## Seminarium Zakładu Mechaniki i Fizyki Płynów## Perturbation problems at low Reynolds number, part 4.## prof. Francois Feuillebois, AMAS visiting professor, PMMH, ESPCI, Paris, France |

This is the fourth seminar of the AMAS course on this subject. For a small particle in a fluid flow, the Reynolds number is low and viscous effects are dominant. But at second order in the Reynolds number, small fluid inertial effects appear which make e.g. the particle migrate across streamlines. Such effects first demonstrated experimentally by Segré and Silberberg have been the incentive for numerous calculations thereafter. These effects are important e.g. for separation techniques used in analytical chemistry ("Field Flow Fractionation", "SPLITT" cell). The presentation will focus on the resolution of regular and singular perturbation problems for the flow around a sphere at low Reynolds number. It will start from Oseen's solution revisited by Rubinow & Keller and Saffman solution for the lift force on a sphere in a shear flow. Walls effects combined with fluid inertial effects will be presented, both for regular perturbation problems and singular ones.