Professor Ludwig Edward Fraenkel died on 27 April 2019.
Ludwig Fraenkel earned a PhD degree from Cambridge in 1968. His academic positions included a lectureship at Imperial College London and senior positions at the University of Sussex in Brighton, University of Cambridge, and University of Bath.
He was awarded the Senior Whitehead Prize of the London Mathematical Society in 1989 and elected a Fellow of the Royal Society in 1993.
Edward Fraenkel was internationally renowned for his research in the field of hydrodynamics, with high impact results which contributed to the development of both the theory of hydrodynamics and the applications. One of his most famous achievements is a resolution of the Stokes conjecture that concerns gravity waves of permanent form on the free surface of an ideal liquid. The proof of the conjecture was developed in collaboration with C. J. Amick and J. F. Toland and published in Acta Mathematica in 1982 .
A recording of a two-part interview that Prof. Fraenkel gave in 2017 about his life and career is available at the website of the University of Bath.
 C. J. Amick, L. E. Fraenkel, and J. F. Toland. On the Stokes conjecture for the wave of extreme form. Acta Math. Volume 148 (1982), 193-214. https://projecteuclid.org/euclid.acta/1485890159
Image source: https://twitter.com/SAMBa_CDT/status/868084364218961920