Numerical and Experimental Investigation of the Performance of Dynamic Wing for Augmenting Ship Propulsion in Head and Quartering Seas

Flapping-foil thrusters arranged at the bow of the ship are examined for the exploitation of energy from wave motions by direct conversion to useful propulsive power, offering at the same time dynamic stability and reduction of added wave resistance. In the present work, the system consisting of the ship and an actively controlled wing located in front of its bow is examined in irregular waves. Frequency-domain seakeeping analysis is used for the estimation of ship-foil responses and compared against experimental measurements of a ferry model in head waves tested at the National Technical University of Athens (NTUA) towing tank. Next, to exploit the information concerning the responses from the verified seakeeping model, a detailed time-domain analysis of the loads acting on the foil, both in head and quartering seas, is presented, as obtained by means of a cost-effective time-domain boundary element method (BEM) solver validated by a higher fidelity RANSE finite volume solver. The results demonstrate the good performance of the examined system and will further support the development of the system at a larger model scale and the optimal design at full scale for specific ship types.

The Final Battle, DKM Bismarck vs the British Royal Navy May 1941 A Seakeeping Analysis

This paper focuses on the effect of the sea conditions and ship motions on ship operations and combatant activities. Readers interested in an exhaustive discussion of Bismarck, her creation and these epic battles in never before seen detail are encouraged to consult Garzke, 2019. The sea conditions were reported in the ship’s logs and were used to drive modern seakeeping tools to evaluate the probable ship motions. From the ship motions we have calculated the effect that these would have on the ability to train and elevate the guns for range.

Development of a Real-Time Simulation Model for an ASD Tug

A hydrodynamic digital twin of vessel can be used to replicate the behaviour and response of the vessel in a virtual environment. In this paper, a real-time simulation model (RTSM) for an azimuth stern-drive (ASD) tug has been developed for simulating the hydrodynamic performance of the vessel under a range of environmental conditions. Based on the framework of a 4-DoF MMG manoeuvring model, the RTSM comprises manoeuvring, propulsion and environmental loads which are parameterised using numerical results from a combination of computational fluid dynamics (CFD) modelling work, including virtual planar motion mechanism (vPMM), seakeeping analysis, wind drag prediction and propulsion modelling. The RTSM is used to demonstrate the manoeuvrability of the vessel in calm water and under external loads from waves, winds and currents.

Seakeeping Analysis of a Hydrofoil Supported Watercraft (Hysuwac): A Case Study

Considering recent global temperature increase and observed climate change, efforts have been made towards energy efficiency and reduction of green-house gas emission. A foil system is proposed in this study and retrofitted to an existing catamaran to reduce the energy use and to improve the vessel’s seakeeping characteristics. The objective of this study is to investigate the effects of the application of the foil system on the seakeeping performance of the vessel. CFD simulations based on a panel method were carried out to obtain the seakeeping characteristics of the catamaran with and without foil system. Simulation results show that the foil system reduced the vessel motions in a seaway: the heave-, pitch- and roll significant amplitudes were reduced 4.41, 9.97 and 3.30 percent, respectively, due to the application of the foil system. In addition, the vertical accelerations at the fore perpendicular (FP) and at deck were reduced 3.66 and 9.70 percent, respectively. A check against the NORDFORSK criteria for fast small crafts shows that the vessel can operate safely up to sea state 2.

Vertical Motion Optimization of Series 60 Hull Forms Using Response Surface Methods

There are many aspects to analyze seakeeping performance, one of which is the ship's vertical motion. As well-known, vertical motion and its derivatives, vertical velocity and acceleration, will be related to other aspects of seakeeping performance, such as slamming, deck wetness, and MSI. This study discusses optimizing the hull shape with small vertical motion using the Response Surface Methods (RSM). This research aims to minimize the ship's vertical motion so that the ship's performance is better than the initial one. Besides, this research was conducted to apply the RSM in the naval architecture field. The hull's shape used in this study is Series 60 hull form with a length of 31 m. The variables used for the optimization process are the ratio of L/B (X1) and B/T (X2) in the range of ± 10% with fixed displacement. Seakeeping analysis was carried out at a speed of 6.78 knots (Fr 0.2), a heading angle of 180°, and a significant wave height of 0.77 meters. The results show that the optimum model is found in Model 9 where the value of X1 = -2.94 or L/B = 6.71 and X2 = 5 or B/T = 2.75. Model 9 can reduce the vertical motion of the ship by 16.38%.

