Full-scale Ship Research Articles

Passenger evacuation simulation considering the heeling angle change during sinking

In order to simulate the evacuation simulation of a ship during a sinking, the slope angle change of the ship must be reflected during the simulation. In this study, the passenger evacuation simulation is implemented by continuously applying the heeling angle change during sinking. To reflect crowd behavior, the human density and the congestion algorithm were developed in this research and the walking speed experiment in the special situation occurring in the inclined ship was conducted. Evacuation simulation was carried out by applying the experimental results and the change of the walking speed according to the heeling angle of the ship. In order to verify the evacuation simulation, test items suggested by International Maritime Organization (IMO) and SAFEGUARD Validation Data Set conducted on a large Ro-PAX ferry (SGVDS 1) which performed real evacuation trial in full-scale ships were performed and the results of simulation were analyzed. Based on hypothetical scenario of when a normal evacuation command is delivered to the passengers of MV SEWOL in time, we predicted and analyzed the evacuation process and the number of casualties.

CFD validation and grid sensitivity studies of full scale ship self propulsion

A comparison between sea trial measurements and full–scale CFD results is presented for two self–propelled ships. Two ships considered in the present study are: a general cargo carrier at Froude number Fn=0.182 and a car carrier at Fn=0.254. For the general cargo carrier, the propeller rotation rate is fixed and the achieved speed and trim are compared to sea trials, while for the car carrier, the propeller rotation rate is adjusted to achieve the 80% MCR. In addition, three grids are used for each ship in order to assess the grid refinement sensitivity. All simulations are performed using the Naval Hydro pack based on foam-extend, a community driven fork of the OpenFOAM software. The results demonstrate the possibility of using high–fidelity numerical methods to directly calculate ship scale flow characteristics, including the effects of free surface, non–linearity, turbulence and the interaction between propeller, hull and the flow field.

Predicting underwater radiated noise of a full scale ship with model testing and numerical methods

Full scale measurement, model testing and a hybrid CFD method were used to characterize the Underwater Radiated Noise (URN) of a ship at design speed. The CFD method consists of a multiphase Delayed Detached Eddy Simulation and the Ffowcs-Williams Hawkings acoustic analogy. The paper discusses the correlation of the noise spectra with the observed cavitation behavior and compares the measured full scale data with those predicted by the model testing and the CFD method. The comparison shows that the sheet cavity and Tip Vortex Cavitation (TVC) predicted by the model testing are in reasonably good agreement with the full scale observations. The pressure pulses are somewhat higher than the full-scale data. Overall, the predicted URN has a good correlation with the noise spectra obtained from the sea trial.The CFD method shows the potential to resolve turbulence eddy structures in the wake. It captures the dynamic development of sheet cavitation and the collapse and rebound of TVC as observed in the model test and the sea trial, but under-predicts the extent of TVC. The pressure pulses and tonal noise are in close agreement with the respective measured data for the first five orders of blade passing frequency. The method underestimates the broadband noise level in the frequency range 50–112 Hz where the TVC is expected to have an important contribution. The maximum under-prediction in this range is about 28 dB at 72 Hz. At frequencies above 200 Hz, the broadband noise becomes more and more under-predicted with increasing frequency.

Assessment of hydrodynamic characteristics of a full-scale ship at different draughts

Numerical and experimental assessment of resistance and propulsion characteristics for a handymax bulk carrier at full-scale is carried out within this paper. Reynolds Averaged Navier-Stokes equations and Volume of Fluid Method are utilized in numerical simulations of resistance, open water and self-propulsion tests for three load conditions at two speeds. Verification of the obtained numerical results is performed and numerical uncertainty is calculated. Also, comparison of four turbulence models for resistance, open water and self-propulsion tests is made. An extensive towing tank experiments are performed in Brodarski institute and the obtained results are extrapolated to full-scale values using five extrapolation methods. Furthermore, numerical results are validated by comparison with extrapolated values of total resistance, open water and propulsion characteristics. A detailed analysis of the results is provided, and advantages and disadvantages of extrapolation methods are highlighted. Also, the importance of utilizing CFD based on viscous flow in the improvement of reliability of extrapolation methods and in reducing the incremental resistance coefficient is shown. Finally, the advantages of utilizing CFD based on viscous flow for assessment of ship hydrodynamic characteristics at full-scale are presented.

