Proceedings of the 39th International Workshop on Water Waves and Floating Bodies

The International Workshop on Water Waves and Floating Bodies (IWWWFB) is anannual meeting of engineers and scientists with a particular emphasis on waterwaves and their effects on floating and fixed marine structures. The Workshop wasinitiated by Professor D. V. Evans (University of Bristol) and Professor J. N. Newman(MIT) following informal meetings between their research groups in 1984. Firstintended to promote communication between researchers in the UK and the USA,the interest and participation quickly spread to include researchers from many othercountries around the world.The Workshop enhances the basic and applied scientific knowledge on water wavesand their interaction with floating and fixed bodies with various applications andfacilitates the advancement and transfer of knowledge between research groupsacross the globe, and between senior and early career researchers. The workshopproceedings are freely accessible through the dedicated internet addresswww.iwwwfb.org where all contributions from 1986 on can be found.Individual papers from the 2024 conference can be found on the IWWWFB website here: http://www.iwwwfb.org/Workshops/39.htm 

Proceedings of the 39th International Workshop on Water Waves and Floating Bodies

The International Workshop on Water Waves and Floating Bodies (IWWWFB) is anannual meeting of engineers and scientists with a particular emphasis on waterwaves and their effects on floating and fixed marine structures. The Workshop wasinitiated by Professor D. V. Evans (University of Bristol) and Professor J. N. Newman(MIT) following informal meetings between their research groups in 1984. Firstintended to promote communication between researchers in the UK and the USA,the interest and participation quickly spread to include researchers from many othercountries around the world.The Workshop enhances the basic and applied scientific knowledge on water wavesand their interaction with floating and fixed bodies with various applications andfacilitates the advancement and transfer of knowledge between research groupsacross the globe, and between senior and early career researchers. The workshopproceedings are freely accessible through the dedicated internet addresswww.iwwwfb.org where all contributions from 1986 on can be found.Individual papers from the 2024 conference can be found on the IWWWFB website here: http://www.iwwwfb.org/Workshops/39.htm 

Simulation of wave spray cloud

Wave impacts on vessels and offshore structures can induce significant spray. This process leads to topside icing in sufficiently cold and windy conditions. This study establishes the current state of the art understanding of the physical behavior of wave impact and the process of spray cloud formation upstream of a ship or marine structure. The process of spray formation is related to several complicated phenomena including wave slamming, jet formation after impact, sheet and droplet breakup, and production of the spray cloud on the top surface of the ship bow. The process of spray-cloud production and flow kinematics arising from breaking wave impact on a lab-scaled model is investigated using the Bubble Image Velocimetry (BIV) method to measure the wave run-up velocity. In addition to the BIV method, spray characteristics were examined using the Digital Particle Image Velocimetry (DPIV) method. Measurements of droplet size, and velocity, as well as wave run-up velocity, were major elements of this study. Progress has been made in modeling wave spray phenomena, including numerical methods for modeling the free surface, and consideration of slamming, air entrainment, and water breakup. Further, the interaction of single nonlinear wave with a solid vertical surface was numerically simulated in three dimensions. Complex behavior of the wave impact as well as the resulting water sheet and high-speed jet were captured in the numerical model. The maximum wave run-up velocity, instant wave run-up velocity in front of the vertical surface, the break-up length of the water sheet, and the maximum impact pressure were all computed for several input wave characteristics. In addition to the experimental and numerical work, conservation constraints that govern the flow behavior, which is important in the process of spray cloud formation resulting from wave impact, were developed. The size and velocity distribution of spray droplets arising from the maximization of the entropy is subject to these constraints. The prediction is based on a statistical tool called the Maximum Entropy Principle (MEP), and the resulting droplet size distribution is in agreement with the general empirical distributions. The prediction distribution applied to both one- and two-dimensional cases. Finally, four stages of wave spray production are added together to produce a more comprehensive analytical model for predicting the final average droplet diameter from the information related to the inlet wave conditions. These mathematical stages are; 1) the formulation of wave impact velocities based on the input wave characteristics, 2) the formulation of air entrapment at the moment of impact based on the Bagnold-Mitsuyasu scaling law, which calculates the maximum impact pressure, 3) a mathematical relationship between the maximum wave impact pressure and the maximum wave run-up velocities, and finally, 4) the breakup phenomena

Quantitative imaging of the air-water flow fields formed by unsteady breaking waves

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 97-101).An experimental method for simultaneously measuring the velocity fields on the air and water side of unsteady breaking waves is presented. The method is applied to breaking waves to investigate the physics of the air and water flow fields to further our knowledge of the impact of wave breaking on air-sea interaction. The method includes a novel technique for seeding the air flow such that the air velocity can be resolved in the absence of wind. Low density particles which have large Stokes drag and ability to respond to high frequency flow fluctuations are used to seed the air flow. Multi-camera, multi-laser particle image velocimetry (PIV) setups are applied to small-scale shoaling breaking waves, yielding fully time-resolved velocity fields. The surface tension of the fluid is altered and controlled to form both spilling and plunging breaking waves. Application of the developed experimental method to these breaking waves reveals interesting flow physics in the air and water. Results for the velocity and vorticity fields on the water side show qualitative agreement to published data, and comparisons are drawn where applicable. Quantitative experimental data for the air flow induced by wave breaking in the absence of wind has not previously been observed, to the author's knowledge. Revealing physical insights and observations are drawn from this novel data.by Jesse Belden.S.M

Aeronautical Engineering: A special bibliography with indexes, supplement 74

This special bibliography lists 295 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1976

