Tesis sobre el tema "Flipper propulsion (Marine engineering)"

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (p. 101-102).
Podded propulsion systems offer greater maneuvering possibilities for marine vehicles than conventional shaft and rudder systems. As the propulsion unit rotates about its vertical axis to a specified azimuth angle, the entire thrust of the propeller contributes to the steering moment without relying on lift generation by a control surface such as a rudder. However, the larger sideforce and moment cause the ship to enter the nonlinear realm sooner than a ruddered vessel. Furthermore if the rudder or azimuthing propulsor is aft of the vessel's center of gravity then the system is non-minimum phase; during a turn the ship center initially moves in the direction opposite the turn. For these reasons it is necessary to design a robust maneuvering control system to set the azimuth angle of the propulsor in an intelligent and stable manner. This thesis focuses on the path following performance of a vessel with podded propulsion. The enhanced maneuvering abilities of such vessels allow the time constant of cross-track error response to be greatly reduced. Additionally these vessels can follow course changes and waypoints more precisely than ruddered vessels.
(cont.) A simple path following algorithm was developed to achieve this performance; the algorithm uses simulation-based feedforward terms to anticipate the sliding motion of the vessel during a turn. The stability and performance analysis was performed in three domains: linear theory, a nonlinear simulation, and experiments with a 12-foot autonomous surface vessel. Experiments confirmed that path following performance was vastly improved using the feedforward algorithm for waypoints at which the course change angle was large.
by Matthew B. Greytak.
S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.
Includes bibliographical references (leaves 123-124).
by James Taylor Czarnowski.
M.S.

Marine waterjet propulsion is a technology that has been developed and refined since the early 1950’ and is proven highly useful for high speed applications with vessels in varying sizes. The intake grill is a component that is mounted in line with the hull to prevent debris from traveling through the waterjet. The intake grill is affected by viscous forces, contact forces and harmonic excitation forces all while affecting the efficiency of the waterjet. In this report a selection of methods is evaluated and verified with the goal of simplifying the design process of the intake grill. A selection of cross-sections is generated and evaluated to draw general conclusions about the efficiency and stability of the intake grill. A selection of computational fluid dynamics and modal analysis methods are utilized. It is concluded that the intake grill is affected by many parameters and can be evaluated by modal FEM analysis and 2D CFD analysis.
Marina vattenjetmotorer har utvecklats och förfinats sedan tidigt 50-tal och har bevisats mycket användbara för applikationer i hög hastighet med båtar i varierande storlekar. Intagsgaller är en komponent som monteras i linje med skrovet på båtar för att förhindra oönskade föremål att färdas genom intaget på vattenjetmotorn. Intagsgallret är påverkat av viskösa krafter, direkta krafter och harmonisk excitation samtidigt som komponenten påverkar vattenjetmotorns effektivitet. I denna rapport så evalueras ett urval av metoder med målet att simplifiera utvecklingsprocessen av intagsgaller. Ett urval av tvärsnittsgeometrier är genererade och evaluerade för att dra generella slutsatser om effektiviteten och stabiliteten av intagsgallret. Ett par olika sorters flödessimuleringar och finita element metoder används. Slutsatsen är att intagsgallret påverkas av ett flertal parametrar och kan utvärderas med modal finita element metoder samt tvådimensionella flödessimuleringar.

