• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.613-618
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• 2012

For the tug-barge simulation, captive model test(Horizontal Planar Motion Mechanism) of the barge model is carried out. From the result of HPMM test, a resistance coefficient, maneuvering coefficients of the barge are obtained. A mathmatical model of the barge is validated by turning simulations with different angle of towing line applied a simple towing line model and the tactical diameter compared to sea trial data. As a result, the tactical diameter of the barge is smaller as the angle of towing line is bigger. The tactical diameter from simulations is smaller than that from sea trial data, may be caused by increased displacement of the barge.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.790-798
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• 2018

Discrete noise signals from a small scale tactical unmanned aerial vehicle(UAV) propeller were predicted numerically using time domain approach. Two-bladed 29 inch propeller in diameter and 150 kgf in gross weight were used for main parameters of the UAV based on the actual size of the similar scale vehicle. Panel method and Farassat formula A1 were adopted for aerodynamic and aeroacoustic analysis respectively. Time domain signals of both thickness and loading noises were transformed into frequency domain to analyze the discrete noise characteristics. Directivity pattern in a plane perpendicular to the rotating disc plane and attenuation of noise intensity according to double distance were also presented.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.552-557
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• 2015

A numerical simulation studies were performed to investigate a manoeuvring characteristics as function of stern hull form with the mathematical model. In order to consider the effect of the stern hull form and obtain the manoeuvring characteristics, a parameter($C_{wa}$) which is aft. water plane area coefficient is modified. Because modifying $C_{wa}$(${\pm}2%$) means that the stern hull form is modified to V-type or U-type, the numerical simulation was performed with this modified $C_{wa}$. A changing trend for the manoeuvring characteristics not only in deep water but also in shallow water such as directional stability, turning and zig-zag was investigated and presented as the results. Present study showed that the manoeuvrability in shallow water largely changed when the draught and water depth ratio(=d/H) become 0.5, and the stern hull form can affect to the manoeuvrability of a vessel navigating in restricted water depth. In addition, it showed that approaching the stern hull to U-type makes the advance and tactical diameter of turning motion large and the overshoot angle of zig-zag motions small. Otherwise, it showed approaching the stern hull form to V-type makes the advance and tactical diameter of turning motion small and the overshoot angle of zig-zag motions large in the present study.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.572-578
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• 2007

A Rigid Inflatable Boat (RIB) is now widely used for commercial and military purpose. In this paper, it is supposed that seven-meter-class RIB be used as an unmanned target ship for naval training. In order to develop many tactical maneuvering patterns of a target ship, a simple horizontal maneuvering model of a RIB is needed. Therefore, models of speed and yaw rate are constructed as the first-order differential equations based on Lewandowski#s empirical formula for steady turning circle diameter of a conventional planning hull. Some parameters in the models are determined using the results of sea trial tests. Finally, proposed models are validated through the comparison of the simulation result with the sea trial result for a specific scenario. Even though a simple model does not represent the horizontal motion of a RIB precisely, however, it can be used enough to develop tactical trajectory patterns.

• Journal of the Korean Society of Marine Environment & Safety
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• v.8 no.2
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• pp.9-15
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• 2002

Ship operators use anchor dredging for the collision avoidance or safety of ship handling in a harbour or narrow channel. This paper clarifies the technique of the anchor dredging known as a common sense for. the seafarers A mathematical model at low speed range is established for the estimation of ship motion under the assumed environment, simulate the advance speed , and turning ability under the anchor dredging or not. The results shows good agreement with the conventional seamanship and their experiences as follows. Ahead speed used the anchor dredging is slower(speed reduction ratio:40%) than the normal ahead speed and the stopping distance is shorter (distance reduction ratio:40%)than the normal ahead distance without the anchor dredging.. Turning speed used anchor dredging is slower(speed reduction ratio:72%)than the normal ahead speed and the tactical diameter is shorter(distance reduction ratio:24%)than the diameter by the normal turning without the anchor dredging.

• Proceedings of KOSOMES biannual meeting
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• 2002.10a
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• pp.127-134
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• 2002

Ship operators are used to dredge anchor for the collision avoidance or safety of ship handling in a harbour or narrow channel. This paper clarifies the technique using tile anchor dredging known as a common sense for the seafarers. A mathematical model at low speed range has been established for the estimation of ship motion under the assumed environment , simulate the advance speed , and turning ability under the anchor dredging or not. The results shows good agreement with the conventional seamanship and their experiences as follows. Ahead speed used the anchor dredging is slower(speed reduction ratio:40%) than the normal ahead speed and the stopping distance is shorter (distance reduction ratio:40%)than the normal ahead distance without the anchor dredging. Turning speed used anchor dredging is slower(speed reduction ratio:72%)than the normal ahead speed and the tactical diameter is shorter(distance reduction ratio:24%)than the diameter by the normal turning without the anchor dredging.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.209-214
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• 1999

