Head Wave Simulation of a KCS Model Using OpenFOAM for the Assessment of Sea-Margin

The paper presents calm water and head wave simulation results for a KRISO Container Ship (KCS) model. All simulations have been performed using the open source CFD toolkit, OpenFOAM. Initially, a systematic verification study is presented using the ITTC guideline to assess the simulation associated uncertainties. After that, a validation study is performed to assess the accuracy of the results. Next, calm water simulations are performed with sinkage and trim free condition at varying speeds. Later, head wave simulations are performed with heave and pitch free motion. Simulations are repeated for varying wave lengths to assess the encountered added resistance by the ship in design speed. The results are validated against available experimental data. Finally, power predictions are made for both calm water and head wave cases to assess the required propulsion power. The paper tries to assess the validity of using 25% addition as sea margin over calm water prediction to consider wave encounters

Experimental model tests to improve a tanker resistance performance

The ship resistance is one of the most important hydrodynamics performances, being related to the contractual ship speed. The experimental model tests can be used to measure and improve the resistance performance. In this paper, the possibility of using the experimental techniques in order to improve a tanker model resistance is demonstrated, based on a bulbous bow modelling solution. In this context, the results obtained in the Towing Tank of the Naval Architecture Faculty of “Dunarea de Jos” University of Galati, related to a tanker model resistance with and without bulbous bow are presented. The bulbous bow form was realised based on the hydrodynamics principles adapted to the bow forms of the tanker. In the case of the bulbous bow solution, a significant reduction of over 8% of the tanker model resistance was obtained, in the design speed domain.

Selection of the composition and parameters of the propulsive complex of increased speed sea transport vessel

В работе предложена методика выбора состава и основных параметров двигательно-движительного комплекса морского транспортного судна, предложены критерии оценки указанного выбора. С использованием этой методики решена задача выбора числа гребных валов при проектировании транспортных судов повышенной скорости хода. Задача решена применительно к судну RO-RO типа «Сергей Киров» (проектная скорость 17 узлов) и контейнеровозу ФЕСКО «Байкал» (проектная скорость 22 узла). В качестве критериев оценки проектных решений использована совокупность величин: пропульсивный коэффициент, часовой расход топлива в главных двигателях и суммарные затраты денежных средств на покупку и эксплуатацию главных двигателей в течение расчётного срока. Второй из перечисленных критериев использован в составе относительного конструктивного коэффициента энергетической эффективности (EEDI), который по сути является величиной, характеризующей уровень выброса СО2 в атмосферу. В работе использован авторский программный комплекс ENGINES автоматизированного проектирования судового пропульсивного комплекса. В программе предусмотрен расчёт ходкости суда, параметров гребного винта, а также выбор из электронного каталога вариантов главного двигателя. Для каждого двигателя выполнена совместная оптимизация параметров гребного винта и рабочей точки двигателя с целью обеспечения минимального часового расхода топлива. Расчёты показали, что граничная проектная скорость движения судна, при превышении которой целесообразен переход от одновальной установки в двухвальной, составляет: для RO-RO – 16 узлов; для контейнеровоза – 25 узлов. The paper proposes a method for selecting the composition and main parameters of the propulsive complex of a marine transport vessel, and suggests criteria for evaluating this choice. Using this technique, the problem of selecting the number of propeller shafts in the design of increased speed transport vessels is solved. The problem is solved in relation to the RO-RO vessel "Sergey Kirov" (design speed 17 knots) and the container ship FESCO "Baikal" (design speed 22 knots). As criteria for evaluating design solutions, a set of values is used: the propulsive coefficient, the hourly fuel consumption in the main engines and the total cost of funds for the purchase and operation of the main engines during the estimated period. The second of these criteria is used as variety of the relative constructive energy efficiency coefficient (EEDI), which is essentially a value that characterizes the level of CO2 emissions into the atmosphere. The paper uses the author's software package ENGINES for computer-aided design of the ship's propulsive complex. The program provides for the calculation of the ship's seaworthiness, the parameters of the propeller, as well as the selection of the main engine from the electronic catalog of options. For each engine, the parameters of the propeller and the operating point of the engine are jointly optimized to ensure a minimum hourly fuel consumption. Calculations have shown that the limit design speed of the vessel, when exceeding which it is advisable to switch from a single-shaft installation to a two-shaft one, is: for RO-RO – 16 knots; for a container ship - 25 knots.

