Time Domain Analysis on Ship Maneuvering in Adverse Sea State

2016 ◽  
Author(s):  
Bingjie Guo ◽  
Ruth Eivind ◽  
Håvard Austefjord ◽  
Elzbieta M. Bitner-Gregersen ◽  
Olav Rognebakke
Keyword(s):  
Time Domain ◽  
Ghg Emissions ◽  
Weather Conditions ◽  
Time Domain Analysis ◽  
Equilibrium Analysis ◽  
Future Research ◽  
Ship Maneuvering ◽  
Ship Maneuverability ◽  
Adverse Weather ◽  
The Time Domain

Energy Efficiency Design Index (EEDI) introduced by the IMO Resolution MEPC.203 (62) has been the first initiative to regulate the greenhouse gas (GHG) emissions from ships. However, it has raised serious concerns that some ship designers might choose to lower the installed power to achieve EEDI requirements not accounting satisfactorily for ship safety. This has encouraged investigations addressing the ability of ship to maintain maneuverability in adverse sea states. The Interim Guidelines proposed in 2013, in IMO Res. MEPC.232 (65), recommend minimum propulsion power to maintain ship maneuvering ability in adverse weather conditions for bulk carriers and tankers. These guidelines are mainly based on statistical analysis and equilibrium analysis in a steady state. Today, most of the available tools and methods handle ship responses in waves by separating it into seakeeping and maneuvering. The present study investigates ship maneuverability by use of a recently developed time domain code which combines the sea-keeping and maneuvering equation to predict ship responses in waves. In this way, better insight into ship responses in adverse conditions is obtained. The numerical results presented in the study are validated by model tests. The limitations of the time-domain code are discussed and future research needs are pointed out.

Study on Ship Manoeuvering in Adverse Sea State

2017 ◽  
Author(s):  
Bingjie Guo ◽  
Eivind Ruth ◽  
Håvard Austefjord ◽  
Elzbieta M. Bitner-Gregersen ◽  
Odin Gramstad
Keyword(s):  
Time Domain ◽  
Ghg Emissions ◽  
Force Component ◽  
Ship Maneuvering ◽  
Engine Model ◽  
Simulation Speed ◽  
Calm Water ◽  
Force Components ◽  
Energy Efficiency Design Index ◽  
The Time Domain

IMO introduced Energy Efficiency Design Index (EEDI) to regulate the greenhouse gas (GHG) emissions from ships. The cheapest and easiest way to fulfil the EEDI requirement is to reduce installed power for most ships. Therefore, it has raised serious concerns that some ship designers might choose to lower the installed power to achieve EEDI requirements and not consider ship safety in a satisfactory way. This could induce ship manoeuvrability and safety problems in adverse seas, which needs urgent investigations on minimum power to maintain ship manoeuvrability in adverse sea. A time domain code ‘Waqum’ has been developed based on the force superposition of unified theory to study the minimum required power for maintaining ship manoeuvring ability in adverse sea states. The code combines sea-keeping and maneuvering equations, together with an engine model to predict ship responses in waves. The code can help us to study ship responses in transit situation and give us better insight into ship maneuvering ability in adverse sea states. In order to improve the simulation speed, the time domain code does not calculate all the hydrodynamic forces directly. Thus, some precalculations should be done for some force components before launching the simulation for a new ship. Therefore, the methodology and accuracy of each force component will influence the accuracy of the manoeuvring code. The methodology for determining each force component will be discussed, especially the identification of maneuvering derivatives based on CFD simulations. The code has been improved recently, and another rudder model has been implemented. Further, the the code with new rudder model is verified in calm water. The code’s ability to capture ship maneuvering in waves is also demonstrated.

Experimental Study on the Performance of Constrained Damped Rail Vibration Reduction

2011 ◽  
Vol 42 (10) ◽  
pp. 9-14
Author(s):  
L.Y. Liu ◽  
J.Y. Li ◽  
X.J. Yin
Keyword(s):  
Experimental Study ◽  
Time Domain ◽  
Vibration Amplitude ◽  
Impact Load ◽  
Vibration Reduction ◽  
Time Domain Analysis ◽  
Experimental Basis ◽  
Vibration Acceleration ◽  
The Time Domain ◽  
Vibration Performance

To study the vibration reduction performance of damped rail, we take the standard rail and labyrinth constrained damped rail as the study target. By testing the vibration performance of both standard rail and labyrinth constrained damped rail in an anechoic room, we use the time-domain analysis to study the vibration changes with time passing. The results showed that: the labyrinth constrained damped rail vibration can effectively reduce the vibration amplitude and duration. Under the radial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 5% −19%, time of vibration and attenuation greater than 94%; under the axial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 9% −21%, time of vibration and attenuation greater than 92%. The results have provided an experimental basis for the design of new constrained damped rail.