Model Ship Control and Estimation of Full-scale Propeller Torque in Wind and Waves

This paper presents free-running model ship test data estimating full-scale propeller torque fluctuating in wind and waves. The model ship control using the auxiliary thruster ensures the similarity of model ship motion to full scale that leads the similar propeller situation The wind load simulator controls six duct fans on the model ship for simulating the wind loads. The estimation algorithm converts the measured model propeller torque to full scale assuming no scale effect on the wave component in the effective inflow velocity to propeller. The analysis reveals the differences of the fluctuating propeller torque between model and full-scale ships.

제501 오룡호 침몰사고 원인분석을 위한 침수⋅침몰 시뮬레이션 연구

Deep-sea fishing vessel No. 501 Oryong was fully flooded through its openings and sunk to the bottom of the sea due to the very rough sea weather on the way of evasion after a fishing operation in the Bearing Sea. As a result, many crew members died and/or were missing. In this study, a full-scale ship flooding⋅sinking simulation was conducted, and the sinking process was analyzed for the precise and scientific investigation of the sinking accident using highly advanced Modeling & Simulation (M&S) system of Fluid-Structure Interaction (FSI) analysis technique. To objectively secure the weather and sea states during the sinking accident in the Bering Sea, time-based wind and wave simulation at the region of the sinking accident was carried out and analyzed, and the weather and sea states were realized by simulating the irregular strong wave and wind spectrums. Simulation scenarios were developed and full-scale ship and fluid (air & seawater) modeling was performed for the flooding⋅sinking simulation, by investigating the hull form, structural arrangement & weight distribution, and exterior inflow openings and interior flooding paths through its drawings, and by estimating the main tank capacities and their loading status. It was confirmed that the flooding and sinking accident was slightly different from a general capsize and sinking accident according to the simple loss of stability.

Performance prediction of full-scale ship and analysis by means of on-board monitoring. Part\xa02: Validation of full-scale performance predictions in actual seas

In this paper, full-scale ship performance in actual seas, which was predicted by the method described in part 1 of the present study, was validated through a comparison with onboard monitored data. The full-scale performance of a large bulk carrier was monitored by a dedicated on-board monitoring system, and the monitored data were thoroughly analyzed and reduced to the form of performance parameters applicable to the comparison with the prediction results. The full-scale ship performance predictions evaluated in the form of shaft power increase agreed quite well with the analyzed monitored data obtained under actual operating conditions. Thus, the effectiveness of the performance prediction method presented in this study was fully confirmed.

Prediction of ship power and speed performance based on RANS method

This paper adopts virtual tank experimental technology to study ship rapidity performance. Based on RANS method, a new method is put forward to predict the speed and power performance of full scale ship. The open water performance of propeller model, the resistance performance of ship model and the self-propulsion performance of ship model are numerically calculated. Through the analysis of rapidity numerical results of fishing ship and the change law of wake flow field, some conclusions can be drawn. The numerical prediction accuracy of propeller open water efficiency has a direct influence on total thrust efficiency. The interference between hull, propeller and rudder leads to the formation of a lower pressure zone on stern hull surface and rudder surface. The axial velocity and radial velocity are affected by the interference between the flow of hull stern and propeller, the absolute value of axial velocity on blade leaf is smaller than that on blade back, and the radial velocity induces vortices on the blade tip of the propeller. The increase of propeller rotation speed nearly has no effect on the free surface wave pattern. The prediction results deviations of full scale ship speed and propeller rotation speed between RANS method and EFD method are 0.04 kn and 0.4 r/min, and therefore they are negligible. The proposed method can provide reference for engineering application.

