Displacement Ship Research Articles

A Hybrid Approach to Motion Prediction for Ship Docking—Integration of a Neural Network Model Into the Ship Dynamic Model

While automatic controllers are frequently used during transit operations and low-speed maneuvering of ships, ship operators typically perform docking maneuvers. This task is more or less challenging depending on factors, such as local environment disturbances, the number of nearby vessels, and the speed of the ship as it docks. This article proposes a tool for onboard support that offers position predictions based on an integration of a supervised machine learning (ML) model of the ship into the ship dynamic model. The ML model is applied as a compensator of the unmodeled behavior or inaccuracies from the dynamic model. The dynamic model increases the amount of predetermined knowledge about how the vessel is likely to move and, thus, reduces the black-box factor typically experienced in purely data-driven predictors. A prediction horizon of 30 s ahead of real time during docking operations is examined. History data from the 29-m coastal displacement ship Research Vessel (RV) Gunnerus are applied to validate the approach. Results show that the inclusion of the data-based ML model significantly improves the prediction accuracy.

Development of an Energy Efficient Stern Flap for Improved EEDI of a Typical High speed Displacement Vessel

The surge in maritime trade is leading to large scale deployment of high-speed displacement ships by all nations. Cargo vessels are designed for a voyage in pre-determined routes at consistent speeds. On the other hand, high-speed displacement vessel engines designed with a capability to cater for top speeds are under-utilised during their normal course of operation. This sub-optimal utilisation impacts efficiency and increases emissions. In this study, a most favourable stern flap is designed for reducing the energy efficiency design index of a typical high-speed displacement vessel with a slender hull. CFD simulations and experimental model testing were conducted for 12 different stern flap configurations for determining most favourable flap design in the Froude no of 0.17-0.48. Performance of the most favourable stern flap was established by calculating, energy efficiency design index (EEDI) and fuel consumption based on typical operating profile. NOx, VOC and PM emissions were estimated in with and without flap condition. Studies demonstrated that the stern flap reduced effective power demand, average fuel consumption and emissions by about 8 per cent, which when considered for the ship’s operating life cycle, are significant. The most favourable stern flap reduced EEDI by 3.74 units and 1.98 units as compared to the bare hull condition and the required EEDI respectively, thereby demonstrating that EEDI could be used as an index to indicate stern flap efficiency.

High Incidence of Intraoperative Fractures With a Specific Cemented Stem Following Intracapsular Displaced Hip Fracture

BackgroundTo reduce costs of orthopedic implants, the government decided to standardize implants used across different specialties in a group of hospitals located in the same geographic area. The usual cemented stem used in the context of intracapsular displaced geriatric hip fractures was replaced by another stem. Abnormal intraoperative calcar and trochanteric fractures were noted. The purpose of this study is to determine the incidence of intraoperative periprosthetic fractures following an intracapsular displaced hip fracture treated with this specific cemented stem compared to the previous implant. MethodsThis is a retrospective cohort study comparing an historic cohort of hip fractures treated with the OmniFit EON (Stryker, Kalamazoo, MI) cemented stem with a new cohort of patients who received the Corail (DePuy Synthes, Warsaw, IN) cemented stem. Four orthopedic surgeons reviewed operative reports and postoperative radiographs. ResultsThe treatment group included 348 patients who received the Corail stem. The control group included 77 patients. The 2 groups had similar baseline characteristics (P > .05) except for the presence of dementia. Incidence of intraoperative calcar or greater trochanteric fracture was 15.5% for the Corail group and 2.7% for the control group (P < .05). No patient-related factors or surgeon-related factors were related to a higher number of fractures in the treatment group (P > .05). ConclusionThe Corail cemented stem presents an abnormal number of iatrogenic intraoperative fractures following displaced femoral neck fracture in our geriatric population. No external factor seems to explain this high number of fractures. Implant design should be questioned. Level of EvidenceIII.

