Numerical Simulation And Analysis Of Added Resistance In Waves Of Monohull And Catamaran

With more demands on improving economic performance and enhancing environment protection in the last decades, the study on energy efficiency and emission reduction of a ship has been focused. Different from sailing in the calm water, additional ship resistance would be generated for a ship sailing in wave condition, namely the added resistance in waves. The added resistance can lead to extra fuel consumption and speed loss in seaway, which have negative effects on ship resistance and seakeeping performance. It is very necessary and meaningful to consider the ship performace in waves for the design and construction of new ship to meet the requirement of EEDI in the future. As a result, it is of great importance to predict and analyze the added resistance in waves accurately and efficiently.By the CFD solver naoe-FOAM-SJTU, which is developed for naval architecture and ocean engineering based on the open source toolbox Open FOAM, the added resistances and motion resoponses of a specificied monohull and catamaran in regular wave conditions are computed and analyzed. Main contents are followed.First of all, a benchmark ship case of KCS sailing in still water is simulated in order to validate the correction and reliability. On this basis, the numerical simulation on viscous flow field of Wigley modified model called Blunt model under different wave height and wave length conditions. Its added resistance coefficient and RAO of heave and pitch motion responses are calculated. What’s more, the diffraction component of added resistance is computed by fixing the 6Do F motion totally. The results show the diffraction component is the most important part of total added resistance in short waves, while radiation component is dominated in longer wave conditions. Moreover, a new modified model called Slender model with larger L/B is investigated. The added resistance coefficicents in waves of the two models with different hull dimensions are compared and analyzed.The resistances of Delft-372 catamaran model sailing in calm water along with sinkage and trim with different Froude numbers are computed by using naoe-FOAM-SJTU. After that, different wave conditions of large wave steepness with Fr equaling to 0.7 are taken into account. Furthermore, three different intervals between the demihulls are generated to study the wave interference effects. The numerical results of catamaran with normal demihull interval H=0.7m is compared with that of catamarans with H=0.5m and H=0.9m. Results show the intense of interference effect is inversely proportional to the demihull interval within a certain range, which could provide meaningful reference for catamaran design.