High-speed Boats Research Articles

Numerical Modeling of a Planing Hull Maneuvering in a Regular Wave, Part 1: Dynamic Instability

The surf rescue boat (SRB) of the U.S. Coast Guard is a class of high-speed planing boats. This 9-meter craft is capable of operating at speeds up to Froude number 1.7. However, when it begins to maneuver in incident waves near its maximum speed, dynamic instability occurs immediately. In this instance, the craft trims and rolls to a large heel angle with “plow-In,“ even with small-amplitude incident waves and small course changes. In this study, a fully nonlinear ship motion model named the Digital Self-consistent Ship Experimental Laboratory (DiSSEL) is used as a numerical tool to understand the physics that cause the dynamic instabilities. DiSSEL showed that when SRB reached Froude number 1.698, acceleration resulting from heading change would cause a dynamic force and moment imbalance, resulting in heel and pitch motion instabilities. DiSSEL also showed that if the heading is fixed, and other conditions remain the same, the instability did not occur. Unfortunately, there is no detailed record of the data or numerical simulation of the ship motions in the stable and unstable regions, except for the description of the ship motions by Codega and Lewis (1987). The simulations by DiSSEL agree well with this description.

Environment Manipulation: Force Multiplier in a Maritime Operation

January 26, 2013; Somewhere off the Sir Creek: An important naval operation is called for during the early morning hours to support a team of the Army's elite Special Forces (SF) deployed inland as part of a force committed to breaking up a concentration of terrorists with ties to an international organisation. The weather forecast predicts clear skies. As the operation commences just after sunrise heavy fog descends on the sea coast. The SF team moves in as per the previously decided H-hour expecting fire support from sea. The laser designator to direct the missile from the ship fails to acquire the target. The fire support however, continues without accurate spotting due to reduced visibility. Radio communications between the SF team and the naval ship become unreliable. By the time news of the SF advance and their new positions are relayed to the naval commander, the SF team has taken significant casualties. Some terrorists escape although the operation is declared a success. However, the conduct of such joint operations in the future is now endangered. Subsequent analysis released by the navy's meteorological department suggests that an early morning temperature inversion was the cause of the fog build-up and the strong atmospheric gradient resulted in poor radio communications. August 15, 2013; Somewhere off the Coast of Andaman and Nicobar Islands: A ship suspected of carrying contraband arms has been tracked and is heading for the harbour of a hostile naval base. A Marine Commando team is to be dispatched by a high-speed boat to intercept, board, and take control of the vessel. The team leader checks with the Met officer and ascertains that the wave heights are averaging 3 feet from the southeast. He estimates the intercept can be made a few miles before the ship enters hostile waters if the boat averages 10 knots. The moment the mission is launched at 2300 hours, a tornado develops and the wave height reaches 6 feet. As the boat picks up speed, the violent shocks of the craft engaging the 6-foot seas directly on the bow become unbearable to the team and the boat crew. The boat had to slow to 5 knots and finally the intercept is missed.

Effects of Waves by Boats on Mangrove in Dongzhai Harbor of Hainan

The effect of boat-generated waves on mangrove forests could be reflected by width change of tidal inlets by using satellite image in this study. Our results showed that the distributions of mangrove zone on the side of tidal inlets were degenerated by boat-generated waves from 2009 to 2011 in Dongzhai Harbor Mangrove Natural Reserve. The main reason of this change was strong erosion of tidal flat caused by the waves generated by high speed and frequencies boats for tourists. To protect the mangrove forests of the tidal inlets, the drive speed and pass frequencies of the boats in waterway should be restricted and decreased.

파라메트릭 설계법에 의한 파워보트 설계를 위한 연구

The hull form design technique for high speed power boat based on the parametric design method is presented in this paper. While the design methods of conventional vessels that are currently in use have been well developed in various aspects from existing database. However, an easy and simple design program for high speed power boats needs to be provided for the relatively small boat builders who are in lack of experience and skilled manpower. This paper presents a parametric design technique which is aimed to provide an easier creation of a new model by inputting several parameters, such as angles and lengths, which correlate with hydrodynamics characteristic for high speed boats. The paper also introduces the prototype program developed to design power boat with parametric design technique.

