Boat Speeds Research Articles

Distribution and speed of recreational boats in Danish waters based on coastal observations and satellite images: Predicting where boats may affect harbour porpoises

Danish coastal waters are a hotspot for recreational boating and harbour porpoises (Phocoena phocoena), but as there is little data on the boats’ speeds and distributions, it is difficult to determine where porpoises are likely to be affected by boat noise. To gain knowledge on the potential impacts of small boats we 1) used coastal observations to assess how boat speed is related to boat size, type, distance to marinas, and wave height, and 2) used satellite images to assess the spatial distribution of small boats in Kattegat, the Sound, the Belt Sea and the Western Baltic areas (see map in Sveegaard et al., 2015). This made it possible to determine how the probability of observing boats was related to distance to the coast and number of people living within a radius of 5 km from a given area. We found that boat speeds varied among marinas and that speed was positively correlated with distance to the marina. The relationship between boat speed and size depended on boat type, with motorboats being the fastest. The satellite image analysis showed that motorboats were the dominant type in coastal waters, constituting 61.4% of the observed boats. The probability of observing boats on a satellite image covering 0.25 km2 dropped from 0.13 by the shore to 0.04 at a distance of 5 km from shore. The probability of observing boats was >10% in 6.6% of the study area, and the probability of observing boats and porpoises in the same area was >10% in 3.0% of the study area. Coastal waters are important habitats for many aquatic species, e.g., fish, invertebrates and porpoises, that use sound for communication or navigation. Our study uses a combination of observation and satellite data to identity areas where boats overlap with harbour porpoise presence and thus where the animals may be affected by boat noise. The study also illustrates how combining these two methods can yield important information on the potential impacts of boats on wildlife.

Effects of a power plant closure on home ranges of green turtles in an urban foraging area

A natural experiment was conducted to determine effects of a fossil-fueled power plant on home ranges of east Pacific green turtles Chelonia mydas in an urban foraging ground. The power plant, located in south San Diego Bay, California, USA, co-existed with a resident foraging aggregation of ~60 green turtles for ~50 yr. It was decommissioned during a long-term green turtle monitoring study, thus providing a rare opportunity to evaluate how the cessation of warm-water effluent affected turtle movements and habitat use in the area. During pre- and post-decommissioning of the power plant, 7 and 23 green turtles, respectively, were equipped with GPS-enabled satellite transmitters. Useful data were obtained from 17 turtles (4 for pre- and 13 for post-decommissioning). Core use areas (50% utilization distribution [UD]) increased from 0.71 to 1.37 km2 after the power plant decommissioning. Increase in post-power plant 50% UD was greater during nighttime (0.52 to 1.44 km2) than daytime (1.32 to 1.43 km2). Furthermore, UDs moved from the effluent channel to an area closer to seagrass pastures, a presumed foraging habitat of the turtles. The observed expansion of green turtle home ranges may increase turtle-human interactions, such as boat strikes, within the foraging ground; this underscores how seemingly innocuous human actions contribute to inadvertent consequences to wildlife. Possible management and conservation actions include increasing awareness of the public regarding turtle presence in the area through signage and education as well as legislating for a reduction in boat speeds in select areas of the bay.

Peculiarities of Distance Pacing of Lithuanian Rowers at the European Championship 2012

