High-speed Catamaran Research Articles

Incremental robust predictive control for anti-pitching in catamarans with appendage constraints

To solve the problem that high-speed catamarans have excessive amplitude of vertical motion in rough sea conditions, an anti-pitching method based on incremental robust predictive control of catamarans is proposed, which takes into account the model uncertainty and input rate of appendage requirements. Thus, a high-speed catamaran vertical control model is established with T-foils and flaps serving as anti-pitching appendages, and the hydrodynamic coefficient uncertainties is analyzed, which is converted into a state space model with norm-bounded uncertainty to facilitate control system design; moreover, transforming the norm-bounded uncertainty model of a high-speed catamaran into an incremental model, which can increase the integral action to improve the anti-pitching performance. On this basis, the hybrid H2/H∞ robust predictive control method is proposed to achieve wave disturbance resistance capability and robust stability of the catamaran system, taking the rate of input of the anti-pitching appendages as the input constraints, and the linear matrix inequality (LMI) receding-horizon optimization is used to solve the incremental control input of appendages. Ultimately, the effectiveness of the proposed algorithm is verified by digital simulation.

Modeling a Zero-Emissions Hydrogen-Powered Catamaran Ferry Using AVL Cruise-M Software

This work focuses on the modeling of a zero-emissions, high-speed catamaran ferry employing a full-electric propulsion system. It addresses the global emphasis on full-electric vessels to align with IMO regulations regarding ship emissions and energy efficiency improvement. Using the AVL Cruise-M software, this research verified the implementation of an onboard fuel cell power-generating system integrated with a propulsion plant, aiming to assess its dynamic performance under load variations. The catamaran was 30 m long and 10 m wide with a cruise speed of 20 knots. The power system consisted of a proton-exchange membrane fuel cell (PEM) system, with a nominal power of 1600 kWe, a battery pack with a capacity of 2 kWh, two 777 kW electric motors, and their relative balance of the plant (BoP) subsystems. The simulation results show that the battery effectively supported the PEM during the maneuvering phase, enhancing its overall performance and energy economy.

Ship Performances CFD Analysis of Hydrofoil-Supported High-Speed Catamaran Hull Form

Fast ferries with efficient fuel use are becoming increasingly in demand as fossil fuels become more in short supply and metropolises expand all over the globe in coastal and estuarine environments. These criteria need to be fulfilled by the Hydrofoil Supported Catamaran (HYSUCAT). A catamaran with wings between its demi hulls is known as an HYSUCAT, and it combines the positive traits of both the catamaran (manoeuvrability, big deck area) and the wing in-ground vehicle (excellent lift-to-drag ratio). In this research, a concept design Delft-372 catamaran is refitted with a high Reynolds number foil system to lower its overall resistance. The numerical solution of the Reynolds-averaged Navier–Stokes (RANS) equations employing the k-w SST turbulence model is used to simulate the flow around a high-speed catamaran with a hydrofoil. According to the simulation findings, the hydrofoil-assisted catamaran was determined to be a viable alternative to the current catamaran. This is due to a significant decrease in the overall resistance of the ship, reaching up to 42%, as well as notable improvements in pitch angle, reaching up to 26%.

Reducing wave impacts on high-speed catamarans through deployment of ride control: Analysis of full-scale measurements

Full-scale trials on a 98 m wave piercer catamaran were conducted in the North Sea and North Atlantic region. In order to examine, amongst other things, the effectiveness of the ride control system, the ship was deliberately operated in sea conditions likely to induce a large number of wave impact events. Primary ship motion and structural response parameters, such as angles, rates and accelerations, and strains at various locations were recorded. Slam and minor wave impact events were identified in the data records and analysed to determine the influence of wave headings, vessel speeds, sea states and ride control system activation on their occurrence rates and severity. The Empirical Mode Decomposition technique was used to remove both noise and the rigid body response from the acceleration signals. This was based on prior work by the authors and found to provide more reliable slam identification than traditional methods. A prediction of extreme slam occurrences was modelled using logistic regression. A key outcome of the study was the finding that the activation of ride control significantly reduces the probability of extreme slams occurring.

