Suppression of turbulence in magnetically stabilized ferroliquids

Abstract

Under conditions of saturated magnetization ferroliquids obey Boussinesq equations in which the body force term is a combination of the ordinary gravitational force and a magnetic force that is proportional to the gradient of the magnetic field and the local temperature fluctuation. Hence non-isothermal flows of ferroliquids can be stabilized or destabilized by the application of a magnetic field. In this paper we examine the effects of magnetic stabilization which can be used to delay the transition from laminar to turbulent flow, or to suppress the level of turbulent transport in fully turbulent flows. The analogy between ferroliquid flows and stratified flows is developed to permit the application of results from studies of stratified flows. Using this analogy the magnitude of turbulence suppression is examined for a limiting case of fully developed turbulent channel flow with constant transverse heat flux. It is found that the channel friction factor can be reduced perceptably with attainable magnetic field strengths and moderate heat fluxes, and that reductions exceeding one order of magnitude can be achieved in extreme conditions. The friction factor reduction is largest for small Reynolds number and decreases with increasing flow rate when the heat flux is held constant.