Research background and hypothesis. In rowing, not enough attention is paid to the peculiarities of distance pacing and race tactics. At the same time the annually increasing boat speeds and closeness among the results of the world and the European championship winners, the race tactics can be of decisive importance. Although many scientific articles on Lithuanian rowing have already been published, there are not enough scientific studies on the peculiarities of distance pacing of Lithuanian rowers.Research aim was to determine the peculiarities of distance pacing of Lithuanian rowers at the European championship 2012.Research methods. The following study methods were used: literature review and competition records analysis. In accordance with the technical records of the European championship 2012 (http://www.worldrowing.com/results/), the average speed in the distance and speed changes in different sections of 84 crews were analysed. The peculiarities of distance pacing and tactics variants of the Lithuanian men single scull, double scull and women single scull and the best European rowers were compared.Research results. Lithuanian rowers were the fastest in the first 500 m section of the distance and applied 1–3 and 1–4 tactical variants. The speed changes at the European championship 2012 were 1.70–2.69%. At the European championship 2012, the crews who took 4–6 th places were more likely to exceed their average distance speed in the first section of the distance than the crews who took places 1–3 (p < 0.05).Discussion and conclusions. Speed changes in the distance of Lithuanian men single scull and double scull rowers were one of the lowest and the average pace was the highest compared to the records of other finalists. The speed changes in distance of women single scull rowers were among the highest while the average pace was the lowest compared to the records of other Final A participants. Although Lithuanian women single scull rowers had high speed changes in the distance and their rowing pace was low, high average speed in the whole distance allowed them winning at the European championship.Keywords: boat speed, tactics, number of strokes.

Toward the development of a hydrofoil tailored to passively reduce its lift response to fluid load

The objective of this research is to explore the possibility of using Passive Adaptive Composite (PAC) on structures to help control the lift generated by hydrofoils on boats such as the International Moth. Introducing composite fibres oriented at off-principal axis angles, allow a foil to passively control its pitch angle to reduce the lift generated at higher boat speeds helping to achieve a stable flight in a wide range of weather conditions. PAC utilises the inherent flexibility of a composite structure to induce a twist response under bending load which could be used to minimise the use of active control systems, or even improve the dynamic response of foils in waves. However, to design flexible foils requires numerical and experimental tools to assess the complex fluid structure interactions involved. This paper evaluates a simplified hydrofoil geometry designed to reduce its lift coefficient with increased flow speed. A coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) methodology is presented to predict flexible foil performance. Validation of these numerical tools is achieved through the use of wind tunnel experiments including full field deformation measurements. Twist deformations resulted in a reduction in the effective angle of attack by approximately 30% at higher flow speeds reducing the foil lift and drag significantly.

Flexible hydrofoil optimization for the 35th America's Cup with constrained EGO method

This paper investigates the use of constrained surrogate models to solve the multi-design optimization problem of a flexible hydrofoil. The surrogate-based optimization (EGO) substitutes the complex objective function of the problem by an easily evaluable model, constructed from a limited number of computations at carefully selected design points. Associated with ad-hoc statistical strategies to propose optimum candidates within the estimated feasible domain, EGO enables the resolution of complex optimization problems. In this work, we rely on Gaussian processes (GP) to model the objective function and adopt a probabilistic classification method to treat non-explicit inequality constraints and non-explicit representation of the feasible domain. This procedure is applied to the design of the shape and the elastic characteristics of a hydrofoil equipped with deformable elements providing flexibility to the trailing edge. The optimization concerns the minimization of the hydrofoil drag while ensuring a non-cavitating flow, at selected sailing conditions (boat speed and lifting force). The drag value and cavitation criterion are determined by solving a two-dimensional nonlinear fluid-structure interaction problem, based on a static vortex lattice method with viscous boundary layer equations, for the flow, and a nonlinear elasticity solver for the deformations of the elastic components of the foil. We compare the optimized flexible hydrofoil with a rigid foil geometrically optimized for the same sailing conditions. This comparison highlights the hydrodynamical advantages brought by the flexibility: a reduction of the drag over a large range of boat speeds, less susceptibility to cavitation and a smaller angle of attack tuning range.

