Tug Boats Research Articles

Experimental Analysis of the Near Wake from a Ducted Thruster at True and Near Bollard Pull Conditions Using Stereo Particle Image Velocimetry (SPIV)

Thrusters working at low advance coefficients are employed in a wide range of offshore and marine applications on Floating, Production, Storage, and Offloading (FPSO) systems; shuttle tankers; tug boats; and mobile offshore units. Therefore, an understanding of the flow around the thrusters is of great practical interest. Despite this interest, there is lack of knowledge in the description of the hydrodynamic characteristics of a ducted thruster’s wake at bollard pull and low advance coefficient values. This work was aimed at providing detailed data about the hydrodynamic characteristics of a Dynamic Positioning (DP) thruster near wake flow at different low advance coefficient values. Wake measurements were made during cavitation tunnel tests carried out on a ducted propeller model at the Italian Ship Model Basin (INSEAN), Rome, Italy. Through these experiments, the DP thruster near wake velocity components at different downstream axial planes, up to 1.5 diameters downstream, were obtained using a Stereoscopic Particle Image Velocimetry (SPIV) system. These experiments were carried out at different advance coefficient (J) values [bollard pull (J=0), J=0.4 and J=0.45].

Continuously extruded long length polyethylene pipes for seawater intakes and marine outfalls

Pipelife Norge AS' Statheile plant has a unique production facility in the PE pipe industry which enables continuous production (extrusion) of PE pipes in long lengths directly to the sea bay that lays in front of the factory. The long pipes, up to 600 m in length, are then plugged in both ends, or prepared with flange connections and towed, with tug boats, to the construction site/marine installation. A solution is presented for projects where water intakes, sea outfalls and other installations that could use the presented solution are needed, and quality control is described.

一軸タグボートの規則向い波中の曳引力特性に関する模型実験

一軸タグボートの規則向い波中の曳引力特性に関する模型実験

Application of Side Scan Sonar to Disposed Material Analysis at the Bottom of Coastal Water and River

Due to the growth of population and industrial development at the coastal cities, there has been much increase in necessity to effective control of the wastes into the coastal water and river. The amount of disposal at those waters has been increased rapidly ana it is necessary for us to track of it in order to keep the waterway safe and the water clean. The investigation and research in terms of water quality in these regions have been conducted frequently but the systematic survey of the disposed wastes at the bottom was neglected and/or minor. In this study we surveyed the status of disposed waste distribution at the bottom of coastal water and river from the scanned images. The intensity of sound received by the side scan sonar tow fish from the sea floor provides information as to the general distribution and characteristics of the superficial wastes. The port and starboard side scanned images produced from two arrays of transducers borne on a tow fish connected by tow cable to a tug boat have the area with width of 22m~112m and band of 44m~224m. All data are displayed in real-time on a high-resolution color display ( pixels) together with position information by DGPS. From the field measurement and analysis of the recorded images, we could draw the location and distribution of bottom disposals. Furthermore, we could make a database system which might be useful for navigation and fundamental for planning the waste reception and process control system.

Anchor deployment for deep water floating offshore equipments

In this work a planning methodology for deep water anchor deployment in offshore platforms and floating production systems aiming at operational resources optimization is explored, by minimizing a multi criteria objective function. As an additional advantage provided by the proposed methodology, planning automation is achieved. Planning automation overcomes the traditional way, using a trial error basis. With it, an engineer, using an anchoring software, decides how much work wire and anchoring line must be paid out from both the floating system and the tug boat. Additionally, he decides which horizontal force must be applied to the line, trying to settle the anchor on a previously defined target on the ocean floor.

タグボート推進器後流による曳引力減少に関する一検討 : 深水域の模型実験

We have well known that the towing ability of a tugboat decreases because of a reaction of the jet stream caused by tugboat propeller, which acts on the ship hull of a VLCC. However at present, this fact has not yet been taken into account in the estimation of towing force. Maybe it is the reason that the influence of the jet stream on the towing force is not examined exactly and systematically and also series data on the reduction of towing force are not shown. In this paper, the change of the towing force reduction relating to the length of towing line was studied experimentally. Model experiments were carried out by using a water-tank and a pair of ship models, namely a VLCC model and a tugboat model. And two kinds of examination conditions were selected, namely (1) the rest condition which both ship models were fixed by two dynamo-meters respectively and (2) the moving condition which the VLCC model was moved laterally by the tugboat model. We obtained following results ; (1) It could be confirmed that the towing force decreased by the jet stream of the tug boat propeller. And the efficiency of the towing force relating to the length of tug line was suggested based on series experiment. (2) The above efficiency more decreased in the moving condition which the VLCC was moved by the tugboat.

Model study of log feeding technology at the dam of ertan hydropower station in China

The log float technology from timber depot at the reservoir to log feeding rolls was studied by model tests. The model test was taken with the rule of gravitation similitude and ratio of 1:10. Main parameters, like the amount of tug boats, hydro-accelerators and the structure of feeding rolls, were determined. The more suitable float process is put forward and the reliable basis for the design is supplied.

