REVIEW OF PRACTICAL ASPECTS OF SHALLOW WATER AND BANK EFFECTS

2021 ◽  
Vol 158 (A3) ◽  
Author(s):  
H O Duarte ◽  
E Lopez Droguett ◽  
M R Martins ◽  
M Lutzhoft ◽  
P S Pereira ◽  
...  
Keyword(s):  
Shallow Water ◽  
Common Sense ◽  
Maritime Industry ◽  
Water Effects ◽  
Bank Effects

The ship’s behaviour and manoeuvrability change as depth of water decreases and/or when the ship is near a bank or shoal. This paper conducts a review on shallow water effects (SWE) and bank effects (BE). It summarizes the varying opinions from both experienced mariners and hydrodynamicists about SWE on factors such as resistance, trim, steering, manoeuvrability and stopping, as well as BE on elements such as bank suction and cushion and it is shown that there is not a common sense in the bibliography. This is strange because the successful navigation of a ship along the channel to the dock is an identifiable task whose outcome is the same in all cases. Yet surprisingly it is a subject upon which there are different opinions documented. This review refreshes mariner’s memory and raises controversial topics that need clarification for the benefit of mariners, simulator modellers and the maritime industry they work.

Wave Effects on the Turning Ability of an Ultra Large Container Ship in Shallow Water

2019 ◽  
Author(s):  
Manases Tello Ruiz ◽  
Marc Mansuy ◽  
Luca Donatini ◽  
Jose Villagomez ◽  
Guillaume Delefortrie ◽  
...  
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Experimental Studies ◽  
Scale Model ◽  
Confined Water ◽  
The North ◽  
Calm Water ◽  
Wave Effects ◽  
Water Effects ◽  
Large Container

Abstract The influence of waves on ship behaviour can lead to hazardous scenarios which put at risk the ship, the crew and the surroundings. For this reason, investigating the effect of waves on manoeuvring is of relevant interest. Waves may impair the overall manoeuvring performance of ships hence increasing risks such as collisions, which are of critical importance when considering dense traffic around harbour entrances and in unsheltered access channels. These are conditions met by Ultra Large Container Ships (ULCS) when approaching a port, e.g. in the North Sea access channels to the main sea ports of Belgium. Note that due to the large draft of ULCS and the limited water depth, shallow water effects will also influenced the ship. Thus, in such scenarios the combined effects of shallow water and waves on the ship’s manoeuvring need to be studied. The present work investigates the effect of waves on the turning ability of an ULCS in shallow water. Simulations are carried out using the two time scale approach. The restricted water depth corresponds to 50% Under Keel Clearance (UKC). To gain a better insight on the forces acting on the ship, the propulsion, and the rudder behaviour in waves experimental studies were conducted. These tests were carried out in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University) with a scale model of an ULCS. Different wave lengths, wave amplitudes, ships speeds, propeller rates, and rudder angles were tested. The turning ability characteristics obtained from simulations in waves and calm water are presented, and discussed.

scholarly journals ‘Underkeel Clearance’

1968 ◽  
Vol 21 (1) ◽  
pp. 91-91
Author(s):  
J. A. Ewing
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Ship Motion ◽  
Water Effects ◽  
The Waves

I would like to comment on the change in underkeel clearance due to the motion of a ship in a seaway (A. F. Dickson, this Journal, 20, 363).Captain Dickson, in his conclusions, states that known techniques do not allow underkeel clearance to be calculated when ship motion is present. In fact there are a number of reliable ways of calculating the motions of a ship in waves (for example References (1) and (2), which treat the case of pitch and heave) which may help in this problem. These methods usually assume the ship is in deep water and is heading directly into the waves which are further assumed to be long-crested; but I believe it may also be possible to make reliable calculations for shallow-water effects and for waves which are, in reality, short-crested.

SUBCRITICAL WAVE WAKE UNSTEADINESS

2021 ◽  
Vol 153 (A3) ◽  
Author(s):  
A Robbins ◽  
G A Thomas ◽  
M R Renilson ◽  
G J Macfarlane ◽  
I W Dand
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Deep Water ◽  
Hull Form ◽  
Non Linear ◽  
Water Effects ◽  
Wave Angle ◽  
Soliton Generation

Vessel wave wake in deep water is well understood, shallow water less so, specifically the effect of restricted water. This operational zone is highly dynamic and non-linear in nature, thus being worthy of closer examination. The paper reviews the primary mechanisms for unsteadiness in wave wake: starting acceleration and soliton generation. A comprehensive set of experiments was conducted using an NPL catamaran hull form to investigate unsteadiness in both wave height and wave angle. The results show that the unsteadiness was primarily due to soliton generation, and that blockage has a significant effect. As a result, additional metrics, aimed at defining shallow water effects in the transcritical region, are proposed.

