Advantages of twin rudder system with asymmetric wing section aside a propeller : the new hull form with twin rudders utilizing duct effects

This study presents a new twin rudder system with asymmetric wing section, aside a propeller, as a new category energy saving device (ESD) for ships. The energy saving principle of the new ESD, which is called "Gate rudder", is described and its applicability on a large bulk carrier is explored using experimental and numerical methods. The study makes emphasis on the cost-effectiveness of the proposed ESD and presents a potential energy saving up to 7–8 % with the new device as well as an attractive return investment in 0.37–0.9 year. These estimations are based on the conventional powering methods, whereas the accuracy of the ESD design method is confirmed by model test measurements

Constraining Cosmological Parameters by the Cosmic Inversion Method

We investigate the question of how tightly we can constrain the cosmological parameters by using the ``cosmic inversion'' method in which we directly reconstruct the power spectrum of primordial curvature perturbations, $P(k)$, from the temperature and polarization spectra of the cosmic microwave background (CMB). In a previous paper, we suggested that it may be possible to constrain the cosmological parameters using the fact that the reconstructed $P(k)$ does not depend on how many polarization data we incorporate in our inversion procedure if and only if the correct values of the cosmological parameters are used. The advantage of this approach is that we need no assumption regarding the functional form of $P(k)$. In this paper, we estimate typical errors in the determination of the cosmological parameters when our method is applied to the PLANCK observation. We investigate constraints on $h$, $\Omega_b$, $\Omega_m$, and $\Omega_\Lambda$ through Monte Carlo simulations.Comment: 18 pages, 15 figures, version to be published in Prog. Theor. Phy

A prediction program of manoeuvrability for a ship with a gate rudder system

The Gate Rudder is a special twin rudder system with two rudder blades placed aside of a propeller. Main advantage of this system is the energy saving originated from the rudder thrust which is induced by the two cambered rudder blades comparably efficient to ducted propellers. However, as any rudder’s prime task, the performance of manoeuvrability is critical to the Gate Rudder too. With the currently available Manoeuvring Modelling Group (MMG) simulation programs, the simulation is only applicable to the traditional single rudder located behind the propeller. Therefore, how to predict the manoeuvring performance for the gate rudder is the focus of this paper. On the other hand, a recent study of the Gate Rudder reveals that this innovative system has remarkable flap effect which is well known as a manoeuvring interaction between rudder blades and ship stern. This phenomenon has been observed in the case of conventional rudder and introduced into an MMG-based theoretical model as interaction factor aH. However, the average values of aH for conventional rudder is between 0.1-0.2 in general whilst the aH value for the Gate Rudder is more than twice as much, showing a superior course keeping ability of the Gate Rudder. The paper presents the manoeuvrability simulation method of a ship with this Gate Rudder system and introduces some examples of comparisons between the model tests and free running tests which was conducted with 2.5 m ship model in the manoeuvring tank at Kyushu University, Japan

Towards a realistic estimation of the powering performance of a ship with a gate rudder system

This paper presents an investigation on the scale effects associated with the powering performance of a Gate Rudder System (GRS) which was recently introduced as a novel energy-saving propulsion and maneuvring device. This new system was applied for the first time on a 2400 GT domestic container ship, and full-scale sea trials were conducted successfully in Japan, in 2017. The trials confirmed the superior powering and maneuvring performance of this novel system. However, a significant discrepancy was also noticed between the model test-based performance predictions and the full-scale measurements. The discrepancy was in the power-speed data and also in the maneuvring test data when these data were compared with the data of her sister container ship which was equipped with a conventional flap rudder. Twelve months after the delivery of the vessel with the gate rudder system, the voyage data revealed a surprisingly more significant difference in the powering performance based on the voyage data. The aim of this paper, therefore, is to take a further step towards an improved estimation of the powering performance of ships with a GRS with a specific emphasis on the scale effect issues associated with a GRS. More specifically, this study investigated the scale effects on the powering performance of a gate rudder system based on the analyses of the data from two tank tests and full-scale trials with the above-mentioned sister ships. The study focused on the corrections for the scale effects, which were believed to be associated with the drag and lift characteristics of the gate rudder blades due to the low Reynolds number experienced in model tests combined with the unique arrangement of this rudder and propulsion system. Based on the appropriate semi-empirical approaches that support model test and full-scale data, this study verified the scale effect phenomenon and presented the associated correction procedure. Also, this study presented an enhanced methodology for the powering performance prediction of a ship driven by a GRS implementing the proposed scale effect correction. The predicted powering performance of the subject container vessel with the GRS presented an excellent agreement with the full-scale trials data justifying the claimed scale effect and associated correction procedure, as well as the proposed enhanced methodology for the practical way of predicting the powering performance of a ship with the GRS

