Interaction of Ships within Navigable Ice Channel

Transcription

1 RescOp - Development of rescue operations in the Gulf of Finland International Seminar: MARITIME SAFETY IN THE GULF OF FINLAND Interaction of Ships within Navigable Ice Channel Vadim K. Goncharov Department of Oceantechnics and Marine Technology St.-Petersburg State Marine Technical University, St.-Petersburg, RUSSIA November 8, 013

2 For maintenance of navigation during wintertime in Arctic seas, icebreakers create the wide channel in the fast or pack ice cover at water areas near to ports with intensive traffic of vessels, in which vessels can move in both directions independently without icebreaker pilotage. Currently navigable ice canals have become principal lanes for navigation in the eastern part of the Gulf of Finland during winter and spring time. Ice channel behind icebreaker. Ice floes sizes and concentration within channel define conditions for navigation. Histogram of ice floes sizes. Logarithmically normal distribution: log average.5, log deviation.35.

3 After forming, ice channel represents open water lane limited with compact ice pack or fast ice and partly filled with ice floes (fresh channel - a). Then freezing over on the open water surface and freezing of separate ice floes filling the canal take place, and gradually water areas free of ice disappear, and channel becomes filled with ice brush (old channel - b). At intensive navigation, the ships should separate under movement on opposite courses or make overtaking of slowly moving cargo vessels in the water areas covered with ice. Side force and yawing moment that appear on ship hull under these manoeuvres are different from items on the water area without ice cover. Owing to the intensive traffic, maneuvers of ships on opposite courses or overtaking are carried out very often. The width of ice channel is limited; therefore, at manoeuvrings the accidents are possible: collision of vessels or vessel blow in a channel border.

4 Previous experimental investigations under Project MS GOF Maritime safety in the Gulf of Finland ( ) a d c e b Experiments in Ice Towing Tank (Krylov State Research Center): a towed model (overtaking ship), b immovable model (overtaken ship), c trolley car with dynamometer, d ice channel with broken ice floes, e border wall of towing tank. Side force during overtaking Yawing moment during overtaking

5 Appearance of vessel among ice floes change the ice concentration in depend on the hull beam, width of channel and total area of ice floes relation in the section of channel. If vessel navigates nearer to some edge of channel, the ice concentration along respective board will be more than on opposite side. Ice concentration s 0 before vessel is less than concentration s 1 between left board of vessel and edge of channel, and s 1 is less than concentration s between right board and edge of channel. Therefore, the difference between ice concentration s 1 and s will result in the ice resistances on vessel boards and this difference will determine the affect of channel borders on vessel movement 1 border, ice floes, 3 ship hull; s 0 ice concentration in the channel, s 1 and s - ice concentrations between hull and channel borders. s s s. 1 0

6 Origination of yawing moment on hull under ship motion near border of the ice channel because difference of ice resistance on boards connected with difference of ice floes concentration. Similar approach was applied for parameterization of the interaction of ships moving within fresh ice channel. Scheme of simulation of opposite ships movement (or overtaking) by means of narrowing of the ice channel.

7 It is supposed to simulate the overtaken vessel (or opposite moving one) by means of narrowing of the ice channel width during passing. The ice concentration s increases in inverse proportion to the beam distance between ships d in comparison with ice concentration between reverse board and edge of channel. Increase of ice concentration effects the increase of ice loads on ship hull that result in initiation of additional ice resistance R, side force F and yawing moment M during passing. The speed of ship at issue is equal to difference of both vessels speed (V 1 -V ) under overtaking, or equal to their sum (V 1 +V ) under opposite motion. Developed conceptual model allowed to parameterize the additional ice resistance, side force and yawing moment that arise under interaction of vessels within ice channel by the difference of ice loads on left and right boards of ship at issue.

8 Second step is application of method to calculate the ice resistance of vessel that navigates in the broken ice floes field developed Kashtelian (et al, 1980), that is formula: B L Ice Ice Ice Ice 1 ID Ice Ice Ice ID 0 R 10 b h k 1 f k b h B f tg Fr B k b h Ltg Fr. 3 Ice Ice Ice 0 R Ice - ice resistance of the broken ice (without water resistance); b Ice average size of ice floes; h Ice average thickness of ice floes; Ice density of ice; f ID ice friction factor against hull plating; L - length and B width of the vessel; - waterline area coefficient; E angel between tangent to waterline at nose and centre line; Fr Froude number; k 1, k, k 3 empiric coefficients depending on ice concentration s. Average dimension of ice floes b Ice h Ice is relatively constant (data of trial observations), and within ice channel made by an ice-breaker the value b Ice h Ice depends on ice (pack or fast) cover thickness h Ice : b h h h Ice Ice 0.54 Ice 0.45 Ice.

9 Loads caused by deformation of ice cover at moving apart ice floes by ship hull and their friction on hull plating produce main contribution to ice resistance of ship. First item in Kashtelian s formula defines these loads. Scheme of the ice forces effect on element of a waterline in point A: - N load from moving apart ice floes, - S - a friction of ice floes on plating - y(x) co-ordinate of waterline. Resultant affect of ice loads in projections to axes of co-ordinates: - dr elementary ice resistance - df elementary side force, and - dm elementary yawing moment.