Modeling the Maneuvering Behavior of Container Carriers in Shallow Water

2007 ◽  
Vol 51 (04) ◽  
pp. 287-296 ◽  
Author(s):  
G. Delefortrie ◽  
M. Vantorre
Keyword(s):  
Mathematical Model ◽  
Shallow Water ◽  
Independent Set ◽  
Model Tests ◽  
Forward Speed ◽  
Ship Maneuvering ◽  
Model Based ◽  
Captive Model Tests ◽  
Water Effects ◽  
The Mathematical Model

Due to the expansion of the dimensions of container vessels, the available maneuvering space in harbor areas and their access channels is decreasing as waterway authorities are often unable to increase the channel dimensions at the same pace. The under keel clearance is an especially important parameter for ship maneuver-ability and controllability. After an overview of the shallow water effects on ship maneuvering, a new mathematical maneuvering model based on captive model tests is introduced. The mathematical model is valid in a large under keel clearance range and is applicable in four quadrants of forward speed: propeller rate combinations, drift angles, and yaw angles. The mathematical model has been validated by means of an independent set of captive model tests.

Determination of Hydrodynamic Masses and Roll Periods of Ships in Shallow Water

2021 ◽  
Author(s):  
Larissa Jannsen ◽  
Stefan Krüger
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Hydrodynamic Forces ◽  
Ship Design ◽  
Design Stage ◽  
Ship Motions ◽  
Design Environment ◽  
Early Design ◽  
Early Design Stage ◽  
Water Effects

Abstract Due to the fast increase of the vessels’ size over the past few years the actual water depth is becoming more and more relevant for seakeeping problems. The highly frequented sea route TSS Terschelling – German Bight for example is a shallow water route for large vessels which are now affected by the reduced keel clearance. Many shallow water depth areas occur also in coastal areas or inland seas. If a vessel is travelling in shallow water sea states, the hydrodynamic forces will change compared to deep water sea states and they are essential for further seaway calculations. Furthermore, a rough but easy evaluation of the incoming seaway is the roll period. Shallow water effects should be taken into account for calculating roll periods and thereby predicting a manageable or risky seaway situation. This paper presents the implementation of shallow water effects into an existing 2D panel code. With this panel code the hydrodynamic forces for the vessel’s frames are calculated based on the potential theory in the frequency domain, which is a validated approach in the early design stage. The panel code is part of the ship design environment E4 which is being developed by the Institute of Ship Design and Ship Safety, among others. With the expanded method it is possible to calculate hydrodynamic forces also in shallow water in all degrees of freedom. Therefore, the frame motions are converted to global ship motions. Furthermore, for the usage in the early design stage the calculations should be fast but also accurate. The obtained calculation results are therefore validated with full scale measurement using Inertial-Measurement-Units.

Low Frequency Motions of LNG Carriers Moored in Shallow Water

2004 ◽  
Author(s):  
Mamoun Naciri ◽  
Bas Buchner ◽  
Tim Bunnik ◽  
Rene´ Huijsmans ◽  
Jerome Andrews
Keyword(s):  
Shallow Water ◽  
Low Frequency ◽  
Test Program ◽  
Analysis Methodology ◽  
Wave Drift ◽  
Water Effects ◽  
Near Shore ◽  
Numerical Tools ◽  
Wave Drift Forces ◽  
Drift Forces

With the LNG market booming, the need for reliable and safe means of transferring LNG from a producing, floating facility to an LNG carrier and from this carrier to a near-shore terminal is becoming acute. The Soft Yoke Mooring and Offloading (SYMO©) system has recently been model tested in MARIN’s offshore basin. Results of these tests are presented. Insight has been gained, from these model tests and from the calibration of numerical tools performed thereafter, on the following issues: • The inherent weakly damped nature of a moored LNG carrier, • Shallow water effects in wave drift forces, • The effect of current on drift forces, • The structure of low frequency long waves in a shallow water basin. These issues will be discussed and guidance regarding their importance will be provided. Consequences in terms of system design, mooring analysis methodology and model test program will be discussed.

Sign in / Sign up

Export Citation Format

Share Document