Abstract : A series of constant-deadrise models, varying in length, was tested in smooth water and regular waves to define the effects of deadrise, trim, loading, speed, length-beam ratio, and wave proportions on the added resistance, on heave and pitch motions, and on impact accelerations at the bow and center of gravity. Each of these parameters was varied independently of the others so as to obtain a proper evaluation of the effects of changing a single quantity. The results, presented in the form of response characteristics, cover a wide range of operating conditions; and show, quantitatively, the importance of design parameters on the rough-water performance of planing hulls.

A systematic study of the rough water performance of planing boats. Part II: Irregular waves

Experimental and numerical hydrodynamic analysis of a stepped planing hull

The paper presents an overview of studies of slamming on ship structures. This work focuses on the hull slamming, which is one of the most important types of slamming problems to be considered in the ship design process and the assessment of the ship safety. There are three main research aspects related to the hull slamming phenomenon, a) where and how often a slamming event occurs, b) slamming load prediction and c) structural response due to slamming loads. The approaches used in each aspect are reviewed and commented, together with the presentation of some typical results. The methodology, which combines the seakeeping analysis and slamming load prediction, is discussed for the global analysis of the hull slamming of a ship in waves. Some physical phenomena during the slamming event are discussed also. Recommendations for the future research and developments are made.

Review of ship slamming loads and responses

The present paper studies the fluid dynamics during the flooding of a damaged ship numerically and experimentally. Attention is focused on the fluid flow characteristics and the fluid-structure interactions. The Smoothed Particle Hydrodynamics (SPH) method with an improved boundary treatment is established, which is able to capture the flow behaviors effectively. Fairly good agreement is obtained between the computational and experimental results. Based on the SPH method, the simulations are carried out for the flooding of a damaged ship with different opening sizes, opening positions, and numbers of the flooding cabins. Besides, the effects of the wave are also taken into account. The fluid behaviors are described and analyzed in detail. It is found that, during the first phase of flooding, an inflow jet with a large velocity is formed, significantly influencing the inner flows and the ship responses. During the progressive flooding phase, sloshing, crushing of the free surface, wave breaking, and vortex shedding are observed which are coupled with the ship motions. In addition, some relevant conclusions are enclosed for the motion laws of the damaged ship. This work provides physical insight into the flooding of the damaged ship, which is helpful to understand the coupled dynamics of the ship and flooding water.

Study on coupled dynamics of ship and flooding water based on experimental and SPH methods

Although sea and ocean waves have been widely acknowledged to have the potential of providing sustainable and renewable energy, the emergence of a self-sufficient and mature industry is still lacking. An essential condition for reaching economic viability is to minimise the cost of electricity, as opposed to simply maximising the converted energy at the early design stages. One of the tools empowering developers to follow such a virtuous design pathway is the techno-economic optimisation. The purpose of this paper is to perform a holistic optimisation of the PeWEC (pendulum wave energy converter), which is a pitching platform converting energy from the oscillation of a pendulum contained in a sealed hull. Optimised parameters comprise shape; dimensions; mass properties and ballast; power take-off control torque and constraints; number and characteristics of the pendulum; and other subcomponents. Cost functions are included and the objective function is the ratio between the delivered power and the capital expenditure. Due to its ability to effectively deal with a large multi-dimensional design space, a genetic algorithm is implemented, with a specific modification to handle unfeasible design candidate and improve convergence. Results show that the device minimising the cost of energy and the one maximising the capture width ratio are substantially different, so the economically-oriented metric should be preferred.

https://www.mdpi.com/2077-1312/8/7/482/pdf

Techno-Economic Optimisation for a Wave Energy Converter via Genetic Algorithm

Resistance assessment of warped hullform

Experimental seakeeping assessment of a warped planing hull model series

Experimental assessment of intact and damaged ship motions in head, beam and quartering seas

Verification and validation of numerical modelling of DTMB 5415 roll decay

A proper design of the mooring systems for Wave Energy Converters (WECs) requires an accurate investigation of both operating and extreme wave conditions. A careful analysis of these systems is required to design a mooring configuration that ensures station keeping, reliability, maintainability, and low costs, without affecting the WEC dynamics. In this context, an experimental campaign on a 1:20 scaled prototype of the ISWEC (Inertial Sea Wave Energy Converter), focusing on the influence of the mooring layout on loads in extreme wave conditions, is presented and discussed. Two mooring configurations composed of multiple slack catenaries with sub-surface buoys, with or without clump-weights, have been designed and investigated experimentally. Tests in regular, irregular, and extreme waves for a moored model of the ISWEC device have been performed at the University of Naples Federico II. The aim is to identify a mooring solution that could guarantee both correct operation of the device and load carrying in extreme sea conditions. Pitch motion and loads in the rotational joint have been considered as indicators of the device hydrodynamic behavior and mooring configuration impact on the WEC.

https://www.mdpi.com/2077-1312/8/3/180/pdf

Ermina Begovic

Papers

Resistance assessment of warped hullform

Experimental seakeeping assessment of a warped planing hull model series

Experimental assessment of intact and damaged ship motions in head, beam and quartering seas

Verification and validation of numerical modelling of DTMB 5415 roll decay

Experimental Investigation of the Mooring System of a Wave Energy Converter in Operating and Extreme Wave Conditions