Depth Optimization of Designed New Ferry Berth

Transcription

1 International Journal on Marine Navigation an Safety of Sea Transportation olume Number 4 December 2007 Depth Optimization of Designe New Ferry Berth S. Gucma & S. Jankowski Maritime University of Szczecin, Szczecin, Polan ABSTRACT: Increasing sea ferries traffic on Baltic Sea has in the recent years motivate the esign of larger ferries. Currently the lengths of the most ferries, which call at port of Świnoujście, o not excee the limit of 70 meters. The new projecte ferry berth will be aopte for ferries with LOA equal 220 an even 230 meters. It is obvious that propeller of that sea ferries will prouce a propeller stream with greater velocity an initial iameter as well, particularly that they will maneuver without any tugs. That water jet can much easier cause bottom erosion especially at mooring berth. This article is a presentation of epth optimization process at berth No of Sea Ferries Terminal (SFT) in port of Świnoujście. INTRODUCTION The paper presents the simulation metho of etermination the propeller jet stream s velocity at the bottom an epth optimization metho for berths, which take avantage of jet streams velocity at the bottom for ifferent value of epth. The presente metho was use to etermine the epth of berth no, at Świnoujście Sea Ferries Terminal (SFT). The ships moel that was use in simulations was worke out in Institute of Marine Traffic Engineering at Maritime University of Szczecin. The simulations of mooring maneuvers were conucte for maximum allowe Ro-Pax ferry s at new builing berth no in Świnoujście SFT. The safety of navigation is etermine by vessel s size an her maneuvering characteristics. Those parameters efine a maximum vessel, which is the biggest vessel which may safety maneuver at given area, at given navigational conitions. essel may be consier maximum if only one of her imensions is maximum (e.g.: raft, beam, length, spee). After ferry market analysis an navigational analysis of port of Świnoujście were one, the maximum ferry was etermine. It turne out, that maximum Ro-Pax ferry for Świnoujście is 220 m long an her main engines power is 4000 kw. 2 SIMULATION METHOD OF DETERMINATION THE PROPELLER WATER-JET ELOCITY AT THE BOTTOM Presente metho of etermination the propeller jetstream, takes avantage of simulation trials. The series of trials are one for given vessel an given conitions. During trials vessel movement s parameters are recore as a text files. After trials are one, the jest stream s velocity is calculate for every single vessel s position recore (fig. ). Jet stream s velocities at the bottom are etermine for the whole area, ue to aopte level of iscretisation. The jest stream s velocity is a function of following variables: ( x, y, h, x, y, KR, N R) = f s s x, y, () 407

2 where x,y = stream velocity at (x, y) point of the bottom, h = epth, (x s, y s ) = vessel s coorinates, KR = vessel s heaing, N = current main engine comman, R = ruer eflection. x, r [m/s] Simulation Time of simulation [s] x Simulation n r Bottom of the area Fig.. Determination of maximum stream velocity, in the (x, y) point of bottom area, for each simulation The following vessel s parameters, which are of static nature, play also a vital role: length over all, vessel s raught, power elivere on propeller, propeller coorinates shifting from recore vessel s position (usually center of gravity s position is recore), istance between the horizontal axis of propeller an the bottom. Existence of any harbor s structure is also taking into account. The velocity of water jet stream is consier zero, if any part of hyrotechnical structure is locate in iscrete area or obscure it (fig. 2). Marine engineering structures Fig. 2. Propeller stream obscure by harbor s structures. The algorithm to etermine the jet stream velocities at the bottom is as follows: Calculate a spee of inucte water jet near the propeller: k 3 P 0 2 = K s ς w (2) where 0 = stream velocity nearby propeller, K = empirical coefficient equal.48 for free propeller, k = power utilization coefficient, P = a power elivere on propeller, s = propeller iameter, ς w = water ensity. 2 Choose centre point of the iscrete area (x, y) accoring to iscretisation level; 3 Check following items: is centre point of iscrete area locate on water area? is it not covere by other quay structures? 4 Calculate the istance s, between the propeller plane an projection of the point (x, y) onto a propeller s horizontal axis; 5 Calculate the spee x max, in calculate istance s rom the propeller (ruer angle is 0); s max = e hp 0.6 s s s a (3) where x, max = the istance from the propeller plane, h p = istance between bottom an propeller horizontal axis, s = the istance from the propeller s plane an projection of point (x, y). At given ruer angle: s max = ( δ ) 3.25 s 2.8 s b (4) where δ= ruer angle. 6 Calculate the istance r between propeller s horizontal axis an the centre of the iscrete area (x, y), 7 Calculate the velocity of the propeller jet stream at the bottom, in a mile of iscrete area; 2 r m s = e (5) s, r s max where s,r = the stream velocity in istance s from the propeller plane an istance r from the propeller axis, r = the istance from the propeller axis (a raius). 8 Recor, as a text file, the maximum value of screw jet stream velocity at the bottom for given coorinate (x, y). 408

