Experimental investigation of the water entry and/or exit of axisymmetric bodies

Breton, Thibaut; Tassin, Alan; Jacques, Nicolas

doi:10.1017/jfm.2020.559

Cited by 27 publications

(30 citation statements)

References 24 publications

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“…The motion imposed to the body is similar to the motion of the water entry and exit experiments performed by Breton et al. (2020) with a deadrise-angle cone and is defined as where is the maximum submergence depth, , m is the maximum wetted surface half-width, is the maximum velocity and mm. Note that the body touches the water slightly after because of the term which has been introduced to reproduce the conditions of the experiments of Breton et al.…”

Section: Results For a Varying Entry Velocitymentioning

confidence: 99%

“…The accuracy of the semi-analytical approach for the water entry of a body with a varying speed is also demonstrated through the simulation of a wedge and a cone entering water with deceleration (up to full stop). The motion imposed to the body in these simulations is similar to the one imposed in the experiments by Breton, Tassin & Jacques (2020) which were used in Del Buono et al (2021) to validate the FNPF solver. The simulations are run with and without gravity to show the capability of the SAM to accurately predict the effect of gravity on the force and the width of the wetted surface.…”

Section: Introductionmentioning

confidence: 99%

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Gravity effects in two-dimensional and axisymmetric water impact models

et al. 2022

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The effect of gravity during the water entry of two-dimensional and axisymmetric bodies is investigated analytically and numerically. An extension to the Wagner model of water impact is proposed in order to take into account the effect of gravity. For this purpose, the free-surface condition is modified. The pressure is computed using the modified Logvinovich model of Korobkin (Eur. J. Appl. Maths, vol. 6, 2004, pp. 821–838). The model has been implemented and validated through comparisons with fully nonlinear potential flow simulations of different two-dimensional and axisymmetric water entry problems. Our investigation shows that it is equally important to account for gravity when computing the pressure distribution and to account for gravity when computing the size of the wetted surface in order to obtain accurate force results with the Wagner model. Simulations of wedges and cones with different values of deadrise angle ( $\beta$ ) entering water at constant speed ( $V$ ) demonstrate the accuracy of the semi-analytical model and show that the effect of gravity in such water impacts is governed by the effective Froude number defined as $Fr^*=V/(\sqrt {gh}\sqrt {\tan \beta })$ , with $g$ the acceleration due to gravity and $h$ the penetration depth. The accuracy of the semi-analytical model for decelerated water entries is also demonstrated by investigating the water entry of a wedge and a cone with a $15^\circ$ deadrise angle with deceleration until full stop. The semi-analytical model is able to accurately predict the effect of gravity during both two-dimensional and axisymmetric water entry problems with deceleration.

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Section: Results For a Varying Entry Velocitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gravity effects in two-dimensional and axisymmetric water impact models

et al. 2022

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“…Both strategies have been found able to improve the numerical stability of the solution providing similar results in the wedge case, where a very accurate prediction of the free-surface, pressure distribution and vertical hydrodynamic force time histories has been obtained. The combined use of the two strategies both in the cone and the wedge cases FNL with g FNL without g Experiments [8] MVK [8] Korobkin [8] (b) Figure 15: Cone: evolution of the total force acting on the body (a) and of the contact line (b) as a function of time has demonstrated further improvement of the stability of the free-surface dynamics. Such combined approach seems the best in terms of computational effort and robustness of the solver.…”

Section: Discussionmentioning

confidence: 99%

Water entry and exit of 2D and axisymmetric bodies

Del Buono,

Bernardini,

Tassin

et al. 2021

Preprint

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The present paper is dedicated to the development of a numerical model for the water impact of two-dimensional (2D) and axisymmetric bodies with imposed motion. The work is a first step towards the implementation of a 2D+t procedure to be used for the analysis of aircraft ditching. The problem is investigated under the assumptions of an inviscid and incompressible fluid, which is modelled by a potential flow model with fully non-linear boundary conditions at the free-surface. The unsteady boundary value problem with a free-surface is numerically solved through a boundary element method, coupled to a simplified finite element method to describe the thinnest part of the jet. The study is aimed at describing the entry and exit phases. Specific numerical solutions are developed to tackle the exit phase and to improve the stability of the model. Results are presented in terms of free-surface shape, pressure distribution and hydrodynamic load acting on the impacting body. The model is used to study the water entry and exit of a 2D wedge and an axisymmetric cone, for which numerical or experimental results are available in the literature. The numerical investigation shows that the proposed model accurately simulate both the entry and exit phases. For the exit phase, it is shown that the proposed model, being fully non-linear, provides a much better prediction of the loads and the wetted area compared to simplified (analytical) approaches. The effects of the gravity, usually missing in the approaches available in the literature, are also investigated, showing they are rather important, especially, in the exit phase.

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“…Mathematical models for the water entry of an asymmetric wedge are developed in studies such as Semenov & Iafrati (2006) and Semenov & Wu (2018). Breton, Tassin & Jacques (2020) performed an experimental study on the vertical water entry/exit of axisymmetric bodies. The evolution of the wetted surface under the body and the force on the body during the process were measured.…”

Section: Introductionmentioning

confidence: 99%

The controlled impact of elastic plates on a quiescent water surface

Wang

Wong

et al. 2022

J. Fluid Mech.

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The impact of flexible rectangular aluminum plates on a quiescent water surface is studied experimentally. The plates are mounted via pinned supports at the leading and trailing edges to an instrument carriage that drives the plates at constant velocity and various angles relative to horizontal into the water surface. Time-resolved measurements of the hydrodynamic normal force ( $F_n$ ) and transverse moment ( $M_{to}$ ), the spray root position ( $\xi _r$ ) and the plate deflection ( $\delta$ ) are collected during plate impacts at 25 experimental conditions for each plate. These conditions comprise a matrix of impact Froude numbers ${Fr} = V_n(gL)^{-0.5}$ , plate stiffness ratios $R_D= \rho _w V_n^2 L^3D^{-1}$ and submergence time ratios $R_T= T_sT_{1w}^{-1}$ . It is found that $R_D$ is the primary dimensionless ratio controlling the role of flexibility during the impact. At conditions with low $R_D$ , maximum plate deflections on the order of $1$ mm occur and the records of the dimensionless form of $F_n$ , $M_{to}$ , $\xi _r$ and $\delta _c$ are nearly identical when plotted vs $tT_s^{-1}$ . In these cases, the impact occurs over time scales substantially greater than the plate's natural period, and a quasi-static response ensues with the maximum deflection occurring approximately midway through the impact. For conditions with higher $R_D$ ( $\gtrsim 1.0$ ), the above-mentioned dimensionless quantities depend strongly on $R_D$ . These response features indicate a dynamic plate response and a two-way fluid–structure interaction in which the deformation of the plate causes significant changes in the hydrodynamic force and moment.

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Experimental investigation of the water entry and/or exit of axisymmetric bodies

Abstract: Abstract

Cited by 27 publications

References 24 publications

Gravity effects in two-dimensional and axisymmetric water impact models

Gravity effects in two-dimensional and axisymmetric water impact models

Water entry and exit of 2D and axisymmetric bodies

The controlled impact of elastic plates on a quiescent water surface

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