Pressure impulse theory for a slamming wave on a vertical circular cylinder

Ghadirian, Amin; Bredmose, Henrik

doi:10.1017/jfm.2019.151

Cited by 29 publications

(17 citation statements)

References 22 publications

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“…Hence, in all of our analysis, we have shown that pre-impact air cushioning has an important influence just after touchdown, but that this influence diminishes as time increases. These findings may be of significance in industries where the primary interest is in effects very close to touchdown/entry, for example, in ship-slamming or wave impacts on coastal structures, where the peak stresses are of interest [58,59]. Our analysis has shown that classical Wagner theory significantly overestimates, for example, the extent of the effective contact set and the slamming force at these times.…”

Section: Summary and Discussionmentioning

confidence: 66%

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Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

Moore¹

2021

J Eng Math

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In this analysis, we consider the effects of non-quiescent initial conditions driven by pre-impact air–water interactions on the classical Wagner model of impact theory. We consider the problem of a rigid, solid impactor moving vertically towards a liquid pool. Prior to impact, viscous forces in the air act to deform the liquid free surface, inducing a flow in the pool. These interactions are then incorporated as initial conditions in the post-impact analysis. We derive expressions for the size of the effective contact set, the leading-order pressure and force on the impactor, and the speed and thickness of the jet at its base. In all cases, we show that the effect of the pre-impact behaviour is to cushion the impactor, reducing the size of the effective contact set and, hence, the force on the impactor. Small- and large-time asymptotic solutions are derived for general power-law impactors, and we show that the effects of the air die away as the impact progresses, so that we approach the classical Wagner solution.

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Section: Summary and Discussionmentioning

confidence: 66%

“…Note that as time increases, we converge (slowly) onto this line. The inset displays a log-log plot of the behaviour just after touchdown, with the blue-dashed line indicating the asymptotic limit (58). (Color figure online) as in (54).…”

Section: Large-time Behaviourmentioning

confidence: 99%

Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

Moore¹

2021

J Eng Math

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“…34 Because linked to the overall momentum conservation law, the pressure impulse–time integral shows a smaller variation. 35 This is proposed by Bagnold 36 first when investigating the wave impact experimentally, suggesting the pressure impulse defined as…”

Section: Resultsmentioning

confidence: 97%

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

Hong

Wang

Liu

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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The hydrodynamic loads of a disk impacting pure and aerated water are investigated experimentally and numerically. Experiments are performed on a rigid disk with different aeration levels and focus on the spatial and temporal pressure distribution. Drop tests are conducted by a specially designed apparatus to prevent the variation of velocity during the slamming period. A specially designed bubble generator, able to adjust the void fraction, is utilized to generate uniform and tiny bubbles. A high-speed camera is utilized to record the water spray and splash curtain. A homemade compressible multiphase solver based on the reduced five equation model is adopted to evaluate the impact loads, which assumes the water and bubbles sharing the same velocity and pressure. The results show that bubbles in the water have a significant influence on the impact loads. As the void fraction increases from zero to nearly 1%, the peak impact pressure is reduced considerably and the impact duration is becoming obviously longer. In aerated water impact, the disk has a more uniform pressure distribution on the surface. However, the pressure impulse in aerated impact tests is basically unchanged compared with that in pure water.

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“…Therefore, breaking wave forces can be divided into two components: an impact force (or slamming force) component and a quasi-static component. The quasi-static components can be fully described using Morison's equation (FD + FM), but not the impact force (FI), as highlighted by several authors such as Goda et al (1966), Chaplin et al (1992), Wienke (2001) and Ghadirian and Bredmose (2019) [20][21][22][23]. Morison's force (FD + FM) model was extended with an additional impact force component (FI) to account for breaking wave forces, calculated using Equation (2).…”

Section: Impulsive Wave Loading Descriptionmentioning

confidence: 99%

Influence of the Spatial Pressure Distribution of Breaking Wave Loading on the Dynamic Response of Wolf Rock Lighthouse

Dassanayake

Antonini

Pappas

et al. 2021

JMSE

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The survivability analysis of offshore rock lighthouses requires several assumptions of the pressure distribution due to the breaking wave loading (Raby et al. (2019), Antonini et al. (2019). Due to the peculiar bathymetries and topographies of rock pinnacles, there is no dedicated formula to properly quantify the loads induced by the breaking waves on offshore rock lighthouses. Wienke’s formula (Wienke and Oumeraci (2005) was used in this study to estimate the loads, even though it was not derived for breaking waves on offshore rock lighthouses, but rather for the breaking wave loading on offshore monopiles. However, a thorough sensitivity analysis of the effects of the assumed pressure distribution has never been performed. In this paper, by means of the Wolf Rock lighthouse distinct element model, we quantified the influence of the pressure distributions on the dynamic response of the lighthouse structure. Different pressure distributions were tested, while keeping the initial wave impact area and pressure integrated force unchanged, in order to quantify the effect of different pressure distribution patterns. The pressure distributions considered in this paper showed subtle differences in the overall dynamic structure responses; however, pressure distribution #3, based on published experimental data such as Tanimoto et al. (1986) and Zhou et al. (1991) gave the largest displacements. This scenario has a triangular pressure distribution with a peak at the centroid of the impact area, which then linearly decreases to zero at the top and bottom boundaries of the impact area. The azimuthal horizontal distribution was adopted from Wienke and Oumeraci’s work (2005). The main findings of this study will be of interest not only for the assessment of rock lighthouses but also for all the cylindrical structures built on rock pinnacles or rocky coastlines (with steep foreshore slopes) and exposed to harsh breaking wave loading.

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Pressure impulse theory for a slamming wave on a vertical circular cylinder

Cited by 29 publications

References 22 publications

Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

Influence of the Spatial Pressure Distribution of Breaking Wave Loading on the Dynamic Response of Wolf Rock Lighthouse

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