Resistance In Shallow Water Research Articles

Experiment and numerical simulation study on resistance performance of the shallow-water seismic survey vessel

In this paper, a new type of shallow-water seismic survey vessel is proposed to solve the problem that the traditional seismic survey vessels cannot satisfy the requirements of the shallow-water marine resources exploration. To reveal the influence of shallow water effect on resistance and flow field, this research is to obtain the resistance and shallow-water characteristics of this shallow-water seismic survey vessel through ship model experiments and numerical methods. Firstly, the ship model experiment predicted the resistance at different speeds in shallow water and obtained the benchmark data to validate numerical methods. Then, the CFD methods were used to calculate the resistance of the ship in deep and shallow water. The numerical results are in good agreement with the experimental results. Finally, this paper provided details of the distribution of wave, pressure and flow fields at different water depth conditions in order to explain the causes of increased resistance in shallow water, providing a reference for the shallow-water seismic survey vessel design.

Reanalysis of the revised EEDI parameters for inland ships of Bangladesh

A revision of the Energy Efficiency Design Index (EEDI) formulation was previously proposed to be useful for inland ships of Bangladesh. The study incorporated the shallow water effect using Schlichting’s method which has been developed in 1934 based on a large number of ship model tests to show how a ship’s resistance in shallow water deviates from that in deep water. However, the evaluation and presentation of Schlichting’s results did not cover all range of ship parameters. This reanalysis has considered the shallow water effect by actual measurement of 15 inland ships of Bangladesh. Later, the results of Schlichting’s method were compared with (a) actual investigation, (b) an improved version of Schlichting’s method proposed by Lackenby in 1963, and (c) a new method proposed by C B Barrass in 2004. It was found that the deviations of Schlichting’s results are much higher than Lackenby and Barrass’s methods in comparison to the investigated results. In a previous analysis of the inland ships of Bangladesh, the Maximum Continuous Rating (MCR) of the main engine was considered by using the Holtrop-Mennen method. As this method requires too much ship data, that analysis had assumed some unknown required ship data. This reanalysis has overcome that problem by the physical investigations of the same 15 inland ships of Bangladesh. The average MCR for inland cargo ships and oil tankers of Bangladesh are measured as 70% by the investigations, whereas it is 80% for passenger ships.

On the viscous resistance of ships sailing in shallow water

Accurate resistance prediction for ships sailing in vertically restricted waterways is highly required to improve the design and operation for large ships entering harbors and for vessels navigating in inland waters. The methods derived from deep water may lead to large errors, and studies considering shallow water effects are needed. As most ships sailing in shallow water operate at a low Froude number, the viscous resistance dominates the total resistance and becomes the main concern. In this study, a Wigley hull and the KCS (KRISO Container Ship), which have available benchmark data, are applied. A typical 86 m long inland ship is then chosen to further investigate the influence of a different hull form. Results show that the friction and the viscous pressure resistance depend on ship types, speeds, and water depths. A formula to predict a ship's friction in shallow water is given with some constants determined based on ship's characteristics. A form factor defined based on computed ship's friction is suggested, and an empirical expression is provided for each ship applied. With the investigations for three ship forms, this study is expected to provide inspirations to further improve the prediction of ship's viscous resistance in shallow water.

Prediction of Shallow Water Resistance for a New Ship Model Using CFD Simulation: Case Study Container Barge

The importance of ship hydrodynamic parameters has increased since the advent of power-driven vessels in the 19th century. The required power for the propulsion unit depends on the ship resistance and speed. There are three approaches for the assessment of ship resistance: analytical methods, model tests in basins, and computational fluid dynamics (CFD). The rapid developments in computers and computational methods increased the opportunities for CFD to be used in the ship design process. The present article aims at simulating ship resistance in shallow water using ANSYS-Fluent software package, Canonsburg, Pennsylvania. As a case study, a container barge operated in the river Nile is investigated. The results show the wave pattern in the subcritical, critical and supercritical regions. In addition, the total resistance/drag is calculated at various ship speeds in shallow water using CFD and compared with the calculated deep water resistance. Finally, the calculated drag results from the CFD analysis are compared with that of the standard Schlichting method. 1. Introduction Inland waterway transport plays an important role for the transport of goods all over the world especially along the river Nile's sides. Moreover, transportation substantially shapes the growth and development of countries. To sustain and enhance the economic growth and vitality, as well as productivity of commerce, a healthy and responsive transportation system is essential. The ability of barge transport to efficiently carry large cargo volumes through long distances makes it a fuel efficient and environmentally friendly means of transport (Wiegmans & Konings 2017). The inland water units' dimensions have to comply with the existing waterway infrastructure, reduced length, breadth, and draught, according to the locks and bridges. Also the hull and cargo hold structures must comply with the national and international rules for safety inland navigation (Pacuraru & Domnisoru 2017).

