## Seminarium Zakładu Mechaniki i Fizyki Płynów## "Brownian motion of a particle immersed in a viscous compressible fluid between two parallel plane walls"## prof. B.U. Felderhof, RWTH Aachen, Germany (ABIOMED visiting professor) |

23.11.2005, godz. 12:30, sala 100 prof. B.U. Felderhof, RWTH Aachen, Germany (ABIOMED visiting professor) "Brownian motion of a particle immersed in a viscous compressible fluid between two parallel plane walls" The motion of macromolecules in a fluid in confined geometry, such as a biological cell, is strongly influenced by the presence of the walls. Brownian motion of the particle leads to diffusion with a diffusion coefficient dependent on the position relative to the walls. The diffusion coefficient can be calculated from steady-state hydrodynamics and is independent of the compressibility of the fluid. The velocity correlation function of Brownian motion on a short time scale requires a more complicated hydrodynamic calculation. In confined geometry on a small length scale compressibility of the fluid becomes important. We find that for motion between two plane walls the velocity relaxes at long times with a negative long-time tail inversely proportional to the square of time.