Water entry of stripe-coated hydrophobic circular cylinders

Ueda, Y.; Iguchi, Manabu

doi:10.1007/s12650-011-0106-x

Cited by 8 publications

(1 citation statement)

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“…As the inclined angle decreases, the cavity evolution is similar to that caused by a horizontal cylinder. 6 As the inclined angle increases, it is similar to that caused by a vertical cylinder, the effect of these parameters on the cavity evolution will be discussed in the future. The effects of the initial inclined angle on the evolution of the cavity as the cylinder impacts on and penetrates into water are not surprising.…”

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Evolution of three-dimensional cavitation following water entry of an inclined cylinder

Wei

Shi

2012

Theoretical and Applied Mechanics Letters

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The water entry of an inclined cylinder is firstly studied experimentally for low Froude number. The cylinder is 50 mm in diameter and 200 mm in length, with a moderate length to diameter ratio. As it is submerged below the water surface, the cavity is fully three-dimensional. Due to the rotation of the cylinder caused by the initial inclined impact, the cavity evolution is quite complicated and a new phenomenon is revealed. The cylinder moves along a curved trajectory in water, which greatly affects the evolution of the cavities. The cavity breaks up into two sub-cavities, and finally collapses because of hydrostatic pressure.The water entry problems of two-dimensional cylinders have been widely studied for a very long time. A typical result of the experimental images was provided by Greenhow and Lin. 1 In their experiment, the flow could be approximated as a two-dimensional one. After that, a lot of studies were conducted to predict the hydrodynamic load both for two-dimensional rigid circular cylinders and elastic cylinders. 2,3 Even nowadays, only a few studies on the water entry of three-dimensional cylinders are reported for the complexity of the problems. As the initial inclined angle is introduced, the phenomenon of the water entry of the cylinders will become more complicated, which is very different from that related to a two-dimensional cylinder. 1 For relatively short cylinders, the length to diameter ratio is small. As the cylinder touches the water surface, the initial impact will cause the cylinder to rotate with relatively larger angular velocity compared with the entry of an inclined "rod" described by Ueda et al. 4 The rotation will obviously influence the evolution of the cavities. For some special inclined angles and length to diameter ratios, the cavity breaks up into two parts. The trajectory of the cylinder in water is curved. These new phenomena will be revealed and discussed as follows.The schematic illustration of the experimental apparatus is shown in Fig. 1. The Polypropylene cylinder used in the experiment has a density of ρ = 902 kg/m 3 , diameter of D = 50 mm, length of L = 200 mm, thus the length to diameter ratio is L/D = 4. The contact angle of the cylinder surface is about 98 • . The cylinder is cleaned by ethanol only, and no other surface treatment is applied. The initial gravity center of the cylinder is 2.0 m high above the water surface. The impact tank has a dimension of 1.35 m × 1.35 m × 1.35 m, and the water depth is 1.0 m. As the cylinder is released freely by a clamp, it impacts the water with an initial velocity of V 0 = 6.10 m/s and an inclined angle a) Corresponding author. Email: weimuru@163.com. Fig. 1. Schematic illustration of the experimental apparatus.of 60 • . The Froude number is F r = V 0 / √ gD = 8.72. As the back lighting, foreground lighting and lateral lighting are set in their best conditions (Fig. 1), the high speed digital camera (FASTCAM-APX RS) with a 105 mm Nikon lens is used to study the water entry phenomenon. The camera is arranged at the same...

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