Effectiveness of Suspension Seats in Maintaining Performance Following Military High-Speed Boat Transits

The aim of this study was to investigate whether suspension seats (SS) fitted to rigid inflatable boats (RIB) could help maritime boarding teams maintain running performance during the high-risk posttransit phase. High-speed RIB transits have been reported to cause reductions in the running performance of boarding teams posttransit. In this experiment, two pairs of teams completed a 3-hr transit in either calm or rough seas (calm, 5 vs. 5; rough, 6 vs. 6) in an RIB fitted with either fixed (FS) or Suspension seats (SS). Exhaustive shuttle run distance was measured pre- and immediately posttransit. Transit heart rate and perceived exertion (RPE) were measured and deck and seat pan acceleration recorded; the latter were reported as impacts count and peak magnitude. Distance run was reduced for the FS teams following both transits (calm,-250 m,-20%, p < .07; rough, -398 m, -26%, p < .05), whereas it was unchanged for the SS teams. All transit heart rates and RPE indicated light exertion levels. Seat pan impacts were similarly reduced during the calm transit (FS, -42%; SS, -30%); however, during the rough transit, the SS was more than twice as effective (FS, -32%; SS, -71%). Peak impact magnitudes were reduced by the SS (calm, -38%; rough, -57%) and amplified by the FS (calm, +3%; rough, +28%). Suspension seats effectively maintained posttransit running performance by reducing magnitude of the vertical shocks imposed on the passengers. High-speed RIB transits followed immediately by high-intensity activity are intrinsic to contemporary maritime operations; suspension seats can maintain post-transit physical performance, thereby enhancing safety and operational effectiveness.

Modeling of longitudinal motions of a hydroplane boat

A dynamic model is developed for vertical-plane motions of a hydroplane boat supported by aerodynamic, hydrodynamic, and propulsive forces. The model is based on unsteady nonlinear formulations of the extreme ground effect theory for the hydroplane platform and the added-mass strip theory for planing hulls. The steady-state attitudes, thrust-to-weight ratios, and static stability margins are calculated for a selected hydroplane configuration with several variable parameters. Simulations of unsteady regimes are also carried out, including responses to an initial disturbance, reactions to wind gusts, and motions in head and following regular waves. The developed model can be applied for aero-hydrodynamic design of hydroplanes with realistic geometries and other types of air-supported high-speed boats.

Effect of Wind Chill on Wire Ladder Climbing and Running Performance

Maritime Interdiction (MI) operations may require Special Forces personnel, in open high-speed boats (OHSB) to chase and board large ships using wire ladders followed by an assault involving running and jumping. We have previously demonstrated a reduction of 40% in running performance following a 3-hour OHSB transit in the cold (ambient temperature (tamb) -2.5°C; air speed (v) 17.9 m·s-1; wind chill index (WCI) 1435 W·m-2; chilling temperature (tch) -23°C). It is unclear if the same level of performance degradation would have occurred if personnel had been sheltered from the high airflow. PURPOSE: To quantify the effect of high airflow in cold ambient conditions on ladder climbing and run performance. METHODS: Twelve men (age 21 ± 1 y; height 182 ± 6 cm; nude mass 78 ± 2 kg) completed a familiarization session and then in a crossover design, two 60-min cold (tamb 0°C) environmental chamber exposures (CON, v 0.04 m·s-1; WCI 479 W·m-2; tch 14°C; WIND, v 3.6 m·s-1; WCI 986 W·m-2; tch -5°C) followed by a timed 14 m wire ladder climb and an incremental 10 m shuttle run to exhaustion, wearing a standardized clothing ensemble (thermal base-layer, coveralls, specialist MI boots) with additional thermal protection (hands, head, face) during the exposures. Core temperature (tcore) was recorded continuously and thermal comfort ratings ((TC) global, face, hands, feet) every 10 min. RESULTS: Ladder climb times increased (CON, 43 ± 6 s; WIND, 46 ± 8 s, 11%; p<0.01) and distance run decreased (CON, 1003 ± 108 m; WIND, 891 ± 109 m, 7%; p<0.05) following the WIND exposure compared to CON. In both conditions tcore was maintained, but WIND reported lower global TC ratings (p<0.05). CONCLUSION: Ladder climbing and shuttle running require strength, endurance and neuromuscular coordination all of which appear to be degraded by cold exposure and more so with a high airflow. The lower global TC ratings reported in the WIND condition suggest localized muscle cooling may be a cause of this degradation. The ladder climb has been identified as a key MI mission failure point, therefore the performance degradation observed for this and subsequent shuttle running, following exposure to a high airflow and WCI may have a serious operational impact. It is recommended that the provision of airflow protection for personnel during the MI insertion phase be addressed.