Research on High-Speed Catamaran Motion Reduction with Semi-Active Control of Flexible Pontoon

A high-speed catamaran with a suspension system and flexible pontoons to reduce motion is proposed, and the vertical motion characteristics of the vessel are investigated. The results demonstrate that altering the stiffness of the flexible pontoon can significantly alter the motion characteristics of a high-speed vessel when subjected to wave excitation. The maximum relative error between the theoretical and experimental values of the vertical dynamic characteristics of the flexible pontoon, considered as a gas spring, is 10.5%. The vertical force exerted by the pontoon exhibits nonlinear behavior in response to compression, yet displays approximately linear behavior within its primary operational range. The design of the Linear Quadratic Regulator controller, utilizing genetic algorithm optimization, avoids the issue of subjectively setting weight coefficients typically found in traditional control systems. This approach achieves the objective of determining the optimal feedback matrix within specified constraints. Simulation results illustrate that the LQR controller developed using genetic algorithm significantly enhance the semi-active suspension performance compared to the passive suspension system. The Root Mean Square value of the main cabin acceleration is reduced by 85.82%, simultaneously reducing the RMS value of the suspension dynamic travel by 85.03% and the RMS value of the pontoon dynamic displacement by 24.42%. These outcomes thoroughly substantiate the effective reduction in vertical motion, effectively attenuating the motion of high-speed vessels under wave excitation.

Experimental study on the drop test on wet deck slamming for a SWATH segment model

Wet deck slamming is a serious issue for high-speed catamarans if the relative vertical motions are higher. In this study, a drop test on wet deck slamming is conducted for a small waterplane area twin hull segment model, and the vertical water-entry model test is performed under different drop heights and speeds. The slamming pressure under the wet deck and the acceleration are measured. The flow field is obtained through particle image velocimetry measurement. A high-speed camera observation during wet deck slamming shows that air is pressed into water, and a water–gas mixture is formed due to the air compressibility effect. The slamming pressure shows an oscillating property with multiple frequency components, which is due to the air cushion effect caused by the volume variation of the water–gas mixture and the acoustic wave oscillation with the air pocket. The effects of the drop height variation and the constant-drop speed on the slamming load are analyzed. The results show that the pressure peak appears during the demihull's bottom slamming and wet deck slamming. The acceleration time record produces two peaks, one for the demihull's bottom slamming and another for the wet deck slamming. In conclusion, the air cushion effect can reduce the wet deck slamming pressure.

INTELLIGENT MONITORING OF A LARGE CATAMARAN FERRY

Wave load cycles, wet-deck slamming events, accelerations and motion comfort are important considerations for high-speed catamarans operating in moderate to large waves. Although developing a hull monitoring system according to classification guidelines for such vessels is broadly acceptable, the data processing requirements for outputs such as rainflow counting, filtering, probability distribution, fatigue damage estimation and warning due to slamming can be as sophisticated to implement as the system components themselves. Advanced analytics such as machine learning and deep learning data pipelines will also create more complexities for such systems, if included. This paper provides an overview of data analytics methods and cloud computing resources for remotely monitoring motions and structural responses of a 111 m high-speed catamaran. To satisfy the data processing requirements, MATLAB Reference Architectures on Amazon Web Services (AWS) were used. Such combination enabled fast parallel computing and advanced feature engineering in a time-efficient manner. A MATLAB Production Server on AWS has been set up for near real-time analytics and execution of functions developed according to the class guidelines. A case study using Long Short‑Term Memory (LSTM) networks for ship speed and Motion Sickness Incidence (MSI) is provided and discussed. Such data architecture provides a flexible and scalable solution, leading to deeper insights through big data processing and machine learning, which supports hull monitoring functions as a service.

