对二元复合结构聚合物涂层阻力特性与形貌特征参数之间的关系进行了实验研究,并采用计算流体力学方法对形貌效应作用下形貌壁面的阻力特性进行了数值模拟,在此基础上讨论了聚合物涂层的减阻机理。结果表明,一阶形貌特征长度以及二阶形貌分布密度对聚合物涂层的减阻性能有显著影响;在来流条件下,聚合物涂层在二元复合结构表面形貌效应作用下,近壁面流场出现涡结构和流动分离现象,导致相应区域内的流场发生漩涡空化,促使二阶凹坑内驻留的微气泡生长形成气膜,在固/液界面间构建出气相结构,以气/液剪切代替固/液剪切实现界面效应减阻,有效降低了形貌壁面的摩擦阻力。
Experiments were performed to investigate the relationship between drag reduction property and surface topography characteristics of polymer coating with binary structured surface,and computational fluid dynamic methods were conducted to numerically simulate the process of vortex cavitation caused by binary structured surface.And based on the experiments and simulations,the effect mechanism of binary structured surface on drag reduction was analyzed.According to the results,gas phase was generated due to vortex cavitation and developed in low pressure condition provided by surface topography.With the gas phase at the solid-liquid surface,the shear force at the solid-liquid interface was partly replaced by gas-liquid interfacial shear.As the gas-liquid interfacial shear is much smaller compared with the solid-liquid interfacial shear,the skin friction drag was reduced effectively.
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