Water Depth Effect to Ferry Ship Resistance with Computational Fluid Dynamic Method

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.

To investigate the flow field characteristics of full-scale ships advancing through confined waters, the international standard container ship (KRISO Container Ship) was considered as a research object in this study. Using the RANS equation, the volume of fluid method and the body force method were selected to investigate the hydrodynamic characteristics of a model-scale ship (the model-scale ratio λ=31.6) and a full-scale ship advancing through confined waters at low speed. A virtual disk was used in the full-scale model to determine the influence of the propeller on the ship’s flow field. First, the feasibility of the numerical calculations was verified. This proves the feasibility of the numerical and grid division methods. The self-propulsion point of the full-scale ship at Fr=0.108 is determined. The calculation cases of model-scale and full-scale ships (with or without virtual disks) at different water depths and distances between the ship and the shore were calculated, and the changes in the hull surface pressure, the flow field around the ship, and the wake fraction near the ship propeller disk in different calculation cases were determined and compared. The variations in the surge force, sway force, and yaw moment between the model- scale and full-scale ships were generally consistent. In very shallow water (H/T=1.3), the non-dimensional force and moment coefficients for model-scale ships increase more rapidly with decreasing distance from shore, suggesting that using model-scale ships to investigate the wall effect in very shallow water will result in predictions that are biased towards safety. By comparing full-scale ships with and without propellers, it was discovered that the surge force, sway force, and yaw moment were marginally greater in the propeller-equipped ship due to the suction effect, and the accompanying flow before and after the propeller was slightly smaller, with less asymmetry.

Temporal coherence of acoustic signals determines the processing of a sonar system for various applications. This paper studies the frequency and range dependence of the temporal coherence time of signal propagation in deep water versus that in shallow water. The signal coherence time has been measured in deep water since the 1970s, in terms of a parameter called the phase rate (the rate of phase change of the signal). Signal coherence time in shallow water has received little attention until only recently. We compare measurement data from more than a dozen of experiments covering a wide range of frequencies at different source‐receiver ranges in deep and shallow water. We find that the signal coherence time in both shallow and deep water can be fitted with a universal equation, which exhibits a 3/2 power frequency dependence and 1/2 power range dependence. The signal coherence time in shallow water is two to five times longer than the signal coherence time in deep water at the same frequency and range. The signal coherence times are comparable between shallow and deep water if measured in terms of the range‐to‐depth ratio. [This work is supported by the U.S. Office of Naval Research.]

This paper concerns laboratory wavemaking in shallow and intermediate water conditions. A comparison is made between two wave generation techniques, a first based on controlling the wavemaker displacement, and a second based on controlling the wavemaker force. Nonlinear wave generation in position control is well understood, and many laboratories rely on established second-order or Stream-function inputs. In deep water, using flap-type wavemakers, a force-control approach based on a linear demand signal was recently shown to offer benefits in terms of wave quality. The shallow water operation of such force-control strategies is less certain, which motivates the present study.To investigate the influence of the water depth on this type of control, a range of generation scenarios is considered, including small amplitude and large amplitude regular waves. Adopting both supporting calculations and experimental evidence, the work demonstrates that first-order force-based wave generation in shallow water suffers from similar limitations as first-order position control. This principally concerns the contamination of the testing area due to unwanted free waves, where the present focus is placed on the superharmonic range.The main advance of the work lies in the solutions it offers to overcome this free wave contamination. A number of nonlinear wave solutions upon which force-based generation can be based are discussed, and a suitable methodology is proposed and validated for each case. The developed methodology allows for high quality wave generation, whilst maintaining the benefit of active wave absorption. The work is timely in the sense that is responds to two recent developments. First, the majority of wavemaking facilities commissioned over the past two decades are computer controlled, and active absorption has become commonplace. The work presented offers solutions highly relevant to such installations. Second, developments particularly in offshore wind, have seen many new structures placed in relatively shallow-water depth. It is essential that the model testing of such structures adequately accounts for the issues and solutions presented herein.

Numerous practical and mathematical techniques have been piloted to study ships’ behavior in deep water conditions with and without waves, and shallow water conditions without waves, while only limited investigations have been carried out to assess ships’ behavior in shallow waters with wave conditions as the flow around the stern region and appendages and the interaction effects are intricate. Therefore, this study attempts to understand the infrequently explored subset of a vessel’s behavior in regular waves in shallow water conditions (channel depth to ship draft ratio taken as 1.5). A container ship (S175) model scaled at 1:36 was the subject of a numerical study in which it was subjected to static and dynamic maneuver simulations in head sea conditions. The waves were induced using the dispersion relationship of waves in a given depth. The trends of forces and moments acting on the hull while undergoing maneuvering motions were obtained using a smooth particle hydrodynamics-based computational fluid dynamics solver. The resulting periodic trends of forces and moments were analyzed using the Fourier series method to extract the Fourier coefficients and, in turn, calculate the hydrodynamic derivatives. The trajectories in turning circle and zigzag maneuvers were also simulated using a MATLAB code. The results demonstrate an increase in trajectory parameters and improvement in counter maneuverability owing to the complex flow physics around the hull when encountering regular waves in shallow water conditions compared to waves in deep waters and a lack of waves in shallow waters.

