The effect of forward speed on ship roll damping

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1983.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERINGIncludes bibliographical references.by Douglas Bruce Colbourne.M.S

Rewinding the waves: tracking underwater signals to their source

Analysis of data, recorded on March 8th 2014 at the Comprehensive Nuclear-Test-Ban Treaty Organisation’s hydroacoustic stations off Cape Leeuwin Western Australia, and at Diego Garcia, reveal unique pressure signatures that could be associated with objects impacting at the sea surface, such as falling meteorites, or the missing Malaysian Aeroplane MH370. To examine the recorded signatures, we carried out experiments with spheres impacting at the surface of a water tank, where we observed almost identical pressure signature structures. While the pressure structure is unique to impacting objects, the evolution of the radiated acoustic waves carries information on the source. Employing acoustic–gravity wave theory we present an analytical inverse method to retrieve the impact time and location. The solution was validated using field observations of recent earthquakes, where we were able to calculate the eruption time and location to a satisfactory degree of accuracy. Moreover, numerical validations confirm an error below 0.02% for events at relatively large distances of over 1000 km. The method can be developed to calculate other essential properties such as impact duration and geometry. Besides impacting objects and earthquakes, the method could help in identifying the location of underwater explosions and landslides

Targeted metatranscriptomics of compost derived consortia reveals a GH11 exerting an unusual exo-1,4-β-xylanase activity

Background: Using globally abundant crop residues as a carbon source for energy generation and renewable chemicals production stands out as a promising solution to reduce current dependency on fossil fuels. In nature, such as in compost habitats, microbial communities efficiently degrade the available plant biomass using a diverse set of synergistic enzymes. However, deconstruction of lignocellulose remains a challenge for industry due to recalcitrant nature of the substrate and the inefficiency of the enzyme systems available, making the economic production of lignocellulosic biofuels difficult. Metatranscriptomic studies of microbial communities can unveil the metabolic functions employed by lignocellulolytic consortia and identify new biocatalysts that could improve industrial lignocellulose conversion. Results: In this study, a microbial community from compost was grown in minimal medium with sugarcane bagasse sugarcane bagasse as the sole carbon source. Solid-state nuclear magnetic resonance was used to monitor lignocellulose degradation; analysis of metatranscriptomic data led to the selection and functional characterization of several target genes, revealing the first glycoside hydrolase from Carbohydrate Active Enzyme family 11 with exo-1,4-β-xylanase activity. The xylanase crystal structure was resolved at 1.76 Å revealing the structural basis of exo-xylanase activity. Supplementation of a commercial cellulolytic enzyme cocktail with the xylanase showed improvement in Avicel hydrolysis in the presence of inhibitory xylooligomers. Conclusions: This study demonstrated that composting microbiomes continue to be an excellent source of biotechnologically important enzymes by unveiling the diversity of enzymes involved in in situ lignocellulose degradation

A three component method of analyzing icebreaking resistance

This thesis presents a broad based review of current literature in the field of ship icebreaking and ice mechanics relevant to icebreaking. -- A dimensional analysis of the ship icebreaking problem is presented, leading to a system of non-dimensional numbers based on division of the problem into three independent components; an ice breaking component, an ice clearing component and a viscous drag component. Results from a comprehensive set of model tests are presented, validating the three component analysis method. In addition the method is applied to a number of model scale and full scale data sets with considerable success. It is concluded that testing and analysis of icebreaking by dividing the problem into components is practically feasible and offers an improved method of analysis, presentation and scaling

Hydrodynamic study of submerged ice collisions

Most of the research done on ice-structure interaction deals with the ice at the sea surface. Whereas majority of icestrengthened regions of ships and offshore structures are well below the waterline. The aim of this research is to examine the mechanics of ice loads caused by submerged ice blocks colliding with the structure. The kinematics is an essential determinant of the energy that is available to drive the ice crushing process during the collision. The present research aims to develop a model to represent the mechanics of such collisions and set a direction for future work. This study includes experimental and numerical components. Various physical experiments have been conducted using a submerged ice model moving solely due to its buoyancy. Using high speed camera the experiments are recorded and analysed to determine the kinematics of collision. These include location, velocity and acceleration of the model ice as a function of time. In parallel, numerical simulations have being conducted using FLOW 3DTM software. The results of the experiments are used to validate the numerical model of the underwater collision. The results shows that added mass plays an important role during the underwater impact collisions. The paper presents some preliminary results obtained during this research.Peer reviewed: YesNRC publication: Ye