Numerical investigation on fast displacement ship hydrodynamics

In last decade, sustained efforts have been made to improve ship energy efficiency, to reduce fuel consumption and carbon dioxide emissions by means of optimizing the hull forms and propulsion system. The aim of the present paper is to search for solutions to improve the fast-displacement hull forms of passenger ships that navigate on the Danube river and the Black Sea coast, leading to high energy efficiency, reduced emissions and minimised shore-side effects. To investigate the flow around a 31 m fast-displacement monohull passenger ship, a series of 5 numerical simulations for a range of speeds between 4.5 and 12.5 m/s were performed in order to estimate the forces acting on the ship, but also to analyse the hydrodynamic parameters of the flow. Based on the first series of calculation, several solutions to improve the hydrodynamic performance of the hull are considered. The two most effective solutions found have been the trim edge and the interceptor. Different configurations and angles have been systematically investigated in order to find the most efficient geometrical parameters. Finally, the hull with trim wedge leads to a reduction of the power consumption by 2.4 to 5.5% and the interceptor by 2.8 to 8.8%, for speeds higher than 8.4 m/s. For speeds lower than 8.4 m/s the power consumption is higher than bare hull. Moreover, the solutions proposed are easy to implement for new built ships, but also for ships in operation.

On the application of empiric methods for prediction of ship manoeuvring properties and associated uncertainties

In relation to development of ship manoeuvrability standards, in particular those accounting for adverse weather conditions there is a need for relatively simple but reliable prediction methods. A number of popular published empiric methods for predicting manoeuvring properties of surface displacement ships have been briefly described and analysed. An extension of the Pershitz method to low speed manoeuvres has been implemented. Sixteen empiric methods and hybridizing combinations of hull and rudder sub-models were tested numerically through simulation of standard manoeuvres for the KVLCC2 benchmark ship. The obtained numerical results have demonstrated that very few methods or combinations give reasonably accurate results for this vessel and some simulated responses even look unacceptable. The primary conclusion drawn from the study is that in general application of universal empiric methods can lead to unacceptably large prediction uncertainties and such methods must be used with great care and preferably tuned on prototype ships.

Model Test Study on Parameter Optimization of Stern Flaps of Series Displacement Ships

The design of stern flaps generally pursues the resistance reduction of ships at high speed. Moreover, for some surface warships, the parameter selection of stern flap needs is the key consideration due to the wide range of ship speed from cruising to design speed. In this paper, model ship experiments for a series displacement ship are conducted to optimise the configuration of stern flaps. From the model ship resistance and self-propelled model ship experiments, the stern flap impacts to the lowest effective Froude number, resistance of ship, self-propelled status and voyage status are studied. After the analysis of the results and optimizing of the design, the ship with stern flaps has lower resistance and could save 3% and 5% of energy at cruising and design speed respectively. The authors hope the results of this paper could provide help and reference to the design of ship stern flaps in the future.

Locking Plate Fixation with Multiple Telescoping Sliding Screws for Femoral Neck Fractures

Non-displaced femoral neck fractures are mostly treated with internal fixation, while in dis-placed fractures this surgical option is under debate and the benefits are still not clear. The purpose of this study was to identify the factors that affect the treatment of non-displaced and displaced hip fractures using ahead-preserving plate. From August 2011 to May 2015, we reviewed eighty-two adult patients who had sustained undisplaced and displaced intracapsular femoral neck fracture treated with a locking plate system with telescoping sliding screws. Fracture reduction, healing rate and implant related complications were primary objectives. Other complications (e.g. avascular necrosis, nonunion, hematoma, infection) and revision surgery were recorded as well. According to the Garden classification system, atotal of 51.2% fractures were classified as non-displaced (type 1 and 2) and 48.8% were displaced fractures (type 3 and 4). Anatomic reduction was achieved in 58.5% and valgus in 41.5% of patients and it did not influence the healing. Varus reduction was not observed in any case. The total average complication rate was 18.1%, where screw cutout was the most frequent complication (8.5%). The timing of surgery did not affect the healing of femoral neck fractures. Age over 60 years combined with a displaced fracture was associated with impaired healing potential and ahigher complication rate. Revision surgery was performed in 17.1% of patients, mainly those with displaced fractures. 1. The use of a locking plate system with telescoping sliding screws was associated with lower rates of postoperative complications in undisplaced, but also in displaced femoral neck fractures in patients younger 60 years. 2. Patients over 60 years with displaced fractures were more likely to have healing problems and implant failure.