An experimental investigation of the effect of ride control systems on the motions response of high-speed catamarans in irregular waves

To ensure high-quality passenger comfort and enhance the operability and performance of high-speed catamarans, reducing the severity of motions and structural loads using Ride Control Systems (RCS) is beneficial. To optimize ride control algorithms, it is essential to have a thorough understanding of the RCS in actual ship sailing conditions. In this paper, a set of towing tank tests was undertaken to study the effectiveness of different control algorithms, including linear and nonlinear versions of the heave control, pitch control, and local control, on motion responses of a 2.5 m scaled model of a 112 m INCAT Tasmania high-speed catamaran in irregular waves. The RCS included a centre bow-fitted T- Foil and two transom-mounted stern tabs. Obtained results were also compared with the scale model responses with passive RCS and with no RCS fitted. Heave and pitch motion responses as well as vertical accelerations of the catamaran were calculated in head seas at a model speed of 2.89 m/s (37 knot full scale), a modal period of 1.5 s (10 s full scale) and two significant wave heights of 60 mm and 90 mm, simulating full scale wave heights of 2.7 m and 4 m, respectively. It was demonstrated that deploying a passive RCS led to modest reductions in the peak motion responses. The most significant reductions in ship motions took place in the nonlinear modes of the heave and pitch control algorithms at a significant wave height of 60 mm (full-scale 2.7 m). In this condition, the nonlinear pitch control mode was demonstrated to be the most effective algorithm since this control mode mitigated the peak pitch RAO by 41% and vertical accelerations by 46%. This was a substantial reduction in ship motions with the RCS at an equivalent full-scale speed of 37 knot at 2.7 m wave height in the random sea condition.

Numerical Analysis of Resistance Characteristics of a Novel High-Speed Quadramaran

Abstract This paper utilised computational fluid dynamics (CFD) technology to calculate the resistance of a novel high-speed quadramaran in calm water using the Navier‒Stokes (N‒S) equation, analysed the total resistance, frictional resistance, and residual resistance characteristics of this novel high-speed quadramaran at different length Froude numbers, and compared them with the results of a conventional high-speed catamaran with the same displacement. The results showed that the total resistance of the quadramaran had a significant hump at the Froude number of 0.6, due to the complexity of the wave interference among the four demihulls, and the hump value was about 1.6 times that of the catamaran. Above the hump speed, the total resistance of the quadramaran decreased with the increase of the Froude number, until reaching the Froude number of 1.06, when the curve became flat, and it showed a maximum resistance reduction of 40% at the Froude number of 1.66 compared with the catamaran, where the total resistance curve was steep. The frictional resistance of the quadramaran increased gradually with the growth of the Froude number, which was basically consistent with the change trend of the catamaran. The residual resistance of the quadramaran first rose and then reduced with the rising Froude number, the curve showed a large hump due to the adverse wave interference, and the hump value was about 1.7 times that of the catamaran. Above the Froude number of 1.06, as the wave interference changed from adverse to favourable, the quadramaran had lower residual resistance than the catamaran. The bow and stern demihulls of the quadramaran were also analysed for their resistance characteristics. The total resistance of the bow demihulls increased gradually with the increase of the Froude number, the curve had a small hump at the Froude number of 0.7, and above the hump speed, the curve was steep. The total resistance of the stern demihulls first increased and then decreased with the growth of the Froude number, the hump value at the Froude number of 0.85 was significant and was about 2 times that of the bow demihulls, and the curve became flat above the Froude number of 1.51.