Modern Autonomous Underwater Vehicle (AUV) technology has a number of limitations and one of these is vehicle manoeuvrability. Conventional flight style AUVs generally have turning circle diameters of five or more vehicle lengths, but most marine animals can turn in under one body length. This shows there is merit in looking at marine animals for inspiration to improve the manoeuvrability of AUVs. Aquatic flight propulsion is one marine animal propulsion strategy that was identified early in the research as having the potential to full fill this role. Aquatic flight propulsion has been studied experimentally in the past, but most of the past research focused in one or two axis aquatic flight (foil pitch and dorsoventral roll). However, marine animal literatures show animal aquatic flight is a three axis problem and there is an additional motion component in anteroposterior yaw. The effect of this yaw motion is not well understood and this will be the focus of this thesis’s research. The effect of aquatic flight yaw motion is investigated using a combination of computation modelling and experimental studies. It found two-axis aquatic flight is better for producing propulsive thrust for most scenarios, but three-axis aquatic flight is useful for producing additional off axis force. In particular, the three axis slanted foil actuation path can produce a sizeable vertical force with very little change to the horizontal thrust coefficient, which would be very useful for a positively buoyant AUV to control its depth. The experiment verified the model’s results and many of the experiment data points were within 30% of the model prediction. The experiment has a relatively large uncertainty due to turbulences in the recirculating water channel, so 30% is a reasonably good fit. Whilst there is room for improvement for both the model and the experiment, the current model is sufficient to produce provisional estimates for actuator and control system design as well as identification of various cases of interest for further in depth analysis.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
This thesis presents an impulse framework for analyzing the hydrodynamic forces on bodies in flow. This general theoretical framework is widely applicable, and it is used to address the hydrodynamics of fish propulsion, water entry of spheres, and the offdesign performance of marine propellers. These seemingly-unrelated physics problems share a key common thread: The forces on these fish, spheres, and propellers can be modeled as the sum of the reaction to the rate of change of (1) the pressure impulse required to set up the potential flow about the body, and (2) the vortex impulse required to create the vortical structures in the wake of the body. Fish generate propulsive forces by creating and manipulating large-scale vortical structures using their body and tail. High-speed particle image velocimetry experiments show that a fish generates two vortex rings during a C-turn maneuver and that the change in momentum of the fish balances the change in pressure impulse plus the vortex impulse of these rings. When a sphere plunges into a basin of water and creates a sub-surface air cavity in place of a vortical wake, the vortex impulse is zero, and the force on the sphere is given by the pressure impulse component. Using data from high-speed imaging experiments, a semi-empirical numerical simulation is developed herein; this numerical model shows how the presence of the cavity alters the unsteady pressure force on the sphere and modulates the dynamics of the impact event. During steady propeller operation, the pressure impulse is constant, and the loads on the propeller are given by the vortex impulse component. To analyze these loads, a computational design and analysis tool is presented; this code suite is based on propeller lifting line theory, which is shown to be a special case of the general impulse framework of this thesis. A marine propeller is designed, built, and tested over a range of off-design operating conditions. Experimental results match the predicted performance curve for this propeller, which provides important validation data for the numerical method presented herein. 3 Bringing this thesis full circle, the unsteady startup of the propellor is addressed, which is analogous to the impulsive maneuvering of the swimming fish. As in the fish maneuvering problem, the propellor generates a ring-like vortical wake, and it is shown herein how the vortex impulse of these rings provides thrust for the propellor. With the perspective of the impulse framework developed in this thesis, the results of these tandem experimental investigations and numerical simulations provide deeper insight into classical fluid-dynamics theory and modern experimental hydrodynamics.
by Brenden P. Epps.
Ph.D.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2003.
Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 55-56). Also available online.

Autonomous Underwater Vehicles (AUVs) are a developing technology with multiple applications including oceanographic research, military missions and commercial activities such as oil and gas field exploration. The reported research covers two main areas, namely, the assessment of the survey performance of AUVs and the development of the next generation of multi-purpose AUVs. The performance characteristics of long range survey-style AUVs are examined and improvements in performance are sought through the use of hybrid devices. Hybrid devices are defined as those that provide both propulsion and manoeuvring forces. Two devices were chosen for detailed investigation; a vectored thruster and a collective and cyclic pitch propeller. The manoeuvring performance of both devices was found to be insufficient to justify the additional engineering complexity associated with them. The aim of the next generation of AUVs is to be able to combine long range survey capabilities with low speed investigation of the environment encountered. An assessment of a likely mission profile and a review of the available design options demonstrate that maintaining the survey efficiency of the AUV is of principal importance. Therefore the investigation focuses on approaches to the addition of low speed control to an existing survey-style AUV design using propeller based thrusters. Externally mounted thrusters and through-body tunnel thrusters are reviewed and new experimental investigations are reported to provide insight into the performance characteristics on a survey-style AUV hull form. The main body of the experimental programme characterises forward and aft mounted tunnel thruster performance over a range of forward speeds and small yaw angles. The results are used to develop a new, simple modelling procedure representing the performance of tunnel thrusters on an AUV which facilitates the incorporation of the characteristics of tunnel thrusters into numerical simulations of AUV performance. Such a simulation is used to examine approaches to undertaking the transition phase between high speed survey and low speed manoeuvring operation. The results demonstrate the advantageous nature of undertaking a smooth interchange between control approaches considering both the vehicle performance and the energy demands.

