Philip Geoffrey Saffman FRS[1] (19 March 1931 – 17 August 2008) was a mathematician and the Theodore von Kármán Professor of Applied Mathematics and Aeronautics at the California Institute of Technology.

He is known (with his co-author Geoffrey Ingram Taylor) for the Saffman–Taylor instability in viscous fingering of fluid boundaries,[16] a phenomenon important for its applications in enhanced oil recovery, and for the Saffman–Delbrück model of protein diffusion in membranes which he published with his Caltech colleague and Pasadena neighbour Max Delbrück.

[7][8][17][22][23] His nomination for the Royal Society reads: Distinguished for his important contributions to fluid mechanics in more than 140 papers characterised by originality, powerful mathematical analysis, and deep physical insight.

The problems he has illuminated include the following: dispersion in porous media, fingering in a Hele-Shaw cell, the interaction of molecular and macroscopic mixing in turbulent fluid, the forces on a small particle in moving fluid, the effect of dust particles on stability of gas flows, the dynamics of homogeneous turbulence, the shear layers bounding a Taylor column, vortex rings, trailing line vortices from aircraft wings, stability of vortex streets, diffusion of macromolecules in cell walls, nonlinear gravity-capillary waves, and instability of finite-amplitude water waves.

[2]Saffman was survived by his wife (Ruth Arion whom he married in 1954), three children (Mark, Louise, Emma), and eight grandchildren (Timothy, Gregory, Rae, Jenny, Nadine, Aaron, Miriam, Alexandra and Andrey.