Impact of Uniform Surface Roughness on the Aerodynamic Performance of an Axial Compressor Rotor at Different Rotational Speeds

The aerodynamic performance of a compressor rotor is known to deteriorate due to surface roughness. It is important to understand this deterioration as it impacts the overall performance of the engine. This paper, therefore, aims to numerically investigate the impact of roughness on the performance of an axial compressor rotor at different rotational speeds. In this numerical study, the simulations are carried out for NASA Rotor37 at 100%, 80%, and 60% of its design speed. with and without roughness on the blade surface. These speeds are chosen because they represent different flow regimes. The front stages of a multistage compressor usually have a supersonic or transonic regime whereas the middle and aft stages have a subsonic regime. Thus, these performance characteristics can give an estimate of the impact on the performance of a multistage compressor. At 100% speed (design speed), the relative flow is supersonic, at 80% of design speed, the relative flow is transonic and at 60% of design speed, the relative flow is subsonic. Detailed flow field investigations are carried out to understand the underlying flow physics. The results indicate that, for the same amount of roughness, the degradation in the performance is maximum at 100% speed where the rotor is supersonic, while the impact is minimum at 60% speed where the rotor is subsonic. Thus, the rotor shock system plays an important role in determining the performance loss due to roughness. It is also observed that the loss increases with increased span for 100% and 80% speeds, but for 60% speed, the loss is almost constant from the hub to the shroud. This is because, with the increased span, the shock strength increases for 100% and 80% speeds, whereas at 60% speed flow is subsonic.

Research on Truck Traffic Volume Conditions of Auxiliary Lanes on Two-Lane Highways

The larger the proportion of truck traffic volume, the greater the impact on traffic efficiency, and overtaking behavior will also have an impact. Therefore, in order to clarify the truck traffic volume of the freight two-lane highway due to the difficulty of overtaking, an actual vehicle test is carried out. This involves selecting the appropriate two-lane test section, recording each moment and speed in the driver’s overtaking behavior, performing multiple regression analysis to examine the relationship between the overtaking conflict time and design speed and traffic volume, determining a reasonable evaluation series of two-lane road overtaking risk and the corresponding overtaking conflict time threshold by the Fisher optimal segmentation method, and giving an overtaking behavior risk evaluation method based on conflict time. Finally, according to the overtaking conflict time model, different truck traffic conditions are obtained. The research results show that overtaking conflict time is negatively correlated with the traffic volume and design speed of the lane. Through the risk assessment of the corresponding overtaking behavior, the three levels of serious conflict, general conflict and non-conflict are determined, and the freight traffic volume corresponding to different conflict levels at different speeds is calculated, which provides a reference for setting auxiliary lanes for the two-lane freight highway.

Assessment of Energy Efficiency and Ship Emissions from Speed Reduction Measures on a Medium Sized Container Ship

Greenhouse gases and other emissions from vessels and related activities in maritime trade have caused significant environmental impacts especially global warming of the atmosphere. Consequently, the International Maritime Organization (IMO) concern significant care to the reduction of ship emissions and improvement of energy efficiency through operational and technical measures. The proposed short-term measure is ship speed reduction in which the ship speed is reduced below its designed value. Therefore, the present paper aims at evaluating the potential energy efficiency and environmental benefits from using speed reduction measure through energy efficiency design index (EEDI), energy efficiency operational indicator (EEOI) and ship emissions calculation models as recommended from IMO. As a case study, a medium sized Container Ship is investigated. The results show that, reducing ship speed by 12.6% will reduce CO2 emissions by about 36%. Moreover, the attained EEDI value will be improved by 31.7% and comply with not only the current IMO requirements but also with the future ones. Additionally, reducing ship speed by 12.6% will reduce EEOI value from its value at design speed by 26.5%. Furthermore, it is noticed that SOx emission will comply with IMO 2020 limit if ship speed is reduced by 6.8% and above.