한국 고속 소형 연안어선의 저항성능 연구

The study on the improvement of resistance performance is very important for coastal fishing boats in Korea, because the prices of fuel oil are gradually risen and the demand of high-speed fishing boats is increased lately. This study is concerned with the improvement of the resistance performance for Korean high-speed small coastal fishing boats. A semi-planing hull form of Korean small coastal fishing boat is selected in the role of initial hull. From the modification of the hull form parameters and the local characteristics of the hull form, the improvement of the resistance performance is achieved. The resistance performances of the initial and the modified hull forms are estimated by using a numerical simulation method. Also, ship model tests are carried out in ship model basin.

Ship wake detection by Raman lidar

We carried out a remote study of ship wakes by optical methods. Both Mie and Raman scattering signals and their evolution were simultaneously recorded by gated detector (intensified CCD). The Mie scattering signal was detectable within 1 min after water disturbance by a high-speed boat. According to an approximation of experimental data, Raman signal fluctuations can be detected for a much longer time under the same conditions. We have demonstrated that Raman spectroscopy is substantially more sensitive to water perturbation compared to conventional acoustic (sonar) technique and can be used for ship wake detection and monitoring.

Physiological consequences of military high-speed boat transits

The purpose of this study was to investigate the consequences of a high-speed boat transit on physical performance. Twenty-four Royal Marines were randomly assigned to a control (CON) or transit (TRAN) group. The CON group sat onshore for 3 h whilst the TRAN group completed a 3-h transit in open-boats running side-by-side, at 40 knots in moderate-to-rough seas, with boat deck and seat-pan acceleration recorded. Performance tests (exhaustive shuttle-run, handgrip, vertical-jump, push-up) were completed pre- and immediately post-transit/sit, with peak heart rate (HRpeak) and rating of perceived exertion (RPE) recorded. Serial blood samples (pre, 24, 36, 48, 72 h) were analyzed for creatine kinase (CK) activity. The transit was typified by frequent high shock impacts, but moderate mean heart rates (<45% HRpeak). The TRAN group post-transit run distance (-219 m, P < 0.01) and vertical-jump height (5%, P < 0.05) were reduced, the CON group showed no change. The TRAN group post-transit test RPE increased (P < 0.05), however, HRpeak was similar for each group (98%). Post-transit CK activity increased in the TRAN group up to 72 h (P < 0.01) and also, but less markedly, in the CON group (24 and 48 h, P < 0.05). Post-transit run and jump performances were reduced despite mean transit heart rates indicating low energy expenditure. The greater TRAN CK activity suggests muscle damage may have been a contributory factor. These findings have operational implications for Special Forces/naval/police/rescue services carrying out demanding, high-risk physical tasks during and immediately after high-speed boat transits.

