Experimental Investigations on the Effect of a Wavy Surface on Hydrodynamic Instabilities in a Taylor-Couette System

Abstract

In this work, we propose an experimental study of the effect of surface roughness of the internal cylinder Couette-Taylor system in order to investigate the hydrodynamic instabilities of the flow. During experiments, the inner cylinder, which presents a rough surface with u cylinder corrugations, rotates at a given angular speed and the outer cylinder, which is smooth, is kept fixed. The main objective of the study is to demonstrate the effect of geometric parameters on the flow (the shape of the roughness). Experimental results have shown that the shapes of the surface irregularities have an effect on the appearance of the first instabilities, which strongly depend on the size, shape and nature of the roughness. In fact, the nature of surface roughness not only affects the friction on the wall, but also strongly influences the transport of mass and momentum in a given flow regime. The flow therefore evokes more friction when the inner (rotating) cylinder has a rough surface. This friction, which slows the speed of the fluid particles, strongly depends on the surface nature in contact with the fluid. The movement of the particles in these irregularities will therefore, be damped as a function of the shape of the roughness. In addition, the results also showed that once Couette-Taylor vortices are present, surface roughness can promote continued flow disturbance. The resulting flow then becomes less slow in the troughs of surface irregularities; thus, leads to less friction.