The head shaft angle is associated with hip displacement in children at GMFCS levels III-V - a population based study

BackgroundAn increased Head Shaft Angle (HSA) has been reported as a risk factor for hip displacement in children with cerebral palsy (CP) but opinions differ in the literature. The purpose of this study was to re-evaluate the relationship between HSA and hip displacement in a different population of children with CP.MethodsThe Cerebral Palsy Integrated Pathway Scotland surveillance programme includes 95% of all children with CP in Scotland. The pelvic radiographs from 640 children in GMFCS levels III-V were chosen. The most displaced hip was analysed and the radiographs used were those taken at the child’s first registration in the database to avoid the potential effects of surveillance on subsequent hip centration. A logistic regression model was used with hip displacement (migration percentage [MP] ≥40%) as outcome and HSA, GMFCS, age and sex as covariates.ResultsThe MP was ≥40% in 118 hips with a mean HSA of 164° (range 121–180°) and < 40% in 522 hips with a mean HSA of 160° (range 111–180°). The logistic regression analysis showed no significant influence of age and sex on MP in this population but a high GMFCS level was strongly associated with hip displacement. An increased HSA was also associated with hip displacement, a 10° difference in HSA for children adjusted for age, sex, and GMFCS gave an odds ratio of 1.26 for hip displacement equal or above 40% (p = 0.009) and hips with HSA above 164.5 degrees had an odds ratio of 1.96 compared with hips with HSA below 164.5 degrees (p = 0.002).ConclusionThese findings confirm that HSA is associated with hip displacement in children in GMFCS levels III-V.

Applying the Anticipatory Failure Determination at a Very Early Stage of a System’S Development: Overview and Case Study

Abstract Anticipatory Failure Determination (AFD) is a tool used in the TRIZ (Theory of Inventive Problem Solving) methodology. This article introduces its concept and describes the process of AFD in different versions of the method. The article presents the application of the AFD method at a very early state of a system’s development, i.e. its concept formulation stage, which corresponds to a technology readiness level (TRL) equal to 2. The system under analysis is a set of devices used to reduce displacement ship hull resistance. The system was modelled using functional analysis. An analysis of system resources was then carried out. Possible direct, indirect, and accident-related failures were identified. A multi-criteria analysis of the causes of system failures was conducted from which the top 10 potential failures were selected. Observations were made on the applicability of AFD in respect to systems not yet implemented.

An investigation on HOBEM in evaluating ship wave of high speed displacement ship

A practical numerical tool is developed to evaluate ship waves of high speed displacement ships on the basis of potential flow theory, in which high order boundary element method (HOBEM) based on biquadratic shape functions is applied to solve the boundary value problem. Since the sinkage and trim of ship at high speeds are notable, influences of ship attitude on wave drag are investigated and three kinds of models are used to evaluate them. To make the numerical approach highly efficient, an incomplete LU factorization preconditioner is adopted and incorporated with the restarted generalized minimal residual method GMRES (m) to solve the boundary integral equation. A corresponding Fortran code is developed and applied to evaluate ship waves of the Wigley hull and 4a model, a transom stern ship. Computations are performed for both monohulls and catamarans over a wide range of Froude numbers (Fr = 0.10 - 1.00) . Numerical issues including mesh convergence and computational efficiency are investigated at first. Computed results of the wave drag, sinkage and trim show generally good agreement with experimental data. Reasonable wave patterns are obtained and physical phenomena that wake angle φmax, where the largest waves occur, would become narrow at high speeds is also captured by the present computations. Numerical results indicate the proposed method would be accurate and efficient to evaluate resistance for hull design of high speed displacement ship.