Search for requirements for the width of pedestrian roads in the context of the classification of public space

Walking has long been the primary means of human transport. Nevertheless, in recent decades, the insufficient emphasis has been placed on it in the creation and renewal of public space. It focuses mainly on the needs of road transport, the volume of which is constantly growing enormously. It is only in recent years that the view begins to be re-evaluated and trends in the organization of public space gradually changed, as it is true that a larger supply generates a greater demand. Therefore, leading architects are gradually changing their approaches to the organization of public space and put humans, pedestrian transport, and its requirements first. In the Czech Republic, the trend is gradually changing, as it is worldwide. Walking again plays an important role in the creation of sustainable mobility plans for the cities of the Czech Republic. The main problems arise in the actual implementation of these ideas, as the legislative requirements are formulated only in general, unlike the requirements for road transport, which sets out the requirements for minimum road profiles in the context of design speed and traffic intensity in a given cross-section. These requirements are set out in Decree No. 501/2006 Coll. on general requirements for land use and also in CSN 73 6110 Design of local roads (CSN is Czech technical norm). However, such a categorization of requirements for pedestrian roads is not yet solved uniformly for the entire territory of the Czech Republic, even though CSN 73 6110 deals with sidewalks (functional group D roads). ). So far, this categorization is replaced only by seldom locally valid methodologies, manuals, or requirements and regulations in the town plans of individual cities. This paper aims to search for current approaches, legislative requirements, and approaches to addressing the width requirements for pedestrian roads in public space in the context of the classification of this area.

Noise Measurements and Mitigation for a Foil Assisted Catamaran

Noise control recommendations and mitigation approaches for a foil-assisted catamaran become very sensitive when it comes to weight tradeoff. While weight control on a fast marine craft is critical, it reaches the uppermost limit when it comes to a foil-assisted catamaran. A foil-assisted catamaran is very sensitive to weight growth as well as the Longitudinal Center of Gravity (LCG) of the vessel in terms of reaching foil-assisted planing speeds. An increase in weight leads to a slow pre-planing speed which does not generate sufficient foil lift to transition the vessel into full planing speed. Whereas incorrect LCG of the vessel leads to wrong foil attack angle and thus leading to insufficient foil lift. This paper covers design philosophy, risk management, onboard measurements, weight management, mitigation approaches, and recommendations associated with the design of a 61 ft foil-assisted catamaran designed to reach 38+ knots and meet specific noise criteria limits at the maximum cruising speed as well as other operational conditions. An initial solution was applied, and the noise reduced at intermediate design speeds, however, at design cruising speeds the noise levels still exceeded the limits. Further computational analyses and mitigation methods such as insulation, mass-loaded vinyl, joiner barriers, viscoelastic coatings, trim adjustment, and floating floors were implemented on a trial-and-error basis to minimize the overall weight added to the vessel while achieving vessel design speed.

Multiobjective Railway Alignment Optimization Using Ballastless Track and Reduced Cross-Section in Tunnel

The increasing need for railway planning and design to connect growing cities in inland mountainous areas has pushed engineering efforts toward the research of railway tracks that must comply with more restrictive constraints. In this study, a multiobjective alignment optimization (HAO), commonly used for highway projects, was carried out to identify a better solution for constructing a high-speed railway track considering technical and economic feasibilities. Then, two different and innovative scenarios were investigated: an unconventional ballastless superstructure, which is more environment-friendly than a gravel superstructure, and a reduced cross-section in a tunnel, which enables a slower design speed and then, less restrictive geometric constraints and earthmoving. The results showed that the first solution obtained a better performance with a slight increase in cost. Moreover, both scenarios improved the preliminary alignment optimization, reducing the overall cost by 11% for the first scenario and 20% for the second one.