Computational fluid dynamic investigations of propeller cavitation in the presence of a rudder

This paper presents the preliminary results of a computational study for cavitation modelling of marine propellers particularly developing tip vortex cavitation in the presence of a rudder. The main purpose of the study is to estimate the propeller’s performance in cavitating conditions and to investigate the propeller-rudder interaction especially due to the tip-vortex cavitation. The cavitation simulations were conducted using commercial Computational Fluid Dynamics (CFD) software, Star CCM+. In the study, the INSEAN E779A model propeller was used as a benchmark. Firstly, validation studies were conducted in cavitating conditions using only the propeller in isolation. The cavitation on the propeller was simulated by using a numerical model, which is known as Schnerr–Sauer cavitation model, based on the Rayleigh-Plesset equation. Then, the rudder with an airfoil section was introduced behind the propeller and the simulations were repeated to investigate the effect of the rudder on the propeller performance as well as to study the propeller-rudder interaction from the cavitation point of view. Two cases with different advance coefficients (J) and cavitation numbers (σ) were simulated to compare the computational results with experiments which were obtained from open literature. For the tip vortex cavitation modelling, recently developed volumetric control method using spiral geometry was applied to generate finer mesh around the propeller tip region where the tip vortex cavitation may occur. The comparison with the benchmark experimental data showed good agreement in terms of thrust and torque coefficients as well as sheet and tip vortex cavitation patterns for the propeller in the absence of the rudder. The comparisons also showed good agreement in terms of the velocity and pressure distributions and hence enabled accurate extension of the tip vortex cavitation until the rudder to focus on the interaction of the tip vortex cavitation with the rudder

Scale effect of Gate Rudder

This paper introduces a new power prediction method for an innovative propulsion system which may not be categorized as a conventional energy saving device and it has not been even fully explored so far. Yet this system, which is called “GATE RUDDER“, has been already applied for the first time on a 2400 GT container ship and full-scale sea trials were conducted successfully in November 2017 in Japan. The recent full-scale trials with this domestic container vessel have confirmed the superior performance of the gate rudder system (Sasaki 2018). However, the big discrepancy between the model test and the sea speed trial results was found when those are compared with the data of her sister ship equipped with a conventional flap rudder. After 12 month from her delivery, the voyage data revealed the fact that the difference observed in the speed trial was not negligible and surprisingly much larger difference was found based on the voyage data (Fukazawa 2018). This paper investigates the scale effect of the Gate Rudder system and concludes that the main reason of the discrepancy between the model test and full scale data can be related the scale effect associated with the drag and lift characteristics at low Reynolds numbers for both rudder blades

Investigation into the propulsive efficiency characteristics of a ship with the Gate Rudder propulsion

Following the first successful application of the Gate Rudder® propulsion system on a 2500GT container ship (Lpp=102m) in Japan, excellent manoeuvring performance was reported with a significant fuel saving over her sister ship fitted with a conventional rudder propeller arrangement. Based upon the investigations carried out by using model tests, CFD simulations and the full-scale data of two container vessels, this paper discusses the details of the propulsive efficiency characteristics of a vessel fitted with the GATE RUDDER® propulsion system in comparison those of the same vessel with the conventional rudder-propeller arrangement. In the paper the evolution history of the GATE RUDDER® concept is presented by tracing the development of the state-of-the-art energy saving devices (ESD) involving ducts since the GATE RUDDER® exploits the advantage of the duct effect. The components of the propulsive efficiency parameters, with an emphasis on the thrust deduction and effective wake parameters, are explored and discussed highlighting the differences for the hull with the GATE RUDDER® and the conventional rudder arrangements

