Efficiency improvements of electromagnetic flow control

• Published in: International journal of heat and fluid flow 2005-08, Vol.26 (4), p.635-655
• Main Authors: Spong, E., Reizes, J.A., Leonardi, E.
• Format: Article
• Language: English
• Subjects: Electro-MHD actuators; Exact sciences and technology; Flow control; Flow sensors; Fluid dynamics; Fundamental areas of phenomenology (including applications); Lorentz forces; Near-wall turbulence; Physics; Turbulence control; Turbulent flows, convection, and heat transfer
• ISSN: 0142-727X; 1879-2278
• DOI: 10.1016/j.ijheatfluidflow.2005.04.001

In turbulent flow, frictional resistance and heat transfer are controlled to a large degree by the intensity of the turbulence fluctuations in the near vicinity of a surface. In the case of a weak electrically conducting fluid, such as seawater, turbulence intensity can be controlled by subjecting the fluid to electromagnetic fields. This technique, known as Electro-magneto-hydro-dynamic (EMHD) flow control, has been shown to have promise as a means of reducing the turbulence intensity, and hence heat transfer or frictional drag of turbulent boundary layers. Unfortunately EMHD flow control currently suffers from poor efficiency due to the high energy requirements of the electromagnetic field. A numerical study has been conducted in which a new electromagnetic actuator design has been developed to provide a more efficient spatial distribution of the electromagnetic forces. The new actuator design has then been coupled to an ideal flow sensor. A flow control subroutine, embedded in the numerical model, uses the velocity information from the ideal sensor to determine the appropriate actuating force to apply to the flow at each time step. The new actuator design has been shown to be capable of successfully attenuating a sequence of artificial low speed streaks in a simplified model of a low Reynolds number turbulent boundary layer. Thus, a potential solution to the poor efficiency of EMHD flow control has been offered by providing the means whereby the expensive electromagnetic forces can be strategically and sparingly applied to the flow.