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中文核心期刊

逆向等离子体合成射流抑制低速流动分离的研究

OPPOSING PLASMA SYNTHETIC JET FOR LOW-SPEED FLOW SEPARATION INHIBITION

  • 摘要: 等离子体合成射流是一种能抑制流动分离的高能激励. 通过实验和数值仿真的方法调查了等离子合成射流对低速翼型流动分离的抑制. 激励器的电极内置在翼型内部, 射流孔位于前缘点. 流场烟雾粒子浓度分布和数值模拟的结果均表明逆向等离子体合成射流能推移低速翼型的流动分离点, 并提升翼型的升力特性. 逆向等离子体合成射流推移分离点距离和提升翼型升力特性的能力随迎角的增大而增强. 当迎角为16°时, 等离子体激励推移翼型流动分离点的距离约占弦长的16.5%, 提升翼型升力系数约17.3%. 结果表明低速流动中, 逆向等离子体合成射流产生的热射流与主流相互作用会形成条带状热结构. 条带状热结构具有先导掺混作用, 能增强主流与分离剪切层内流体的掺混. 而射流主体具有掺混和诱导作用, 能诱导分离剪切层的动态重新附壁. 条带状热结构、射流主体与主流的相互作用是逆向等离子合成射流抑制低速翼型流动分离, 提高翼型升力特性的主要机制. 在不同的阶段, 条带状热结构的作用和射流主体的作用不同. 这种差异性导致它们的耦合性也发生了变化, 并使得翼型的升力特性出现了五种典型阶段. 此外, 实验结果还表明放电参数恒定时, 串联阵列式激励器的流动控制效果强于单个激励器.

     

    Abstract: The plasma synthetic jet is a comprehensive high-energy excitation with a strong ability to restrain flow separation. This paper uses experimental and numerical simulation methods to investigate the inhibition of flow separation by plasma synthetic jets on a low-speed airfoil. The actuator's electrodes are built into the wing, and the injection holes are located at the leading-edge point. The smoke particle concentration distribution and the numerical simulation results show that the opposing plasma synthetic jet can move the flow separation point of the low-speed airfoil and improve the lift characteristics of the airfoil. The ability of the opposing plasma synthetic jet to drive the separation point distance and enhance the airfoil's lift characteristics will increase with the angle of attack. At an angle of attack of 16°, plasma actuation pushes the distance of the airfoil flow separation point to about 16.5% of the chord length, increasing the airfoil's lift coefficient by about 17.3%. The results show that in the low-velocity flow, the thermal jet generated by the opposing plasma synthetic jet interacts with the mainstream to form a strip-like thermal structure. The strip-shaped thermal structure has a leading mixing effect, which can enhance the mixing of the mainstream and the fluid in the separated shear layer. The jet body has a mixing-inducing impact, which can induce the dynamic re-attachment of the separated shear layer. The interaction between the strip-like thermal structure and the mainstream and between the jet body and the mainstream are the primary mechanisms for the opposing plasma synthetic jet to inhibit the flow separation of the low-speed airfoil and improve the lift characteristics of the airfoil. The strip-like thermal structure acts differently from the jet body at different stages. The difference leads to the change in their coupling and makes the lift characteristics of the airfoil appear in five typical phases. In addition, the experimental results also show that when the discharge parameters are constant, the flow control effect of the serial array actuator is more potent than that of a single actuator.

     

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