摘要
将表面包覆电磁激活板的翼型,按一定的攻角,置于流动的弱电介质溶液中,电磁激活板可产生作用于流体的切向电磁力(Lorentz力),从而改变流体边界层的结构.在转动水槽中,对翼型绕流及电磁力控制下的绕流形态进行了实验研究.结果表明,未加电磁力时,前缘涡的脱落点是不确定的,与流场具体条件有关,而后缘涡仅在尖角处脱落.前缘涡与后缘涡相互影响,并周期性的脱体,在尾部形成涡街.施加电磁力后,当力的方向与流动方向相同时,可以在一定程度上抑制分离,消除涡街,其效果与减小攻角类似.加反向电磁力时,则相当于加大攻角,在翼型体的背风面形成涡街.
An actuator, consisting of a specific array of alternating stripwise electrodes and permanent magnets, will generate a wall-parallel Lorentz force as submerged in a weakly conducting fluid, which influences the flow in the boundary layer. The experiments have been conducted in a rotating annular tank filled with a copper sulphate （CuSO4） electrolyte, to investigate the flow around a hydrofoil and its electromagnetic control. To reveal the transient behavior of controlled flow from the initial to the final steady state, the flow fields were visualized by potassium permanganate （KMnO4） used as a marker and record by a camera. To verify the influence of flow control on the lift and the drag of a hydrofoil, force measurements have been carried out by strain gages attached to a fixed beam to which the hydrofoil is suspended. It has been shown from the experimental results that, for the absence of the Lorentz force, there exist two kinds of vortex, i.e. shedding on the leading edge and the trailing edge respectively, which affect each other and finally leave the leeward surface of the hydrofoil periodically to form a wake. The influences of the Lorentz force on the flow around the hydrofoil are just something like the variations of the attack angle. The Lorentz force in streamwise direction can suppress the flow separation and the wake, as happened in the cases with a small or zero attack angles. In contradiction, for the reversed Lorentz force, the vortex street on the leeward surface of hydrofoil is introduced, as happened in the cases with a big attack angle.
出处
《力学学报》
EI
CSCD
北大核心
2008年第1期121-127,共7页
Chinese Journal of Theoretical and Applied Mechanics
关键词
电磁场
翼型绕流
流体控制
electromagnetic field, wake of hydrofoil, flow control
