Abstract
A series of experiments are performed in a gravitational low-speed water tunnel to investigate the influence of the hydrophobic coating on the flow past a circular cylinder. The mean velocity and turbulence intensity profiles behind the cylinders are measured using the hot-film anemometer while the separation angles are obtained with the flow visualization technology. For the Reynolds number lower than 3 800, the hydrophobic coatings are in the Cassie state, the velocity deficit and the turbulence intensity in the wake of the hydrophobic cylinders are lower than those of the smooth cylinders which implies the drag reduction effect of the hydrophobic coatings. When the Reynolds number becomes higher than 6 600, the hydrophobic coatings turn into the Wenzel state. Through decomposing the velocity data in the turbulent wake into different scales based on the orthogonal wavelet transform, it is found that the total turbulence intensity in the wake of the hydrophobic cylinders becomes almost the same as in the wake of the smooth cylinders while the intensity of the large scales of vortex components in the wake of the hydrophobic cylinders is still lower. Furthermore, the separation angles show the same trend as a function of the Reynolds number but always take smaller values for the hydrophobic cylinders.
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Acknowledgement
This work was supported by the Innvovation Foundation of Maritime Defense Technologies Innovation Center, the Fundamental Research Funds for the Central Universities (Grant No. 3102018gxc007).
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Project supported by the National Natural Science Foundation of China (Grant Nos. 51679203, 51879218).
Biography: Jun Wen (1991-), Male, Master
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Wen, J., Hu, Hb., Luo, Zz. et al. Experimental investigation of flow past a circular cylinder with hydrophobic coating. J Hydrodyn 30, 992–1000 (2018). https://doi.org/10.1007/s42241-018-0124-4
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DOI: https://doi.org/10.1007/s42241-018-0124-4