Ship Towed by Kite: Investigation of the Dynamic Coupling

This paper presents a series of dynamic simulations for a ship towed by kite. To ensure time efficient computations, seakeeping analysis with forward speed correction factors is carried out in the frequency domain and then transformed in the time domain by convolution. The seakeeping modeling is coupled with a zero-mass kite modeling assuming linear dependence of aerodynamic characteristics with respect to turning rate. Decoupled (segregated) and coupled (monolithic) approaches are assessed and compared in different environmental conditions. Results show that in regular beam waves, strong interactions between the kite and the ship motions are captured by the monolithic approach. Around the wave frequency, especially for the lower one tested (0.4 rad/s), a kite lock-in phenomenon is revealed. It is concluded that the mean kite towing force can be increased whereas the ship roll amplitude can even be decreased compared to a non-kite assisted ship propulsion configuration.

Development of a New Ship Adaptive Weather Routing Model Based on Seakeeping Analysis and Optimization

This paper provides a new adaptive weather routing model, based on the Dijkstra shortest path algorithm, aiming to select the optimal route that maximizes the ship performances in a seaway. The model is based on a set of ship motion-limiting criteria and on the weather forecast maps, providing the sea state conditions the ship is expected to encounter along the scheduled route. The new adaptive weather routing model is applied to optimize the scheduled route in the Northern Atlantic Ocean of the S175 containership, assumed as a reference vessel, based on the weather forecast data provided by the Global WAve Model (GWAM). In the analysis, both wave and combined wind/swell wave conditions are embodied to investigate the incidence on the optimum route assessment. Furthermore, the effect of the vessel speed on the optimum route detection is also investigated. Current results clearly show that it is possible to achieve appreciable improvements, up to 50% of the ship seakeeping performances, without excessively increasing the route length and the voyage duration.

Seakeeping Analysis of Planing Craft under Large Wave Height

The purpose of this paper is to conduct a seakeeping analysis of planing craft under regular wave with large wave height. To obtain a reliable numerical method to simulate the sailing of planing craft in waves, Reynolds-averaged Navier–Stokes (RANS) solver and overset method are adopted. The motion response and resistance of the planing craft USV01 in regular wave were numerical predicted and compared with the corresponding seakeeping experimental tests. The results show that the numerical method has high accuracy. For further study, a new planing craft whose name is improved vessel is selected for simulation, the low steaming of the USV01 and improved vessel in regular wave with large wave height was simulated, and the seakeeping of the two vessels was studied. The analysis about the influence of wave length on the motion response and navigation configurations of the improved vessel under regular wave was carried out. Meanwhile, the influence of speed on different navigation configurations of the improved vessel was also analyzed. The improved vessel can provide better seakeeping, and a reduction in the speed of the vessel will benefit its seakeeping, irrespective of its navigation configuration.

Numerical Analysis of a Surface Ship in Waves

Ship's resistance and engine power to sustain ship's speed in seaways are augmented due to complex non-linear interactions between the ship and the ambient sea (waves). Ship designers, in early design stage, use an ad hoc "sea margin" to account for the effects of seaways in selecting propeller and engine. A numerical tool capable of accurately predicting added resistance and power of a ship cruising in waves would greatly help select its powering (margin) requirement and determine the optimal operating point that can maximize the energy efficiency. For seakeeping analysis, strip theory-based methods have long been used. More recently, nonlinear time-domain three-dimensional (3D) panel methods have started being used widely. A more physics-based avenue to seakeeping analysis is offered by coupled solutions of two-phase unsteady Reynolds-Averaged Navier-Stokes equations and six degrees-of-freedom rigid-body motion (RBM) equations. The URANS approach also avails itself of including the effects of propulsors, either explicitly or approximately. By accounting for all the nonlinear effects in hydrodynamic forces and moments and the resulting ship motions, and the effects of fluid viscosity and turbulence, the coupled URANS-RBM method is believed not only able to predict added resistance and speed loss more accurately, but also to provide valuable insights into the physical mechanisms underlying added resistance and power. The objectives of this study are: (1) to validate a coupled URANS-RBM solver developed for high-fidelity prediction of added resistance, speed loss and added power on ships cruising in regular head sea and irregular waves, and (2) to conduct a detailed analysis of the interactions among ship hull, propeller and waves for a 1/49 scaled model of the ONR Tumblehome (ONRT) (Model 5613) in order to shed light on the physical mechanisms leading to added resistance, speed loss and added power. Figure 1 depicts the ONRT self-propellers with two 4-bladed propellers in regular waves. The main flow features such as the free surface, the hub vortices and blade-tip vortices from the propeller, as well as vortices generated by the sonar dome, shafts, shaft brackets and bilge keels are captured.