Slam and wave load response reconstruction in high speed catamarans using transmissibility on full scale sea trials

In-service measurement of slam and wave load responses provide valuable information in the structural design and weight optimisation of high-speed catamarans. However, a limited number of measurements may be possible due to cost, and data may sometimes be lost or noise contaminated. This paper uses the transmissibility concept to reconstruct a set of unknown responses using a different set of known responses. Transmissibility functions and a transmissibility matrix based on linear response theory are derived from less than 12% of available data. The method is applied to full scale sea trials data on a 98 m high speed catamaran HSV 2 Swift, on which strain, acceleration, and angular velocity were measured. Responses are reconstructed for different vessel headings (head, port bow and starboard seas), speeds (15–35 knots), and sea states. The transmissibility matrix is tested on data from unseen sea states. Excellent agreement is achieved, particularly for larger loading events that would be of interest to structural designers. The study demonstrates the possibility to significantly reduce or build redundancy into the instrumentation.

Estimation of torsional and global loads for a wave-piercing high-speed catamaran at full-scale in irregular bow quartering seas using CFD simulation

Catamarans experience more types of global load than monohulls, these include pitch connecting moment, transverse bending moment, and split force. High-speed catamarans are widely used for passenger transportation but as the speed and size increase the severity of loads rises due to slam induced effects. In this study, full-scale CFD simulations are undertaken to investigate the loads acting on a 98m Incat wave-piercer catamaran (Hull 061) HSV2 Swift. Simulations are performed for conditions of a selected sea trial run in bow quartering seas at 20 knots forward speed undertaken by the Naval Surface Warfare Center, Carderock Division (NSWCCD), enabling comparisons and validation. In order to estimate internal global loads at different sections of the vessel, rigid body dynamics is applied based on the hydrodynamic and inertia forces. Those internal loads include longitudinal bending moment (LBM), pitch connecting moment (PCM), torsional moment (TorM), transverse bending moment (TBM), split force and prying moment. The estimated and measured global loads are also compared with design loads limits provided by DNV GL rules, and peak values of pitch and roll accelerations corresponding to each slam load are determined at the same wave height and wave period as the sea trial. The application of CFD to simulate sea trials runs in oblique seas is shown to provide a reliable estimation of slam induced loads for application in early design stages.

Multi-objective Bayesian hull form optimisation for high-speed craft

Simulation-based design plays an important role in many engineering fields enabled by advancements in computing resources, numerical algorithms and computer aided engineering software. In naval architecture, it opens new opportunities for improving hull form designs by reducing calm water resistance and hence minimising required propulsive energy. In this paper, we propose a low dimensional shape morphing tool suitable for designing novel and realistic hull forms for high-speed craft. We provide an efficient simulation-based design framework for optimising hull forms across multiple operating conditions by taking advantage of a multi-objective Bayesian optimisation method. We demonstrate the proposed framework for optimising the hull form of a conceptual high-speed catamaran at two speeds, corresponding to Froude numbers of Fr=0.35 and Fr=0.65. The results highlight the benefit of multi-objective optimisation for high-speed craft along with a nonlinear CFD (computational fluid dynamics) solver to evaluate design solutions. We show the proposed framework can design highly efficient hull forms along the multi-objective Pareto front that have a reduced total resistance when compared to a generic baseline hull by 31%–43% and 5.7%–8.2% at low and high Froude numbers, respectively.

Numerical and Experimental Investigation of the Aero-Hydrodynamic Effect on the Behavior of a High-Speed Catamaran in Calm Water

Numerical and Experimental Investigation of the Aero-Hydrodynamic Effect on the Behavior of a High-Speed Catamaran in Calm Water

Influence of an active T-foil on motions and passenger comfort of a wave-piercing catamaran based on sea trials in oblique seas

