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Safe maneuvering in adverse weather conditions
Published in Pentti Kujala, Liangliang Lu, Marine Design XIII, 2018
S. Krüger, H. Billerbeck, A. Lübcke
Although ship 1 does not need to comply with EEDI due to keel laying date, we use ship 1 as a first example because of its very large windage area. Fig. 8 shows the results of our analysis in form of polar plots of the required rudder angle for course keeping (top) and the resulting drift angle. The calculation speed was set between 6 and 20 knots. Due to the limited engine power, the achievable speed in head seas is smaller, that is why the polar plots have been cut accordingly. In following seas, the problem arises that at low ship speeds, there is no inflow to the rudders and consequently no rudder yaw moments, that is why certain areas in following seas between 20 and 40 degree can never be reached at slow speeds because the ship is unstable there. In head seas, the ship has not any problems to maintain its course. The polar plots do also show that the ship can reach more than 6 knots speed in all head and beam sea courses. If the speed is above 10 knots, the ship can reach all courses in following seas.
Research Vessel Construction—Terminology, Equipment, and Machinery
Published in George A. Maul, The Oceanographer's Companion, 2017
Figure 3.1 is a view from the starboard side of a proposed research vessel. The vessel particulars are molded length = 78 feet, waterline length = 73 feet, molded beam = 24 feet, and full load draft = 6 feet. The term “molded” refers to the maximum dimension, and molded beam (width) is usually measured amidships; a common term for molded length is length overall (LOA). Waterline length is horizontally measured from the intersection of the bow with the water to the stern, and draft is the vertical dimension from the waterline to the keel (the chief longitudinal structural member along the bottom from bow to stern). To scale, the person standing on the superstructure deck is 6 feet; he or she is standing on the fo'c'sle where the forecastle would be located on a fourteenth-century warship. The pilothouse, also called the bridge or sometimes the wheel house, is located just aft of the standing figure (see also Figure 3.4). On a larger ship, the bridge extends from port to starboard, houses all the navigation equipment, and may have bridge wings protruding out over the side for better visibility and navigation. The “roof” of the pilothouse is called the pilothouse deck, sometimes called the flying bridge.
Inland waterways
Published in P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan, Hydraulic Structures, 2017
P. Novak, A.I.B. Moffat, C. Nalluri, R. Narayanan
The resistance of ships on restricted waters is influenced by many factors, the most important being speed, flow velocity, shape of bow and stern, length, squat and draught (both at bow and stern), keel clearance, and distance from canal banks. A general expression for the resistance, R, of a towed vessel was given by Kaa (1978), in a simplified form, as
Numerical investigation on the effect of hull vane for a high-speed displacement vessel
Published in Ships and Offshore Structures, 2023
Gouthama Chary Soma, R. Vijayakumar
The domain conforms to those recommended in the literature and also with the recommendations of the International Towing Tank Conference (ITTC) namely, ITTC 7.5-03-02-03. As per these standards, the computation grid extends to 2L (where L is the length of the ship) in front of the ship, 3L behind the transom, and 2L above the hull deck, below the keel, and to the sides of the hull. The domain dimensions are shown in Figure 3. Due to the centreline symmetry of the ship as well as to reduce the computational effort, the only half domain is considered. The normal velocity and the normal gradients of all the variables are zero at the symmetry plane and the analysis process considers the dynamic trim based on the two degrees-of-freedom motions in the vertical plane along the hull (Suneela et al. 2021). The boundaries at the inlet, side (both sides), bottom and top are regarded as the velocity inlet. Pressure is taken to exit at the outlet boundary (ITTC 2017).
Integration of long-term planning and mid-term scheduling of shipbuilding
Published in Production Planning & Control, 2023
Figure 9 shows the long-term planning and mid-term scheduling processes. When planning is started, the integrator of ① (berth and capacity planning) is performed using the erection duration of the reference vessel and the workload of each main work category. As a result of optimization in ①, key events are delivered to the mid-term scheduling, and a plan for the erection network of ② is established. The erection network identifies the critical path with the keel laying and launching events among the key events as the start and finish dates and determines the erection date of each erection block. Backward scheduling in ③ of the activity plan is executed using the erection dates of the blocks calculated as the due dates. Next, from the result of the established activity scheduling, the workloads of each activity are summed for each main work category and delivered back to ①. Subsequently, the process ① to ③ is repeated. This study derived improved results through two iterations of the process ① to ③, which started from the reference vessel information at the first starting point and the process of ① to ③, which started from the workload result of backward scheduling.
Weakly nonlinear ship motion calculation and parametric rolling simulation based on the 3DTGF-HOBEM method
Published in Ships and Offshore Structures, 2021
Wen-jun Zhou, Ren-chuan Zhu, Xi Chen, Liang Hong
3-DOF:6-DOF:The freeroll decay curves in the non-zero speed case are displayed in Figure 13. Based on Himeno (1981), the roll damping can be assumed to have composed of skin friction damping, hull eddy shedding damping, lift force damping, bilge keel damping and free surface wave damping. The interactions between the five components are neglected. In this paper, the free surface wave damping is included in the roll damping coefficients as in free decay simulation the velocity has been considered. As only bare ship hull is considered, the bilge keel damping is zero. Furthermore, the lift force damping only takes a small portion in total damping at a low speed, which is also neglected. The skin friction damping and the eddy making damping are both related to fluid viscosity, which is also reflected in the coefficients.