This doctoral thesis presents new ideas and research results on control of marine electric power system.

The main motivation for this work is the development of a control system, power management system (PMS) capable to improve the system robustness to blackout, handle major power system faults, minimize the operational cost and keep the power system machinery components under minimal stress in all operational conditions.

Today, the electric marine power system tends to have more system functionality implemented in integrated automation systems. The present state of the art type of tools and methods for analyzing marine power systems do only to a limited extent utilize the increased knowledge available within each of the mechanical and electrical engineering disciplines.

As the propulsion system is typically consisted of the largest consumers on the vessel, important interactions exists between the PMS and vessel propulsion system. These are interacted through the dynamic positioning (DP) controller, thrust allocation algorithm, local thruster controllers, generators' local frequency and voltage controllers. The PMS interacts with the propulsion system through the following main functions: available power static load control, load rate limiting control and blackout prevention control (i.e. fast load reduction). These functions serve to prevent the blackout and to ensure that the vessel will always have enough power.

The PMS interacts with other control systems in order to prevent a blackout and to minimize operational costs. The possibilities to maximize the performance of the vessel, increase the robustness to faults and decrease a component wear-out rate are mainly addressed locally for the individual control systems. The solutions are mainly implicative (for e.g. local thruster control, or DP thrust allocation), and attention has not been given on the interaction between these systems, the power system and PMS. Some of the questions that may arise regarding the system interactions, are as follows: how the PMS functionality may affect a local thruster control, how the local thruster control may affect the power system performance, how some consumers may affect the power system performance in normal operations and thus affect other consumers, how the power system operation may affect the susceptibility to faults and blackout, how various operating and weather conditions may affect the power system performance and thus propulsion performance though the PMS power limiting control, how propulsion performance may affect the overall vessel performance, which kind of faults can be avoided if the control system is re-structured, how to minimize the operational costs and to deal with the conflicting goals. This PhD thesis aims to provide answers to such questions.

The main contributions of this PhD thesis are:

− A new observer-based fast load reduction system for the blackout prevention control has been proposed. When compared to the existing fast load reduction systems, the proposed controller gives much faster blackout detection rate, high reliability in the detection and faster and more precise load reduction (within 150 miliseconds).

− New advanced energy management control strategies for reductions in the operational costs and improved fuel economy of the vessel.

− Load limiting controllers for the reduction of thruster wear-out rate. These controllers are based on the probability of torque loss, real-time torque loss and the thruster shaft

accelerations. The controllers provide means of redistributing thrust from load fluctuating thrusters to less load fluctuating ones, and may operate independently of the thrust allocation system. Another solution is also proposed where the load limiting controller based on thrust losses is an integrated part of DP thrust allocation algorithm.

− A new concept of totally integrated thrust allocation system, local thruster control and power system. These systems are integrated through PMS functionality which is contained within each thruster PLC, thereby distributed among individual controllers, and independent of the communications and dedicated controllers.

− Observer-based inertial controller and direct torque-loss controller (soft anti-spin controller) with particular attention to the control of machine wear-out rate. These controller contribute to general shaft speed control of electrical thrusters, generators and main propulsion prime movers.

The proposed controllers, estimators and concepts are demonstrated through time-domain simulations performed in MATLAB/SIMULINK. The selected data are typical for the required applications and may differ slightly for the presented cases.

Energy efficiency and propulsive characteristics of a 10 cm undulatory rainbow trout (oncorhynchus mykiss) swimming in a stationary position are considered. Two CFD simulations are performed utilizing dynamic grid meshing (FLUENT 6.3). The first simulation uses a laminar flow model with an added hydrofoil shape in order to test if thrust and drag can be brought to unity. The second simulation uses a Large-Eddy Simulation (LES) turbulence model to determine if transition to turbulence along the fish's surface leads to boundary layer separation. The expected results caused by adding these two features to earlier simulations do not occur. Thrust and drag are not found to be equal with usage of the thicker fish shape; instead both thrust and drag increase by 40-80% while diverging in value. Evidence of boundary layer separation is not present with usage of the LES turbulence model. Swimming energy efficiency is calculated to be 70% in both simulations. A brief analyses of boundary layer and downstream wake are included, showing general agreement with earlier studies. Limitations of the simulation are discussed. Future work regarding the author's preparation for an additional simulation of a rainbow trout utilizing a swimming method known as the Karman Gait is also considered. This preparation includes the creation of a 2-D grid domain and programs to define the kinematics of the fish and produce a specified vortex inlet condition.