Resistance analysis of a semi-SWATH design concept in shallow water

Resistance analysis is an important analytical method used to evaluate the hydrodynamic performance of High Speed Craft (HSC). Analysis of multihull resistance in shallow water is essential to the performance evaluation of any type of HSC. Ships operating in shallow water experience increases in resistance because of changes in pressure distribution and wave pattern. In this paper, the shallow water performance of an HSC design concept, the semi-Small Waterplane Area Twin Hull (semi-SWATH) form, is studied. The hull is installed with fin stabilizers to reduce dynamic motion effects, and the resistance components of the hull, hull trim condition, and maximum wave amplitude around the hull are determined via calm water resistance tests in shallow water. These criteria are important in analyzing semi-SWATH resistance in shallow water and its relation to flow around hull. The fore fin angle is fixed to zero degrees, while the aft fin angle is varied to 0°, 5°, 10°, and 15°. For each configuration, investigations are conducted with depth Froude numbers (Fr H ) ranging from 0.65 to 1.2, and the resistance tests are performed in shallow water at the towing tank of UTM. Analysis results indicate that the resistance, wave pattern, and trim of the semi-SWATH hull form are affected by the fin angle. The resistance is amplified whereas the trim and sinkage are reduced as the fin angle increases. Increases in fin angle contribute to seakeeping and stability but affect the hull resistance of HSCs.

A numerical investigation of the squat and resistance of ships advancing through a canal using CFD

As a ship approaches shallow water, a number of changes arise owing to the hydrodynamic interaction between the bottom of the ship’s hull and the seafloor. The flow velocity between the bottom of the hull and the seafloor increases, which leads to an increase in sinkage, trim and resistance. As the ship travels forward, squat of the ship may occur, stemming from this increase in sinkage and trim. Knowledge of a ship’s squat is necessary when navigating vessels through shallow water regions, such as rivers, channels and harbours. Accurate prediction of a ship’s squat is therefore essential, to minimize the risk of grounding for ships. Similarly, predicting a ship’s resistance in shallow water is equally important, to be able to calculate its power requirements. The key objective of this study was to perform fully nonlinear unsteady RANS simulations to predict the squat and resistance of a model-scale Duisburg Test Case container ship advancing in a canal. The analyses were carried out in different ship drafts at various speeds, utilizing a commercial CFD software package. The squat results obtained by CFD were then compared with available experimental data.

Numerical Estimation of Shallow Water Resistance of a River-Sea Ship using CFD

recent years a great deal of research efforts in ship hydromechanics have been devoted to practical navigation problems in moving larger ships safely into existing harbours and inland waterways and to ease congestion in existing shipping routes. The starting point of any navigational or design analysis lies in the accurate determination of the hydrodynamic forces generated on the ship hull moving in confined waters. The analysis of such ship motion should include the effects of shallow water. An area of particular interest is the determination of ship resistance in shallow or restricted waters at different speeds, forming the basis for the power calculation and design of the propulsion system. The present work describes the implementation of CFD techniques for determining the shallow water resistance of a river-sea ship at different speeds. The ship hull flow is analysed for different ship speeds in shallow water conditions. The results obtained from CFD analysis are compared with available standard results.

A Study on Xizhang Junk Form Barge Train

Time-honoured ancient Xizhang Junk form remains to be predominant in the barge train fleet which plays an important role in domestic transport of the Jiangnan region crisscrossed by waterways in East China. With a view to reduce the formation coefficient of barge train, the shallow water resistance of the Xizhang Junk, both individually and in train, has been investigated both by means of towing tank model tests and full-scale trials in Grand Canal. A modified body plan is proposed. Operational results have shown good energy-saving, if the modified form barge is placed as the first one in the barge train. In the appendix, empirical formulae based on existing vessels are given to show the parametric features of Xizhang Junk form.

The Resistance of a 5×3 Barge Tow Moving in Shallow Water

Estimating barge tow resistance in shallow water by Howe's formula can lead to an error in estimating the tow speed of large tows. While not enough published data is available to update Howe's formula, it is worthwhile to have an accurate formula for typical barge tows. The present note addresses this deficiency by presenting a comparison of the actual barge tow resistance given by estimates made using Howe's formula and the results from extrapolating the deep water resistance estimate using Schlicting's method. A two resistance augment is obtained and then introduced to Howe's equation for V > 6.0 mph to obtain accurate estimates for a 5 × 3 barge tow in waterdepth h = 16 ft (4.88 m).

