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Nowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planing equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD-analysis model.

In this research, a framework for the analysis and design optimization of ship hull-propeller systems (HPSs) in waves is developed. This framework can be utilized as an efficient synthesis tool to determine the main geometric characteristics of the HPSs during the early stage of ship design. The optimization is carried out in two levels and under multipoint operating conditions (OC). Multiobjective evolutionary algorithm based on decomposition (MOEA/D) as an efficient multiobjective evolutionary algorithm, Michell integral and OpenProp tool as low-fidelity hydrodynamic solvers and boundary element method (BEM) as medium-fidelity solver are applied on two case studies to minimize the effective power and maximize the propulsive efficiency of HPSs. To estimate the added wave resistance, an efficient semiempirical formula is also employed. The Series 60 hull form with DTMB P4118 single propeller and S175 hull form with KP505 twin-propeller are considered as the original models. The numerical results show that the framework can find optimized designs with better hydrodynamic performance. [ABSTRACT FROM AUTHOR]

In the present study, hydrodynamic performance and cavitation volume of the marine propeller under different geometrical and physical conditions are evaluated by using three models which are proposed through gene expression programming (GEP). To this accomplishment, computational fluid dynamics (CFD) data of propeller thrust, torque and cavitation volume under different pitch ratio (Pr), rake angle (RA) and skew angle (SA), advance velocity ratio (J) and cavitation number (s) are considered as inputs–outputs of GEP models. Then, mathematical equations are obtained for the thrust, torque and cavitation volume in terms of the geometrical and physical prescribed parameters. In order to evaluate the performance and accuracy of the GEP models, four statistical measures including root mean square error (RMSE), mean absolute error (MAE), scatter index (SI) and coefficient of determination (R2) are used. The final models are found to be of reasonable accuracy between observed and GEP-predicted values. [ABSTRACT FROM AUTHOR]

This work develops a new multi-level hull-propulsor optimization tool, systematically considering the full range of expected operating conditions. Different solvers with variable fidelities are used to evaluate hydrodynamic objective functions and constraints. The bi-fidelity surrogate model is applied to integrate the accuracy advantage of a medium-fidelity solver with the efficiency advantage of a low-fidelity solver. A bi-level technique of infill sampling integrated with a new version of multi-objective evolutionary algorithms is presented to enhance the effectiveness of the surrogate models. A ship velocity- and sea state-based joint probability density function is employed to take into account the real lifetime operational space. The well-known S175 containership, KP505 propeller and a MAN B&W marine engine are utilized as the initial hull-propulsor model. The final results show that the optimization framework is able to achieve some optimum hull-propulsor designs from the lifetime fuel consumption and energy efficiency design index points of view and to reduce the overall lifetime ownership cost significantly. • The goal is fully realization of the importance of achieving a ship with more energy efficiency and less fuel consumption. • The multi-disciplinary optimization tool employed a realistic operational profile of ship speed and sea state to describe the lifetime operation of the ship through a seaway to avoid optimizing for a single operating condition. • A novel multi-fidelity ship optimization tool developed by integrating the MOEA/D_DRA coupled with Co-Kriging surrogate model and bi-level techinque of infill criteria into the optimization process. • The objective functions were the lifetime fuel consumption (LFC) and the energy efficiency design index (EEDI). • The tool used a penalty function combined with MOEA/D_DRA for multi-objective optimization with nonlinear constraints to find energy-efficient ship designs with reasonable geometries and performances. • The multi-disciplinary optimization tool employed a realistic operational profile of ship speed and sea state to describe the lifetime operation of the ship through a seaway to avoid optimizing for a single operating condition. [ABSTRACT FROM AUTHOR]

Propellers usually operate in the ship's stern, where the inflow of the non-uniform wake generates oscillating loads and changes the hydrodynamic performance. Therefore, determination of the forces on propellers and hydrodynamic performance due to a non-uniform wake field are the challenging problems for naval architects and hydrodynamists. The main objectives of the present study are to assess the hydrodynamic performance for a single blade and all the blades. The propeller is a B-series propeller under non-uniform wake field behind the Seiun-Maru (hereafter SM) ship hull. A practical approach is employed to calculate the hydrodynamic oscillating loads of the ship propeller under a non-uniform wake field. Results of the computations on the propeller behind the SM ship, due to a non-uniform wake field, are presented and analyzed using classical mathematical methods over a single cycle. The results show that a variation of thrust with the discussed parameters is the same as that shown for torque, also the blade-frequency of the total force, thrust and torque is an increasing function of radial sections, whereas these parameters decrease with increasing radial blade sections. [ABSTRACT FROM AUTHOR]