In this paper the influence of a Ride-Control System (RCS) on the Response Amplitude Operator (RAO) of a full-scale high-speed catamaran was investigated using sea trials data. A T-foil and stern tabs were installed on a Wave-Piercing Catamaran (Incat Tasmania Hull 061) to improve ship motions and passenger comfort. More than 40 total effective hours of sea trials were conducted by the US Navy in 2004, encountering sea states 4–5 in the Atlantic Ocean near the United Kingdom. The reduction in Motion Sickness Incidence (MSI) was estimated in order to examine the effectiveness of the RCS in improving passenger comfort. By comparing the case of active RCS (T-foil plus stern tabs) with the case of active stern tabs only, it was found that the T-foil plays a vital role in the passenger comfort enhancement. Based on ISO recommended MSI calculation of a 2-h seaway, the percentage reduction in MSI was estimated, and hence the effectiveness of the T-foil deployment, along with the influence of speeds, headings, location on board and encountered wave height were analysed. A notable improvement in passenger comfort was observed in the real world bow quartering sea by deploying the RCS. An MSI reduction of 21% in high speeds (30–35 knots, [Formula: see text] 0.6) was observed, which was almost twice the MSI reduction (11%) in low speeds (15–20 knots, [Formula: see text] 0.3). However, in terms of MSI percentage reduction, the ability of T-foil in vessel motion control in oblique seas was found to be limited compared to the results in head seas.

Fatigue Estimation on a High-Speed Wave Piercing Catamaran During Normal Operations

The estimation of fatigue life in the design process is particularly important for weight-optimised ships such as high-speed aluminium craft, but to date no research has been published on the fatigue accumulation on large wave-piercing catamarans, focusing on long-term operations. This paper assesses the applicability of classification society rules for high-speed catamarans with respect to fatigue design. This was achieved by comparing the long-term distributions of stress, measured on a 111m long wave-piercing catamaran ferry whilst operating in the Canary Islands and during the delivery voyage, with load spectra estimated using a method accepted by the classification society, DNV. The paper also proposes an improved distribution fitment method for fatigue analysis. A detailed method to convert measured stress histories in the time domain into an appropriate stress-spectrum and fitment of Weibull parameters is presented. Results show that the simplified method accepted by the classification society is highly conservative regarding fatigue estimation compared to fatigue results based on measured data. The proposed combined Weibull fitment method substantially improves the accuracy of simplified fatigue analysis methods.

Hydrogen vs. Batteries: Comparative Safety Assessments for a High-Speed Passenger Ferry

Batteries and hydrogen constitute two of the most promising solutions for decarbonising international shipping. This paper presents the comparison between a battery and a proton-exchange membrane hydrogen fuel cell version of a high-speed catamaran ferry with a main focus on safety. The systems required for each version are properly sized and fitted according to the applicable rules, and their impact on the overall design is discussed. Hazards for both designs were identified; frequency and consequence indexes for them were input qualitatively, following Novel Technology Qualification and SOLAS Alternative Designs and Arrangements, while certain risk control options were proposed in order to reduce the risks of the most concerned accidental events. The highest ranked risks were analysed by quantitative risk assessments in PyroSim software. The gas dispersion analysis performed for the hydrogen version indicated that it is crucial for the leakage in the fuel cell room to be stopped within 1 s after being detected to prevent the formation of explosive masses under full pipe rupture of 33 mm diameter, even with 120 air changes per hour. For the battery version, the smoke/fire simulation in the battery room indicated that the firefighting system could achieve a 30% reduction in fire duration, with firedoors closed and ventilation shut, compared to the scenario without a firefighting system.

LOW REYNOLDS NUMBER PERFORMANCE OF A MODEL SCALE T-FOIL

Submerged T-foils are an essential forward component of the ride control systems of high speed ferries. A model scale T-Foil for a 2.5m towing tank model of a 112m INCAT Tasmania high-speed wave-piercer catamaran has been tested for both static and dynamic lift performance. The tests were carried out using a closed-circuit water tunnel to investigate the lift and drag characteristics as well as frequency response of the T-Foil. The model T-Foil operates at a Reynolds number of approximately 105, has an aspect ratio of 3.6 and a planform which is strongly tapered from the inboard to outboard end. All of these factors, as well as strut and pivot interference, influence the steady lift curve slope ( of the model T-foil which was found to be 61% of the value for an ideal aerofoil with elliptic loading. The T-foil dynamic performance was limited primarily by the stepper motor drive system and connection linkage. At the frequency of maximum motion of the 2.5 m catamaran model (about 1.5Hz) the model T-foil has approximately 5% reduction of amplitude and 15 degrees of phase shift relative to the low frequency response. Only very small limitations arose due to the unsteady lift as predicted by the analysis of Theodorsen. It was concluded that the model scale T-foil performed adequately for application to simulation of a ride control system at model scale.