Lidar observation of the bubble trace in the sea surface layer

The evolutions of the signals of the elastic (Mie) and Raman backscattering of the Nd:YAG laser second-harmonic radiation in the upper layer of the sea under cavitational perturbation induced by the passage of a high-speed boat are compared under the conditions of the outdoor experiment. It is shown that the signal of the elastic scattering on bubbles returns to the background level within the time of ∼10 min. The relaxation time of the spontaneous Raman scattering signal can be an order of magnitude larger than this value (the evaluated value under the particular conditions of this experiment is ∼120 min). Interpretation is given to this difference in attenuation time of the elastic and inelastic scattering signals at the cavitational perturbation of the sea.

카타마란형 파워요트의 운동응답 특성에 관한 연구

A very good seakeeping vessel is able to operate effectively even in high sea states and also the passengers and the cargos are ensured in good conditions. The motions of a high speed boats are highly influenced by speed and dynamic forces even in encounter frequencies so that the assessment of seakeeping ability of the design craft in an early stage needs to be calculated for all three motions and for all ralative wave headings. In this paper, it concludes that RAO and RMS values of the catamaran`s 3 motion are calculated according as the variation of Beafort scales and ship`s speed. The ship motion response of the catamaran based on the RAO and RMS by encounter angles and speed was calculated.

Value of paint transfer and damage examinations in the forensic investigation of boat collisions

Key information sought in a boat collision investigation includes: path and direction of boats, speed, impact angle, impact site, and evasive actions. Boat collision and road traffic collision investigations are similar in application of dynamics, Newton's Laws and kinetic energy, and in examiningdamages, contact evidence, and navigation lights. Unlike road accidents, boat collisions do not leave skidmarks and scars on roads. Road vehicles usually follow clearly marked lanes and directions and come to rest on the ground after collision, unlike boats in open seas. The positions and orientations of boats when investigated can differ markedly from those immediately after engagement. Finding collision debris is more difficult in boat collisions— debris could sink to a murky seabed or disperse and float away from the impact site. Like road vehicles, boats may suffer full impact or partial impact collisions. A displacement hull may cause a slamming (full impact) or a sideswipe, dependingwhether impact occurredator away from the impactedboat's point of rotation. A high-speed boat with a planing hull may ramp up onto a low-profile boat, pushing it down into water. The nature and extent of damages depend on relative sizes, boat design, construction, strength of the structural framework, hard parts, and shell plating materials. 3-D movements such as rotation (yaw), pitching, and rolling are easier and more pronounced on water. Flooding due to the entry of water can critically affect buoyancy, centre of gravity and stability, and may capsize and sink the swamped boat. The analysis of damages on the gunwale, bow, deck, and hull, complemented by identification of paint transfers (chips, smears and rub-off), can reveal contacting surfaces and the directionality of the colliding vessels. Contact damage and induced damage include: holes, dents, imprints, bending, collapse, protrusions, fractures, abrasion, scrapes (scoring), and scuffmarks. Damages in the boat and injuries to occupants may indicate occupant kinematics. If undisturbed, the positions of the throttle, levers, gauges and switches, propellers and rudder provide a critical snapshot at collision. GPS equipment and voyage data recorders provide critical information, but unfortunately are usually found only on larger and more sophisticated vessels or military and law enforcement boats. Toxicological analysis indicates whether the boat operator was under influence of medication, alcohol or drugs. Eyewitness accounts must be carefully evaluated against physical evidence. Case studieswill be used to illustrate the value of damage and paint evidence in boat collision investigations.

