In this study, a stability assessment based on work / energy balance principle considering wave and wind effects against IMO intact stability criteria is emphasized. The energy balance approach proposed by Moseley in 1850 is the concept of “dynamic stability” as the work done by in inclining a ship and consequently stored as potential energy balance of the energy of excitation forces and the total response of the ship in the ship stability problem. The energy balance approach, in which the time-dependent variation [(GZ) (fi,t)] of righting arm curve of the ship subjected to wave excitation and wind forces is modeled, provides reliability for stability calculations. Based on this principle, a stability model developed according to the energy balance principle for small boats is discussed and the results obtained from the application of the model are emphasized.

A technical introduction and up-to-date financial evaluation of offshore wind farms, whose popularity has been increasing within the last decade, are presented. Capital and operational expenditures of offshore wind farms are examined from different perspectives and reasons of their preference over onshore wind farms are stated as these farms are technically and financially more demanding compared to onshore wind farms. Based on foreseeable economic estimates the potential of continuing increase in installation of offshore wind farms in the future is discussed and a capital expenditures estimate for an offshore wind farm in Turkish waters is given.

Buckling/collapse analyses of stiffened ship panels under bi-axial thrust loads are carried out and collapse behavior of the panels is investigated. The main purpose of this study is the detailed examination of failure mechanisms of the stiffened panels under combined load cases for developing an approximate method to estimate the ultimate strength of panels. Finite Element Method is employed for the computations. Analysis steps are also provided so that to present a guide for such structural analyses. At first, only longitudinal thrust loads are considered. Then, bi-axial load cases are simulated. The target panels are adopted from bottom of a bulk carrier. Two different stiffener cross-sections, namely Tee bar and Flat bar are considered. Triple span-triple bay (1/2+1+1/2) modeling extent with periodical boundary conditions is employed. Number of stiffeners is utilized as two and four. The obtained ultimate strength values are compared with those available in the literature and a good agreement is achieved. When the transverse compression is dominant loading, it is observed that the ultimate strength values are relatively higher than those of linear buckling analyses. Influence of the number of stiffeners is considered as small on the buckling strength of the panels, while this effect is negligible on the ultimate strength values. Effects of different loading ratios are examined and it is figured out that the evaluated ultimate strength values for s_x:s_y=0.2:1 and s_x:s_y=1:0.2 cases are slightly higher than those of the uniaxial transverse and longitudinal thrust cases, respectively. Moreover, for s_x:s_y=1:0.2 case, the buckling mode shape has two half-waves in longitudinal direction, which apparently shows necessity of the periodical boundary conditions. In case of dominant transverse compressive thrust, the Von Mises stress distributions suggest that some parts of plate behave as plastic hinges while remaining parts in plating are still in elastic range.

In this study, an experimental investigation of cavitation erosion, which is one of the most negative and detrimental consequences of cavitation is presented. Within this context, cavitation and cavitation erosion formations are explained and some of the mathematical parameters used in erosion tests; cavitation number, erosion rate, erosion intensity are examined. There are five different test methods used to investigate the resistance of different materials to cavitation erosion. They can be sorted from the simplest to the most advanced as rotating disc apparatus, vibratory apparatus that generates an ultrasonic environment, air jet technique, water jet (cavitation jet) technique and cavitation tunnel tests. Within the scope of this study, these five techniques are investigated and explained with examples obtained from the literature. Special attention is payed to the air jet technique and water jet technique; examples from the tests carried out by the air jet and water jet test rigs which are built at ITU, the Faculty of Naval Architecture and Marine Engineering were presented.

This paper looks critically at some assumptions and allegations floating around in performance monitoring: data frequency as a cure-all; capability to separate hull degradation and propeller degradation; capability to correct for sea state 4 and above. Lack of error analyses is pointed out as a frequent root cause for questionable confidence and assertions.

The additional resistance due to roughness is studied by means of CFD simulations. The KVLCC2 hull at full-scale Reynolds number is considered as a test case. A wall function formulation is used to model the rough wall turbulent boundary layer, where the roughness function is based on data from towing flat plates coated with paint of similar roughness as for the full-scale vessel. The additional resistance for coatings with various roughness heights is studied, with roughness heights ranging from less than 10 µm to more than 60 µm. Also, the potential in low-cost reduction of frictional resistance is investigated. High-quality paint coating (with low roughness) can be applied at given locations where the skin friction is high, while using cheaper coating and application procedures (resulting in larger surface roughness) at other locations where skin friction is of less importance.