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農(nóng)藥液滴撞擊移動液膜和非對稱冠狀水花形成機理分析
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國家自然科學(xué)基金項目(51806096)、飛行器環(huán)境控制與生命保障工業(yè)和信息化部重點實驗室項目(KLAECLS-E-201902)和江蘇高校優(yōu)勢學(xué)科建設(shè)工程項目


Mechanism Analysis of Pesticide Droplets Impacting Moving Liquid Film and Asymmetric Crown Behavior Formation
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    摘要:

    研究農(nóng)藥液滴在植物表面的撞擊規(guī)律對于提高農(nóng)藥噴霧效率、促進農(nóng)業(yè)病蟲害治理具有重要意義。采用CLSVOF(Coupled level set and volume of fluid)方法建立單液滴撞擊水平運動液膜的數(shù)值模型,通過分析撞擊后液體內(nèi)部的壓力分布、速度分布和渦量云圖,驗證了運動間斷、射流形成和射流頂部末端飛濺機制,揭示了非對稱水花形成機理。由計算結(jié)果可知,液膜流動產(chǎn)生冠狀水花主要體現(xiàn)在兩側(cè)射流發(fā)展行為不一致、冠基厚度不均勻和兩側(cè)射流末端飛濺現(xiàn)象不對稱,并且受液膜流動慣性的影響,冠基隨著液膜流動發(fā)生遷移,當(dāng)無量綱速度U=0.8、無量綱時間T=3.47時,冠基完全遷移至撞擊點右側(cè);頸部壓差機制導(dǎo)致射流形成,射流的發(fā)展由液滴的徑向運動和射流端部的旋渦共同決定,隨著液膜流速的增大(0~0.8),上游的射流沿水平方向快速生長,下游射流則傾向于垂直向上延伸,兩側(cè)射流末端運動速度均增大;液滴徑向運動速度和鋪展速度之間的速度差決定了射流末端飛濺狀態(tài),上游液膜流動方向與液滴鋪展方向相反,故上游末端飛濺行為比下游顯著。

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    Clarifying the impact law of pesticide droplets on the surface of plants is of great significance for improving the efficiency of pesticide spraying and pest control. A numerical model of the horizontal liquid moving liquid film with single droplet impinging was established by the method of coupled level set and volume of fluid. The motion characteristics and dynamic mechanism of the liquid droplet impacting the moving liquid film was studied, by analyzing the pressure distribution, velocity distribution and vortices cloud map inside the liquid after impact, the mechanism of kinematic discontinuity, jet flow formation and jet top-end splash were verified, and the asymmetric crown formation mechanism was revealed, it had guiding significance to explore the effective deposition and loss law of pesticide spraying. It can be seen that the flow of liquid film caused crown showed obvious asymmetric characteristics, such as the development of the upstream and downstream jets flow were inconsistent, uneven crown base thickness and different splashing degree at the end of jet flow on both sides, the crown base migrated with the flow of the liquid film, under the influence of the flow inertia of the liquid film, when the dimensionless velocity U was 0.8 and the dimensionless time T was 3.47, the crown base completely migrated to the right of the impact point;the neck pressure difference mechanism led to the formation of jet flow, and the development of the jet flow was determined by the radial movement of the droplet and the vortex at the end of the jet flow, with the increase of liquid film velocity(U is 0~0.8), the jet flow in the upstream grown rapidly along the horizontal direction, while the jet flow in the downstream tended to extend vertically upward, and the end velocity of the jet flow on both sides was increased;the velocity difference between the radial movement velocity and spreading velocity determined the splashing state at the end of the jet flow, the flow direction of the upstream liquid film was opposite to the spreading direction of the droplet, therefore the splash behavior at the upstream end was more significant than that at downstream.

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趙可,王瑜,蔣彥龍.農(nóng)藥液滴撞擊移動液膜和非對稱冠狀水花形成機理分析[J].農(nóng)業(yè)機械學(xué)報,2021,52(5):83-91. ZHAO Ke, WANG Yu, JIANG Yanlong. Mechanism Analysis of Pesticide Droplets Impacting Moving Liquid Film and Asymmetric Crown Behavior Formation[J]. Transactions of the Chinese Society for Agricultural Machinery,2021,52(5):83-91.

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  • 收稿日期:2020-07-17
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  • 在線發(fā)布日期: 2021-05-10
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