Development and demonstration of PEM fuel-cell-battery hybrid system for propulsion of tourist boat

In this paper, we present the development and demonstration of a polymer electrolyte membrane (PEM) fuel-cell-battery hybrid system for the propulsion of a 20-m-long tourist boat. The PEM fuel-cell-battery hybrid system was developed by integrating PEM fuel cells with Li-ion batteries to supply electric power to the waterjet propulsion system and auxiliary equipment of the boat, which was operated in coastal waters. The PEM fuel cells and Li-ion batteries generated an electric power of 50 kW and stored an energy of 47 kWh, respectively. All of the system components, including the PEM fuel-cell modules, hydrogen storage tanks, DC–DC converters, Li-ion battery packs, and battery charger were newly developed and pre-tested for installation onboard, and the boat was built using an aluminum alloy to arrange the developed PEM fuel-cell-battery hybrid system inside of it. The first fuel-cell-powered boat in Korea was successfully demonstrated in the coastal waters of Busan, Korea. The demonstration exhibited the reliable operation of the fuel-cell-battery hybrid system and boat speeds of 6.6–7.8 knots at a power output of ∼85 kW.

Numerical Prediction of the Best Heel and Trim of a Laser Dinghy

As the Laser Olympic dinghy is one of the highest-level sail racing classes in the world, there is an interest in obtaining physical facts around the experience that already exist. For this reason, a numerical investigation has been carried out to find the best heel and trim angles in upwind sailing. Flat water is assumed. The core of the work is a newly developed Inverse Velocity Prediction Program (IVPP) that computes the required wind speed for a given boat speed. Input to the program is both available towing tank data and CFD results. By keeping speed constant interpolation is avoided in the very non-linear resistance-speed relation, reducing considerably the required number of CFD computations. Another reduction is obtained by a special technique for avoiding interpolation in leeway. Systematic CFD computations are carried out to find the optimum trim versus heel at the speeds 2, 3, 4, 5 knots. Using this relation the required wind speed at the four boat speeds can be expressed as a function of heel only. The heel angle corresponding to the smallest wind speed is the best. Knowing this, and the corresponding optimum trim, the position of the sailor is computed. It turns out that the predicted best positions correspond well with practical experience. However, the results highlight the benefit of a small heel in higher winds, which often is regarded as undesired by sailors.

Bubble–wall interaction and two-phase flow parameters on a full-scale boat boundary layer

Full scale bubbly flow experiments were performed on a 6m flat bottom survey boat, measuring the void fraction, bubble velocity and size distributions as the bubbles naturally entrained at the bow of the boat interact with the boat’s boundary layer. Double-tip sapphire optical probes capable of measuring bubbles down to 50μm in diameter were specifically designed and built for this experiment. The probes were positioned under the hull at the bow near the bubble entrainment region and at the stern at the exit of the bottom flat plate. Motorized positioners were used to vary the probe distance to the wall from 0 to 50mm. The experiments were performed in fresh water (Coralville Lake, IA) and salt water (Panama City Beach, FL), at varying velocities with most data analysis performed at 10, 14 and 18knots. The results indicate that the bubbles interact significantly with the boundary layer. At low velocity in fresh water, bubble accumulation under the hull and coalescence are evident by the presence of large bubbles at the stern. At high speeds bubble breakup dominates and very small bubbles are produced near the wall. It is also observed that salt water inhibits coalescence, even at low boat speeds. The void fraction increases with speed beyond 10knots and peaks near the wall. Bubble velocities show slip with the wall at all speeds and exhibit large RMS fluctuations, increasing near the wall.

PARAMETERS AFFECTING THE PERFORMANCE OF THE C-CLASS WINGSAIL

Wing sails offer a different design challenge to those of more conventional soft sail rigs. This study was undertaken in order to assess which parameters influence wingsail performance of C-Class catamarans, and to what extent, the results from the wind tunnel can be applied in the design developments of future wingsails. A combined wing sail and C- class catamaran was tested in the low-speed section of the 7’ x 5’ wind tunnel at the University of Southampton. Testing assessed the appropriate settings for the movable element of the multiple-element wing sail as well as heeling angle, trampoline porosity, spanwise camber distribution and gap at the foot of the wingsail. Both upwind and downwind conditions were considered through measurement of driving force, heeling force, heeling and yawl moments. The results demonstrate that low heel angles improve overall performance and that the gap underneath the wingsail foot adversely affects the generation of lift by the sail. An airfoil shaped trampoline is suggested in order to benefit both a reduced gap and a better control over the heel. For heavy wind condition, negative twist at the tip of the wingsail allows higher boat speeds.