Cavitation Erosion of 6061 Aluminum Alloy Coated with TiAlN Thin Film

Cavitation erosion is one of the major problems to be solved in hydraulic machinery. Propellers of high speed boats require a light weight metallic material for their improved high performance. This example tells us that solutions are the developments of way for the improvement of cavitation erosion resistance of light weight metallic material. Coatings on aluminum alloy can enhance the cavitation erosion resistance. This study discussed the cavitation erosion behavior of 6061 aluminum alloy coated with TiAlN thin film. TiAlN coatings were deposited by DC magnetron sputtering method at various nitrogen partial pressures of the coating process using Ti based alloy cathode. The composition of target material was 90wt%Ti, 6wt%Al and 4wt%V. Using the TiAlN coated 6061 aluminum alloy specimen, cavitation erosion tests were carried out to investigate its resistance to the ultrasonic cavitation erosion. Prior to and after the tests, the specimen surfaces were analyzed by using the surface analysis techniques such as micro-hardness test, AFM, SEM, GXRD and scratch test to measure the microstructure of thin film and bonding properties of the applied TiAlN coatings to the substrate material. An improvement in cavitation erosion resistance could be seen with TiAlN coating on 6061 aluminum alloy. Especially, the coating at a nitrogen flow rate of 0.85 sccm or more were very effective in reducing the surface cavitation erosion from the ultrasonic cavitation. In the observation of surface damages during the cavitation erosion tests, the surface cracks in TiAlN were created by the bending of TiAlN coating which were resulted from the plastic deformation of the soft substrate material of aluminum alloy. Once the cracks initiate, drastic delaminations of TiAlN from the substrate material occured. The mean depth erosion rate (MDER) could be evaluated by critical and delamination loads measured by scratch test.

Practical Evaluation of Steady Flow Resulting from a Free-Surface Pressure Patch

The linearized potential flow resulting from a distribution of pressure that advances at constant speed along a straight path at the free surface of calm water, of effectively infinite depth and lateral extent, is considered. A practical method for evaluating the free-surface elevation caused by the moving free-surface pressure patch—which can be used to model steady flows of air-cushion vehicles, high-speed planing boats, surface-effect ships, and some types of hybrid ships—is given. The key ingredient of this method is a highly simplified analytical approximation to the local-flow component in the expression for the Green function associated with the classic Michell-Kelvin linearized free-surface boundary condition.

A simplified 3-D human body–seat interaction model and its applications to the vibration isolation design of high-speed marine craft

High-speed boats experience a harsh vibration environment and human response to this environment is of increasing interest to naval architects who wish to mitigate the effects of vibration and shocks. Based on published experiment data, a three-dimensional human body model with one degree-of-freedom in each direction is established. This model is combined with a simple seat model to construct a simplified 3-D human body–seat interaction model for naval architects to investigate the integrated interaction system when subjected to ship motions. The governing equations describing the dynamics of the human body–seat interactions are formulated and their theoretical solutions are derived. This model, in association with the experimental data recorded on board a high-speed marine craft, is used to study seat isolation system designs. The spring coefficient of the seat isolation system is chosen to avoid any resonance of the human–seat interaction system excited by sea waves. The damping coefficient of the seat isolation system is determined to attenuate motions at the most common excitation frequencies. The designed system is further checked by considering its response to an individual slam impact where the designed system is compared with typical existing seats to illustrate the potential advantages of the proposed approach. In addition the designed seat is compared with existing seats excited by actual boat loads. The study provides a simplified, effective approach for high-speed craft seat design in reducing the shock and vibration level experienced by the crew.

Effect of cathodic polarisation on pitting corrosion of AA5083-H321 aluminium–magnesium alloy in stagnant 3·5% NaCl solution

Aluminium–magnesium alloy AA5083-H321 is a suitable material for construction of high speed boats, submarines, desalination systems etc. Cathodic protection is the proposed method for protection against its pitting corrosion. In this research, cathodic polarisation of this alloy has been studied in stationary 3·5% sodium chloride solution at –0·9, –1, –1·1 and –1·2 V(SCE). The electrochemical behaviour of the surface was investigated with EIS and DC methods. Morphological changes on the surface and cross-section of the samples were studied using scanning electron microscope (SEM) and EDAX analyser. The results showed that the fraction of the surface covered by pits, increases with applying more negative potentials. More alkaline electrolyte inside the pits on the surface tends to show non-ideal behaviour for capacitance inside the oxide layer and for oxide layer/solution interface. This behaviour is intensified with increasing of negative potential by deepening of pits during cathodic polarisation of the alloy. The final result is that cathodic protection of this alloy immersed in stationary conditions is impossible.

