Electromagnetic flow control in weakly conducting fluids

Electromagnetic, i.e. Lorentz forces can be used to control the flow of conducting fluids. This holds true even if the electrical conductivity is only weak, as in the case of electrolytes like sea-water.

The applications of streamwise, wall parallel Lorentz forces to generic flow configurations will be exemplified with experimental data from flat plate boundary layers and separated flows around cylinders and hydrofoils. These results demonstrate the ability of stationary Lorentz forces to change the velocity profile in boundary layers and thereby to improve their stability properties, as well as to completely suppress separation. Time dependent Lorentz forces are used to mitigate the lift loss and drag increase of hydrofoils caused by flow separation. In this case, the versatility of Lorentz force actuators allows for detailed experimental investigations especially of the effects of excitation frequency and wave form.

Finally, the impact of the low conductivity on the energy balance of Lorentz force actuators is discussed.