Effects on the various rubber fenders of a tripod offshore wind turbine substructure collision strength due to boat

An analysis is conducted to minimize the damage to tripod type offshore wind turbines substructure caused by collisions with boat. The impact of a wind turbine and a boat takes a complicated form. ANSYS LS-Dyna, a commercial FEM tool, is employed for the impact analysis. The FE model generated using equivalent beams for the blades which are verified the method through the results of static and dynamic analysis between full 3D blade model and equivalent beam model. The investigation is conducted in order to determine the influences of various boat speeds, which result in different loading conditions, and various rubber materials for the fender on strain energy, total deformation, plastic strain, internal energy, and permanent deformation. Natural rubber, composite rubber, and neoprene are modeled using Mooney–Rivlin constants, which are determined by material tests, and a time-marching analysis is conducted to account for their nonlinearity. Based on the analysis results, the minimum thickness of a rubber fender is suggested to decrease the effects of impact for the structures. This study provides relationship trends between the structure thickness and the rubber fender thickness, which may be useful in developing the structural design of a tripod type offshore structure.

Effects of ship‐induced waves on littoral benthic invertebrates

Summary1. Ship‐induced waves can affect the physical characteristics of lake and river shorelines, and laboratory studies have shown effects on littoral invertebrates. Here, we explored whether these effects could be observed under field conditions along a natural lake shore affected by wave sequences (trains) produced by boats.2. Individuals of five invertebrate species (Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeselii, Laccophilus hyalinus) were exposed to waves with increasing shear stress in five habitats differing in structural complexity.3. Detachment of invertebrates increased with increasing shear stress and was best modelled using sigmoid response curves. Habitat structural complexity mitigated the effects of shear stress, and detachment rate was influenced more by habitat type than by species. A threshold (90% of the individual invertebrates unaffected) stress level of 0.64 N m−2 was found for a structurally complex reed habitat, compared to 0.37 N m−2 for a simple sand habitat.4. Shear stress associated with wave trains created by recreational boating at a distance of 35 m from the shore and at a speed of 11 km h−1 resulted in 45% detachment of littoral invertebrates. Decreasing the boat‐to‐shore distance to 20 m increased wave shear stress by 30% and invertebrate detachments up to 75%.5. Disturbance of littoral habitats and invertebrate assemblages are widespread in inland waters used for recreational and/or commercial navigation. Our findings show that the integrity of littoral zones of navigable surface waters could be much improved by implementing management measures such as physically protecting complex habitats with dense reed belts and tree roots, and reducing boat speeds and increasing their minimum shoreline distance.

Spatial Distribution of Submarine Groundwater Discharge and Associated Nutrients within a Local Coastal Area

To understand the local-scale distribution of submarine groundwater discharge (SGD) and dissolved nutrients, a multiple-detector (222)Rn monitoring survey was undertaken along the Mt. Chokai volcanic coast in northern Japan. The surveys revealed that the highest SGD (calculated to be 6.2 × 10(4) m(3) d(-1), within an area of 2 × 10(4) m(2)) with the greatest nutrient fluxes (sum of NO(3)(-), NO(2)(-), and NH(4)(+) (DIN): 9.2 × 10(2) mol d(-1); PO(4)(3-) (DIP): 56 mol d(-1)) is present at the edge of the youngest volcanic lava flow in the area. Recharged groundwater transports nutrients through porous volcanic flows and discharges as SGD near shore. Our results demonstrate that the spatial distribution of SGD in the study area is closely regulated by the local geology and topography. Furthermore, we show that continuous (222)Rn monitoring with a multidetector system at boat speeds of 1-2 knots provides details at a scale one order of magnitude greater than has been reported previously. In addition, the results of our study suggest that SGD-borne DIP may play an important role in the important local oyster production.