Shallow River Pushboat Preliminary Design

The preliminary design of a river pushboat is presented. The design method consists of four parts: (1) Estimation of pushboat “push” EP; (2) estimation of barge tow resistance R\dT; (3) selection of pushboat horsepower based on equilibrium speed from equating 1 and 2; and (4) for the horsepower obtained from 3, determine the pushboat dimensions and tunnel stern arrangement. Using published data, the writer introduces the following expression for pushboat EP: EP=A HP [1.0+C(h/T-1.78)] [1.0-E.V²]lbs. This expression is shown to be in good agreement over the range of 1,800 ≤\N HP ≤\N 5,600: 1.78≤\N h/T ≤\N 5.0; 0≤\N V ≤\N 12mph. For the deep water resistance (h/T=5.0), a modified Howe’s formula is shown to give a good estimate for the barge tow resistance, R\dT. This formula is shown to be unsatisfactory for estimating the shallow water (h/T=1.78) resistance, R\dT. Therefore, the method of P. A. Apukhtin is extended using published barge tow resistance data. The shallow water resistance predicted with Apukhtin’s extended graph is shown to be in good agreement with available data. The estimates of the tow speed and propulsive efficiency are then completed. It is shown that for the two pushboats considered, 1,800 and 2,400 horsepower, the shallow water conditions reduce the propulsive efficiency by 16-23%. Guidelines for estimating the pushboat length, propeller diameter, and tunnel stern arrangement are given. Criteria for insuring adequate tunnel inflow and outflow are presented.

The Wave Resistance of an Air-Cushion Vehicle in Steady and Accelerated Motion

This paper deals with the theoretical wave resistance of an air-cushion vehicle (ACV) traveling over water of uniform finite or infinite depth, in steady or unsteady motion. Referring first to steady motion, it is shown that the unrealistic oscillations in the wave resistance curve at low Froude numbers found by previous workers can be eliminated by using a smoothed-out pressure distribution rather than one with sharp edges studied exclusively in the past. The main result of unsteady motion calculations is that the peak wave resistance in shallow water, even in moderately accelerated motion, is appreciably less than the corresponding steady-state value. An interesting feature of unsteady motion is that besides wave resistance there is another mechanism transferring energy to the free surface, which is here called the dynamic sustention power. Contrary to intuition, the wave resistance in unsteady motion over finite depth sometimes becomes negative at supercritical Froude numbers before finally vanishing at infinite speed.

Shallow Water and Channel Effects on Wave Resistance

Based on Sretenski's formula, the wave resistance in shallow water and in a channel of rectangular cross section is computed for certain mathematical ship forms. The results are plotted as curves and compared with the wave resistance in an unbounded liquid. The use of these curves for the determination of the wave resistance from towing-tank experiments is illustrated through an example.

The effect of shallow water on wave resistance

1. The general character of experimental results dealing with the effect of shallow water on ship resistance may be stated briefly as follows:—At low velocitie the resistance in shallow water is greater than in deep water, the speed at which the excess is first appreciable varying with the type of vessel. As the speed increases, the excess resistance increases up to a maximum at a certain critical velocity, and then diminishes. With still further increase of speed, the resistance in shallow water ultimately becomes, and remains, less than that in deep water at the same speed. The maximum effect is the more pronounced the shallower the water. For further details and references one may refer to standard treatises, but one quotation may be made in regard to the critical velocity: "This maximum appears to be at about a speed such that a trochoidal wave travelling at this speed in water of the same depth is about times as long as the vessel... It was at one time supposed that the speed for maximum increase in resistance was that of the wave of translation. This, however, holds only for water whose depth is less than 0.2 times the length of the vessel. For greater depths the speed of the wave of translation rapidly becomes greater than the speed of maximum increase of resistance." In a recent analysis of the data, H. M. Weitbrecht expresses a similar conclusion by stating that for each depth of water there is a critical velocity, but that the critical velocity does not vary as the square root of the corresponding depth. It should be noted that experimental results are for the total resistance. If we assume that this can be separated into three terms, which are simply additive, namely, eddy, frictional, and wave-making resistance, it must be admitted that probably all are affected by limited depth of water. However, the main differences are due to the altered wave-making, and the general explanation is to be found in the fact that there is a limiting velocity, √( gh ), for simple straight-crested waves on water of depth h .