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.
Highlights
The newly proposed multi-domain 2.5D method is employed to predict the hydrodynamics of an surface effect ship (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
In water-related engineering, there might exist multiple water surfaces with different levels, such as water separated by a dam or seawall, water flows passing through the channels of a M-craft, water under the air cushion of a surface effect ship (SES) or air cushion supported platform (ACSP), and so on
In free surface Green’s functions, only a unique datum water surface can be defined in the flow field, and the water domain and air domain must be completely beneath and above this surface, respectively
Summary
In water-related engineering, there might exist multiple water surfaces with different levels, such as water separated by a dam or seawall, water flows passing through the channels of a M-craft, water under the air cushion of a surface effect ship (SES) or air cushion supported platform (ACSP), and so on. One is to realize the parallel computation technique [7,8,9], which decomposes the fluid domain into multiple regions, allowing calculations to be simultaneously performed in each region Another purpose is to construct boundary conditions for shielded domains, which may be unknown in their original boundary value problems. As far as we know, none of the existing multi-domain methods has been employed in tackling multiple water level problems. The newly proposed method partitions the water domain into an inner domain and an outer domain, which contain, respectively, the interface and outside free surface. The interface could remain at its original position and the multi-domain 2.5D method would be able to precisely consider the multiple water levels and the influence of water level difference on hydrodynamics. The newly proposed multi-domain 2.5D method is validated by solving the hydrodynamics of an SES and comparing the numerical results with experimental ones
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