超疏水沟槽表面在湍流通道中减阻效应的数值研究

IF 2.8 Q2 MECHANICS
Ali Safari, Mohammad Hassan Saidi, Sajad Salavatidezfouli, Shuhuai Yao
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引用次数: 0

摘要

超疏水表面(SHSs)被认为是一种很有前途的实现表面摩擦减阻的技术。开发更有效的技术来模拟SHSs上的湍流边界层仍然是一个感兴趣的主题。在本研究中,由于SHS对壁面受限流动的影响,进行了数值模拟来捕捉近壁行为。为了实现这一目标,采用了高到中等保真度的湍流模型,包括reynolds -average Navier-Stokes、分离涡模拟和大涡模拟。对于滑移条件,在SHS上使用了著名的Navier滑移速度法。为了验证数值解,将滑移速度和表面摩擦与实验结果进行了比较。实验结果表明,旋流轴上的速度分布和雷诺数应力与文献报道的结果相当。然后,将所建立的模型进一步扩展,以研究矩形沟槽SHSs的减阻效果。结果表明,超疏水性与矩形沟槽相结合可以获得更好的性能,最大减阻率为46.1%。这是由于SHS引起的表面滑移和凹槽产生的二次涡效应造成的。结果表明,光滑沟槽表面的雷诺应力高于无剪切条件下沟槽表面的雷诺应力。更重要的是,数值结果表明,对于几何简化的沟槽SHSs,先前的无剪切条件假设是不准确的。因此,在具有沟槽或其他复杂结构的SHSs计算流体动力学模拟中,不应采用过于简化的无剪切边界条件,而应采用几何修正。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Numerical investigation of the drag reduction effect in turbulent channel flow by superhydrophobic grooved surfaces
Abstract Superhydrophobic surfaces (SHSs) are considered to be a promising technology for achieving skin-friction drag reduction. Development of more efficient techniques for simulating the turbulent boundary layer on SHSs continues to be a subject of interest. In this study, numerical simulations were carried out to capture near-wall behaviours due to the effect of the SHS on wall-bounded flows. To achieve this, high- to intermediate-fidelity turbulence models including Reynolds-averaged Navier–Stokes, detached eddy simulation and large eddy simulation were utilized. With regard to slip conditions, the well-known Navier slip velocity method was used over the SHS. For validating the numerical solutions, the slip velocity and skin friction over the SHS were compared with the experimental output. Results showed that the velocity profile and Reynolds stresses on the SHS were comparable to the reported results. Then, the developed models were further extended to investigate the drag reduction effect of SHSs with rectangular grooves. The subsequent results showed that the combination of superhydrophobicity and rectangular grooves led to a better performance with a maximum drag reduction of 46.1%. This is due to the surface slip caused by the SHS and the secondary vortex effect created by the grooves. Our results revealed that Reynolds stresses of the slippery grooved surface were higher than those of the case in which a shear-free condition was employed for the grooved surface. More importantly, the numerical results indicate the previous assumption of the shear-free condition is inaccurate for the geometrically simplified grooved SHSs. Therefore, geometry modifications rather than an overly simplified shear-free boundary condition should be applied in computational fluid dynamics simulations for SHSs with grooves or other complex structures.
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CiteScore
2.40
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