This current work investigates the effect of duct and number of blades on the hydrodynamic performance of the horizontal axis tidal stream turbine (HATST). The numerical method based on Reynolds averaged Navier- Stokes (RANS) equations is employed to compare the hydrodynamic performance for various cases of this device. For validation of the numerical results, a 3-blade HATST without-duct has been compared against experimental data. The analysis and comparison of the simulation results show that using duct for HATST has increased the power coefficient, the torque coefficient, the trust coefficient, and the force on the blade. In addition, the simulation results of the cases with a greater number of blades shows that the trust coefficient increased and the force on the blade decreased. Therefore, it is recommended to use ducted HATST with a great number of blades to extract more energy from the tidal stream. [ABSTRACT FROM AUTHOR]

The research performed in this paper is carried out to calculate the sound pressure level of the marine propeller by Reynolds-Averaged Navier–Stokes solver in low frequencies band. Noise is generated by the induced trailing vortex wake and induced pressure pulses. The two-step Fflowcs Williams and Hawkings equations are used to calculate hydrodynamic pressure and its performance as well as sound pressure level at various points around the propeller. The directivity patterns of this propeller and accurate explanation of component propeller noise are discussed. Comparison of the numerical results shows good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

One of the most effective methods to diminish the drag of a planing craft is to use a step at the bottom of the hull. A stepped hull causes a reduction of the wetted area and, as a result, a decrease in the drag. The step may be designed as a straight line through the entire width of the hull or may be V-shaped with a forward or backward swept angle. In this paper, the effects of the step forward swept angle on the hydrodynamic performance of a hard chine planing vessel are investigated by finite volume method (FVM). Reynolds-Averaged Navier Stokes (RANS) equations with a standard k-ε turbulence model coupled with volume of fluid (VOF) equations are solved in order to simulate a transient turbulent free surface flow around the hull with the help of Ansys CFX software. In order to predict hull motions, equations of rigid body motions for two degrees of freedom (2-DOF) are coupled with fluid flow governing equations. To validate the presented numerical model, first the numerical results are compared with available experimental data, and then the obtained numerical results of the drag, dynamic trim, sinkage, wetted keel length, wetted chine length, pressure distribution on the hull, wetted surface and wake profile at different Froude numbers and step angles are presented and discussed. [ABSTRACT FROM AUTHOR]

• A CFD model is presented for analyzing the flow around a low-pitch marine cycloidal propeller (MCP), and it is validated against experimental data. • The open water hydrodynamic coefficients of low-pitch MCP are calculated for different geometries and operating conditions of MCP by the CFD model. • Neural network models are trained by CFD data of hydrodynamic coefficients to extract predictive functions of hydrodynamic performance. • Two mathematical functions are presented for predicting open water hydrodynamic performance of a low-pitch MCP. Today, various types of propulsion systems are used in different purpose ship types. Marine cycloidal propeller (MCP) is one of these propulsion systems, which has been designed for ships that require high maneuverability. MCP can be considered as an especial type of marine propulsion systems, since it produces the thrust force which is perpendicular to propeller axis of rotation. The magnitude and direction of the thrust force can be adjusted by controlling the pitching angle of the blades, so no separate rudder is needed to manoeuvre the ship. In this study, mathematical functions for predicting the open water hydrodynamic performance of a low-pitch MCP are presented by training a neural network based on computational fluid dynamics (CFD) data. For this purpose, the four nondimensional parameters of blade number (Z), ratio of blade thickness to MCP diameter (t / D), pitch (e) and advance coefficient (λ) are considered as input variables, whereas the hydrodynamic coefficients of thrust (K s) and torque (K d) are considered as targets. CFD simulations are performed for different cases of MCP with different combinations of Z, t / D, e and λ. The results showed that a two-layer feedforward network with one hidden layer of sigmoid neurons and at least 4 neurons in the hidden layer can be well trained by CFD data in order to obtain functions with good accuracy in predicting K s and K d coefficients of a low-pitch MCP. [ABSTRACT FROM AUTHOR]