A seakeeping analysis method for a high-speed partial air cushion supported catamaran (PACSCAT)

2018

Water

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Abstract:The mean water surface (interface) under the air cushion of a surface effect ship (SES) or an air cushion supported platform (ACSP) is generally lower than the outside water surface due to the overpressure of the air cushion. To precisely analyze the hydrodynamics under the air cushion, multiple water levels should be considered in numerical models. However, when using free surface Green's functions as numerical methods, the water level difference cannot be taken into account, because free surface Green's functions normally require users to set in the whole water domain a unique datum water surface that completely separates the air domain and the water domain. To overcome this difficulty, a multi-domain approach is incorporated into a 2.5D method that is based on a time domain free surface Green's function with viscous dissipation effects in this paper. In the novel multi-domain 2.5D method, the water domain is partitioned into inner and outer domains, and the interface is located in the inner domain while the outside water surface is placed in the outer domain. In each domain there exists only one unique water level, while water levels in different domains are allowed to be different. Benefited from this characteristic, the multi-domain 2.5D method is able to precisely consider the water level difference and its influence on hydrodynamics. The newly proposed multi-domain 2.5D method is employed to predict the hydrodynamics of an SES, and it is confirmed that the multi-domain 2.5D method can give better numerical results than the single-domain one for the given case.

“…Table 2. Main characteristics of the PACSCAT [6]. The strip panels of the PACSCAT for the single-domain and multi-domain 2.5D method are portrayed in Figure 5a,b, respectively.…”

Section: Multi-domain 25d Methods For the Hydrodynamics Of An Sesmentioning

confidence: 99%

Section: Multi-domain 25d Methods For the Hydrodynamics Of An Sesmentioning

confidence: 99%

Section: Multi-domain 25d Methods For the Hydrodynamics Of An Sesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Multi-Domain 2.5D Method for Multiple Water Level Hydrodynamics

2018

Water

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A novel 2.5D method for solving the mixed boundary value problem of a surface effect ship

2018

Applied Ocean Research

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When a surface effect ship (SES) sails in waves, the unsteady velocity potential of water can be decomposed into incident potential, sidehull radiation potential, sidehull diffraction potential and radiation potential due to fluctuating air pressure. The potentials related to sidehulls satisfy Neumann boundary conditions (BC) and have been successfully addressed using the 2.5D method. In contrast, the potential related to fluctuating air pressure satisfies mixed BC consisting of homogeneous Neumann BC on the wetted surface of sidehulls and nonhomogeneous Dirichlet BC on the interface between air and water, which has never been studied using the efficient 2.5D method. In this paper, the 2.5D method is firstly proposed to solve the mixed boundary value problem (BVP), which can deal with the coupling between the fluctuating air pressure and sidehulls. By using the 2.5D method, the radiation wave and other relative hydrodynamic parameters of a SES due to the fluctuating air pressure are evaluated. The numerical results on motion response and the fluctuated air pressure of the SES show acceptable agreement with the experimental ones.

A study on hydrodynamics of the air cushion of a high-speed PACSCAT

European Journal of Mechanics - B/Fluids

2018

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This paper presents an approximate but efficient method for modeling the hydrodynamics and seakeeping performance of partial air cushion supported catamaran (PACSCAT) with planing demihulls. This method takes into account of the effects of the waves on the air-water interface under the air cushion induced by the pulsating pressure in the cushion and by the demihulls, which are ignored by existing approximate methods. Specifically, the new developments are made in two aspects.One is that the governing equations of the heave and pitch motions of the PACSCAT are derived to include the effects of the waves under the air cushion due to the pulsating pressure and the demihulls.Another one is that an approximate method is developed for evaluating the waves due to the pulsating pressure. Better agreement between the experimental data and the numerical results for pressure is achieved.