Ankle Dorsiflexion displacement is associated with hip and knee kinematics in females following anterior cruciate ligament reconstruction

ABSTRACTThe purpose of this study was to examine associations between ankle dorsiflexion (ankle-DF) displacement and knee and hip kinematics and kinetics during a jump-landing task in females following anterior cruciate ligament reconstruction (ACLR). Females (n = 23) with a history of unilateral ACLR (≥ 6-months post-ACLR) underwent a three-dimensional lower extremity biomechanical evaluation. Pearson Product Moment (r) correlations assessed associations between ankle-DF displacement and knee and hip kinematic and kinetic variables. On the involved-limb, individuals with lesser ankle-DF displacement demonstrated greater knee abduction displacement during the loading phase (r = -0.645, p = 0.001). On the uninvolved-limb, individuals with greater ankle-DF displacement demonstrated greater hip flexion displacement (r = 0.599, p = 0.003) and knee flexion displacement (r = -0.545, p = 0.007). There were no other significant associations between ankle-DF displacement and ankle, knee, or hip biomechanical variables on either limb (p > 0.05). Our findings demonstrate that reduced ankle-DF motion appears to share a different relationship between the involved- and uninvolved-limbs in females post-ACLR.

Performance of high-speed planing hulls accelerating from rest under the action of a surface piercing propeller and an outboard engine

In this paper, a mathematical model for performance prediction of a high-speed planing hull in forward acceleration motion has been developed. Three degrees of freedom have been considered for solving the problem. Utilizing previous empirical equations of displacement ships, motion of the vessel in displacement regime has been simulated. In order to model pre-planing and planing regimes, 2D + T theory has been used. Equations for prediction of performance of a surface piercing propeller (SPP) and an engine have been presented. Validity of the proposed method has been assessed by comparing its results against previous experimental data, and good agreement between experimental and mathematical results in prediction of performance of planing hulls has been seen. Motion of the vessel has been simulated under the action of a semi-submersible propeller and an outboard engine. Behavior of the vessel has been analyzed and the relationships between forces and moments with displacements, as well as pitch and heave rate have been described. It has shown how hydrodynamic force contributes as the beam Froude Number goes beyond 1.0, which results in increment of vertical position of the vessel. Also, it has been observed that, net pitching moment decreases from a positive value to a negative value in displacement regime, and then, by the appearance of hydrodynamic moment, net moment approaches zero and finally vanishes. The results also have indicated that a sudden jump occurs in thrust force vs. time curve, which is caused at critical advanced ratio. Beside this, it has been seen that, when propeller comes of water, a sharp increase in advanced ratio happens. Effects of surge motion have also been studied, which show that, maximum trim angle occurs at a larger beam Froude Number. It has also been observed that sinkage is larger in the presence of surge motion in pre-planing regime as extra hydrodynamic forces due to damping and added mass contributions in vertical direction occur. Finally, it has been observed that surge is accompanied with larger resistance which is resulted due to contribution of heave and pitch motions in surge direction, especially in pre-planing and planing regimes.

