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

2021 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Kostas Belibassakis ◽  
Evangelos Filippas ◽  
George Papadakis
Keyword(s):  
Time Domain ◽  
Domain Boundary ◽  
Cost Effective ◽  
Time Domain Analysis ◽  
Direct Conversion ◽  
Irregular Waves ◽  
Time Dynamic ◽  
Quartering Seas ◽  
Head Waves ◽  
Seakeeping Analysis

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.

scholarly journals Cost-Effective Brillouin Optical Time-Domain Analysis Sensor Using a Single Optical Source and Passive Optical Filtering

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
H. Iribas ◽  
J. Urricelqui ◽  
J. Mariñelarena ◽  
M. Sagues ◽  
A. Loayssa
Keyword(s):  
Time Domain ◽  
Cost Effective ◽  
Optical Filters ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Optical Source ◽  
Optical Filtering ◽  
Spectral Components ◽  
Optical Time ◽  
The Cost

We present a simplified configuration for distributed Brillouin optical time-domain analysis sensors that aims to reduce the cost of the sensor by reducing the number of components required for the generation of the two optical waves involved in the sensing process. The technique is based on obtaining the pump and probe waves by passive optical filtering of the spectral components generated in a single optical source that is driven by a pulsed RF signal. The optical source is a compact laser with integrated electroabsorption modulator and the optical filters are based on fiber Bragg gratings. Proof-of-concept experiments demonstrate 1 m spatial resolution over a 20 km sensing fiber with a 0.9 MHz precision in the measurement of the Brillouin frequency shift, a performance similar to that of much more complex setups. Furthermore, we discuss the factors limiting the sensor performance, which are basically related to residual spectral components in the filtering process.

Study on a Time Domain Prediction Method for Wave Force: Application for a Point-Absorber WEC

2018 ◽  
Author(s):  
Qiao Li ◽  
Motohiko Murai
Keyword(s):  
Time Domain ◽  
Wave Spectrum ◽  
Time Domain Analysis ◽  
Wave Force ◽  
Domain Analysis ◽  
Irregular Waves ◽  
Floating Body ◽  
Control Force ◽  
Electric Generator ◽  
The Time Domain

There are a lot of numerical analysis for solving hydrodynamic responses of a floating body in the time domain. Most of them can give a theoretical solution in given irregular waves. It means, however, that the solution can be obtained only if the accurate irregular waves represented by the wave spectrum should be given. As we consider the actual operation, we know it is difficult to detect the accurate irregular waves instantaneously as needed accuracy in the most of the time domain analysis for feed backing the control force to the system. This paper proposes a new method to predict the practical wave force from the displacement of waves at a floating body in time domain analysis almost instantaneously. The method, that can apply to predict forces in wave energy converter with linear electric generator, helps us to choose the control force for convert more electric power in irregular waves. We confirm the algorithm and examine its effectiveness.

scholarly journals Cost-effective method for fast Brillouin optical time-domain analysis

2016 ◽  
Vol 24 (22) ◽  
pp. 25424 ◽  
Author(s):  
Aldo Minardo ◽  
Ester Catalano ◽  
Luigi Zeni
Keyword(s):  
Time Domain ◽  
Cost Effective ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Cost Effective Method ◽  
Optical Time

The Simulation of Ship Motions Using a B-Spline–Based Panel Method in Time Domain

2007 ◽  
Vol 51 (03) ◽  
pp. 267-284
Author(s):  
Ranadev Datta ◽  
Debabrata Sen
Keyword(s):  
Time Domain ◽  
Three Dimensional ◽  
Basis Functions ◽  
The Body ◽  
Irregular Waves ◽  
Ship Motions ◽  
B Spline ◽  
Head Waves ◽  
Wigley Hull ◽  
Spline Basis

In this paper, a B-spline-based higher-order method is developed for simulating three-dimensional ship motions with forward speed. The problem is formulated in time domain using a transient free surface Green function. The body geometry is defined by open uniform or nonuniform B-spline basis functions depending on the hull type, whereas the unknown field variables are described by open uniform B-spline basis functions. The collocation method is applied to discretize the integral equation and then solved for the unknown potentials and source strengths. Motion computations in head waves are carried out for three types of ship hulls: a mathematically defined Wigley hull, a typical containership (S175 hull), and a Series 60 hull. Results are obtained for regular and irregular waves and compared with available experimental and computational results. It is found that the results from the present method are in very good agreement with the published results, and in particular with experimental data. Long-duration simulations have also been carried out with an ordinary desktop PC (PIV with 512 MB RAM) to demonstrate the ability of the method to simulate motions over long periods without any visible deterioration using only modest computational resources.

