Diffusion of a Brownian ellipsoid in a force field
  We calculate the effective long-term convective velocity and dispersive motion of an ellipsoidal Brownian particle in three dimensions when it is subjected to a constant external force. This long-term motion results as a "net" average behavior from the particle rotation and translation on short time scales. Accordingly, we apply a systematic multi-scale technique to derive the effective equations of motion valid on long times. We verify our theoretical results by comparing them to numerical simulations. 
Erik Aurell, Stefano Bo, Marcelo Dias, Ralf Eichhorn and Raffaele   Marino
cond-mat.stat-mech cond-mat.soft