Maneuverability of Ships with small Draught in Steady Wind

Abstract

Wind force and moment may force a ship to drastically decrease its speed and use a large drift angle as well as a large rudder angle in order to maintain its course. Ships with a small draught might have more risk in maneuvering to its point of view compared with a ship with a larger draught. This paper discusses maneuverability of a ship with a small draught in steady wind. The effect of wind on ship speed, drift angle, and rudder angle are investigated in a steady state condition. Five different ratios of wind velocity to ship speed from 1.0 to 20.0 are used in the simulation. The variation in wind direction is examined from 0° to 180°. Results of the numerical simulation show that the wind has a significant effect on the reduction in ship speed with a wind direction less than 100°. The drift angle increases due to increasing wind velocity in the same wind direction. Wind direction also has a significant effect on the drift angle especially when the wind direction is less than 140°. The same phenomenon was found for the rudder angle. The necessary rudder angle is greater than the maximum rudder angle of the ship when the wind direction is 60° with a wind velocity to ship speed ratio of 20 or more. AbstrakKemampuan Manuver Kapal dengan Sarat Kecil pada Kecepatan Angin Konstan. Gaya dan momen yang ditimbulkan oleh angin dapat mengakibatkan kecepatan operasi kapal berkurang secara drastis, sudut geser yang besar serta sudut kemudi yang besar untuk mempertahankan arah gerak kapal. Kapal dengan sarat yang kecil mempunyai kemungkinan yang lebih besar untuk mengalami masalah manuvering tersebut dibandingkan dengan kapal dengan sarat yang besar. Tulisan ini membahas performa manuvering kapal dengan sarat kecil pada kondisi angin dengan kecepatan konstan. Lima perbandingan kecepatan angin dan kecepatan kapal tersebut, yaitu 1,0, 5,0, 10,0, 15,0 dan 20,0 digunakan untuk simulasi. Arah data angin terhadap kapal divariasikan mulai dari 0° sampai 180°. Sudut geser kapal bertambah besar dengan bertambahnya kecepatan angin. Arah angin juga mempunyai pengaruh yang signifikan terhadap sudut geser khususnya pada sudut datang angin lebih kecil dari 140°. Fenomena yang sama terjadi pada kasus sudut kemudi. Sudut kemudi yang diperlukan untuk mempertahankan arah gerak kapal maksimum terjadi pada sudut datang angin 60° untuk perbandingan kecepatan angin dan kecepatan kapal (v/c) sama dengan atau lebih besar dari 20.0.

Twin-Rudder-System Configurations’ Impact on Ferry Ships’ Course-Keeping Ability under Windy Conditions

“…In general, when the wind blew from the starboard and portside to the stern (98 o to 268 o ), the ship's track trajectory time tended to benefit compared to conditions with the wind blows from the bow to the starboard and portside, as the simulation results in Figure 7. The ship's reduced speed when the wind blew from the bow to the starboard (less than 100 o ) was similar to the findings of Paroka et al (2016) related to ship-speed changes caused by wind speeds and directions' influence on ferry maneuvering.…”

“…This regression equation is among the models used by Sukas et al (2019) in developing the SINMAN Program to predict turning circles and zigzag maneuvering for ships with twin-rudder and twin-propeller systems, as well as validation through model testing or free-running tests. In many cases, the regression equation has been used to predict ferry ships' maneuvering under active wind and wave conditions (Paroka et al, 2015(Paroka et al, , 2016(Paroka et al, , 2017b. A ship's resistance coefficients for simulation were predicted using the Holtrop method (Holtrop and Mennen, 1982;Holtrop, 1984).…”

“…Many studies have related wind effects to ship maneuvering; wind's load-force and moment have significantly affected transversal and lateral projections of windage areas due to ships' large superstructures, as well as wind velocities and directions relative to ships (Fujiwara and Ueno, 2006). Paroka et al (2016) simulated wind's effect on ferry ships' maneuvering, explaining that ship-speed changes caused by wind highly depend on wind velocity and direction. When the wind blows from the bow direction and passes to the ship's starboard (0 to 100 o ), ship speed tends to decrease.…”

“…Ohtsu et al (1996) reported that a wind blowing from starboard-bow quarters (45 o ) made a ship's steering becomes less sensitive, but steering became more sensitive when the wind came from the port-stern quarters (135 o ). Increasing a ship's speed as wind directions change is crucial (Ohtsu et al, 1996;Paroka et al, 2016). The information informing this behavior is essential to improve ships' course-keeping quality-especially when ships must take appropriate action to handle wind disturbances.…”

Experimental Study on Automatic Control for Collision Avoidance of Ships

“…An Indonesian ro-ro ferry was used as sample ship for the free running experiment. This ship has been used in several researches regarding manoeuvring performance [11,12], therefore some data dealing with manoeuvring may easily be obtained. The ship has smalldraught with large breadth.…”