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

Abstract

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.

Nonlinear air dynamics of a surface effect ship in small-amplitude waves

“…To enhance the computational efficiency, Guo et al . [8][9][10] employed a linear 2.5D method to calculate the hydrodynamic parameters in connection with demihulls of an SES running in small-amplitude waves and obtained satisfactory results. The 2.5D method is highly efficient due to the dimensionality reduction on the control equation and body conditions from 3D to 2D [ 5 , 9 , 10 , 17 ], while only the free surface condition remains 3D.…”

“…In the computational fluid dynamics (CFD) methods, the air pressure hydrodynamics and cushion air dynamics are coupled to each other and need to be simultaneously solved at each time step [1] . Alternatively, in potential theory the air pressure hydrodynamic problem could be deliberately decoupled from the air cushion dynamic problem, and specialized methods can be employed to individually solve the air pressure hydrodynamic problem, e.g., the analytical methods for pressure patches [ 9 , 20 ], 3D Green's function method for zero-speed air cushion supported platform [16] , a single-domain 2.5D method [10] or a multi-domain 2.5D method [11] for high-speed SES.…”

A Study on the Motion of Partial Air Cushion Support Catamaran in Regular Head Waves

“…In 2010, Harbin Engineering University (HEU) begun the research of PACSCAT based on the sidewall hovercraft technology and improved its resistance and sea-keeping performance by a series of hull form optimizations and model tests. Guo et al utilized a numerical method to investigate the seakeeping performance of PACSCT, which combines the 2.5D theory for solving hydrodynamics problem with simplified wave-equation for solving aerodynamic of pressurized air [9]; their method was further improved to evaluate the waves due to pulsating pressure of air cushion [10]; the related studies were also performed for SES (surface effect ship) [11] and T-craft [12]. In order to verify the implementation effect of the developed technology, HEU designed and built a 12 m long aluminous test craft (Figure 3), based on which the experiment could be implemented in real scale and reliable trial data could be recorded-their work laid a good foundation for further investigation.…”

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

“…The computational methods, such as Rankine source method [4,5] and RANS method [6,7], may be able to take into account all dynamic effects, but they require considerable amount of computational resources and can take long computational time [3,8].…”

“…But Guo et al [3] did not take the hydrodynamics of the pulsating air pressure and demihulls on waves into account. To overcome this shortcoming, Guo et al [8] proposed a novel 2.5D method that can solve the mixed BVP for evaluating the waves due to the pulsating air pressure. However, as indicated by Guo et al [19], the 2.5D method is valid only when the advancing speed and the length to beam ratio of the air cushion to be sufficient high, which restricts its application range.…”