Numerical Simulation on Mooring Performance of LNG-FPSO System in Realistic Seas

2005 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Time Domain ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Time Domain Analysis ◽  
Analysis Tool ◽  
Motion Response ◽  
Non Linear ◽  
Floating System ◽  
Exciting Forces ◽  
The Time Domain

The LNG-FPSO concept is receiving much attention in recent years, due to its active usage to exploit oil and gas resources. The FPSO offloads LNG to an LNG carrier that is located close to the FPSO, and during this transfer process two large vessels are in close proximity to each other for daylong periods of time. Due to the presence of neighboring vessel, the motion response of both the vessels will be affected significantly. Hydrodynamic interactions related to wave effects may result in unfavorable responses or the risk of collisions in a multi-body floating system. Not only the motion behavior but also the second order drift forces are influenced by the neighboring structures due to interactions of the waves among the structures. A study is made on the time domain analysis to assess the behavior and the operational capability of the FPSO system moored in the sea having an LNG carrier alongside under environmental conditions such as waves, wind and currents. This paper presents an analysis tool to predict the dynamic motion response and non-linear connecting and mooring forces on a parallel-connected LNG-FPSO system due to non-linear exciting forces of wave, wind and current. Simulation for the mooring performance is also investigated. The three-dimensional source-sink technique has been applied to obtain the radiation forces and the transfer function of wave exciting forces on floating multi-bodies. The hydrodynamic interaction effect between the FPSO and the LNG carrier is included to calculate the hydrodynamic forces. For the simulation of a random sea and also for the generation of time depended wind velocity, a fully probabilistic simulation technique has been applied. Wind and current loads are estimated according to OCIMF. The effects of variations in wave, wind and current loads and direction on the slowly varying oscillations of the LNG and FPSO are also investigated in this paper. Finally, some conclusions are drawn based on the numerical results obtained from the present time domain simulations.

scholarly journals Time-domain analysis of distortion-product otoacoustic emissions using a hydrodynamic cochlea model

2017 ◽  
Vol 3 (2) ◽  
pp. 453-456
Author(s):  
Dennis Zelle ◽  
Ernst Dalhoff ◽  
Anthony W. Gummer
Keyword(s):  
Time Domain ◽  
Otoacoustic Emissions ◽  
Short Pulse ◽  
Human Subjects ◽  
Time Domain Analysis ◽  
Distortion Product Otoacoustic Emissions ◽  
Sound Waves ◽  
Cochlear Function ◽  
Distortion Product ◽  
The Time Domain

AbstractAs a by-product of nonlinear amplification in the cochlea, the inner ear emits sound waves in response to two tones with different frequencies. These sound waves are measurable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). DPOAEs putatively consist of two components emerging at different locations in the cochlea. Wave interference between the two components limits the accuracy of DPOAEs as a noninvasive measure of cochlear function. Using short stimulus pulses instead of continuous stimuli, the two DPOAE components can be separated in the time domain due to their different latencies. The present work utilizes a nonlinear hydrodynamic cochlea model to simulate short-pulse DPOAEs in the time domain. When adding irregularities to the mechanical parameters of the model, the simulated DPOAE signals show two distinguishable components and long-lasting beat tones, similar to band-pass filtered experimental data from normal-hearing human subjects. The model results suggest that the beat tones can occur solely due to interference of the coherent-reflection component with the fading nonlinear-distortion component.

scholarly journals Two optical emission components with different variability in V404 Cygni

2016 ◽  
Vol 12 (S324) ◽  
pp. 43-44
Author(s):  
Yutaro Tachibana ◽  
Taketoshi Yoshii ◽  
Nobuyuki Kawai
Keyword(s):  
Spectral Index ◽  
Power Law ◽  
Time Domain ◽  
Optical Emission ◽  
Time Domain Analysis ◽  
Blackbody Radiation ◽  
Light Curves ◽  
Variable Component ◽  
Single Temperature ◽  
The Time Domain

AbstractV404 Cygni went into an outburst again on June 15, 2015 after 26 years of quietness. Soon after the notifications, we started intense optical observation campaign of this source. The spectral index between RC and IC-band was stable over the outburst, whereas that between g′ and RC-band varied violently. With the time domain analysis of the multi-color optical light curves, we successfully decomposed optical variations into three components: highly-variable component (HVC), little-variable component (LVC). The loci of the LVC in the color-color diagram is consistent with that of a single temperature blackbody radiation or a multi-color blackbody radiation from a standard accretion disk, while those of the HVC trace that of power-law spectra.

scholarly journals STEADY-STATE ANALYSIS OF NONLINEARLY COUPLED CHUA'S CIRCUITS WITH PERIODIC INPUT

2003 ◽  
Vol 13 (11) ◽  
pp. 3395-3407 ◽  
Author(s):  
F. A. SAVACI ◽  
M. E. YALÇIN ◽  
C. GÜZELIŞ
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Transfer Functions ◽  
Piecewise Linear ◽  
Time Domain Analysis ◽  
Steady State Analysis ◽  
Linear Dynamic Systems ◽  
Periodic Input ◽  
The Time Domain ◽  
State Analysis

In this paper, nonlinearly coupled identical Chua's circuits, when driven by sinusoidal signal have been analyzed in the time-domain by using the steady-state analysis techniques of piecewise-linear dynamic systems. With such techniques, it has become possible to obtain analytical expressions for the transfer functions in terms of the circuit parameters. The proposed system under consideration has also been studied by analog simulations of the overall system on a hardware realization using off-the-shelf components as well as by a time-domain analysis of the synchronization error.

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