Novel approach using EIS to study flow accelerated pitting corrosion of AA5083-H321 aluminum–magnesium alloy in NaCl solution

EIS was utilized as a novel approach to study the role of mechanical and electrochemical processes in flow accelerated pitting corrosion behaviour of AA5083-H321 aluminum–magnesium alloy in 3.5% NaCl solution. This alloy is a suitable material for manufacturing of high speed boats, submarines, desalination systems etc. Impedance spectra were obtained during 24 h of exposure of the samples to the test solution at different rotation speeds. The surface and cross section of the samples were studied by scanning electron microscopy (SEM) and EDAX analysis. The results indicated that increasing the rotation speed causes the depth of pits to increase. By further increasing the rotation speed to 5 and 7 m s−1, the flow condition causes the passive layer inside the pits to breakdown. Simultaneously, the thickness of the passive layer on the areas other than the pits becomes thinner. Shear stresses at 10 m s−1 are so severe that the passive layer on the entire surface breaks down and leads to micropitting corrosion.

Morphological characterization of AA5083‐H321 aluminum alloy corrosion in NaCl solution under hydrodynamic conditions

PurposeThe paper aims to focus on the recognition of corrosion product morphologies of AA5083‐H321 corroding aluminum‐magnesium alloys used in the manufacture of aluminum high speed boats and submarines during flow induced corrosion in seawater.Design/methodology/approachAll experiments were conducted in a 3.5 percent NaCl solution as the simulated marine environment. Hydrodynamic conditions were created by an rotating cylinder electrode (RCE) system. Morphological characterization of the surface was undertaken using SEM and EDAX techniques. Cyclic polarization tests were used to determine the electrochemical behavior of the alloy.FindingsThe results obtained reveal that the pit density on the sample surface increased with increasing the rotation speed. The enhanced flow condition also enhanced the tendency for intermetallic particles, including submicron size Al(Mg,Mn) inclusions, to promote pitting corrosion of the alloy. An interesting result was that crystallographic pitting occurred at rotation speeds greater than 5 m/s.Practical implicationsIn the selection of corrosion control methods for high speed aluminum‐hulled boats, control of erosion corrosion was determined to be more important than any other form of corrosion.Originality/valueProvides information about the contribution of mechanical and electrochemical corrosion phenomena in corrosion of high speed aluminum boats under hydrodynamic conditions. Characterization of new intermetallic particles in aluminum‐magnesium alloys that can promote pitting during flow induced corrosion in marine environments. Provides new information about the origin of crystallographic pitting attack on aluminum.

Seating Type and Cognitive Performance After 3 Hours Travel by High-Speed Boat in Sea States 2-3

Transit in high-speed marine craft subjects occupants to a rough ride as the boat impacts the waves. This induces high levels of physical stress, which may inhibit cognitive performance during military operations and life-saving activities. Land-based research suggests that suspension seats reduce vibration and, therefore, stress. We hypothesized that subjects using suspension seats would demonstrate better cognitive performance, lower perceptions of exertion, fatigue, and sleepiness, and lower salivary concentrations of cortisol than those using fixed seats. Subjects, naval personnel, were divided into fixed (N = 6) and suspension seat (N = 6) groups. Subjects undertook forward and backward number recall and random number generation tests pre- and post-transit (3 h in sea states 2-3). Salivary cortisol concentrations were sampled pre- (1100 h) and post-transit (1700 h) and at the same times on a control day. Post-transit perceptions of exertion, fatigue, and sleepiness were measured subjectively. The suspension seat group demonstrated better performance post-transit than the fixed seat group for forward number recall and showed a significant pre- to post-transit improvement in backward number recall. The suspension seat group reported less fatigue and sleepiness. The suspension seat group had significantly higher salivary cortisol concentrations than the fixed seat group post-transit. Regression analyses found a quadratic correlation between delta cortisol concentrations and delta random number generation scores (R2 = 0.68). Results show that the use of suspension seats during transit in high-speed marine craft may be advantageous with regard to cognitive performance.