Fate of stable hips after prophylactic femoral varization osteotomy in patients with cerebral palsy

BackgroundConcurrent prophylactic femoral varization osteotomy (FVO) for stable hips has been performed in patients with cerebral palsy (CP) undergoing hip reconstructive surgery for the contralateral displaced hip. However, there is currently a lack of studies investigating the outcome after the prophylactic FVO in stable hip. This study investigated the outcomes after FVO in stable hips with CP and influencing factors. In addition, this study compared the outcomes with those after hip reconstructive surgery in the contralateral displaced hip.MethodsThis study included 119 CP patients with 224 hips (80 stable, 144 displaced) undergoing hip reconstructive surgery including FVO. Migration percentage (MP), neck-shaft angle (NSA), and head-shaft angle (HSA) were measured through preoperative and follow-up hip radiographs. All hips were divided into the stable (MP ≤ 33%) and displaced hip groups (MP > 33%) according to the preoperative radiographs, and the annual changes in the radiographic indices after FVO were analyzed.ResultsIn stable hip group, MP did not significantly increase over time (p = 0.057) after prophylactic FVO. In displaced hip group, MP significantly increased over time (1.6%/year, p < 0.001). MP was significantly decreased in cases of concomitant Dega pelvic osteotomy in both stable (14.5%, p < 0.001) and displaced hips (18.9%, p < 0.001).ConclusionsProphylactic FVO in the stable hip in patients with CP showed good surgical outcomes, without a risk of hip displacement throughout the follow-up duration, while hip reconstructive surgery in the displaced hip was associated with a risk of increased hip displacement.

Application of potential flow methods to fast displacement ships at transcritical speeds in shallow water

Computer codes implementing three different numerical methods for the prediction of ship squat at transcritical speeds in shallow open-water are tested. SlenderFlow is a potential flow code specifically for ships in very shallow water, based on partially dispersive slender body theory. Flotilla is a potential flow code based on fully dispersive thin-ship theory. Rapid is a general nonlinear free-surface panel code. Code predictions of transcritical sinkage, trim and resistance in laterally unrestricted water were compared to the experimental results of Graff (1964) for two Taylor series hulls in a finite-width towing tank. Once tank width effects were accounted for, each of the three codes was found to give good predictions within the valid range of the underlying theory. A simple method for estimating transcritical wave resistance from trim is presented.

Turning characteristics of waterjet propelled planing boat at semi-planing speeds

It is necessary to investigate the turning characteristics of a waterjet propelled planing boat at the design stage for its safe operations. In this research, two kinds of model tests were carried out for the analyses of turning abilities of a designed planing boat. Towing tank tests were performed for a 1/6.5-scaled bare hull model to confirm the resistance performance according to its forward speeds. Flow patterns around the hull were investigated at semi-planing speeds. And turning tests were carried out for a 1/2.3-scaled free-running model at semi-planing speeds. When the heels during steady turns are less than about 5 degrees, running trims of the free-running model boat are similar to those of the bare hull model boat straight-towed at the same speeds. Speed reduction ratios and advances over tactical diameters of waterjet propelled planing boats show similar tendencies in comparison to those of displacement ships. When the waterjet propelled planing boat turns rapidly with high impeller rpm, ‘side-slip’ can be occurred. In that case, tactical diameter becomes so small and steady turn speed is relatively high. Waterjet propelled planing boat shows large inward roll angles at the beginning of turn, and inward heels increase with increasing steady turn speeds.

An Extended Verification and Validation Study of CFD Simulations for Planing Hulls

In the context of marine application of computational fluid dynamic (CFD), it is well known that the numerical simulations of planing craft are significantly less reliable than that of displacement ships. For this reason, it is important to perform a comprehensive approach to the verification and validation (V&V) methodology and procedures for simulating CFD planing craft. In the first part of this paper, an assessment of the accuracy and effectiveness of different simulation setups and techniques for planing craft is performed. In the second part, the results of the V&V study are reported for three different hull models at four Froude numbers (Fr). The Unsteady Reynolds-Averaged Navier-Stokes code results were validated using benchmark experimental data obtained for three hull models characterized by systematic variation of the length to beam ratio. Grid independence, iteration, and time-step convergence analysis for response variables (resistance coefficients, wetted surfaces, and dynamic trim angles) were conducted using the main error and uncertainty estimation methods available in the literature. The same procedures were followed for the profiles of the wave patterns. The results showed that there was improved reliability of the numerical simulation of the planing craft in terms of the errors and uncertainties, related to the predictions of resistance, running attitude, and wave pattern. The results of the V&V study highlighted the fact that modeling of the planing craft is a critical point to improve the reliability of the numerical simulation.

