Numerical Study on Sea Keeping Performances of Ship by Exact Linear 3-D Potential Method

2007 ◽  
Author(s):  
N. M. Golam Zakaria ◽  
M. S. Baree
Keyword(s):  
Frequency Domain ◽  
Wave Height ◽  
Time Domain ◽  
Domain Analysis ◽  
Potential Method ◽  
Frequency Domain Analysis ◽  
Numerical Calculations ◽  
Irregular Waves ◽  
Linear Potential ◽  
Time Domain Simulation

This paper deals with the numerical calculations of sea-keeping performances of ship in irregular sea condition. Here linear potential theory has been applied for describing the fluid motion and 3-D sink-source technique has been used to determine hydrodynamic forces for surface ship advancing in waves at constant forward speed. Numerical coding based on 3-D potential method has been tested in an extensive manner keeping an eye with the criteria recommended by various ITTC committees [1]. The numerical accuracy of the coding has been examined using some experiment results as well as some other contemporary numerical calculations given by some authors for the case of frequency domain analysis. Taking a typical Panamax Container Vessel and in order to simulate its sea-keeping performances in real sea condition, the frequency domain analysis has been performed. The result is then used for time domain simulation in short crested irregular waves. Unequal frequency spacing has been taken into account to get longer simulation time and also empirical nonlinear roll damping has been taken in the way of time domain simulation. From this time domain simulation, relative wave height has been calculated which could sometimes damage deck equipment as well as posing a risks to personnel in severe sea condition. The effect of speed & wave direction on relative wave height has been considered and finally the numerical results of the maximum and significant values of irregular relative wave heights for these conditions are discussed.

scholarly journals Analysis of Three-Phase Wye-Delta Connected LLC

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3606
Author(s):  
Jing-Yuan Lin ◽  
Chuan-Ting Chen ◽  
Kuan-Hung Chen ◽  
Yi-Feng Lin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Operation Time ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Complete Analysis ◽  
Plane Analysis ◽  
Analysis Methods ◽  
Three Phase

Three-phase wye–delta LLC topology is suitable for voltage step down and high output current, and has been used in the industry for some time, e.g., for server power and EV charger. However, no comprehensive circuit analysis has been performed for three-phase wye–delta LLC. This paper provides complete analysis methods for three-phase wye–delta LLC. The analysis methods include circuit operation, time domain analysis, frequency domain analysis, and state–plane analysis. Circuit operation helps determine the circuit composition and operation sequence. Time domain analysis helps understand the detail operation, equivalent circuit model, and circuit equation. Frequency domain analysis helps obtain the curve of the transfer function and assists in circuit design. State–plane analysis is used for optimal trajectory control (OTC). These analyses not only can calculate the voltage/current stress, but can also help design three-phase wye-delta connected LLC and provide the OTC control reference. In addition, this paper uses PSIM simulation to verify the correctness of analysis. At the end, a 5-kW three-phase wye–delta LLC prototype is realized. The specification of the prototype is a DC input voltage of 380 V and output voltage/current of 48 V/105 A. The peak efficiency is 96.57%.

A Frequency Domain Analysis of Learning Control

1994 ◽  
Vol 116 (4) ◽  
pp. 781-786 ◽  
Author(s):  
C. J. Goh
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Linear Time ◽  
Planning Horizon ◽  
Time Domain Analysis ◽  
Learning Control ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Convergence Criterion ◽  
The Time Domain

The convergence of learning control is traditionally analyzed in the time domain. This is because a finite planning horizon is often assumed and the analysis in time domain can be extended to time-varying and nonlinear systems. For linear time-invariant (LTI) systems with infinite planning horizon, however, we show that simple frequency domain techniques can be used to quickly derive several interesting results not amenable to time-domain analysis, such as predicting the rate of convergence or the design of optimum learning control law. We explain a paradox arising from applying the finite time convergence criterion to the infinite time learning control problem, and propose the use of current error feedback for controlling possibly unstable systems.

scholarly journals Frequency-domain analysis of dynamically applied strain using sweep-free Brillouin time-domain analyzer and sloped-assisted FBG sensing

2012 ◽  
Vol 20 (26) ◽  
pp. B581 ◽  
Author(s):  
Asher Voskoboinik ◽  
Dvora Rogawski ◽  
Hao Huang ◽  
Yair Peled ◽  
Alan E. Willner ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Applied Strain

Hydrodynamic Interactions and Relative Motions Analysis for Installation of an Extendable Draft Platform

2009 ◽  
Author(s):  
Bonjun Koo ◽  
Jang Whan Kim
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Hydrodynamic Interactions ◽  
Coupled Analysis ◽  
Heave Plate ◽  
The Time Domain ◽  
Stabilized Platform ◽  
Relative Motions

