| Turbulence control using electromagnetic forces has been demonstrated over the last few years. A number of questions arose from these early experiments. Firstly, the role three-dimensionality played due to the arrangement of electrodes and magnetic poles; and secondly, the non-dimensional scaling to much larger free stream velocities and to the boundary layers of different thickness. To avoid some of the complexity of the earlier experiments and to more clearly illuminate the underlying physics of electromagnetic control, we have studied, in this work, a two-dimensional channel flow with both “type I” and “type II” electromagnetic turbulence control (EMTC) and, in particular, with the simplest configuration for the electromagnetic fields.; “Type I” EMTC experiments have been performed in channel flows with a novel single tile and injection of 5M NaOH solution. In the range of Reynolds number 4,000 < Re < 6,000, we found a reduction in near the wall velocity by as much as 20% with a uniform magnetic field | B| ∼ 0.7 Tesla and an average current density |J| in the range of 570–900 mA/cm2. The corresponding effects of Richardson number in both the buoyancy case and Lorentz force case were measured. The equivalent Richardson number for the Lorentz force was estimated to be an order of magnitude larger than the corresponding buoyancy force in the channel flow at the same injection rate.; A very simple source of vorticity (effectively in the streamwise direction) was generated by an array of EMTC tiles and for the “type II” experiments. With a similar range of Reynolds number and electromagnetic fields as in the “type I” case, a reduction in the near wall velocity by as much as 10% was found and a particularly reduction (approximately 18%) was found at one Reynolds number for a particular Interaction number. More work is needed to clarify this finding.; In either case a critical Richardson number and Interaction number was found, below which no effect was measured.; These experiments provide a simple flow field and a well-defined set of measurements against which numerical predictions can be compared. |