공기층 음향반사 현상을 이용한 프로펠러 캐비테이션 유발 가진력 저감

Single nozzle arrangement in the full-scale ship reveals that a significant reduction of propeller cavitation induced pressure amplitude is possible at the outside of air-bubble layer, where the isolation effect of the air is not involved. Resulting hull-vibration reduction is approximately 75 %. Instead of excessive consumption of air, that is, considerably small amount is necessary for a reduction of propeller excitation, which can make the constitution of relevant system simple. Hence the purpose of this study is to provide a physical proof for such a beneficial phenomenon. By approximating the solution of acoustic reflection from a bubble, we could find that phase-reversal reflection provoking a destructive interference is the main reasoning for a pressure reduction outside the layer.

Numerical prediction analysis of the fluctuating pressure and rudder force of full-scale hull-propeller-rudder system

In order to analyze the fluctuating pressure and rudder force characteristics of a full-scale hull-propeller-rudder system, a hybrid structured/unstructured grid was combined with the Reynolds-averaged Navier-Stokes (RANS) and volume of fluid (VOF) methods to perform a numerical prediction of model and full-scale performance for the Kriso Container Ship (KCS) case. A numerical simulation for the self-propulsion test of a full-scale ship was first performed to obtain the propeller velocity under the self-propulsion point, the results of which indicated a notable wake fraction and velocity scale effect at the self-propulsion point. Transient two-phase flow calculations were then performed for the model and full-scale KCS hull-propeller-rudder systems. According to the monitoring data, the hull surface fluctuating pressure and rudder force fluctuated periodically over time and the full-scale fluctuating pressure exhibited a higher time-average value as compared to the model-scale pressure. The frequency spectrum curves were also generated by the fast Fourier transform algorithm. The analysis of the frequency spectrum data indicated that the peaks of the fluctuating pressure and rudder force reached their respective maximums at the blade passing frequency (BPF), after which the peak gradually decreased and the full-scale ship reduced more quickly. Furthermore, fluctuating amplitude of full-scale ship was bigger than model-scale.

A universal prototype design framework of the stem and stern contours of hull surface and the self-adaptive solving strategy

Ship geometry reconstruction technology is a key technique and research focus in the ship design. And the optimization algorithm used in the ship design is always a hot research area. To establish the control points’ distribution model database of characteristic curves, based on the NURBS control mesh of the hull surface, an approach to approximate the initial stem and stern contours of hull form modeling using the concept of parametric generation is proposed. The optimization model is constructed with the homogeneous coordinate component of the fitted contour’s control points as the design variables. The objective function is set to minimize the maximum relative difference among the longitudinal coordinates of the approximated contour and the original ones corresponding to the same drafts. The appropriate constraints are set according to the characteristics of the contours and the geometrical characteristic of NURBS. Considering a number of empirical knowledge existing in the process of ship design, and the conventional quantum-behaved particle swarm optimization (QPSO) algorithm depending upon good initial population, the immune quantum-behaved particle swarm optimization (IQPSO) is specifically designed and used to solve this complex nonlinear constrained optimization problem through the immune operator of the immune genetic algorithm combining with the QPSO algorithm. Meanwhile, the self-adaptive constraint evolution strategy is proposed to improve the IQPSO algorithm. The simulation results of the full-scale ship’s contours demonstrate the feasibility and effectiveness of the proposed algorithm and method.