In this paper, we systematically investigate the effect of the five most important ship hull form parameters, namely the longitudinal centre of buoyancy (LCB), the half angle of entrance of the design waterline ((½))αE), and the length (CLPR), cross-section (CABT) and volume (C∇ PR) parameters for the bulbous bow on the ship resistance using a computational fluid dynamics method. The parent ship hull form investigated in this study is a 4600DWT cargo ship, which operates on Vietnam’s river-sea routes. To save time and reduce costs, only 25 test cases designed with the orthogonal array Taguchi method are simulated, and the resistance is calculated in deep and shallow water at speeds of 10.0 and 9.0 knots, respectively. The optimal combination of the five ship hull form parameters is obtained using Taguchi-grey relational analysis. The results indicate that the optimum ship hull form depends on the water depth, and that LCB is the most critical parameter in regard to resistance. Of the combinations studied here, the variant with (½)αE=42°, CLPR=0.0141, CABT=0.1600, C∇ PR=0.00173, LCB=48.654%LBP is found to be optimal.

In case of offshore support vessels, it is quite important for their behaviours in low speed manoeuvrability. It is not easy to operate offshore support vessels and it raises an importance to train crew by a ship handling simulator. Therefore it is quite hot issue for ship handling simulator vendors to provide mathematical model of support vessels, but from the users’ point-of-view the model used for the simulator is not clear. Up to now some mathematical models are proposed in the literature, but the validation is not yet done carefully. For example, cross flow model is the main part for hydrodynamic force in low speed ship manoeuvring. From model ship experiments of various types of ships and from some comparison study, it is found that further discussion is necessary. In this paper, sway force and yaw moment as well as surge force will be treated in low speed condition with certain sway and yaw motions. There are many experiment results for such hydrodynamic forces and moment, especially for sway force and yaw moment, for sway motion, but those for yaw motion is quite limited. In this paper, such hydrodynamic forces and moment for both sway and yaw motions are calculated and validated with experiment results. Some manoeuvring simulation will also demonstrate which terms and/or expressions in the mathematical model are affecting the motion.

Preliminary design and dynamic analysis of constant tension mooring system on a 15 MW semi-submersible wind turbine for extreme conditions in shallow water

<div>This study introduces an innovative intelligent tire system capable of estimating the risk of total hydroplaning based on water pressure measurements within the tread grooves. Dynamic hydroplaning represents an important safety concern influenced by water depth, tread design, and vehicle longitudinal speed. Existing intelligent tire systems primarily assess hydroplaning risk using the water wedge effect, which occurs predominantly in deep water conditions. However, in shallow water, which is far more prevalent in real-world scenarios, the water wedge effect is absent at higher longitudinal speeds, which could make existing systems unable to reliably assess the total hydroplaning risk. Groove flow represents a key factor in hydroplaning dynamics, and it is governed by two mechanisms: water interception rate and water wedge pressure. In both the shallow water and deep water cases, the groove water flow will increase as a result of increasing the longitudinal speed of the vehicle for a constant water depth. Therefore, the water pressure in the tread grooves will also increase as the longitudinal speed of the vehicle approaches the critical hydroplaning speed. Unlike conventional systems, the proposed intelligent tire design utilizes the amplitude and shape of the measured pressure signals from the tread grooves for estimating the total hydroplaning risk in both shallow and deep water conditions. Experimental results indicate that peak groove water pressure increases with the risk of total hydroplaning. Furthermore, the overall shape of the pressure signal will also be influenced by the total hydroplaning risk. By addressing the limitations of current intelligent tire systems, the proposed intelligent tire design offers a robust solution for real-time total hydroplaning risk estimation across diverse driving conditions.</div>

Numerical PMM test in finite depth

This study aims to the estimation of the ship manoeuvrability in shallow water by using the numerical PMM approach, which analyses the hull hydrodynamic responses and manoeuvring performance from the viewpoint of coefficients. The test model is a scaled KVLCC2 tanker operating at a low Froude number of 0.0514. Static drift test and pure yaw test are considered, and the water depths vary from deep water to very shallow water of 20% under-keel clearance. The numerical tank is built based on an OpenFOAM+ package. The free surface is modelled by volume-of-fraction method, and the k-ω SST model associating with wall functions is applied for turbulence. After the convergence tests and validation works, the numerical tank is employed to investigate the wave-depth effect on hydrodynamic forces and manoeuvring coefficients. The present results show that the forces of static drift test, particularly sway force, can be significantly changed as the water depth decreases.

