrum of ocean waves, in: SG Sajjadi, N .H. Thomas, JCR Hunt (Ed.), Wind-over-wave couplings. Perspectives and prospects, Oxford University Press, 1999, pp. 127-137.

literature

ID Abrahams, PA Martin: Fritz Joseph Ursell. April 28, 1923 - May 11, 2012 , Biographical Memoirs of Fellows of the Royal Society, 2013, pp. 407-421
ID Abrahams, PA Martin, AN Norris: GR Wickham: An appreciation , Wave Motion, Volume 33, 2001
PA Martin, GR Wickham (Ed.): Wave Asymptotics: The Proceedings of the Meeting to Mark the Retirement of Professor Fritz Ursell from the Beyer Chair of Applied Mathematics in the University of Manchester. Cambridge University Press 1992

Web links

Individual evidence

↑ Fellow students at the time were Freeman Dyson and James Lighthill
↑ At the conference on the occasion of his retirement in 1990 in Manchester, he also gave a lecture: Some unsolved and unfinished problems in the theory of waves

personal data
SURNAME	Ursell, Fritz
ALTERNATIVE NAMES	Ursell, Fritz Joseph (full name)
BRIEF DESCRIPTION	German-British applied mathematician
DATE OF BIRTH	April 28, 1923
PLACE OF BIRTH	Dusseldorf
DATE OF DEATH	May 12, 2012
Place of death	Manchester

[1] Fellow students at the time were Freeman Dyson and James Lighthill

[2] At the conference on the occasion of his retirement in 1990 in Manchester, he also gave a lecture: Some unsolved and unfinished problems in the theory of waves