The purpose of this study is to compare the life-cycle cost and environmental impact of the existing fuel-based propulsion system, on public commuter ferries in Stockholm, with a battery based propulsion system. The study is divided into multiple layers. First, the operating characteristics of the route Line 80 within Stockholm’s waterborne public transportation (WPT) are collected, such as fuel consumption, propulsion power output, speed, voyage time and propulsion system configuration. Second, based on the energy demand of the route, important parameters related to the existing fuel-based propulsion system and the battery-based propulsion system are accounted for and modeled. Third, Life Cycle Assessment (LCA) and the cost assessment methods are applied to examine the effectiveness of the electrification of commuter ferries on a financial and environmental scale. With the help of the software GaBi 2020, GREET 2020, and other literature studies, the environmental impacts at the construction, use and end-of-life (EOL) phase are evaluated. There are in total 8 scenarios considered, 4 for the fuel-based and 4 for the battery-based propulsion system. The environmental performance of these 8 scenarios are discussed in terms of Globalwarmingpotential(GWP), Acidificationpotential(AP), Eutrophicationpotential(EP) and Photo-chemical ozone creation potential (POCP). Themostpollutingphaseistheusephase for all scenarios. Propulsion system powered by diesel (scenario 1) is considered as a reference for comparative analysis of 7 other scenarios. The best performing system is the one powered by batteries with the assumption of an electricity mix based on hydro, wind and nuclear power, which is scenario 7 and 8 with a net reduction of GWP by more than 98%, AP by 90%, EP by 96%, and the POCP by 96%. If we consider the current Swedish electricity mix (scenario 5 and 6), the decrease in GWP, AP, EP and POCP are 90%, 80%, 82% and 91% respectively. Alternative fuels also present promising results for GWP in comparison to diesel (with the origin of the feed-stock creating mostly negative impacts) but the contribution to other impact categories is significantly higher. With inputs from the industry and the environmental evaluation, the cost assessment compares the costs related to fuel-based and battery-based propulsion systems with different energy sources. For the battery-based system, 3 scenarios are modeled for two different types of Li-ion batteries. The vessels in the developed scenarios are charged more frequently than the existing electric vessel and the number of charging stations is varied. The costs that are included in the assessment are the initial capital cost, the cost for fuel/electricity, maintenance cost, end-of-life cost and emissions cost. When concerning all the cost categories, the battery-based system is more cost-efficient than a fuel-based system, if run on the Swedish electricity mix, due to the lower cost for electricity and emissions. The reduction of cost is more than 68% when comparing traditional diesel with battery-based systems, but the source of the electricity is very important.
Syftet med denna studie är att jämföra livscykelkostnaden och miljöpåverkan av de befintliga framdrivningssystemen på pendelbåtarna inom Stockholms kollektivtrafik, med batteridrivna system på motsvarande båtar. De befintliga framdrivningssystemen drivs av olika typer av diesel. Studien är uppdelad i flera steg. Först samlas driftsegenskaperna in, såsom bränsleförbrukning, framdrivningseffekt, hastighet, färdtidochframdrivningssystemetsuppbyggnad, etc, på linje 80, som är en del av Stockholms vattenburna kollektivtrafik. För det andra undersöks det befintliga framdrivningssystemet som drivs av diesel eller alternativa bränslen som RME eller HVO och fullt batteridrivna system utifrån energibehovet. För det tredje tillämpas metoderna för kostnadsanalys och livscykelanalys (LCA) för att undersöka hur elektrifieringen av pendelbåtar påverkar ekonomin och miljön. Med hjälp av programmet GaBi 2020, GREET 2020 och andra litteraturstudier utvärderas miljöpåverkan av faserna tillverkning, användning och avfallshantering. Det är totalt 8 scenarier som övervägs, 4 för bränslebaserade och 4 för batteri baserade framdrivningssystem. Hur bra dessa 8 scenarier presterar miljömässigt diskuteras i termer av växthuseffekt (GWP), försurning (AP), övergödning (EP) och marknära ozon (POCP). Den fasen med mest utsläpp, för alla scenarier, är användningsfasen. Framdrivningssystemet som drivs av diesel (scenario 1) används som referens att jämföra de övriga 7 scenarierna mot. Det system som presterar bästa är det som drivs av batterier, med antagandet att elmixen är baserad på vatten-, vind-och kärnkraft, detta motsvarar scenario 7 och 8 med en reduktion av GWP på mer än 98%, AP med 90%, EP med 96% och POCP med 96%. Om vi tittar på den aktuella svenska elmixen (scenario 5 och 6) så är minskningen av GWP, AP, EP och POCP 90%, 80%, 82% respektive 91%. Alternativa bränslen ger också lovande resultat för GWP jämfört med diesel (där råvarans ursprung skapar mest negativa effekter) men bidraget till andra påverkanskategorier är betydligt högre. Med input från företag och miljöutvärderingen kan kostnadsanalysen jämföra kostnaderna för bränslebaserade och batteri baserade framdrivningssystem med olika energikällor. Det batteri baserade systemet modelleras även på 3 utvecklade scenarier för 2 olika typer av batterier. Fartygen i de utvecklade scenarierna laddas oftare än det befintliga batteridrivna fartyget och antalet laddstationer varierar mellan scenarierna. De kostnader som inkluderas i analysen är de initiala kapitalkostnaderna, kostnaden för bränsle/el, underhållskostnader, avfallshanteringskostnader ochutsläppskostnader. Medallakostnaderinkluderadeiberäkningarna är batteri baserade system mer kostnadseffektiva än bränslebaserade system om de körs på svensk elmix, tack vare de lägre kostnaderna för el och utsläpp. Minskningen av den totala kostnaden är mer än 68% när man jämför traditionell diesel med batterisystem, men elens ursprung är mycket viktig.

