A two-dimensional analytical model of vertical water entry for asymmetric bodies with flow separation

Abstract

The vertical water entry of asymmetric two-dimensional bodies with flow separation is considered. As long as there is no flow separation, linearised Wagner's theory combined with the Modified Logvinovich Model has been shown to provide computationally fast and reliable estimates of slamming loads during water entry. Tassin et al. (2014) introduced the Fictitious Body Continuation (FBC) concept as a way to extend the use of Wagner's model to separated flow configurations, but they only considered symmetric bodies. In the present study, we investigate the ability of the FBC concept to provide accurate estimates of slamming loads for asymmetric bodies. In this case, flow separation may not occur simultaneously on both sides of the body. During an intermediate phase, slamming loads are governed by a competition between the local drop in pressure due to partial flow separation and the ongoing expansion of the wetted area. As a first benchmark for the model, we consider the water entry of an inclined flat plate and compare the FBC estimates with the results of a nonlinear model. Then, we consider the case of a foil and compare the FBC results with Computational Fluid Dynamics predictions. In both cases, we find that the FBC model is able to provide reliable estimates of the slamming loads.

Stochastic prediction of wave impact kinematics and loads for ship appendages

“…In the present study, the stochastic approach has been coupled with the semi-analytical water entry model introduced by [7]. Combining Wagner's approach with the concept of "Fictitious Body Continuation" [8], this water entry model can account for flow separation (when the fluid detaches from the edges of the body).…”

“…Combining Wagner's approach with the concept of "Fictitious Body Continuation" [8], this water entry model can account for flow separation (when the fluid detaches from the edges of the body). In the present case study, the considered body is the same as in [7], i.e. a two-dimensional foil of section NACA 0028 (as represented in Fig.…”

“…the free-surface elevation starts decreasing, initiating a water exit phase) before the flow has detached from both sides of the body, then t ip = t we , where t we is the duration of the water entry stage. Otherwise, the considered impact duration correspond to the time, t sep , when the flow has detached from both sides of the body (after flow separation, hydrodynamic loads start decreasing rapidly, see [7]). Two different approaches were used to estimate hydrodynamic loads: (a) approximate approach assuming that the flow acceleration is constant during the impact (hence only the initial values of w and w ,t need to be drawn), (b) Monte Carlo simulation of the stochastic evolution of kinematic variables after up-crossing (this option is numerically more demanding).…”

Structural response characteristics of TMA during water-entry procedure

“…al. [14]. A CIP-based model for the water-entry of the two-dimensional structures with complex geometry, which was the highorder difference model, was given by Zheng, Zhao, and Yan [15].…”

Effect of forward speed on the level-crossing distribution of kinematic variables in multidirectional ocean waves

“…[22]), such as the acceleration (added-mass effect), the tangential velocity, or the angular position of the object relative to the local free surface (e.g. [23]). Going beyond a univariate approach, the early study of Belik and Price (1982) [24] investigated the effect of accounting for the tangential component of the water entry velocity, in the context of slamming on high-speed vessels.…”