A shallow water disconnectable STL turret mooring and riser system has been developed for water depth between 30 and 50 m. This technology is based on APL’s disconnectable STL (Submerged Turret Loading) and STP (Submerged Turret Production) technologies which had been widely applied for water depth between 70 m to 2600 m for FPSOs and LNG offshore terminals. The advantage of disconnectable system is that the mooring and riser system can be designed to a preferred sea state. When the sea state is higher than design sea state (like hurricane), the vessel can be disconnected and sail away. The shallow water STL system consists of STL buoy, mooring lines, riser system and landing pad. The interface with vessel is the same as traditional STL system. The mooring and riser system are connected to the vessel through STL buoy and can be pulled into vessel by using ship winch. Unlike traditional STP and STL buoys, the shallow STL buoy has a net weight and will stay on the landing pad when disconnected from vessel. The landing pad is designed to support the impact load from STL buoy and supply enough friction for the STL buoy to stay in position during 100-year storm. The mooring system design has taken the advantage of directionality of weather when close to the shore by using different mooring line length in different directions. Further an innovative Hold-Back-Wave riser configuration has been developed for shallow water system. The riser configuration has a larger flexibility compared to traditional wave configuration and has proved to be feasible for significant wave height at least 7 m when connected to the vessel and 10+ m when disconnected from the vessel. Model test for the disconnectable shallow water turret mooring and riser system had been performed in MARINTEK, Trondheim with a LNG re-gasification vessel model at 30 m water depth. For connected system, significant wave height Hs = 6 m and 8 m has been tested. The mooring and riser system perform well, as predicted. For disconnected system (when the buoy sitting on the landing pad), significant wave height Hs = 10 m has been tested. The STL buoy is sitting on the landing pad without significant movement and the riser system performs well. SIMO program has been used to calibrate the model test results with numerical simulations. By adjusting surge, sway, yaw damping and 2nd order wave drift force, the calibrated SIMO model agrees well with model test results and can be used for similar development.

Shipwrecks with wooden hulls are underrepresented in the archaeological record from shallow federal waters of the central and western Gulf of Mexico (defined as less than 600 feet deep), yet they tend to be older and arguably more abundant than shipwrecks with metal hulls. This paper quantifies the extent of bias in favor of metal hulls in the archaeological record; examines its potential causes; discusses factors affecting the preservation and discovery of wooden hulls; and proposes a research strategy that might accelerate discoveries of wood-hulled shipwrecks. Introduction The waters of the central and western Gulf of Mexico have been extensively studied by archaeologists for several decades (Figure 1). This is largely due to the intensity of oil and gas production in the area. The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) regularly sponsors archaeological studies in addition to reviewing archaeological reports submitted on behalf of oil and gas operators in connection with offshore energy leases. Figure 1 shows locations of roughly 7,000 geo-hazard surveys conducted by the oil and gas industry in the central and western Gulf of Mexico. Each of the smallest colored squares in Figure 1 represents a 3x3-mile mineral lease block. Archaeologists have reviewed geophysical data and prepared archaeological assessment reports for 3,161 lease blocks (those colored blue or purple). Green blocks have been surveyed for geo-hazards but have not been assessed by an archaeologist. Pipeline route surveys are not included in Figure 1. BOEMRE also maintains a GIS database that includes over 3,000 historic reports of vessels lost, over 6,000 Coast Guard hazards to navigation, and over 17,000 net hangs reported by fishing trawlers. As a result of such studies, a great deal is known about the archaeology of this area. The BOEMRE database (2007) contains locations for 195 shipwrecks in the central and western Gulf of Mexico, including 12 wooden shipwrecks (Table 1; 7 shallow and 5 deep) and at least 91 wrecks believed to have metal hulls (74 shallow and 17 deep). Twelve percent of shipwrecks in shallow and deep waters, combined, have wooden hulls. In shallow water the proportion of wooden shipwrecks is 9 percent, and in deep water it is 23 percent. Thirty-one wrecks, all of which are visible on sonar, are confirmed as metal by the BOEMRE database. Another 60 are presumed to be metal from their descriptions or because they have prominent ship-shaped sonar targets that clearly resemble sunken vessels. Wood does not survive exposure in shallow Gulf waters for more than a few years, thus sonar images are unlikely for any except recent wooden hulls in shallow water. Information regarding the other database entries is insufficient to suggest the composition of their hulls. Historic records summarized below indicate that prior to the mid-twentieth century shipwrecks with wooden hulls outnumbered those with metal hulls by 13 to 1. Yet metal hulls in the archaeological record appear to outnumber wooden hulls by about 8 to 1. The discrepancy between historical records and archaeological observations cannot be entirely explained by an abundance of metal shipwrecks over the past 60 years, as the modern (2010) ratio of metal to wooden hulls in the U.S. Merchant Vessel fleet is only 3 to 1. It is clear that shipwrecks with wooden hulls are underrepresented in shallow waters of the central and western Gulf of Mexico. This paper examines the extent and causes of archaeological bias away from wooden hulls; discusses factors affecting the preservation and discovery of wooden hulls; and proposes a research strategy that might accelerate discoveries of wooden shipwrecks. Wooden Versus Metal Shipwrecks from the U.S. Merchant Vessel Fleet Government statistics of losses sustained by U.S. Merchant Vessels suggest that the proportion of wooden to metal hulls in the Gulf of Mexico should be much higher than 9 percent (shallow) or even 23 percent (deep). In fact for the period from 1876 through 1947, it is estimated that 93 percent of all U.S. Merchant Vessels lost worldwide had wooden hulls (Figure 2).