PRESSURE DISTRIBUTION DUE TO STERN TAB DEFLECTION AT MODEL SCALE

Trim tabs form an important part of motion control systems on high-speed watercraft. By altering the pitch angle, significant improvements in propulsion efficiency can be achieved by reducing overall resistance. For a ship in heavy seas, trim tabs can also be used to reduce structural loads by changing the vessel orientation in response to encountered waves. In this study, trials have been conducted in the University of Tasmania hydraulics laboratory using a closed- circuit water tunnel to measure model scale trim tab forces. The model scale system replicates the stern tabs on the full- scale INCAT Tasmania 112 m high-speed wave-piercer catamaran. The model was designed for total lift force measurement and pressure tappings allowed for pressures to be measured at fixed locations on the underside of the hull and tab. This investigation examines the pressures at various flow velocities and tab deflection angles for the case of horizontal vessel trim. A simplified two-dimensional CFD model of the hull and tab has also been analysed using ANSYS CFX software. The results of model tests and CFD indicate that the maximum pressure occurs in the vicinity of the tab hinge and that the pressure distribution is long-tailed in the direction forward of the hinge. This accounts for the location of the resultant lift force, which is found to act forward of the tab hinge.

PERFORMANCE PREDICTION OF A 112M WAVE-PIERCING CATAMARAN

The prediction of power required to propel a high-speed catamaran involves the hydrodynamic interactions between the hull surface and the surrounding fluid that may be difficult to compute numerically. In this study model-scale experiments are used as a basis for comparison to full-scale sea trials data measured on a 112m Incat wave-piercing catamaran to predict the full-scale powering requirements from model-scale testing. By completing water jet shaft power measurements on an Incat vessel during sea trials, comparison of these results was made to model-scale test results to provide good correlation. The work demonstrates that the International Towing Tank Conference (ITTC) extrapolation techniques used provide a good basis for extrapolating the data from model-scale to full-scale to predict the power requirements for the full-scale catamaran vessel operating at high Froude Number with water jet propulsion. This provides a useful tool for future designers and researchers for determining the power requirements of a catamaran vessel through model tests.

FULL-SCALE MOTIONS OF A LARGE HIGH-SPEED CATAMARAN: THE INFLUENCE OF WAVE ENVIRONMENT, SPEED AND RIDE CONTROL SYSTEM

To assess the behaviour of large high-speed catamarans in severe seas, extensive full-scale trials were conducted by the U.S. Navy on an INCAT Tasmania built vessel in the North Sea and North Atlantic region. Systematic testing was done for different speeds, sea states and ride control settings at different headings. Collected data has been used to characterise the ship’s motions and seakeeping performance with respect to wave environment, vessel speed and ride control system. Motion response amplitude operators were derived and compared with results from a two-dimensional Green function time-domain strip theory seakeeping prediction method. An increase of motion response with increasing vessel speed and a decrease with the vessel moving from head to beam seas was found. In higher sea states and headings ahead of beam seas an increasing influence of the centre bow on pitch motion damping was found. Significant motion RAO reduction was also found when the ride control system was active. Its effectiveness increased at higher speeds and contributed to heave and pitch motion RAO reduction. Predicted motion magnitudes with the time domain seakeeping code were consistent with the measured motion responses, but maximum heave was predicted at a rather higher frequency than was evident in the trials.