Development and Preliminary Experimental Validation of a Wind- and Solar-Powered Autonomous Surface Vehicle

The design and initial testing of a wind- and solar-powered (WASP) autonomous surface vehicle (ASV) are presented. The concept vehicle is a 4.2-m length overall monohull keelboat powered by a rigid wing sail with a 5-m span. It is designed to operate in 7-10 km of wind and a maximum sea state of 2. Specific attention is placed on the aerodynamic, hydrodynamic, and systems integration aspects of the design. Rigid wing sails are shown to have superior performance to conventional cloth sails for use on ASVs owing to their higher aerodynamic efficiency and robustness. The manual design process involved in selection of the airfoil cross section for the wing sail and the resulting aerodynamic performance predictions are presented. Through mathematical derivation, the optimal angle for switching the sail configuration from an upwind/crosswind lift-generating mode to a downwind drag-generating mode is found to be 135 . To simplify implementation of the control system when operating in the lift-generating sailing mode, a control scheme that decouples heading and speed control by simply setting the wing sail to an angle of attack of 10 and independently controlling heading was used. The simulation results from a velocity prediction program (VPP) used to verify the feasibility of this control approach are presented. Initial field trials of the vehicle using the control approach with autonomous wing control and manual rudder control are presented. It is shown that the measured boat speeds and wind speed/directions are within the range of values expected from the VPP. Temperatures recorded in a thermal plume during the field trials of the ASV are shown as a function of global positioning system (GPS) location and time.

Material properties of manatee rib bone

AbstractWatercraft‐related mortality of the Florida manatee Trichechus manatus latirostris accounts for 24% of all deaths from 1974 to 2006. Of these, the proportion of deaths due to impact accounts for 66% of all watercraft fatalities. To establish safe boat speeds for manatee protection, an estimate of the material properties of their bone is needed to quantify the biomechanical effects of boat strikes on manatees. Manatee ribs are unique in that they are pachyostotic. Machined specimens from ribs were tested in three point flexure. Strength, modulus, work of fracture and fracture toughness were determined for three size classes, by sex. The mean flexural strength ranged from 62 to 160 MPa, elastic modulus from 4 to 18 GPa and work of fracture from 3 to 6 MJ m−3. Fractographic analysis was used to calculate toughness, which averaged 1.4–2.9 MPa m1/2. The results show that manatee bone material is less strong and tough than other mammalian bone. Although the bone increases in static strength as the animals grow, it is not able to absorb more energy. In fact, the ability to absorb impact energy appears to decline with increasing size in animals over 265 cm body length. This decline is due in part to the bone's high density and mineral content. There was little change in mineral content with size, suggesting that material properties are likely correlated with bone quantity. There were no differences in mechanical variables between the sexes. The pachyostotic nature of the bone, which makes the manatee well adapted to its environment, also leaves it highly susceptible to fatal injuries from boats.

REVIEW: Slower boat speeds reduce risks to manatees

Collisions with boats account for approximately 25% of all documented manatee Trichechus manatus latirostris deaths in Florida. The state of Florida, as well as the US Fish and Wildlife Service and various local governments, have established boat speed limits in areas fre- quented by manatees as a means of reducing risks. Boat speed limits are believed to reduce risks in 3 primary ways: (1) greater reaction time for the boat operator; (2) greater reaction time for the man- atee; and (3) reduced severity of injuries in the event that a manatee is hit by a boat. We review the current research and other available information that forms the conceptual basis for this risk reduc- tion method and also examine the primary objections that have been raised against requiring slower boat speeds. The available information supports the position that reducing boat speeds in specific areas is an appropriate, reasonable, and defensible management action. Additional research on how manatees detect and respond to boats would be very useful, as would further empirical studies assessing the effectiveness of existing boat speed limits.