The Extendable Draft Platform (EDP) is a deep draft, column stabilized platform with a deck box support for topsides and a single, deep draft heave plate that provides suitable motion characteristics to enable the use of dry tree top tensioned risers. The EDP can be fabricated with topsides installed on the deck box and commissioned quayside in a typical construction yard. With the columns in the retracted position, the EDP floats on its deck box and can be towed, in this configuration, to the location of interest. Once the EDP is transported to its final site, the columns and heave plate are lowered to their final operating draft. During the lowering sequence, the deck box and the lower hull become two relatively independent bodies, mechanically connected by chains that control the lowering of the columns and heave plate, and the guides between the deck box and the columns. This multi-body system is hydrodynamically coupled because of radiated and diffracted waves. The global performance analyses of the installation process (lowering of the lower hull) are carried out by three different methods. The first method is frequency-domain analysis by WAMIT and a frequency domain motion solver. In the frequency domain analysis, all the mechanical connections are modeled as linear springs. The second method is time-domain, partially coupled analysis using HARP/WINPOST. In this analysis, the off diagonal 6×6 hydrodynamic interactions are ignored. The last method is a time domain, fully coupled analysis using HARP/WINPOST. In this analysis, full 12×12 hydrodynamic interactions are considered. In the time domain analyses, the mechanical couplings between each column and deck box are modeled with linear springs and the chain connections are modeled with slender rods by using the nonlinear finite element method. This paper presents and compares analysis results based on the three methods for relative motions and loads between the deck box and the lower hull during the lowering of the columns and heave plate.

Children Display Adult-Like Kinetic Patterns in the Time Domain, But Not in the Frequency Domain, While Walking With Ankle Load

2015 ◽  
Vol 31 (5) ◽  
pp. 292-308 ◽  
Author(s):  
Jianhua Wu ◽  
Toyin Ajisafe ◽  
Matthew Beerse
Keyword(s):  
Young Adults ◽  
Frequency Domain ◽  
Body Mass ◽  
Time Domain ◽  
Second Harmonic ◽  
Reaction Force ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Spatiotemporal Parameters ◽  
The Time Domain

This study used both time and frequency domain analyses to investigate walking patterns with ankle load in children and adults. Twenty-two children aged 7–10 years and 20 young adults participated in this study. Three levels of ankle load were manipulated: no load, low load (2% of body mass on each side), and high load (4% of body mass on each side). An instrumented treadmill was used to register vertical ground reaction force (GRF) and spatiotemporal parameters, and peak vertical GRFs were determined. A frequency domain analysis was conducted on the vertical GRF data. Results demonstrate that, in the time domain, children showed adult-like spatiotemporal parameters and adult-like timing and magnitude of the 2 peak vertical GRFs under each load. In the frequency domain, children produced a lower power from the second harmonic than young adults, although both groups showed the highest power from this harmonic and increased this power with ankle load. It was concluded that children aged 7–10 years may start showing adult-like neuromuscular adaptations to increasing ankle load and display similar spatiotemporal control of foot falls and foot–floor kinetic interaction; however, a frequency domain analysis is effective in revealing different kinetic and neuromuscular characteristics between children and adults.

Behaviour of a Suspended Wellbay Module and Flare Tower in Waves During Transit to Shore

2019 ◽  
Author(s):  
Hoi-Sang Chan ◽  
Evren Armaoğlu ◽  
Matthew Thomson ◽  
Alistair Garner
Keyword(s):  
Frequency Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Irregular Waves ◽  
Scale Model ◽  
Response Analysis ◽  
Regular Waves ◽  
The North ◽  
Response Amplitude Operators

Abstract The extended lift operation to deliver the Wellbay module (M5) combined with the Flare Tower (M8) from the Miller Platform in the North Sea to the shore using the Semi-Submersible Crane Vessel S7000 was restricted by the clearances between M5/M8 and the vessel crane booms. A method to calculate the clearances of the M5/M8 normal to the vessel crane booms has been developed and used in a frequency-domain response analysis to define operability limits. Investigations based on a series of scale model tests in regular waves and irregular short-crested waves including motion decay tests in calm water, conducted by the Maritime Research Institute (MARIN) in the Netherlands, were also made to further evaluate the behaviour of the suspended M5/M8 on S7000’s main hooks during transit. The time series of decay motions of the suspended M5/M8 obtained from the decay motion tests and a time domain analysis are compared and used to derive rigging damping. The numerical results of the frequency-domain analysis are validated with the experimental data for response amplitude operators (RAOs) found in regular waves and pink noise waves, significant and 3 hour most probable maximum/minimum (MPM) responses of interest in irregular waves.

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