ORIGINAL ARTICLE Numerical simulation of interference effects for a high-speed catamaran Riccardo Broglia • Stefano Zaghi • Andrea Di Mascio Received: 19 March 2010 / Accepted: 29 May 2011 / Published online: 30 June 2011 Ó JASNAOE 2011 Abstract The simulations of the ﬂow around a high- speed vessel in both catamaran and monohull conﬁgura- tions are carried out by the numerical solution of the Reynold averaged Navier–Stokes (RANS) equations. The goal of the analysis is the investigation of the interference phenomena between the two hulls, with focus on its dependence on the Reynolds number (Re). To this aim, numerical simulations are carried out for values of Re ranging from 10 6 to 10 8 for two different values of the Froude number (Fr = 0.30, 0.45). Wave patterns, wave proﬁles, limiting streamlines, surface pressure and velocity ﬁelds are analyzed; comparison is made between the cat- amaran and the monohull conﬁgurations. Dependence of the pressure and viscous resistance coefﬁcients, as well as of the interference factor, on the Reynolds number is investigated. Veriﬁcation and validation for both resistance coefﬁcients and wave cuts is also performed. Keywords Catamaran  RANS based simulations  Interference  Scale effects 1 Introduction The demand for high-speed multihull vessels has strongly increased during the last decades for both commercial and military purposes; in particular, catamaran conﬁgurations are very attractive because of their excellent performance with respect to speed, safety, resistance and transversal stability. As a consequence, a large number of theoretical, experimental and numerical studies were carried out in recent years. Experimental studies were primarily dedi- cated to the analysis of the effect of the hull separation on both resistance components and wave interference. Resis- tance components of high-speed catamarans were analyzed by Insel and Molland [20] and by Molland et al. [26], the investigation being focused on the effect of the separation distance, length over beam, length over displacement and breadth over draught ratios for a systematic series of high- speed displacement catamarans; valuable experimental results were reported in terms of viscous and non viscous resistance components, as well as wake contours. A similar analysis was carried out in shallow water by Molland et al. [27]. Millward [25] used the thin ship theory to investigate the effects of demihull separation in both deep and shallow water over a range of Froude number. In order to quantify the viscous effects on resistance and interference, Armstrong [1] tested a double model in a wind tunnel; it has been shown that there is a signiﬁcant interference of purely viscous nature between hulls in close proximity; however, it has to be pointed out that in this experiment the inﬂuence of factors such as wind tunnel blockage effects, model mounting effects, etc. could have affected the results. A rather complete analysis of the resistance components of high-speed catamarans, as well as of suitable form factor to be used for resistance scaling has been provided by Couser et al. [10]. In a recent paper, Souto-Iglesias et al. [32] made an accurate experimental analysis of the effect of separation distance between the demihulls; resistance, trim and sinkage, as well as inner R. Broglia (&)  S. Zaghi  A. Di Mascio Istituto Nazionale per Studi ed Esperienze di Architettura Navale, CNR, via di Vallerano, 139, 00128 Rome, Italy e-mail: r.broglia@insean.it S. Zaghi e-mail: s.zaghi@insean.it A. Di Mascio e-mail: a.dimascio@insean.it 123 J Mar Sci Technol (2011) 16:254–269 DOI 10.1007/s00773-011-0132-3