Factors Influencing Behavior in a Boating Speed Zone

The greatest source of human-related mortality for endangered Florida manatees is collisions with watercraft. Regulation of boat speeds is the principal management tool to minimize this threat. Demands on law enforcement limit their ability to monitor boater behavior and managers seek alternative strategies to increase compliance. The purposes of this study were to: (1) explore the effectiveness of an on-site sign to enhance boater compliance in a boating speed zone, and (2) examine the environmental and boating characteristics that influence the probability of compliance. Signs designed to increase compliance were posted halfway through the 18-week study period. The signs were not related to compliance level. Logistic regression models showed that only time of day and boat type were significantly related to compliance. Results suggest that passive methods of persuasion may not be an effective means of influencing boater behavior.

A Portable Retractable ADCP Boom-Mount for Small Boats

This paper describes the design, testing, and application of a portable and retractable shipboard acoustic Doppler current profiler (ADCP) boom-mount. The boom is specifically adapted for small fiberglass boats working with a minimal crew. The design permits the rapid collection of ADCP data on discontinuous transects which would be difficult or impossible using a large displacement hull vessel or with a towed vehicle. This capability is particularly useful in shallow wind-driven estuaries and in tidal channels where flow time scales are often on the order of several hours. Tests of the boom show that high quality ADCP data (as measured by percent good) can be obtained at boat speeds up to 4.0 m s−1 and that data quality depends on transducer depth. The utility of the retractable design is demonstrated with an 8 m boat on two nearly synoptic ADCP surveys of a shallow estuary. With minor modifications to accommodate different vessel geometries, the design could be readily adapted for use on similar vessels.

Investigations of 3D Turbulent Flow Inside and Around a Water-Jet Intake Duct Under Different Operating Conditions

In this paper the flow field in the intake duct of a model water-jet unit is studied by using a commercial 3D CFD code. In order to model the intake duct/hull interaction, the computational domain includes a large section of the hull in the vicinity of the intake duct opening. Appropriate boundary conditions are used on the far upstream and downstream of the duct inlet in order to minimize the effect of the domain boundaries on the flow field in the vicinity of the intake duct. Computations are performed for different boat speeds and flowrates. In addition, the effects of the impeller shaft, shaft rotation, boat trim as well as the traverse flow across the hull are investigated. The results of the computations are compared with some preliminary experimental results obtained from model self-propulsion tests in a towing tank. Good correlation is obtained between the predictions and the experimental results.

入港時の船速の違いと港口での出会い波との関係に関する基礎的研究

Many habors have been constructed facing to the open sea front in Japan. In a rigorous season the shipping activities are often interrupted due to strong wind and heavy seas. However, these severe situation is not recognized for the poor information. So, we developed measurement system of ship motions and we carry out a filed observation of fishery boat entering into harbor under quartering sea condition. Furthermore, we observe wave heights and wave directions using wave sensors installed on the sea bottom of harbor entrance. The obtained results are summarized as follows : (1) The encounter waves can be calculated by wave heights observed at a fixed point, the two-dimensional ship positions and the main wave direction obtained from the wave direction sensor data. (2) As an example, the period of the observed waves is about 8.4 seconds, whereas that of the encounter waves is about 20 seconds. As the breakwater is constructed in order to shelter the main waves, the entering boat receives the waves almost from behind, and the period of encounter waves becomes longer than that of the actual waves. (3) It is found that the water velocity along running boat direction correspond with the changing of boat speeds beneath the encounter waves.

Boat Wash at Channel Banks

ABSTRACTThe general characteristics of boat wash, as affected by boat speed and water depth, are discussed. The classical deep‐water wave pattern, with the most prominent waves at the forward edges of a V‐shaped region of semi‐angle 19 1/2°, becomes modified at high speeds. The effective angle of the V is then reduced and the waves become very long‐crested.In moderately shallow water, the level of the water surface close to the boat (on either side of it) can be depressed by an amount which is greater than the amplitude of the downstream waves. In still shallower water, for boat speeds which would cause appreciable waves in deep water, the boat squats markedly and makes very large waves.Possible implications of these facts for bank erosion are discussed.