1 29 th Symposium on Naval Hydrodynamics Gothenburg, Sweden, 26-31 August 2012 URANS Study of Delft Catamaran Total/Added Resistance, Motions and Slamming Loads in Head Sea Including Irregular Wave and Uncertainty Quantification for Variable Regular Wave and Geometry Wei He 1,2 , Matteo Diez 1,3 , Daniele Peri 3 , Emilio Campana 3 , Yusuke Tahara 4 , and Frederick Stern 1,† ( 1 IIHR–Hydroscience & Engineering, The University of Iowa, Iowa City, US, 2 NAOCE, Shanghai Jiao Tong University, China, 3 CNR–INSEAN, Natl. Research Council–Maritime Research Centre, Rome, Italy, 4 NMRI, National Maritime Research Institute, Tokyo, Japan) ABSTRACT 1 A methodology is assessed for uncertainty quantification (UQ) of resistance, motions and slamming loads in variable regular wave representing a given sea state, and compared to irregular wave (benchmark) and deterministic regular wave studies. UQ is conducted over joint distribution of wave period and height; irregular wave inlet boundary condition is based on wave energy spectrum; deterministic study is conducted at most probable condition. Application to the high-speed Delft Catamaran at Fr=0.5 in sea state 6 is presented and discussed. Deterministic regular wave study shows average error for design optimization-related quantities (expected values of resistance, motions amplitude and slamming loads) equal to 25%. Variable regular wave UQ shows average error close to 6%, providing in addition empirical distribution functions. Extension to uncertain design through Karhunen-Loève expansion is presented and discussed; variable geometry studies show a potential reduction of 6.5% for calm water resistance and 3.9% for resistance in wave, with small variations in motions amplitudes; an increase of 6.4% of maximum slamming load is experienced by reduced- resistance geometry, revealing a trade-off between performances and loads. UQ with metamodels reveals Kriging and polyharmonic spline as the most effective metamodels overall. † Corresponding author. Email: frederick- stern@uiowa.edu 1 INTRODUCTION University of Iowa, CNR–INSEAN, NMRI collaboration has successfully developed and applied its Simulation Based Design (SBD) tool box for deterministic shape optimization (Campana et al., 2006, 2009). Capabilities include multiple optimization methods [sequential quadratic programming (SQP), genetic algorithms (GA), and particle swarm optimization (PSO)]; multifidelity solvers (CFDShip-Iowa, WARP, and FreDOM); multiple geometry modification methods [free-form deformation (FFD), B-splines, and morphing]; high performance computing (MPI based parallel processing taking advantage of advance reservation system in DoD HPC machines); and portability (modular components allow for easy plug and play). Demonstration applications include 5415 bow shape optimization for 70% wave slope reduction (Campana et al., 2006); HSSL A shape optimization for 9% reduction in resistance (Stern et al., 2008); HSSL B shape optimization for resistance and heave RAO reduction (Tahara et al., 2011a); high-speed ferry shape optimization for 10% reduction of far- field energy (Kandasamy et al., 2011a); JHSS bow and waterjet inlet/duct shape optimization for 14% powering reduction (Kandasamy et al., 2011b); Delft catamaran (DC) hull and waterjet inlet/duct shape optimization for 5% powering reduction (Kandasamy et al., 2011a); and DC hull shape optimization for resistance reduction over range of Froude number, Fr (Tahara et al. 2011b). Towing tank experiments at CNR-INSEAN validated most applications.