INKJET PRINTING: FACING CHALLENGES AND ITS NEW APPLICATIONS IN COATING INDUSTRY

This study is devoted to some of the most important issues for advancing inkjet printing for possible application in the coating industry with a focus on piezoelectric droplet on demand (DOD) inkjet technology. Current problems, as embodied in liquid filament breakup along with satellite droplet formation and reduction in droplet sizes, are discussed and then potential solutions identified. For satellite droplets, it is shown that liquid filament break-up behavior can be predicted by using a combination of two pi-numbers, including the Weber number, We and the Ohnesorge number, Oh, or the Reynolds number, Re, and the Weber number, We. All of these are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria are shown to have merit in comparison to currently used criteria for identifying filament physical features such as length and diameter that control the formation of subsequent droplets. In addition, this study performs scaling analyses for the design and operation of inkjet printing heads. Because droplet sizes from inkjet nozzles are typically on the order of nozzle dimensions, a numerical simulation is carried out to provide insight into how to reduce droplet sizes by employing a novel input waveform impressed on the print-head liquid inflow without changing the nozzle geometry. A regime map for characterizing the generation of small droplets based on We and a non-dimensional frequency, Ω is proposed and discussed. In an attempt to advance inkjet printing technology for coating purposes, a prototype was designed and then tested numerically. The numerical simulation successfully proved that the proposed prototype could be useful for coating purposes by repeatedly producing mono-dispersed droplets with controllable size and spacing. Finally, the influences of two independent piezoelectric characteristics - the maximum head displacement and corresponding frequency, was investigated to examine the quality of filament breakup quality and favorable piezoelectric displacements and frequencies were identified

Simulating the Hydrodynamics of Offshore Floating Wind Turbine Platforms in a Finite Volume Framework

There is great potential for the growth of wind energy in offshore locations where the structures are exposed to a variety of loading from waves, current and wind. A variety of computer-aided engineering (CAE) tools, based largely on engineering models employing potential-flow theory and/or Morison\u27s equation, are currently being used to evaluate hydrodynamic loading on floating offshore wind turbine platforms. While these models are computationally inexpensive, they include many assumptions and approximations. Alternatively, high-fidelity computational fluid dynamics models contain almost no assumptions, but at the cost of high computational expense. In this work, CFD simulations provide detailed insight into the complex fluid flow that has not been captured experimentally, nor can be attained with reduced-order models. This work includes a thorough validation of the various CFD toolboxes necessary for simulating offshore floating wind turbine platforms in the ocean environment, from numerical wave propagation to fluid-structure interactions. The fundamental physics of flow around complex structures is examined through various studies to better understand the effects of a fluid interface, truncated ends, structure size, multi-member arrangements and environmental conditions. These factors are explored in terms of drag, lift and frequency of the loads. Additionally, motion of structures in free decay tests and waves are investigated. The work provides insight into the complex fluid flow around floating offshore structures of small draft in a variety of environmental conditions. CFD simulations are used to assess assumptions and approximations of reduced-order engineering models, and explain why, and in which conditions, these models perform inaccurately. Finally, the work provides suggestions for improvements to engineering tools often used for hydrodynamics modeling of floating offshore wind turbines

Concept design of a fast sail assisted feeder container ship

A fast sail assisted feeder container ship concept has been developed for the 2020 container market in the South East Asian and Caribbean regions.The design presented has met the requirements of an initial economic study, with a cargo capacity of 1270 twenty-foot equivalent unit containers, meeting the predictions of container throughput derived from historical data. In determining suitable vessel dimensions, account has also been taken for port and berthing restrictions, and considering hydrodynamic performance. The vessel has been designed for a maximum speed of 25 knots, allowing it to meet the demand for trade whilst reducing the number of ships operating on the routes considered.The design development of the fast feeder concept has involved rigorous analyses in a number of areas to improve the robustness of the final design. Model testing has been key to the development of the concept, by increasing confidence in the final result. This is due to the fact that other analysis techniques are not always appropriate or accurate. Two hull forms have been developed to meet requirements whilst utilising different propulsor combinations. This has enabled evaluation of efficiency gains resulting from different hydrodynamic phenomena for each design. This includes an evaluation of the hydrodynamic performance when utilising the sail system. This has been done using a combination of model test results and data from regression analysis. The final propulsor chosen is a contra-rotating podded drive arrangement. Wind tunnel testing has been used to maximise the performance of a Multi-wing sail system by investigating the effects of wing spacing, stagger and sail-container interactions. This has led to an increase in lift coefficient of 32% from initial predictions. The savings in power requirement due to the sail system are lower than initially predicted. However, another benefit of their installation, motion damping, has been identified. Whilst this has not been fully investigated, additional fuel savings are possible as well as improved seakeeping performance.The design is shown to be environmentally sustainable when compared to existing vessels operating on the proposed routes. This is largely due to the use of low-carbon and zero-sulphur fuel (liquefied natural gas) and improvements in efficiency regarding operation. This especially relates to cargo handling and scheduling. Green house gas emissions have been predicted to fall by 42% and 40% in the two regions should the design be adopted. These savings are also due to the use of the Multi-wing sail system, which contributes to reductions in power requirement of up to 6% when the vessel operates at its lower speed of 15 knots. It is demonstrated that the fast feeder is also economically feasible, with predicted daily cost savings of 27% and 33% in the South East Asian and Caribbean regions respectively. Thus the fast feeder container ship concept is a viable solution for the future of container transhipment. <br/