Regulation of epithelial cell adhesion and repulsion : role of endocytic recycling

A proper balance between cell adhesion and repulsion is essential for cellular morphogenesis during epithelial-mesenchymal transition and mesenchymal-epithelial transition. A number of ligand-receptor pairs including hepatocyte growth factor/scatter factor-Met and semaphorin-plexin are known to control this balance through the complex intracellular signaling pathways. Cell adhesion to other cells and extracellular matrix (ECM) is mediated by cell adhesion molecules (CAMs) and ECM receptors, respectively, which are associated with cytoskeleton through a variety of plaque proteins strengthening and/or weakening adhesion activities. Cell repulsion requires the downregulation of cell adhesion and the extensive changes in cytoskeletal dynamics. The endocytic recycling of CAMs and ECM receptors has recently emerged as an important mechanism to control the balance between cell adhesion and repulsion. Molecule interacting with CasL (MICAL) family proteins are originally identified as a plaque protein associated with ECM receptors integrins and implicated in semaphorin-plexin dependent repulsive axon guidance. We have recently shown that MICAL family protein JRAB/MICAL-L2 functions as an effector protein for Rab family small G protein Rab13 and regulates the endocytic recycling of tight junctional CAM occludin and controls the adhesion and repulsion of epithelial cells

Hydropod : an on-board deployed acoustic-visual device for propeller cavitation and noise investigations

Conducting noise trials with big merchant vessels could constitute serious economic and time losses for the ship operators. This study aims to introduce an experimental acoustic–visual device enabling economical and cost-effective noise trials in full scale. Noise emission and dynamics of propeller cavitation are investigated on a research vessel equipped with a customized submerged device called “Hydropod” that consists of hydrophones and a high definition, wide-angle underwater camera. Previously conducted noise trials following the international standards with an off-board hydrophone array are utilized for the validation of the adopted approach. The comparisons between the Hydropod measurements and conventional noise trial measurement results have shown promising correlations, except for a self-noise hump present in the noise spectra of the Hydropod measurements. Furthermore, by taking advantage of the replacement of the conventional propellers of the catamaran with a set of new profile technology (NPT) propellers, additional trials were conducted using the Hydropod. This enabled interpretation of the relative performance of both sets of propellers in terms of acoustics and cavitation extent. The NPT propellers were superior compared to the conventional propellers over the cavitation extent and resulting acoustic emissions

Remedial solutions to control excessive propeller induced hull vibrations on a landing craft

Although landing craft are not sophisticated vessels, their functional/operational requirements often result in a hull shape which may encounter unusual hydrodynamic phenomena, requiring remedial attention. One such instance is discussed in this paper, which presents hull form solutions adopted to address excessive vibration experienced on-board an enhanced landing craft operating in the Arabian Gulf region. Through Computational Fluid Dynamics (CFD) simulations, the sources of excessive vibration experienced by this vessel were identified. The sources included the current bow design, which promoted aeration; an extensive flat bottom, which channelled the air to a shallow buttock-flow stern region; angled pram type stern fitted with blunt-ended appendages generated a non-uniform flow that was too severe for the existing propeller-hull clearances. The combination of these unfavourable flow conditions with the cavitating propellers resulted in undesirable Propeller-Hull Vortex Cavitation (PHVC) which manifested itself with excessive aft end vibrations and noise. To remedy the situation and to control the excessive vibrations, further CFD simulations guided the necessary hull form modifications. The identified countermeasures included anti-Propeller Hull Vortex (PHV) plates and streamlining of stern appendages. Subsequent sea trials showed horizontal vibration levels were reduced by 85%, which significantly improved the conditions on-board. This paper presents a technical summary of the above countermeasures, their implementations on the vessel, which included full-scale trials to measure the speed-power performance, hull vibrations and cavitation observations using a borescope system, and discussions of the results of these countermeasures. The paper concludes with an outline proposal for further design study, which could reduce on-board vibrations even further as well as providing other operational benefits regarding propulsive efficiency and manoeuvrability using the recently developed "Gate Rudder System®" as a novel Energy Saving Device (ESD)