Ce travail porte sur la modélisation et le dimensionnement des moteurs à aimants
permanents et asynchrones destinés à la propulsion marine par POD. Un état de l'art est
présenté, où les différentes topologies de moteurs pour ce type d'application y sont abordées. La
Machine à aimants permanents et la machine asynchrone on été retenue pour notre application.
Dans le cas de la machine à aimants permanents, une analyse par éléments finis est
effectuée pour dimensionner la machine à aimants permanents et minimiser les principaux
harmoniques de la FÉM. Un modèle éléments finis 2D en magnétostatique couplé à un modèle
circuit est développé pour la prédiction des couples pulsatoires dues aux harmoniques du
convertisseur.
En ce qui concerne la machine asynchrone, Pour tenir compte des harmoniques d'espace
et évaluer leurs pertes, un modèle électromagnétique utilisant la résolution par éléments finis 2D
en magnétodynamique couplé à un modèle circuit est développé. Par ailleurs, un autre modèle
basé sur le principe de couplage éléments finis- circuit électrique est développé pour tenir compte
des harmoniques de temps du variateur, ce modèle permet d'évaluer à la fois les pertes dues aux
harmoniques de temps, mais aussi des couples pulsatoires.
Dans la phase de validation et vérification des différents calculs, nous avons utilisé l'outil
Flux2D de calcul par éléments finis qui tient compte de la rotation du rotor (pas à pas dans le
temps) et effectué certaines mesures (cas de la machine à aimants permanents). Les résultats des
calculs obtenus par les modèles développés concordent avec ceux obtenus par la méthode
temporelle (pas à pas dans le temps) et les quelques mesures dont nous disposons.

