Numerical study on interference effects and wetted area pattern of asymmetric planing catamarans

Abstract

Asymmetrical planing catamarans are increasingly used in moderate to very high-speed applications due to some tempting qualities such as less wetted surface and better seakeeping behavior. The present numerical study attempts to provide new insight into hydrodynamics of such vessels by highlighting the distinguishing aspects and employing novel appropriate approaches to deal with them. A systematic investigation has been carried out on a prismatic geometry at various demihull separations (including zero separation, that is, symmetric monohull) and different trim angles in a wide range of speed coefficients, using a computational fluid dynamics solver. Obtained numerical results of steady-state resistance and lift forces are compared against different empirical methods. In order to offer an adequate explanation about the nature of forces and interference mechanisms, an analysis has been performed on viscous and pressure resistance components. Furthermore, the ability of the employed numerical method in estimation of wetted area pattern at the bottom of the planing hulls has been evaluated to provide explanation for some observed hydrodynamic behaviors of the asymmetric planing catamarans. It is seen that a significant reduction is reached in wetted surface area of catamaran configuration in comparison with corresponding monohull.

A new phenomenon in interference effect on catamaran dynamic response

“…Hence the two ends of the spectrum were the minimum of 0.09 and the maximum of 1.0. Intriguingly, the case of s/L = 0 was also reported by some researchers examined the interference effects at high Froude numbers including Savitsky and Dingee [41], Sherman [45] (who studied 0 < s/L < 0.33), Liu and Wang [42], Lee [44], and [57].…”

“…Although two-dimensional analysis of water entry problem has provided precious information for planing catamarans, investigation in three dimensions presents new insight into and reveals more realistic findings of interference effects. Yengejeh, Amiri, Mehdigholi, Seif and Yaakob [57] applied three dimensional Computational Fluid Dynamics (CFD) to solve Reynolds-Averaged Navier Stokes (RANS) equations in order to determine the flow field around a prismatic asymmetric planing catamaran. They examined interference effect on viscous, pressure, air, and water resistance separately and found that at very high speeds the viscous and air components are as important as the pressure and water resistance, besides both the lift force and the wetted surface, also known as the pressure area [43], increased by decreasing demi-hulls separation.…”

Numerical investigation of interference effects for the Delft 372 catamaran

“…Lately, Computational Fluid Dynamics (CFD) has imposed itself as a very valuable tool for many numerical studies related to the investigation of the total resistance of a catamaran and the interference phenomenon. [12][13][14][15][16][17][18][19][20] The combination of experimental and computational fluid dynamics currently represents the best practice for the investigation of catamaran hydrodynamics. 21 The influence of a bulbous bow on the total resistance of a yacht was investigated using both towing tank tests and numerical simulations.…”

Numerical Investigation of the Resistance of a Zero-Emission Full-Scale Fast Catamaran in Shallow Water

“…With the fast development of computer science and numerical methods, computational fluid dynamics (CFD) has become a feasible approach with sufficient accuracy to investigate ship hydrodynamics [21]. Various CFD solvers have been applied to examine the calm water resistance and seakeeping of both monohulls [22][23][24] and multihulls [25][26][27][28][29]. A combined experimental and numerical study was carried out by Zaghi et al [30] to analyse the interference effects between the demihulls and the dependency on the separation of a high-speed catamaran.…”