Motion of micro-particles of complex shape

Motion of a particle suspending in a Newtonian fluid subject to an external force and flow becomes complex if the particle shape is not simple. For example, a propellar like particle rotates as it settles down, and a helical particle migrates normal to the ambient fluid velocity in shear flow. These properties are important in separating and manipulating micro-particles. To analyse the motion, we constructed a simulator which calculates the Brownian motion of a particle of general shape subject to force, torque and external flow. The basic principle of the simulator, and several applications are discussed.