3 3 PROPELLER JET STREAM DETERMINATION FOR FERRY BERTH DESIGN The esign vessel s parameters, for berth no at Świnoujście SFT, is as follow: LOA 220 [m], Beam 32 [m], Draft 7.0 [m], Nominal power of ME 2 x 4000 [kw], Diameter of propeller 4.0 [m], Two pitch ajustable, left hane propellers. Several conitions were chosen for simulations trials. Number of single trials within given conitions was at least 5. The following conitions were consiere the harest: unmooring an swinging by port sie, win W 5 m/s, inboun current.5 kn, mooring with port sie, win E 5m/s, inboun current.5 kn, unmooring an swinging by starboar sie, win W 5 m/s, outboun current.3 kn, Two series were one, for zero-state conitions no win, no current: mooring with port sie, unmooring an swinging by any sie. N Fig. 3. Berth no layout with a ferry moore at Maximum propeller jet stream s velocity was calculate for the epth shown in table. Mean sea level in port of Świnoujście, which has been recore for many years, is 4.90m. Minimal mean sea level, calculate for the last 0 years is meter less than mean sea level. Therefore, an appropriate epth allowance was consiere. Bottom at berth no was loae with jet streams the most uring maneuvers with the inboun current. The mooring maneuvers were one with the pushing away eastern win, whilst unmooring maneuvers were conucte with pushing western win. In both cases, vessel was to stan up the great win force, which prouce significant lateral pressure. That pressure force captain to use top comman on main engine telegraph. The istribution of maximum jet streams velocity is shown on fig. 4. The epth of consiere area is 8 meters. The istributions iffer in that areas heavily loae with jet streams are shifte. For mooring operations that area is move to the mile of investigate area, whilst for unmooring manoeuvres the area is smaller an is close to berth s wall. It is worth to emphasize, that jet stream s velocities were higher for unmooring manoeuvres. The maximum velocity of jet streams whilst mooring was 8.9 m/s, an whilst unmooring it exceee 9.5 m/s. However the area affecte by streams with velocity more than 8.5 m/s was not extensive. Taking that into consieration, as well as meter epth allowance for area epth 9 m, it was assume that bottom affecting velocity of jet streams is m/s Table. Depths an istances to a bottom [m] Available epth 9 2 Depth for calculation 8 Uner keel clearance 4 Distance from propeller s axis to bottom A) B) Fig. 4. Distribution of maximum water jet velocity at a bottom, epth 8m. A) mooring port sie, win E 5 m/s, current inboun average max (.5 kn); B) unmooring an swing by port sie, win W 5 m/s, inboun current average max (.5 kn) Distributions of maximum velocities at berth no, for mooring an unmooring maneuvers are shown on fig.5. The available epth is 2 meters. The 409