The turning circle of a ship is the path followed by her center of gravity in making a turn of 360$^{\circ}$degrees or more with helm at constant angle. But generally it means her path traced at full angle of the rudder. For the ordinary ship the bow will be inside and the stern outside this circle.It has been usually understood that the turning circle is not essentinally affected by ship's speed at Froude numbers less than about 0.30. However, it is recently reported that the speed provide considerable effects upon the turning circle in piloting many ships actually at sea. In this paper, the author analyzed what effects the speed could provide on the turning circle theoretically from the viewpoint of ship motions and examined how the alteration of the speed at Froude no. under 0.30 affect the turning circle actually, through experiments of actual ships of a small and large size.The main results were as follows.1. Even though ship's speed at Froude no. under 0.30, the alteration of the speed affects the turning circle considerably.2. When the full ahead speeds at Froude no. under 0.30 of small and large ships were increased about 3 times slow ahead speeds, the mean rates of increase of the advances, tactical diameters and final diameters of thease ships were about 16%, 21% and 19% respectively.3. When the full ahead speeds at Froued no. under 0.30 of small and large ships were increased about 3 times slow ahead speed, the mean rate of increase of the turning circle elements of large ships was greater 10% than that of small ships. 4. When the full ahead speeds at Froued no. under 0.30 of small and large ships were increased about 3times slow ahead speeds, the mean rates of increase of the tactical diameter and final diameter of thease ships were greater than that of the advances of thease ships. 5. When only alteration of speed or sip's head turning is the effective action to avoid navigational fixed hagards, reducing the speed is always more advantageous than increasing the speed in order to shorten fore or transverse distance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.210-210
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• 1999

The turning circle of a ship is the path followed by her center of gravity in making a turn of 360$^{\circ}$degrees or more with helm at constant angle. But generally it means her path traced at full angle of the rudder. For the ordinary ship the bow will be inside and the stern outside this circle.It has been usually understood that the turning circle is not essentinally affected by ship's speed at Froude numbers less than about 0.30. However, it is recently reported that the speed provide considerable effects upon the turning circle in piloting many ships actually at sea. In this paper, the author analyzed what effects the speed could provide on the turning circle theoretically from the viewpoint of ship motions and examined how the alteration of the speed at Froude no. under 0.30 affect the turning circle actually, through experiments of actual ships of a small and large size.The main results were as follows.1. Even though ship's speed at Froude no. under 0.30, the alteration of the speed affects the turning circle considerably.2. When the full ahead speeds at Froude no. under 0.30 of small and large ships were increased about 3 times slow ahead speeds, the mean rates of increase of the advances, tactical diameters and final diameters of thease ships were about 16%, 21% and 19% respectively.3. When the full ahead speeds at Froued no. under 0.30 of small and large ships were increased about 3 times slow ahead speed, the mean rate of increase of the turning circle elements of large ships was greater 10% than that of small ships. 4. When the full ahead speeds at Froued no. under 0.30 of small and large ships were increased about 3times slow ahead speeds, the mean rates of increase of the tactical diameter and final diameter of thease ships were greater than that of the advances of thease ships. 5. When only alteration of speed or sip's head turning is the effective action to avoid navigational fixed hagards, reducing the speed is always more advantageous than increasing the speed in order to shorten fore or transverse distance.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.2
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• pp.53-65
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• 2018

The load condition significantly influences ship maneuverability in calm water. In this research, the effect of the load condition on turning performance of a very large crude oil carrier (VLCC) sailing in adverse weather conditions is investigated by an MMG-based maneuvering simulation method. The relative drift direction of the ship in turning to the wave direction is $20^{\circ}-30^{\circ}$ in ballast load condition (NB) and full load condition (DF) with a rudder angle $35^{\circ}$ and almost constant for any wind (wave) directions. The drifting displacement in turning under NB becomes larger than that under DF at the same environmental condition. Advance $A_d$ and tactical diameter $D_t$ become significantly small with an increasing Beaufort scale in head wind and waves when approaching, although $A_d$ and $D_t$ are almost constant in following wind and waves. In beam wind and waves, the tendency depends on the plus and minus of the rudder angle.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.99-112
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• 2021

The prediction of maneuverability is very important in the design process of an underwater vehicle. In this study, we predicted the steady turning ability of a symmetrical underwater vehicle while considering interactions between the yaw rate and drift/rudder angle through a simulation-based methodology. First, the hydrodynamic force and moment, including coupled derivatives, were obtained by computational fluid dynamics (CFD) simulations. The feasibility of CFD results were verified by comparing static drift/rudder simulations to vertical planar motion mechanism (VPMM) tests. Turning motion simulations were then performed by solving 2-degree-of-freedom (DOF) equations with CFD data. The turning radius, drift angle, advance, and tactical diameter were calculated. The results show good agreement with sea trial data and the effects on the turning characteristics of coupled interaction terms, especially between the yaw rate and drift angle.