10 Formulas for effecting on an element of waterline loads: - elementary additional ice resistance - elementary side force - elementary yawing moment dr k x b h y x k y x dx 1 Ice Ice Ice 1 fr 1, df k1 x Ice bice hice y1 x 1 k fr y1 x dx, Ice Ice Ice dm x df y x dr k x b h y x x 1 y x dx. Empirical coefficient k 1 based on model and full scale experiments is function of ice concentration s and relative width of ice channel m, that is k1 s, m s.15s 3.9 if m 1, k1 s, m s.15s m 0.041m if m 1, k 1 0 if s6.

11 Kinematic schema of vessel 1 overtaking of slowly moving vessel : initial stage a and termination stage b. Ice concentration between hulls Relative width of canal Coefficient k 1 along right and left boards s d t x s d y x y L V t x 0, 0, 0 1 B c, x d0 y x, mt, x d0 y L V t x. B k s0.15so 3.9. k1 t, x s t, x.15 s t, x m t, x m t, x,

12 Ice loads: additional ice resistance R S, side force F S and yawing moment M S, on the first stage of overtaking. t R t b h k t, x k y x k y x dx, s Ice Ice Ice fr 1 0 t t F ( t) b h k x k y x 1 k y x dx, s Ice Ice Ice fr 1 0 1, M s t Ice bice hice k t x k y x x y x dx 0 if ( t) L.

13 Ice loads: additional ice resistance R S, side force F S and yawing moment M S, on the second stage of overtaking. t t 1 1, t L 1 1 R t b h k t, x k y x k y x dx, s Ice Ice Ice fr 1 L L F ( t) b h k x k y x 1 k y x dx, s Ice Ice Ice fr 1 L L M s t Ice bice hice k t x k y x x y x dx L if ( t) L.

14 Equations for waterline y 1 (x) of overtaking ship L1 Lf 1 tg 0/1 B1 x y1 x 0.5B1 1 1 if 0 x 0.5 L1 L f 1, 0.5L1 Lf 1 f f y x 0.5B if 0.5 L L x 0.5 L L, L1 Lf 1 tg 0/1 B1 x L 1 y1 x 0.5B1 1 1 if 0.5 L1 Lf 1 x L1. 0.5L1 L f 1 Form for waterline of overtaking ship y 1 (x) and angles of its slope = arctg[y 1 (x)]

15 Equations for waterline y (x) of overtaken ship in system coordinates xoy connected with overtaking ship: LLf tg0/ B L V t x f y x 0.5 B 1 1 if L V t x x 0.5 L L, 0.5L Lf f f y x 0.5 B if 0.5 L L L V t x 0.5 L L, LLf tg 0/ B L L1 V t x y x 0.5B 1 1 if 0.5L Lf L 0.5L L f V t x L.

16 Computer modeling of ship interaction during passing within ice channel Input data (basic version): 1. Overtaking ship 1 : L 1 = 10 m, B 1 = 0 m.. Overtaken ship : L = 90 m, B = 16 m. 3. Velocity of passing: V = 3 m/s. 4. Ice thickness: h = 0.5m, ice concentration s 0 = 7 balls. 5. Minimal traverse distance between board of ships: d T = d min /B 1 = 0.3. Variation of input data: 1. Distance between boards: 0.15 < d T < Ice thickness: 0.05m < h < 1.0m. 3. Ice concentration: < s 0 < 9.5 balls. 4. Length of overtaking ship: 90 m < L 1 < 180m. Normalization of results: 1. Forces on 0.5 ρ w L 1 B 1 coefficients of forces: C R and C F.. Moment on 0.5 ρ w L 1 B 1 B 1 - coefficient of moment: C M.

17 Variation of additional resistance C R, side force C F and yawing moment C M on overtaking ship during passing. C F < 0, it means side force F 1 effects in direction on the border of ice channel, t, s C M > 0, it means yawing moment M 1 effects on overtaken ship. As result, it is possible collisions: a. by bow with overtaken ship and b. by stern with channel border.

18 Dependence of additional resistance C R on minimal traverse distance between board of ships d T and ice concentration s 0.

19 Dependence of side force C F on minimal traverse distance between board of ships d T and ice concentration s 0.

20 Dependence of yawing moment C M on minimal traverse distance between board of ships d T and ice concentration s 0.

21 Dependence of additional resistance C R, side force C F and yawing moment C M on thickness of ice cover h.

22 Dependence of additional resistance C R, side force C F and yawing moment C M that effect overtaking ship on her relative length L 1 /L.

23 CONCLUSION Developed mathematical model is closed one and gives possibility to calculate the side force and yawing moment affecting on overtaking ship during passing along overtaken ship or opposite traffic and side force and yawing moment affecting on overtaken ship also. Model can be applied to create special programs for simulators for training navigators to traffic within ice channel. It is possible to apply model to define the safe regimes of maneuvering within the navigable ice channel (speed and distance between ships hulls) in dependence on the ship dimensions and speeds, width of ice channel and ice conditions. Executives of these investigations: 1. Professor Vadim K. Goncharov,. Senior Researcher Natalia Yu. Klementieva, 3. Senior Researcher Mikhail Yu. Mironov, 4. Postgraduate Student Ekaterina S. Zoueva.

24 Studies were implemented within Projects RescOp Development of rescue operations in the Gulf of Finland. Projects are co-funded by the European Union, the Russian Federation and the Republic of Finland. Thank you very much for your attention