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Influences of Lorentz force on the hydrofoil lift

Acta Mechanica Sinica 2009年第5期25卷 589-595页

作者： yaohui chen baochun fan zhihua chen hongzhi li laboratory of transient physics,nanjing university of {3. and Technology,210094 nanjing, china laboratory of transient physics Nanjing University of Science and Technology 210094 Nanjing China

In this paper, Lorentz forces are proved to be able to suppress separation in flows over hydrofoils. Furthermore, a differential equation of pressure distributions on the hydrofoil surface is derived, from which it is found that BVF （boundary vortex flux） σ is a suitable criterion for describing the lift coefficient variations during the electromagnetic control process. According to our numerical results, the periodic variations of lift for a hydrofoil at an attack angle of 17 ° are analyzed and its inherent mechanism is discussed in detail with the concept of BVE On the other hand, the effects of Lorentz force on the hydrofoil＇s lift are investigated both experimentally and numerically for different magnitudes and locations.

关键词： Lorentz force lift coefficient Hydrofoil

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Flow pattern and lift evolution of hydrofoil with control of electro-magnetic forces

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science china(physics,Mechanics & Astronomy) 2009年第8期52卷 1364-1374页

作者： chen yaohui fan {3. chen zhihua li hongzhi National Key laboratory of transient physics Nanjing University of Science&TechnologyNanjing 210094China

The initial responses and evolutions of the flow pattern and lift coefficient of a hydrofoil under the action of electro-magnetic (Lorentz) force have been studied experimentally and numerically, and trace particle methods are employed for them. With the introduction of BVF (boundary vortex flux), the quantitative relation among Lorentz forces, BVF and lifts is deduced. The influences of flow patterns on the hydrofoil lift coefficient have been discussed based on the BVF distribution, and the flow control mechanism of Lorentz force for a hydrofoil has been elucidated. Our results show that the flow pattern and lift of the hydrofoil vary periodically without any force. However, with the action of streamwise Lorentz forces, the separation point on the hydrofoil surface moves backward with a certain velocity, which makes the flow field steady finally. The streamwise Lorentz force raises the foil lift due to the increase of BVF intensity. On the other hand, Lorentz force also increases the hydrofoil surface pressure, which makes the lift decrease. However, the factor leading to the lift enhancement is determinant, therefore, the Lorentz force on the suction side can increase the lift, and the stronger the Lorentz force, the larger the lift enhancement. Our results also show that the localized Lorentz force can also both suppress the flow separation and increase the hydrofoil lift coefficient, furthermore, the Lorentz force located on the tail acts better than that located on the front.

关键词： Lorentz force hydrofoil wake flow control

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Experimental Research on the Mechanism of lift Amplification and Vibration Suppression of Lorentz Force

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Defence Technology（防务技术） 2013年第2期9卷 110-116页

作者： ZHANG Hui fan baochun chen {3. li hongzhi li Baoming science and Technology on transient physics {3. Nanjing University of Science and Technology

The Lorentz force generated by electromagnetic field on the surface of the cylinder in the electrolyte solution may modify the structure of the flow boundary layer effectively. The transient control process of Lorentz force is investigated experimentally for lift amplification and vibration suppression. The experiments are conducted in a rotating annular tank filled with a low-conducting electrolyte. A cylinder with an electro-magnetic actuator is placed into the electrolyte. The lift force of cylinder is measured using the strain gages attached to a fixed beam, and the flow fields are visualized by the dye markers. The results show that the upper vortex on the cylinder is suppressed, and the wake becomes a line and leans to the lower side under the action of upside Lorentz force while the lower vortex on the cylinder is suppressed and limited in a small region. Therefore, the value of lift increases with the variation of flow field. However, the vortexes on the cylinder are suppressed fully under the action of symmetrical Lorentz force which leads to the suppression of lift oscillation and then the vibration of cylinder are suppressed fully.

关键词： hydromechanics flow control Lorentz force vortex-induced vibration cylinder wake

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