Observing magnetic objects in fluids

This thesis describes two topics dealing with objects moving through fluids. The first project considers centimetre-sized magnetic particles submerged in a turbulent water flow. We have studied how these particles interact with each other and self-assemble into clusters. By investigating their motion using multiple cameras we have compared their behaviour with the theory of thermodynamics. The second project deals with magneto tactic bacteria, which are self-propelled micro-organisms aligning with external magnetic field. By observing the response of both individual and entire cultures of bacteria we have characterised properties corresponding to their motion.