Computational fluid dynamics investigation on total resistance coefficient of a high-speed “deep-V” catamaran in shallow water (original) (raw)
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Catamarans continue to increase in size and application, with proposals circulating within the shipbuilding industry for bigger and better designs than the present generation of catamarans. The present paper attempts to show a comparison of resistance calculation of a small fast catamaran carried out by experimental and CFD techniques. Experimental tests were carried out with a scaled model at the Towing Tank facilities at University Austral of Chile. CFD simulation using the RANSE code TDYN and Potential Flow code SHIPFLOW was used to calculate the resistance of a prototype catamaran for high-speed operation. The code includes automatic modification of the free surface and therefore dynamic trim and sinkage changes are considered in the solution. Several published articles in well-known journals have detailed various procedures to estimate the resistance characteristics of catamarans. Since few published articles are in existence regarding experimental data on catamarans, it is the aim of this research to undertake a CFD analysis to predict the wave resistance and ultimately the total resistance. Experimental investigation appears to provide very good agreement as has been observed in the resistance curves showing that CFD methods may adequately deal with the problem of wave interference produced by both demihulls. A further conclusion by the authors is that panel density on free surface needs to be defined adequately to capture the waves in the transom at higher Froude numbers.
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This study attempts to extend the analysis of several resistance prediction procedures based on experimental work carried out by researchers and, subsequently, wave resistance estimation as illustrated in Part I of this study by . All the methods used have been analysed and compared with results obtained from towing tank tests, CFD analysis by use of SHIPFLOW and a computational analysis is software package CATRES, whose operation is based around thin ship theory. The results obtained from each of the resistance prediction methods have been investigated, and the limitations and areas of effectiveness for each of the resistance methods have been determined in relation to the vessels tested. Throughout this study, the primary objective of validating the resistance equations developed in Part I of this study has been achieved. The level to which the resistance prediction tool can be utilized during the designing of high-speed catamarans was further determined through the analysis of the results.
Journal of Marine Science and Engineering, 2021
This paper numerically investigates the resistance at full-scale of a zero-emission, high-speed catamaran in both deep and shallow water, with the Froude number ranging from 0.2 to 0.8. The numerical methods are validated by two means: (a) Comparison with available model tests; (b) a blind validation using two different flow solvers. The resistance, sinkage, and trim of the catamaran, as well as the wave pattern, longitudinal wave cuts and crossflow fields, are examined. The total resistance curve in deep water shows a continuous increase with the Froude number, while in shallow water, a hump is witnessed near the critical speed. This difference is mainly caused by the pressure component of total resistance, which is significantly affected by the interaction between the wave systems created by the demihulls. The pressure resistance in deep water is maximised at a Froude number around 0.58, whereas the peak in shallow water is achieved near the critical speed (Froude number ≈ 0.3). I...
EPI International Journal of Engineering
In presence of complex hydrodynamic interferences between two demihulls on a catamaran ship has been prone to have a reliable prediction to her optimum total resistance. To achieve this, the author presents a Computational Fluid Dynamic (CFD) modelling incorporated with Design of Experiment (DOE) approach. Several parameters such as effect of Froude number ( ) with respect to various lateral separation ratios (S/L) of the catamaran have been taken into account. Here, the optimum total resistance coefficient (CT) has been mainly set within the range of S/L ratio 0.2 ≤ S/L ≤ 0.4 associated with Froude number 0.56 ≤ ≤ 0.66. The primary objective function of this optimization model has led towards minimizing a drag force and increased a lift force with respect to the above S/L ratios. In general, the simulation results had seemed quantitative similarity values for the optimum of 0.6589, 0.6599 and 0.6596 with S/L ratios of 0.2, 0.3 and 0.4, respectively. In the case of = 0.56, the op...
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Resistance of catamaran is one of the most important aspects of Naval Architecture, Marine, Offshore and Ocean Engineering. There are various works from previous researches dealing with this challenge. Since catamarans have been introduced, resistance components have been evaluated by focusing on many aspects such as hull form, speed (Fn), hull separation to length ratio (S/L). Many methods to estimate resistance were also proposed such as direct measurement from model and full scale, theoretical mathematical model, potential flow, and computational fluid dynamics (CFD). However, resistance prediction of catamarans requires more details to overcome all resistance characteristics to achieve the most suitable design. Resistance of full scale ship is highly relied on two main extrapolation methods following Froude (1872) and Hughes (1954) and this approach is adopted by International Towing Tank Conference (ITTC).
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