Este trabalho trata da questão da redução de consumo de combustível fóssil em instalações de máquinas de navios. É um tema de grande interesse no momento, devido ao alto custo operacional e à emissão de poluentes decorrentes do processo da combustão desses derivados de petróleo. Apresenta-se, inicialmente o cenário atual e tendências futuras das instalações propulsoras convencionais que usam óleo pesado ou Diesel. Em seguida, são examinadas alternativas propostas para redução de consumo de combustíveis fósseis nos navios, que são enquadradas em três categorias. A primeira delas envolve possíveis melhorias de projeto para redução da demanda de energia. As outras categorias se referem ao emprego de fontes alternativas de energia, que introduzem uma força propulsora adicional, reduzindo o empuxo requerido do hélice, ou uma potência suplementar no eixo propulsor. Em ambos os casos há também uma redução de demanda de potência requerida do motor Diesel. Na seqüência, são apresentados e discutidos fundamentos termodinâmicos, com ênfase nas análises energética e exergética, como ferramentas para avaliação das máquinas dos navios. A análise exergética, diferentemente do enfoque apenas energético, é a ferramenta mais apropriada para tratar as questões ligadas ao meio ambiente, pois a própria definição de exergia está relacionada com o ambiente de referência. Finalmente, utilizando dados de um navio porta contêineres da frota nacional, é exercitado um exemplo de aplicação com as análises termodinâmicas do motor de propulsão; são também avaliadas e simuladas as diversas alternativas de melhorias e novas fontes de energia, que visam a redução de consumo de combustível fóssil.
This work addresses the issue of reduction of fossil fuel use on ship machinery. Presently it is an interesting topic due to high operational cost and the pollution emissions generated by the combustion process. Initially, it is introduced the present scenario and future trends regarding conventional ship machinery that use heavy or diesel fuel oil. In the sequence, the proposed alternatives for reducing the use of fossil fuel on ships are presented and examined. These alternatives are classified into three categories. The first category comprises possible improvements to the design of ships for reduction of total energy demand. The other categories refer to the use of alternative energy sources, that produce and additional force on the ship reducing the required propeller thrust; or a supplementary power added to the propulsion shaft. For both cases there is also a reduction in the power required from the Diesel engine. Afterwards, the pertaining thermodynamics theory is revised and discussed with focus on the energy and exergy analysis as aid tools for evaluation of ship machinery. The energetic analysis, different from the sole energetic focus, is the most applicable tool to be employed for environmental issues as the self definition of exergy relates to an environment reference. Finally, using data from a typical container ship belonging to the national fleet, an application example using the thermodynamic analysis is performed to the propulsion main engine; as well as it is also simulated several alternative conditions for improvements and new energy sources, aiming to the reduction of fossil fuel consumption.

Liquefied Natural Gases (LNG) has been an alternative fuel in the marine industry for several years, but lately, the amount of ships that have been powered by methane has increased a lot. Some of the reasons for this is because LNG does not contain any sulfur and releases less nitrogen oxides than traditional maritime fuels. In this essay, LNG will be compared to diesel from an environmental perspective with focus on CO2 emissions and its equivalents. International Maritime Organization (IMO) implemented Energy Efficiency Design Index (EEDI) requirements that adjusts how much CO2 is allowed in the exhaust gas per produced kilowatt-hour (kWh). However, these requirements will increase in intervals in the future, the next one is coming 2022 for specific ship types. The method that is used to compare the fuels is Mole-calculations for LNG as well as diesel, then calculate the amount of carbon dioxide (CO2) and its equivalents they release. The results show that under optimal conditions, LNG was the superior choice. However, the maritime industry might have a problem with the requirements that will be introduced to greenhouse gas (GHG) emissions in 2050.
Flytande Naturgas (LNG) har under flera år funnits som ett alternativt bränsle inom sjöfarten, men på senare tid så har skeppen som drivs av metan ökat markant. En anledning till detta är att LNG innehåller inget svavel samt släpper ut mindre NOX jämfört med traditionella bränslen. I denna uppsats så kommer LNG att jämföras mot diesel ur ett klimatperspektiv med fokus på koldioxidutsläpp och dess ekvivalenter. International Maritime Organisation (IMO) har infört Energy Efficiency Design Index (EEDI) krav som justerar hur mycket CO2 man får släppa ut per kilowattimme (kWh), dessa krav kommer dessutom att öka i flertalet intervaller i framtiden, varav nästa intervall redan sker i 2022 för speciella fartygstyper. Metoden som användes för att jämföra bränslena var att beräkna mol-innehållet för både LNG samt diesel, sen från den beräknade data se hur mycket koldioxid (CO2) inklusive ekvivalenter de släppte ut. Resultatet visade att under optimala förutsättningar så var LNG ett klart bättre alternativ än diesel. Däremot så kan sjöfarten ha ett problem inom framtiden från de krav som berör växthusgaser som kommer att ställas från och med 2050.

This thesis deals with computing the pressure distribution around a swimming slender fish and the thrust generated by its flapping motion. The body of the fish is modeled as a missile like slender body to which a tail is attached that is modeled as a swept wing. The tail is attached to the tip of the slender body and maintains its slope with it. The motion for the swimming fish is prescribed. The fluid flow is modeled as an unsteady potential flow problem with the flow around the slender body modeled as flow over an array of cylinders of varying radii and the flow over the swept wing modeled using the vortex panel method. The pressure distribution is computed using the unsteady Bernoulli equation. The overall thrust & drag for different parameters are studied and compared