Hull form optimisation in waves based on CFD technique

ABSTRACTThe seakeeping behavior of a ship in waves is different from its behavior in calm water. The resistance and seakeeping performance of a ship must be considered in the early-stage design. Therefore, this paper proposes a hull form optimization framework aiming to achieve the minimum total resistance in waves using a computational fluid dynamics (CFD) technique. A sinusoidal wave is adopted to establish the numerical wave tank and the overset mesh technique is used to facilitate the motions of the ships in question. The total resistance of the hull in waves is regarded as the objective function which is calculated using the Reynolds averaged Navier–Stokes (RANS) method. The arbitrary shape deformation (ASD) technique is used to change the geometry. Under displacement and design variables, a hybrid algorithm is developed to evaluate the objective function combining the optimal Latin hypercube design (Opt LHD) and the non-linear programming by quadratic Lagrangian (NLPQL) algorithm. Finally, two examples of hull form optimization are presented and discussed for David Taylor Model Basin (DTMB) model 5512 and WIGLEY III cases. The results show the effectiveness of the optimization framework developed in the present study, which can lay the foundation for further optimization of full-scale ships.

Powering performance analysis of full-scale ships under environmental disturbances

The fuel efficiency of marine vessels can be increased through operational considerations such as improved cargo arrangements and weather routing. The first step toward this goal is to analyze how the ship’s powering performance changes under different operational settings and weather conditions. Existing analytical and empirical methods are not sufficiently satisfactory in accurately predicting the powering performance of full-scale ships. In this study, we suggest the use of machine learning techniques to estimate the ship’s powering performance by constructing a regression model that can predict the ship speed and engine power under various weather conditions.

Model- and Full-Scale RANS Simulations for a Drift Tanker

The flow around a full scale (FS) ship can be simulated by mean s of Reynolds Averaged Naiver Stokes (RANS) method, which provides a way to obtain more knowledge about scale effect s on ship hydrodynamics. In this work, the viscous flow around a static drift tanker in full scale is simulated by using the RANS solver based on the open source platform OpenFOAM. The 𝑘−𝜔 SST model is employed to approximate the eddy viscosity. To reduce computational time, wall function approach is applied for the FS simulation. The flow around the ship in model scale is simulated as well, but without using any wall function, i.e. using Low Reynolds number mode. In order to verify the computations, de-tailed studies on the computational grid including investigation of the sensitivity of computed forces to 𝑦+ (dimension-less distance of first grid point to wall) and grid dependency study are carried out. The computed forces are compared with available measured data The scale effect s are analysed and discussed by comparisons.

Practical evaluation of sinkage and trim effects on the drag of a common generic freely floating monohull ship

A practical method to account for the influence of sinkage and trim on the drag of a freely floating (free to sink and trim) common monohull ship at a Froude number F≤0.45 is considered. The sinkage and the trim are estimated via two alternative simple methods, considered previously. The drag is also estimated in a simple way, based on the classical Froude decomposition into viscous and wave components. Specifically, well-known semiempirical expressions for the friction drag, the viscous pressure drag and the drag due to hull roughness are used, and the wave drag is evaluated via a practical linear potential flow method. This simple approach can be used for ship models as well as full-scale ships with smooth or rough hull surfaces, and is well suited for early ship design and optimization. The method considered here to determine the sinkage and the trim, and their influence on the drag, yields theoretical predictions of the drag of the Wigley, S60 and DTMB5415 hulls that are much closer to experimental measurements than the corresponding predictions for the hull surfaces of the ships in equilibrium position at rest. These numerical results suggest that sinkage and trim effects, significant at Froude numbers 0.25<F, on the drag of a typical freely floating monohull ship can be realistically accounted for in a practical manner that only requires simple potential flow computations without iterative computations for a sequence of hull positions.

Discussion About Conducting the Full-scale Ship Structural Collapse Test in China

In order to study the structural failure mechanism and mode of the warship and improve the ultimate strength, this paper analyzes the contents and results of the tests carried out by western developed countries such as America and Europe. Taking account of the design and building of warship and navy development, it talks about the necessities and feasibilities to do the full-scale warship collapse test by us objectively and concludes that the test is badly needed. It puts forward the method and suggests that the full-scale ship structural collapse test should be carried out with two self-designed decommissioned warships of similar structure. With the test data, the real ultimate bearing capacity and the safety coefficient of ship structures can be ensured. A more perfect standard system of ship design and evaluation can be built.

