Dynamic analysis of cable roofs under transient wind: A comparison between time domain and frequency domain approaches

2008 ◽  
Vol 13 (S1) ◽  
pp. 53-57 ◽  
Author(s):  
S. Ali Ghafari Oskoei ◽  
Ghyslaine McClure
Keyword(s):  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Transient Wind

scholarly journals Time and Frequency Domain Dynamic Analysis of Offshore Mooring

2021 ◽  
Vol 9 (7) ◽  
pp. 781
Author(s):  
Shi He ◽  
Aijun Wang
Keyword(s):  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Linearization Method ◽  
Euler Method ◽  
Single Component ◽  
Hydrodynamic Drag ◽  
Lumped Mass ◽  
Mooring Lines ◽  
The Time Domain

The numerical procedures for dynamic analysis of mooring lines in the time domain and frequency domain were developed in this work. The lumped mass method was used to model the mooring lines. In the time domain dynamic analysis, the modified Euler method was used to solve the motion equation of mooring lines. The dynamic analyses of mooring lines under horizontal, vertical, and combined harmonic excitations were carried out. The cases of single-component and multicomponent mooring lines under these excitations were studied, respectively. The case considering the seabed contact was also included. The program was validated by comparing with the results from commercial software, Orcaflex. For the frequency domain dynamic analysis, an improved frame invariant stochastic linearization method was applied to the nonlinear hydrodynamic drag term. The cases of single-component and multicomponent mooring lines were studied. The comparison of results shows that frequency domain results agree well with nonlinear time domain results.

Dynamic Analysis of a Flexible Hanging Riser in the Time and Frequency Domain

2006 ◽  
Author(s):  
Ying Min Low ◽  
Robin S. Langley
Keyword(s):  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Random Waves ◽  
Lumped Mass ◽  
Explicit Integration ◽  
Integration Schemes ◽  
Simple Boundary ◽  
The Time Domain

This paper outlines the dynamic analysis of flexible risers in the time and frequency domain using lumped mass discretization, where tension and bending are modeled with extensional and rotational springs respectively. For the time domain analysis, integration is carried out using the Wilson-theta implicit scheme, which allows the use of relatively large time steps without compromising stability. This increases computational efficiency and automatically filters the high frequency axial responses. The time domain code is validated with the commercial software Orcaflex, which employs an explicit scheme, and results are found to match for the same number of elements. The relative merits of implicit and explicit integration schemes are discussed. For the frequency domain analysis, the added mass, damping, axial/bending stiffness matrices are formulated in global coordinates. The nonlinear drag force is linearized iteratively for both regular and random waves. The range of accuracy for the linearized frequency domain simulations is assessed by methodical comparisons with the nonlinear time domain results for varying loading amplitudes. One problem encountered during the early development of an analytical tool is the lack of published results for validation, especially where access to commercial packages and test facilities is unavailable or limited. Hence, the simulation results presented herein are for a flexible hanging riser with simple boundary conditions and load cases to facilitate benchmarking.

Comparison of frequency- and time-domain analyses for guyed masts in turbulent winds

2006 ◽  
Vol 33 (2) ◽  
pp. 169-182 ◽  
Author(s):  
B F Sparling ◽  
L D Wegner
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Element Model ◽  
Mode Shapes ◽  
Nonlinear Behaviour ◽  
Element Analysis ◽  
Guyed Mast

Both frequency- and time-domain methods have been employed in the dynamic analysis of guyed telecommunication masts subjected to turbulent winds. Although the probabilistic frequency-domain approach offers some advantages in terms of its relative ease of implementation and in the statistical reliability of wind load descriptions, the deterministic time-domain method permits a more realistic treatment of system nonlinearities. In this study, a numerical investigation was undertaken to compare frequency- and time-domain dynamic response predictions for a selected guyed mast in gusty winds. Two different analysis techniques were employed, with the frequency-domain calculations performed using response influence lines and the time-domain analyses carried out using a stiffness-based finite element model. Good agreement was observed in root-mean-square and peak dynamic response estimates after compensation was included for differences in turbulence intensity levels assumed in the two models. In general, natural frequencies and mode shapes were also similar.Key words: guyed mast, dynamic analysis, wind, turbulence, nonlinear behaviour, finite element analysis, cables, frequency domain, time domain.

Comparison Between Frequency Domain and Time Domain Riser Analysis

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Fernanda Cristina de ◽  
Moraes Takafuji ◽  
Clóvis de Arruda Martins
Keyword(s):  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Iterative Process ◽  
Nonlinear Effects ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Riser Design ◽  
Analytical Correction ◽  
Parametric Analyses

In the optimization or parametric analyses of risers, several configurations must be analyzed. It is laborious to perform time domain solutions for the dynamic analysis, since they are time-consuming tasks. So, frequency domain solutions appear to be a possible alternative, mainly in the early stages of a riser design. However, frequency domain analysis is linear and requires that nonlinear effects are treated. The aim of this paper is to present a possible way to treat some of these nonlinearities, using an iterative process together with an analytical correction, and compare the results of a frequency domain analysis with the those of a full nonlinear analysis.

Transfer Function Development and Dynamic Analysis of a Heat Pipe Cooled Reactor

2021 ◽  
Author(s):  
Songmao Pu ◽  
Peiwei Sun ◽  
Xinyu Wei
Keyword(s):  
Transfer Function ◽  
Dynamic Analysis ◽  
Heat Pipe ◽  
Frequency Domain ◽  
Dynamic Model ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Reactor Power ◽  
The Time Domain

Abstract The heat pipe cooled reactor adopts the solid-state reactor design concept and the heat is passively transferred out of the core through heat pipes. It is characterized by high inherent safety and simple operation and has broad application prospects in deep space exploration and propulsion, sea submarine navigation and exploration. The design of heat pipe cooled reactor is unique, and its dynamics are different from traditional water-cooled reactors. Therefore, it is necessary to develop its dynamic model and perform dynamic analysis, and in this paper, the study object of the heat pipe cooled reactor is the 100kW nuclear silent thermoelectric reactor (NUSTER-100). A nonlinear dynamic model is derived from the conservation equations of mass, energy and momentum. Point reactor kinetics equations are adopted. The linear dynamic model is constructed by linearization of the nonlinear model based on the disturbance theory and the transfer function is further derived applying Laplace transform. Both models including the nonlinear model and transfer function model are established on the MATLAB & Simulink simulation platform. Dynamic characteristic analysis contains time domain analysis and frequency domain analysis. For the time domain analysis, by introducing a variety of boundary condition disturbances, the results were compared with those from transfer function. The results are consistent and can correctly reflect the dynamic characteristics of the heat pipe cooled reactor. Therefore, the transfer function model can be applied to the subsequent design of the heat pipe cooled reactor power control system. For the dynamic analysis, it is divided into time domain and frequency domain. The time domain is to observe the change of core power and sodium temperature by introducing reactivity disturbance. For the frequency domain, after drawing the Bode plot of the transfer function, the system’s characteristics at different frequencies are analyzed. In addition, it can provide a theoretical basis for the design of the heat pipe cooled reactor power control system.

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

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