Reducing Water Entry Impact Loads on Marine Structures by Surface Modification

Abstract

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.

Numerical Simulation on Dynamic Characteristics of Longitudinal Launching of Large Container Ships

“…The study considered several parameters, including the angle and length of the launch platform. Güzel et al [14] used the same method to examine the effect of hydrophobicity in reducing the impact loads acting on marine structures. A theoretical calculation in restricted waters by Li et al [15] was to study the effect of external forces due to wave-making and viscous resistance.…”

Impact force reduction by consecutive water entry of spheres

“…2016; Sharker et al. 2019; Güzel & Korkmaz 2020), but also by modifying the near-surface region via, for example, aeration (Elhimer et al. 2017) or liquid jet-induced acceleration (Speirs et al.…”

“…(Kornhauser 1964;May 1975;Seddon & Moatamedi 2006;Guillet et al 2020). Previous studies have shown that impact forces can be reduced not only through object geometry (McGehee, Hathaway & Vaughan 1959;Thompson 1965;Li & Sigimura 1967;May 1970;Qi et al 2016;Sharker et al 2019;Güzel & Korkmaz 2020), but also by modifying the near-surface region via, for example, aeration (Elhimer et al 2017) or liquid jet-induced acceleration (Speirs et al 2019a). An interesting extension to the idea of free surface modification is to launch a precursory object to agitate the free surface before entry.…”

Impact force reduction by consecutive water entry of spheres

“…Reducing this peak impact force is of significant interest because it presents structural failure risk to impinging bodies like aircraft landing on water, water landing spacecraft, underwater missiles, divers, base jumpers, etc., (Kornhauser 1964;May 1975;Seddon & Moatamedi 2006;Guillet et al 2020). Previous studies have shown that impact forces can be reduced not only through object geometry (McGehee et al 1959;Thompson 1965;Li & Sigimura 1967;May 1970;Qi et al 2016;Sharker et al 2019;Güzel & Korkmaz 2020), but also by modifying the near-surface region via, for example, aeration (Elhimer et al 2017) or liquid jet-induced acceleration (Speirs et al 2019a). An interesting extension to the idea of free surface modification is to launch a precursory object to agitate the free surface before entry.…”