Sea Trials of the Ducted Tip Propeller

Sea trials of a 45 ft seine boat, fitted first with a conventional tip, and subsequently with a ducted tip, 36 in. diameter propeller have been conducted. The trials consisted of careful propeller efficiency measurements at a number of advance ratios, and underwater video imaging of the different propellers under Bollard pull conditions. The trials have shown that flow-through ducts installed at the blade tips suppress the tip vortex roll-up, thus resulting in a substantial delay in the onset of tip vortex cavitation. The cavitation inception index for the ducted tip propeller is 50 percent lower than for the conventional propeller. This cavitation improvement comes without any efficiency penalty. In fact, the efficiency of the ducted tip propeller is up to 6 percent higher (at high advance ratios) than the efficiency of the same propeller fitted with conventional tips. The ducted tip propeller was originally thought to be useful only for boats with heavily loaded propellers, such as tug boats and trawlers. The current research has shown that the ducted tips may have much broader application.

AN EXPERIMENTAL RESEARCH OF CONTROL RUDDERS ON TUG MANOEUVRING

A series of manoeuvres have been carried out on an operating tug boat in order to determine new relationships between the turning circle diameter, the revolutions of the propellers, the torque in the rudder stock and the most significant stresses. The tests have been accomplished with two configurations: the first with a steering system composed by rotating nozzle and a fixed rudder blade, the second with a fixed nozzle with two coordinated helm blades.

最短時間操船に関する研究-I : 外乱のない場合の着桟操船

For mariners, it is very important to know the optimal maneuvering of their ships. Particularly, berthing manevering without tug boats in a harbour is difficult problem even for the experienced mariners. The mariners gain their own technique through their experiences for a long period. They always pay strong attentions to their ship's safety, economical performance and other many elements on ship handling. This paper gives mathematical unique solution to the minimum time berthing problems of a small training ship by using the optimal control theory and a robust numerical solution technique. This calculation bases on sophisticated ship's mathematical nonlinear model which can cover from high to low speed. In this paper, the berthing problem with a rudder and a CPP are treated at first. The berthing maneuvering with a rudder, a CPP and moreover bow and stern thrusters are also discussed here.

Nonlinear stability and simulation of two-line ship towing and mooring

The horizontal plane motions — surge, sway, yaw — of a ship towed by two tug boats, or moored to two terminals, are modelled by the nonlinear third order maneuvering equations without memory. Nylon lines, chains, or steel cables are used as towing/mooring lines. Excitation consists of time independent current, wind an mean wave drift forces. The resulting Nonlinear Time Varying (NTV) model is studied by simulation, local linear, and global nonlinear stability analyses. Two-Line Towing/Mooring (TLT/M) systems exhibit, in general, three equilibria. Linear analysis reveals that equilibria may be attractor or repellor nodal or focus points. Near first equilibrium, it is shown that of the five Routh-Hurwitz criteria only two can be active in TLT/M systems of conventional ship hulls. Subsequent parametric study reveals the complexity of stability boundaries which may exhibit fold or cusp singularities. Global analysis is used to find attractor limit cycles and chaotic behavior. A barge with or without stabilizing skegs, a marinetype cargo ship, and a tanker with and without propeller which have different stability characteristics are used in nonlinear numerical simulations to verify all theoretical conclusions.

Fresh-water transport by sea

The concept of a submerged, flexible water container and a semi-submerged tug boat is presented. it provides low-cost fresh-water transport by sea from regions of abundant fresh water to arid lands on the sea coast. Total transport cost is estimated at ∼ US $ 0.03 ton per 1000 km .

A Consideration on the Design of Screw Propellers of Tug Boats and Trawlers

A Consideration on the Design of Screw Propellers of Tug Boats and Trawlers

Communication in railroad operation

The object of this paper is to show the part played by the different means of electrical communication in operating a large railroad system. The telegraph, which was the original and sole means of handling communications requiring immediate attention, has given way largely to the telephone and the printer. The development of the selector was essential to the general use of the telephone for train operation and message work, the train wire being considered the most important circuit in railroad operation. Extensive and special facilities are required in some instances to provide necessary telephone communication with the public. This includes telephones on certain limited trains in terminals. The telautograph is important but limited to local service in terminals and junction points. Same problems in engineering, construction, maintenance and operation as with the commercial telegraph and telephone companies, except that smoke conditions are worse along the railroad and continuity of service is possibly more important. Radio has possibilities as a means of providing information and entertainment to passengers on trains and in the operation of freight trains and tug boats. In handling train orders the train conductor must verify the instructions or orders he receives. The quality and accuracy of radio reception when a train runs through rock cuts, over or under certain types of steel bridges, through tunnels and during certain weather conditions prevents this means of communication from being used at this time for handling train orders. The volume of communication traffic is affected by the seasons, holidays and emergencies. The size of the communication system on some railroads compares favorably with that of some of the large commercial telegraph and telephone companies. An ideal communication system would provide accurate information between any two points on a railroad system or between the public and the railroad company without delay and under all operating conditions.

Carriers. Depot Regulations. Exclusive License to Tug Boat Company

Carriers. Depot Regulations. Exclusive License to Tug Boat Company

Tug Boats. Collision. Rodgers v. Adriatic Fire Ins. Co., 69 Federal Reporter, 157

Tug Boats. Collision. Rodgers v. Adriatic Fire Ins. Co., 69 Federal Reporter, 157

Particulars of a tug boat for Lake Ontario

Particulars of a tug boat for Lake Ontario