Like most aspects of underwater sound, the noise in the sea received its first quantitative attention during World War II, when a team under the venerable acoustician V. O. Knudsen made measurements in the shallow coastal waters off Southern California and Florida—ostensibly for the purposes of acoustic mines and harbor protection sonars. At that time too, the pernicious snapping shrimp of the warm shallow tropic waters of the Pacific were investigated. One of the principal features of shallow water noise is its variability—from place to place and time to time. Yet it may be said that there are only three major noise sources in shallow water: ships and other man‐made activities at moderately close ranges, biologics, and the wind or waves. Strangely, when the first two of these are absent, the noise levels in shallow water at frequencies above 1 kHz or so are the same as in deep water; the so‐called ‘‘Knudsen’’ curves have long been used in deep water. At lower frequencies, many shallow locations are often more quiet than deep water because of the absence of deep‐going favorable transmission paths. When environmental conditions can be estimated, one’s knowledge of shallow‐water noise should be good enough to permit a prediction of the expectable noise level at an arbitrary location—at least as good as one’s prediction capability of transmission loss out to useful ranges. [Work supported by the Applied Research Laboratory, The Pennsylvania State University, and the Office of Naval Research.]

This paper describes a theoretical method for predicting the forces induced by irregular waves on very large crude carriers, in which the hull section is modeled as a prismatic elliptic cylinder. Diffraction of the wave around the elliptic cylinder is taken into account and results are presented for surge and sway force and yaw moment for incident wave angles from 0° (head on) to 90° (broadside-on) at several increments and water depth to draft ratios. Thus, the effect of underkeel clearance is taken into account. In order to verify the-method, an experimental study utilizing the captive model technique was carried out at the Netherlands Ship Model Test Basin (NSHB). In this study, forces (and moments) in the surge, sway and yaw directions were measured as the real tanker shape models were subjected to irregular waves incident from to 90°at several values. The comparisons, which are presented in terms of the non-dimensional force (or moment) ratios, are considered to be excellent. The procedure described herein can be employed to synthesize external loading histories due to irregular waves acting on very large crude carriers of specified dimensions for a variety of incident wave angles and water depth/draft ratios. The technique can also be employed to derive added mass and damping coefficient functions for the specified tanker. From these functions, constant inertia coefficients end impulse response functions can be derived. The letter are needed to evaluate various terms in the time domain formulation of the system of non-linear equations of motion. Thus, the procedure is an intermediate step in the process of determining the behavioral response of the moored vessel. The vessel can be considered as moored to conventional piers in relatively protected areas or to sea islands or sea berths in exposed locations. The combination of low computational cost and reasonable accuracy makes it an ideal procedure to employ for a number of engineering applications. INTRODUCTION Forces induced by irregular waves on obstructions (including moored vessels) are of considerable interest to designers of moored-ship systems and harbor facilities because of the increasing awareness of environmental risks arising from the failure of such systems and/or excessive vessel motions. In order to evaluate the capability of proposed designs to safely moor these vessels, solutions to the system of equations of motion are needed. For this purpose, a knowledge of the wave induced forces (and moments) is required moreover, these forces need to be determined for the parameter range of engineering significance. To illustrate the latter, the real world problem is one where the waves approach a vessel moored in shallow water (low water depth/draft ratio) at an oblique angle (i.e., other than head-on or beam-on). In contrast to many contemporary analyses (appearing in the open literature) the size of these vessels dictates that diffraction effects be considered.