Scale Effect Analysis and Hydrodynamic Performance of High-Speed Catamarans

Simulations of the flow around an high-speed catamaran have been carried out by the numerical solution of the Reynold Averaged Navier-Stokes equations. The focus is on the analysis of the viscous effects on the interference between the twin hulls, and its dependency on the Reynolds number. To this aim, numerical simulations were carried out for Re ranging from ~ 10^6 to ~ 10^8 , for two different values of the Froude number (F r = 0.30, 0.45). The analysis is carried out by means of an in-house parallel unsteady RANS solver, based on a finite volume discretization with second order accuracy. The free surface is handled by means of a suitable single phase level set algorithm; moreover, Chimera overlapping grid capabilities have been implemented. Wave patterns, wave profiles, limiting streamlines, surface pressure and velocity fields are analyzed and comparison is made with the demihull configuration. Dependencies of the pressure and viscous resistance coefficients, as well as of the interference factor on the Reynolds number, is investigated. Verification and validation of the computed resistance coefficients is also performed.