An Extended Verification and Validation Study of CFD Simulations for Planing Hulls

In the context of marine application of computational fluid dynamic (CFD), it is well known that the numerical simulations of planing craft are significantly less reliable than that of displacement ships. For this reason, it is important to perform a comprehensive approach to the verification and validation (V&amp;V) methodology and procedures for simulating CFD planing craft. In the first part of this paper, an assessment of the accuracy and effectiveness of different simulation setups and techniques for planing craft is performed. In the second part, the results of the V&amp;V study are reported for three different hull models at four Froude numbers (Fr). The Unsteady Reynolds-Averaged Navier-Stokes code results were validated using benchmark experimental data obtained for three hull models characterized by systematic variation of the length to beam ratio. Grid independence, iteration, and time-step convergence analysis for response variables (resistance coefficients, wetted surfaces, and dynamic trim angles) were conducted using the main error and uncertainty estimation methods available in the literature. The same procedures were followed for the profiles of the wave patterns. The results showed that there was improved reliability of the numerical simulation of the planing craft in terms of the errors and uncertainties, related to the predictions of resistance, running attitude, and wave pattern. The results of the V&amp;V study highlighted the fact that modeling of the planing

Wash waves generated by high speed displacement ships

It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.

정상인에서 유도된 첨족에 따른 신체 보행의 특성

The purposes of this study was to investigate the physical compensation for gait on induced equinus in normal subjects. Ten subjects were participate in the experiment (age: 23.8±2.8 yrs, height: 177.3±4.3 cm, weight: 70.8±4.6 kg). The study method adopted 3D analysis with six cameras and ground reaction force with two force-plate. Induced equinus were classify as gait pattern on unilateral and bilateral equinus. The results were as follows; In displacement of COM, medio-lateral and anterior-posterior COM were no significant, but in vertical COM, unilateral equinus gait was higher than bilateral equinus gait. In displacement hip joint, left hip joint was more extended in FC1 and FC2 during unilateral equinus gait. In displacement knee joint, left knee joint was more extended in FC2, right knee joint was more extended in all event during unilateral equinus gait. In trunk tilt, unilateral equinus gait was more forward tilt in TO1 and TO2. ROM of each joint was no significant. In Displacement of pelvic tilt angle, X axis of unilateral equinus gait was more increase than bilateral equinus gait at FC2, TO2 and MS2. Y axis of unilateral equinus gait was more increase than bilateral equinus gait at MS1, FC2 and MS2. Z axis was no significant in both equinus gait. In GRF, right Fx and Fy were no significant in both equinus gait, Fz was more bigger vertical force in bilateral equinus gait. Left Fx was more bigger internal force in unilateral equinus gait, Fy and Fz were no significant in both equinus gait.

A numerical study of the second-order wave excitation of ship springing by a higher-order boundary element method

ABSTRACT This paper presents some of the efforts by the authors towards numerical prediction of springing of ships. A time-domain Higher Order Boundary Element Method (HOBEM) based on cubic shape function is first presented to solve a complete second-order problem in terms of wave steepness and ship motions in a consistent manner. In order to avoid high order derivatives on the body surfaces, e.g. mj-terms, a new formulation of the Boundary Value Problem in a body-fixed coordinate system has been proposed instead of traditional formulation in inertial coordinate system. The local steady flow effects on the unsteady waves are taken into account. Double-body flow is used as the basis flow which is an appropriate approximation for ships with moderate forward speed. This numerical model was used to estimate the complete second order wave excitation of springing of a displacement ship at constant forward speeds.