This paper presents experimental measurements by the time-resolved particle image velocimetry (TR-PIV) for the turbulent boundary layer (TBL) over the smooth surface, the superhydrophobic (SH) surface, and the superhydrophobic-riblets (SR) surface in an open-surface recirculating water channel. The Reynolds number based on the wall friction velocity and the thickness of the TBL over the smooth surface is 702. The SH surface and the SR surface are manufactured by the laser texturing method on the smooth surface and the riblets surface, respectively. By employing the (modified) Clauser method, a superior efficacy of the drag reduction of about 22.1% is obtained on the SR surface, while the drag reduction rate for the SH surface is about 18.7%. Comparing with the SH surface, the declining 2-order statistics in the near-wall region also indicates a significant drag reduction over the SR surface. The large-scale structure components extracted by the proper orthogonal decomposition are found to generate a majority of the Reynolds shear stress in the region y⁺ > 40. The strength of the large-scale features over the rough surfaces (SH and SR surfaces) at disparate wall-normal positions is visualized by the Quadrant splitting method and the conditional averaging. The appearance of the large-scale structures such as the hairpin packets characterized by the two-point correlation shows an excellent consistency with the statistics profile. The hairpin packets over the SH surface seem always smaller and weaker than those over the smooth surface. Over the SR surface, the hairpin packets in the region 0.1 ≤ y δ < 0.3 are the smallest and weakest among those over the three surfaces, while the scale and the strength of the hairpin packets exceed those over the smooth surface in the region 0.3 < y δ < 0.6.

本文通过时间分辨粒子图像测速 (TR-PIV) 对光滑表面、超疏水 (SH) 表面和超疏水肋 (SR) 表面上的湍流边界层 (TBL) 进行了实验测量。 -地表循环水通道。基于壁面摩擦速度和光滑表面上 TBL 厚度的雷诺数为 702。SH 表面和 SR 表面分别在光滑表面和凹槽表面通过激光​​纹理化方法制造。通过采用（改进的）克劳瑟方法，SR表面获得了约22.1%的优异减阻效果，而SH表面的减阻率约为18.7%。与 SH 表面相比，近壁区域中下降的 2 阶统计数据也表明 SR 表面的阻力显着减少。发现通过适当的正交分解提取的大尺度结构分量在该区域产生大部分雷诺剪应力y ⁺ > 40。在不同壁法线位置的粗糙表面（SH 和 SR 表面）上的大规模特征的强度通过象限分裂方法和条件平均来可视化。以两点相关为特征的发夹包等大规模结构的外观与统计剖面具有极好的一致性。SH 表面上的发夹包似乎总是比光滑表面上的发夹包更小和更弱。在SR表面上，0.1 ≤ y δ < 0.3区域内的发夹包在三个表面上的区域中最小和最弱，而发夹包的规模和强度超过了光滑表面上的区域0.3 < y δ < 0.6。