Hydrodynamic study of submerged ice collisions

Most of the research done on ice-structure interaction deals with the ice at the sea surface. Whereas majority of icestrengthened regions of ships and offshore structures are well below the waterline. The aim of this research is to examine the mechanics of ice loads caused by submerged ice blocks colliding with the structure. The kinematics is an essential determinant of the energy that is available to drive the ice crushing process during the collision. The present research aims to develop a model to represent the mechanics of such collisions and set a direction for future work. This study includes experimental and numerical components. Various physical experiments have been conducted using a submerged ice model moving solely due to its buoyancy. Using high speed camera the experiments are recorded and analysed to determine the kinematics of collision. These include location, velocity and acceleration of the model ice as a function of time. In parallel, numerical simulations have being conducted using FLOW 3DTM software. The results of the experiments are used to validate the numerical model of the underwater collision. The results shows that added mass plays an important role during the underwater impact collisions. The paper presents some preliminary results obtained during this research.Peer reviewed: YesNRC publication: Ye

Experimental Investigation of Propeller Wake Velocity Field to Determine the Major Factors Affecting Propeller Wake Wash

The propeller jet from a ship has a significant component directed upwards towards the free surface of the water, which can be used for ice management. This paper describes a comprehensive laboratory experiment where the operational factors affecting a propeller wake velocity field were investigated. The experiment was conducted using a steady wake field to investigate the characteristics of the axial velocity of the fluid in the wake and the corresponding variability downstream of the propeller. The axial velocities and the variability recorded were time-averaged. Propeller rotational speed was found to be the most significant factor, followed by propeller inclination. The experimental results also provide some idea about the change of the patterns of the mean axial velocity distribution against the factors considered for the test throughout the effective wake field, as well as the relationships to predict the axial velocity for known factors

A large double-pendulum device to study load, pressure distribution and structure damage during ice impact tests in the lab

The design and functioning of a new impact device is described, where its eventual intended use is the study of damage associated with pressure distributions arising from ice impacts on ships. The large apparatus is a double-pendulum type device that is capable of achieving fairly high impact energies and velocities while remaining relatively \u2018compact\u2019 with respect to the confines of the laboratory space that is available. For example, at a drop angle of 35o from vertical for each pendulum the impact energy and relative velocity are ~ 31 kJ and 5.32 m/s respectively. Conical-shaped ice samples, one meter in diameter are held in a cylindrical ice holder that attaches to one arm of the double pendulum. For one type of test a unique instrumented panel (Impact Module), that records load and high spatial resolution pressure distribution during impacts, attaches to the opposite pendulum arm. For another test type the Impact Module is replaced by ship grillage (full-scale or reduced scale) so that ice impact tests can be performed that cause damage to the grillage. The pendulum arms are designed in a manner such that no rotation of the colliding masses occurs during tests. The effective masses of the colliding objects can be adjusted by adding or removing heavy metal plates. Similarly, the drop angles of the pendulum arms can be adjusted to achieve a range of impact velocities. These two adjustable features enable a variety of impact velocities and energies to be obtainable and allow for some degree of parameter-based study where either velocity or energy is fixed while the other is varied. To date a number of tests have been performed involving ice impacts on the Impact Module. Some representative sensor data that includes a few examples of the ice pressure distribution from one test are presented.Peer reviewed: YesNRC publication: Ye

Hydrodynamic study of submerged ice collisions

Most of the research done on ice-structure interaction deals with the ice at the sea surface. Whereas majority of icestrengthened regions of ships and offshore structures are well below the waterline. The aim of this research is to examine the mechanics of ice loads caused by submerged ice blocks colliding with the structure. The kinematics is an essential determinant of the energy that is available to drive the ice crushing process during the collision. The present research aims to develop a model to represent the mechanics of such collisions and set a direction for future work. This study includes experimental and numerical components. Various physical experiments have been conducted using a submerged ice model moving solely due to its buoyancy. Using high speed camera the experiments are recorded and analysed to determine the kinematics of collision. These include location, velocity and acceleration of the model ice as a function of time. In parallel, numerical simulations have being conducted using FLOW 3DTM software. The results of the experiments are used to validate the numerical model of the underwater collision. The results shows that added mass plays an important role during the underwater impact collisions. The paper presents some preliminary results obtained during this research.The article from: V. 7, Ocean EngineeringPeer reviewed: YesNRC publication: Ye