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航行器在水中行驶时产生的摩擦阻力是影响其耗能和速度最主要的原因，主动减阻技术对降低水下航行器航行过程中摩擦阻力，提升航行器综合性能具有重要意义．本文采用分子动力学方法研究了通入气体后Couette流在纳米通道内液体的流动特性和边界减阻特性，分析了表面润湿性、剪切速度和气体通入量对边界滑移速度和减阻效果的影响规律．研究结果表明：当气体以离散气泡形式吸附于固体表面时，气泡会阻碍近壁面液体流动及滑移减阻，增强表面疏水性、提高剪切速度及增加气体通入量可促进气泡横向铺展，减弱对液体流动的阻碍作用，提升滑移效果；提高表面疏水性、剪切速度和气体通入量均有利于离散气泡形成气膜；气膜形成后，剪切应力显著降低，滑移速度随润湿性、剪切速度和气体通入量的变化呈现不同的变化规律．研究结果为船舶和水下航行器中主动气膜减阻技术和表面结构设计提供理论依据．Friction resistance is the primary factor influencing the energy consumption and speed of underwater vehicles. Active air layer drag reduction is an active boundary layer control technique that reduces wall friction drag by injecting gas into the solid-liquid boundary layer. Compared to other drag reduction methods, which are often difficult to scale due to high costs and potential environmental concerns, this technology utilizes a simple auxiliary device. By employing inexpensive and environmentally friendly compressed air or combustion exhaust gases, it effectively lowers fluid resistance. Therefore, active drag reduction technology plays a crucial role in minimizing friction and enhancing overall performance. In this study, molecular dynamics simulations are used to construct a Couette flow shear model with gas injected at the boundaries of a nanochannel. This paper investigates the flow characteristics and boundary drag reduction of Couette flow in a nanochannel. The influence of gas injection on these characteristics is examined, along with the effects of surface wettability, shear velocity, and gas injection rate on boundary slip velocity and drag reduction. The results indicate that gas adsorption on the solid surface in the form of discrete bubbles hinders liquid flow and slip near the wall, leading to increased drag. However, increasing surface hydrophobicity, shear rate, and gas injection rate facilitates the transverse spreading of bubbles, reduces flow obstruction, and enhances slip. Additionally, these factors promote the formation of a continuous gas layer from discrete bubbles, further improving drag reduction. Once the gas layer forms, shear stress decreases significantly, and slip velocity varies with surface wettability, shear velocity, and gas injection rate. These findings provide a theoretical foundation for active gas layer drag reduction technology and the optimization of surface structures in ships and underwater vehicles.
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Keywords:
- Active drag reduction /
- boundary slip /
- Couette flow /
- molecular dynamic
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