Maneuverability of &lt;i&gt;C&lt;sub&gt;b&lt;/sub&gt;&lt;/i&gt;-Series Full Hull Ships

Maneuvering simulations for full hull ships were conducted by the MMG model, which is one of a maneuvering simulation method, based on the hydrodynamic force characteristics obtained in the captive model tests presented in previous paper1), and compared with the free-running model test results. The purpose of this study is to investigate the applicability of the MMG model to the full hull ships with very large block coefficient. We found that the original formula for longitudinal velocity component to rudder (uR) in the MMG model is not well working in case that the block coefficient (Cb) is very large as Cb = 0:87. To settle the problem, an improved formula of uR proposed by Yoshimura et al.3) was used and it was confirmed that the formula can capture the behavior of the rudder normal force just after steering better. Turning and course keeping performances in fullscale ships become worse comparing to those in ship model due to the worse rudder force performance comes from smaller propeller load in fullscale. Although the level of the worse turning performance is not so serious in fullscale, there is a possibility that overshoot angle of zig-zag maneuvers is over the IMO regulation for the present ship with Cb = 0.87.

Full-scale Ship Collision, Grounding and Sinking Simulation Using Highly Advanced M&S System of FSI Analysis Technique

To ensure an accurate and reasonable investigation of marine accident causes, full-scale ship collision, grounding, flooding, capsizing, and sinking simulations would be the best approach using highly advanced Modeling & Simulation (M&S) system of Fluid-Structure Interaction (FSI) analysis technique of hydrocode LS-DYNA. The objective of this paper is to present the findings from full-scale ship collision, grounding, flooding, capsizing, and sinking simulations of marine accidents, and to demonstrate the feasibility of the scientific investigation of marine accident causes and for the systematic reproduction of accident damage procedure.

Estimation of stopping ability of full-scale ship using free-running model

The authors discuss how to estimate full-scale stopping ability of ships using free-running model test equipped with an auxiliary thruster. Theoretical analysis based on a modular mathematical model clarified the similarity of three-degree-of-freedom stopping manoeuvre cannot be ensured by the use of the auxiliary thruster. The authors, however, propose J and speed correction, JSC, ensuring the equality of propeller advance ratio J and the similarity to full-scale of speed response of free-running model ship during stopping manoeuvre. JSC is a control method of free-running model ship equipped with an auxiliary thruster for estimating stopping ability of full-scale ship from the viewpoint of safety. Numerical simulation confirmed JSC gives safe side estimates of stopping ability in terms of track reach and stopping time with acceptable margin, which proved the advantage of JSC comparing with possible other control methods. Tank test data demonstrate how JSC works well.

Numerical prediction analysis of propeller bearing force for full-scale hull–propeller–rudder system

The hybrid grid was adopted and numerical prediction analysis of propeller unsteady bearing force considering free surface was performed for mode and full-scale KCS hull–propeller–rudder system by employing RANS method and VOF model. In order to obtain the propeller velocity under self-propulsion point, firstly, the numerical simulation for self-propulsion test of full-scale ship is carried out. The results show that the scale effect of velocity at self-propulsion point and wake fraction is obvious. Then, the transient two-phase flow calculations are performed for model and full-scale KCS hull–propeller–rudder systems. According to the monitoring data, it is found that the propeller unsteady bearing force is fluctuating periodically over time and full-scale propeller's time-average value is smaller than model-scale's. The frequency spectrum curves are also provided after fast Fourier transform. By analyzing the frequency spectrum data, it is easy to summarize that each component of the propeller bearing force have the same fluctuation frequency and the peak in BFP is maximum. What's more, each component of full-scale bearing force's fluctuation value is bigger than model-scale's except the bending moment coefficient about the Y-axis.