Numerical Simulation of the Oblique Water Entry of Wedges With Vortex Shedding

Yang, Xiaobin; Xu, Guochun

doi:10.21278/brod69406

“…During the water entry of wedges, the wetted area and the impact force grow gradually as the object penetrates water [20]. The maximum slamming load occurs when the root of the jet flow leaves the wedge from the chine during the water entry event with constant velocity [26]. There is longer attachment of water as opposed to the water entry of cylinders and spheres in which there is early separation of jet flow with hydrophobic surfaces.…”

Section: Wet Deck Slammingmentioning

confidence: 99%

Reducing Water Entry Impact Loads on Marine Structures by Surface Modification

Güzel

¹

,

Korkmaz

²

2020

brod

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In this study, the effect of hydrophobicity in reducing the impact forces during the water entry of complex geometries has been demonstrated on bow flare slamming and wet deck slamming. Superhydrophobic surfaces with a contact angle of 160 0 and a hysteresis of 3 0 which shows a wetting regime in the Cassie-Baxter state were obtained via a chemical coating. By conducting drop tests with a bow flare ship section model and a catamaran section model at various impact velocities, jet flows, water pileups and air cavities were compared between the hydrophilic and hydrophobic cases via high speed camera images. The impact loads acting on the test bodies under hydrophobic effects were also compared via strain gauge measurements. The rise time of the strain values was measured shorter with smaller magnitudes in the hydrophobic cases. The modification in the jet flow propagation affects the total impact force. The results showed that hydrophobicity modifies the water uprising characteristics and energy balances, and reduces the impact loads acting on marine structures during slamming events.

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“…While the entrance velocity in free fall tests is determined by the drop height, ensuring the verticality of the entrance, i.e. entering the free water surface with zero roll angle and without any trim, is crucial to maintain the repeatability of the experiments, although the impact force is not increased much until the roll angle of 20 0 [24,25,26]. The free surface elevation and the cavity formation during a free fall entry of the bow flare section are shown at different time instances in Fig.…”

Section: Bow Flare Slammingmentioning

confidence: 99%

Untitled

2020

brod

0

View full text Add to dashboard Cite

In this study, the effect of hydrophobicity in reducing the impact forces during the water entry of complex geometries has been demonstrated on bow flare slamming and wet deck slamming. Superhydrophobic surfaces with a contact angle of 160 0 and a hysteresis of 3 0 which shows a wetting regime in the Cassie-Baxter state were obtained via a chemical coating. By conducting drop tests with a bow flare ship section model and a catamaran section model at various impact velocities, jet flows, water pileups and air cavities were compared between the hydrophilic and hydrophobic cases via high speed camera images. The impact loads acting on the test bodies under hydrophobic effects were also compared via strain gauge measurements. The rise time of the strain values was measured shorter with smaller magnitudes in the hydrophobic cases. The modification in the jet flow propagation affects the total impact force. The results showed that hydrophobicity modifies the water uprising characteristics and energy balances, and reduces the impact loads acting on marine structures during slamming events.

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“…Most of previous investigations concern on the traditional ship and offshore structures such as flat plate [19], stiffened panel [20][21], V-type wedges [22][23][24], spherical ball [25][26], cylindrical projectile [26] and propeller blade wedge section [27] et al In these studies, the common perspective of water entry phenomenon is a typical FSI problem. Obviously, the elasticity of the structures is expected to influence the results of this problem (here, which calls "hydroelasticity").…”

mentioning

confidence: 99%

Water Entry Hydroelasticity Analysis of Lattice Sandwich Panel With Imperfection: Simulation and Engineering Model

Wang¹,

Cheng²,

Pei³

et al. 2019

brod

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In the present work, the three dimensional (3D) hydroelasticity characteristics of imperfect lattice sandwich panel (ILSP) subjected to water entry via analytical prediction and numerical simulations are proposed. Firstly, numerical investigations are performed on water entry characteristics based on Arbitrary Eulerian-Lagrange (ALE) coupling method for modeling fluid-structure interaction (FSI) at an impact velocity of 5.0m/s. The results show the impact pressure on total FSI surface of ILSP is generally lower than that of the perfect lattice sandwich panel. Then a novel semi-analytical method to calculate the elastic constants of ILSP is introduced. Based on this approach, an engineering computational model is developed to predict the deformation of ILSP, in which the total deformation is separated into two parts; local field deformation and global field deformation. Good agreement between the numerical and analytical results is achieved. And the effects of geometric parameters such as the thickness of face sheet, height of ILSP and relative density of core are discussed.

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Numerical Simulation of the Oblique Water Entry of Wedges With Vortex Shedding

Cited by 6 publications

References 31 publications

Reducing Water Entry Impact Loads on Marine Structures by Surface Modification

Reducing Water Entry Impact Loads on Marine Structures by Surface Modification

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Water Entry Hydroelasticity Analysis of Lattice Sandwich Panel With Imperfection: Simulation and Engineering Model

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