The time-frequency interpretation for transient evolution of wave propagation through dispersive medium

2001 ◽  
Vol 11 (6) ◽  
pp. 267-269
Author(s):  
Dong Xiaoting ◽  
Jiang Yansheng ◽  
Wang Wenbing
Keyword(s):  
Wave Propagation ◽  
Dispersive Medium ◽  
Time Frequency ◽  
Frequency Interpretation

Measurement of Low-Frequency Wave Propagation in a Railway Contact Wire with Dispersive Characteristics Using Wavelet Transform

2006 ◽  
Vol 321-323 ◽  
pp. 1609-1615 ◽  
Author(s):  
Sung Yong Park ◽  
Byung Uk Jeon ◽  
Jang Moo Lee ◽  
Yong Hyeon Cho
Keyword(s):  
Wave Propagation ◽  
Wavelet Transform ◽  
Propagation Velocity ◽  
Beam Model ◽  
Wave Propagation Velocity ◽  
Essential Information ◽  
Frequency Wave ◽  
Contact Wire ◽  
Time Frequency ◽  
Cross Correlation Analysis

The railway contact wire, which supplies electric railways with electric power, plays an important role in determining the maximum railway velocity. In general, the maximum allowable velocity of an electric railway is less than seventy percent of the wave propagation velocity of the contact wire. Because the contact wire is more a beam model with dispersive wave characteristics than a string model, the wave propagation velocity depends on the frequency. For this reason, there have been only few studies on the wave propagation of the contact wire. In this paper, we proposed two useful methods for estimating the wave propagation velocity of the railway contact wire by using the Gabor wavelet transform on the experimental signals. In the first method, the ridges of wavelet transform, which contain the essential information about dispersive characteristics, are used. Specifically, the wave propagation velocity of the contact wire can be extracted from the time difference of the wavelet ridges of the measured signals. In the second method, the cross-correlation analysis of each wavelet transform is used to extract the wave propagation. The selection of the optimal Gabor shaping factor for the best time-frequency localization by using the Shannon entropy cost function is also discussed.

Numerical Analysis of Lateral Wave Propagation in Drill-String for Stability Monitoring

2014 ◽  
Author(s):  
Yu Liu ◽  
Andrew J. Dick
Keyword(s):  
Wave Propagation ◽  
Drill String ◽  
Lateral Impact ◽  
Monitoring Scheme ◽  
Time Frequency ◽  
Impact Wave ◽  
Lateral Wave ◽  
Stability Monitoring ◽  
The Stability ◽  
Spectral Finite Element

In this paper, the propagation of lateral waves in a drill-string are studied by using a new numerical method and a stability monitoring scheme is proposed. The drill-string is modeled as a linear beam structure under gravitational field effects. An iterative wavelet-based spectral finite element method (WS-FEM) model is developed to obtain a high fidelity response. Numerical simulations of the lateral impact wave propagation at the bottom-hole-assembly (BHA) are conducted and a time-frequency analysis technique is applied to the response in order to identify the relationship between the position of the transition point between positive and negative strain and the dispersive properties of the lateral wave. Based on the results, a new monitoring scheme is proposed to monitor the stability of the drill-string based on a combination of lateral impact wave analysis at the BHA and the axial acoustic telemetry technique.

Numerical Investigation of Lateral and Axial Wave Propagation in Drill-Strings for Stability Monitoring

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Yu Liu ◽  
Yi Ji ◽  
Andrew J. Dick
Keyword(s):  
Wave Propagation ◽  
Numerical Method ◽  
Acoustic Waves ◽  
Drill Pipe ◽  
Drill String ◽  
Lateral Impact ◽  
Monitoring Scheme ◽  
Time Frequency ◽  
Impact Wave ◽  
Stability Monitoring

In this paper, the propagation of lateral waves and axial acoustic waves in a drill-string are studied by using a new numerical method and a stability monitoring scheme is proposed. The drill-string is modeled as a linear beam structure under gravitational field effects. Lateral and axial motions are assumed to be decoupled, and the corresponding equations of motion are derived. An iterative wavelet-based spectral finite element method (WSFEM) model is developed to obtain a high fidelity response. Numerical simulations of the lateral impact wave propagation at the bottom-hole-assembly (BHA) are first conducted, and a time-frequency analysis technique is applied to the response in order to identify the relationship between the position of the transition point between positive and negative strain and the dispersive properties of the lateral wave. Next, axial acoustic wave propagation through the upper drill-pipe is studied to explore the banded transmission properties of the drill-string introduced by periodic joints. Based on the results, a new monitoring scheme is proposed to monitor the stability of the drill-string by conducting a combination of lateral impact wave analysis at the BHA and the axial acoustic telemetry technique. The new numerical method used in this study provides a unified approach to study the wave propagation in drill-strings, and the proposed stability monitoring scheme is expected to be applicable in drill-string operations.

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