Comparative analysis of drag reduction characteristics of two-type riblets based on numerical simulation

基于数值模拟的2种条纹沟槽减阻特性对比分析

¹ School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China
² AVIC Xi’an Flight Automatic Control Research Institute, Xi’an 710076, China

Received: 29 June 2021

Abstract

Turbulent drag reduction has always been a hot issue in fluid mechanics. Among various turbulent drag reduction methods, riblets has attracted wide attention due to its simple structure and convenient application. In order to investigate the effect of the riblets shape on the drag reduction, the effect of the triangular and trapezoidal riblets on the turbulent boundary layer flow field and drag reduction characteristics has been studied numerically by adopting the CFD method and based on the large eddy simulation (LES). The numerical simulation of turbulent channel flow was conducted by RANS, DES and LES methods respectively, and their results were compared with the results of direct numerical simulation (DNS) to verify the accuracy and feasibility of the large eddy simulation method. According to the experimental results in references, the flow field parameters such as integral statistics, first-order statistics and second-order statistics of the triangular and trapezoidal riblets on the turbulent boundary layer flow fields were compared and analyzed. The drag reduction characteristics of two-type riblets were investigated by studying the variation in physical parameters such as drag reduction rate, time-averaged velocity, root mean square velocity fluctuation, shear stress, turbulent kinetic energy generation and contour of spanwise velocity fluctuation, and it was concluded that the trapezoidal riblets have better drag reduction effect than the triangular riblets under the same dimensionless condition.

摘要

湍流减阻是流体力学研究的热点问题，在诸多湍流减阻方法中，条纹沟槽因其结构简单和使用方便等特点，受到广泛关注。为了探究沟槽形貌对沟槽减阻效果的影响，采用基于大涡模拟的CFD方法，数值研究三角形与梯形沟槽对湍流边界层流场的影响及减阻特性。通过RANS、DES和LES方法分别对光滑槽道湍流进行数值模拟，并与直接数值模拟的结果进行对比，验证了大涡模拟方法的准确性和可行性。基于参考文献的实验结果，对三角形与梯形沟槽湍流边界层流场的积分统计量、一阶统计量和二阶统计量等流场参数进行了对比分析，并通过对减阻率、时均速度、速度脉动均方根、剪应力、湍动能生成项和展向脉动速度等物理参量变化及影响规律研究，探讨了2种条纹沟槽减阻特性，由此得出结论: 在相同无量纲条件下，梯形沟槽相较三角形沟槽减阻效果更好。