Effect of stern appendages configurations on the course-keeping of ships in stern-quartering seas

2021 ◽  
pp. 1-29
Author(s):  
Christian Lena ◽  
Matteo Bonci ◽  
Frans van Walree
Keyword(s):  
High Speed ◽  
Domain Boundary ◽  
Potential Method ◽  
Irregular Waves ◽  
Ship Hulls ◽  
Quartering Seas ◽  
Lifting Surfaces ◽  
Semi Empirical ◽  
The Waves ◽  
Control Surfaces

Ships can experience serious difficulties in keeping a straight course when sailing in stern-quartering seas. Design modifications like the addition of stern passive fins, or the modification of active control surfaces, are common solutions to improve the ship course-keeping. However, the success of such design modifications depends on the delicate balance between the excitation forces induced by the waves on the appended hull, the stabilization forces provided by the lifting surfaces as appended fins, and the steering forces provided by the control surfaces. This research investigates which of these aspects of a ship design play a concrete role in improving the ship course-keeping in waves. The study is carried out with the intention of looking at the different behaviors of the ship originating from different stern appendages configurations. Three modifications of stern appendages on three different ship hulls were investigated in various mild-to-rough sea conditions. The behavior of the vessels were simulated using a time domain, boundary element potential method, with the addition of semi-empirical formulations for the modelling of the stern lifting surfaces. The simulations were carried out in long crested irregular waves at three different direction, using the JONSWAP spectrum. The results showed that although larger stern appendages improve the directional stability of relatively large and slow vessels, in most cases they worsen their course-keeping ability, increasing the yaw motions. For smaller and faster vessels instead, passive and active fins tend to improve the course-keeping, because at high speed the lift provided by the appendages stabilizes the vessel. This effect is compensated by the wave excitation force at lower speed. Similarly to yaw, the roll motions increases with larger stern appendages.

Study on the Parametric Rolling of Medium-Sized Containership Based on Nonlinear Time Domain Analysis

2020 ◽  
Author(s):  
Seung Ho Yang
Keyword(s):  
Mathematical Model ◽  
Numerical Model ◽  
Wave Height ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Wave Period ◽  
Irregular Waves ◽  
Parametric Rolling ◽  
Nonlinear Numerical Model

Abstract The numerical analysis of parametric rolling of medium-sized containership has been carried out. Target containership was modeled by using two different numerical models, which are nonlinear numerical model and simplified dynamic mathematical model respectively. The simulations were performed in full-loaded operating condition for regular and irregular waves. For regular waves, the analysis was conducted with a wide range of wave periods including the vicinity of the wave period expected to cause parametric rolling of the target containership. On the other hand, regarding irregular waves, the wave period range that is highly likely to occur according to significant wave height was selected and used as input values of wave spectrum for nonlinear time domain analysis. The analysis results are summarized as wave height versus wave period diagrams with the occurrences of parametric rolling motions for each speed. And also, time series based on time domain analysis are represented and compared between nonlinear numerical model and simplified dynamic mathematical model. In addition, the sensitivity of key parameters such as vessel speed, wave period, and roll damping to parametric rolling was investigated and estimated under operating condition. Finally, when the parametric rolling occurred, the characteristics of heave, pitch, and roll motions were analyzed. This study could be used as the basic data for determining the operational conditions for safe operation as well as initial design of the medium-sized containership.

Efficient Dynamic Analysis of Floating Bodies Nonlinear Behavior in Wave Energy Conversion

2013 ◽  
Author(s):  
P. D. Spanos ◽  
A. Richichi ◽  
F. Arena
Keyword(s):  
Wave Energy ◽  
Time Domain ◽  
Water Waves ◽  
Nonlinear Behavior ◽  
Time Domain Analysis ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Equivalent Linearization ◽  
Energy Converter ◽  
Stiffness And Damping

Floating oscillating-bodies are a kind of wave energy converter developed for harvesting the great amount of energy related to water waves; see Falcão [1] for a review. In this paper a particular energy converter model is considered. A nonlinear analysis of its dynamic behavior is conducted both in the time and the frequency domains. The model involves a tightly moored single-body floating wave energy converter. It captures motion in the horizontal and vertical directions. The nonlinear stiffness and damping forces are functions of the horizontal and vertical displacements and velocities and make the system a nonlinear one. In addition to the time-domain analysis of the nonlinear behavior of the system, the method of equivalent linearization is used to determine iteratively the effective linear stiffness and damping matrices and the response of the buoy in the frequency domain. The analysis pertains to the surge and the heave directions response of the wave energy converter under harmonic mono-frequency excitation (regular waves). The reliability of the linearization based approach is demonstrated by comparison with time domain integration data. This approach offers the appealing feature of conducting efficiently a variety of parameter studies which can expedite preliminary evaluations, inter alia, of competing design scenarios for the energy converter. Suggestions for extending this approach to the case of fully nonlinear and random irregular waves are also included.

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