4 maximum velocity for mooring is 5.7 m/s an for unmooring is 6. m/s. Taking that into consieration, as well as meter epth allowance, it was assume that bottom affecting velocity of jet streams is m/s A) B) Fig.5. Distribution of maximum water jet velocity at a bottom, epth m. A) mooring port sie, win E 5 m/s, current inboun average max (.5 kn); B) unmooring an turn by port sie, win W 5 m/s, inboun current average max (.5 kn) The picture below presents ecreasing of jet streams velocity at the bottom as a result of epth increase up to 2 meters. Stream velocity [m/s] Depth [m[ Fig. 6. Distribution of maximum water jet velocity at a bottom, epth m Increase of available epth consierably reuce jet streams velocities at the bottom. But there is one question, concerning economical aspect of newbuiling berth. Either more profitable is to rege the consiere area or apply proper be protection? 4 BERTH NO OF ŚWINOUJŚCIE SFT AS AN EXAMPLE OF BED PROTECTION PARAMETERS OPTIMIZATION Evaluating the optimizing function of berth epths optimize as a cost of berth builing an be reinforce, following assumptions were aopte: investigate vessel maneuvers on restricte area, her position is efine on Cartesian axes, investigate area is a set of elements x X, y Y, coorinates that efine the set are Cartesian s prouct, on investigate area, only vessels that are inclue within set i I, are allowe to maneuver. It concerns either vessel s size (LOA, beam, raft) or engine power an type, vessel maneuvering on the area, may perform one of the maneuvers, that are within set j J. It is the set of all available maneuvers on given area, investigate vessels may maneuver in conitions that are within set k K. It concerns either hyro meteorological (win, current, sea, ice) conitions or navigational an traffic conitions. The safety of navigation an harbor s structures, evaluate by means of berth epths optimizing moel, is etermine by following items: uner keel clearance, jet streams velocity at the bottom. Aopting above assumptions, optimizing function may be presente as a following formula: Z = a l b h + q l b + c l min (6) where l = f (D), b = f 2 (D), q = f 3 ( x,y ), c = f 4 (h), with following constraints:. ijk D where i I, j J, k K 2. h xy T i + ijk 3. xyijk > xyna 4. xyijk xy where: Z costs of builing new berth, reging maneuvering area, be protection; a cost of reging of m3; l berth length; b be protection with; 40

5 h epth of area at esigner berth; q cost of protection of m3 of be; c cost of m of berth; ijk maneuvering area, for ith vessel, jt type of maneuvers, kt navigational conitions, where xy > xyna; D maneuvering area, that meet requirement xy > xyna, for investigate set of vessel I, maneuvers J, an navigational conitions K. T i maximum raft of ith vessel, ijk uner keel clearance, for ith vessel, jt type of maneuvers, kt navigational conitions, xyijk maximum jet streams velocity at the bottom in certain position (x, y) for ith vessel, jt type of maneuvers, kt navigational conitions, xyna available velocity of water at the bottom, for position (x, y) for existing be type, xy available velocity of water at the bottom, for position (x, y) for be after protection. Base on simulations results, existing bathymetrical an hyro meteorological conitions an above etaile costs of esigne berth No at Świnoujście SFT, the safety epth at berth was set to 2,5 m. During the whole optimization project, the epth of waterways near berth an southern swinging area epth were consiere as well. 5 CONCLUSION The paper presents epth optimizing moels at ferry terminals, which take avantage of propeller jet velocities at the bottom, etermine by means of original simulation metho. The metho was use to etermine the epth at the new builing berth no at Świnoujście Sea Ferries Terminal. The metho is all purpose. After aaptation, it may be use to optimize the epths at any berth, for any type of vessels. REFERENCES Blaauw H.G., an De Kaa E.J., Erosion of bottom an sloping banks cause by the screw of manouvring ships, 7th International Harbour Congress, Antwerp 978. Fuehrer M, Pohl H, Römisch K. Effects of moern ship traffic on inlan an ocean waterways an their structures, 24th International Navigation Congress, Leningra 977. erhey H.J., The stability of bottom an banks subject to the velocities in the propeller jet behin ships Delft Publication no 303, Delft Hyraulics Laboratory 983. Römisch, K.: Propellerstrahlinuzierte Erosionserscheinungen in Häfen. HANSA, Nr. 8,