A Waveguide-Invariant-Based Warping Operator and Its Application to Passive Source Range Estimation

2015 ◽  
Vol 23 (01) ◽  
pp. 1550003 ◽  
Author(s):  
Yu Bo Qi ◽  
Shi Hong Zhou ◽  
Ren He Zhang ◽  
Yun Ren
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Low Frequency ◽  
Cross Correlation Function ◽  
Range Estimation ◽  
Waveguide Invariant ◽  
Correlation Component ◽  
The Cross ◽  
The Relationship ◽  
Warping Operator

A formula for the instantaneous phase of the cross-correlation function of two different modes using the relationship between the horizontal wavenumber difference and frequency described by the waveguide invariant is deduced in this paper. Based on the formula, a waveguide-invariant-based warping operator suitable for both reflected and refracted modes in shallow water at low frequency is presented, providing an effective tool to filter the cross-correlation function of modes from the signal autocorrelation function. Using the phase of the filtered cross-correlation component in the frequency domain, a passive source ranging method on a single hydrophone is proposed. Simulated and experimental data using impulsive signals verify the validity of the derived warping operator and source ranging method.

Simultaneous Measurement of Temperature and Velocity Using µPIV

2006 ◽  
Author(s):  
Pramod Chamarthy ◽  
Steven T. Wereley ◽  
Suresh V. Garimella
Keyword(s):  
Brownian Motion ◽  
Correlation Function ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
Motion Information ◽  
Peak Broadening ◽  
Constant Temperature Water Bath ◽  
Gravity Driven ◽  
The Cross ◽  
Gravity Driven Flow

In μPIV, for a uniform velocity field the displacement of the cross-correlation function gives the velocity of the fluid and the broadening of the peak-width represents the amount of Brownian motion present. In the presence of a linear or a parabolic shear, the shape of the cross-correlation function would have both the Brownian motion information as well as the velocity distribution information. In the present work, the broadening of the cross-correlation function caused by the velocity gradient was subtracted from the total peak broadening in order to isolate the Brownian motion information and thus infer temperature. To the authors' knowledge, this technique has not been applied to measure the temperature of a moving fluid. The experiments were conducted in a gravity driven flow through a tube surrounded by a constant temperature water bath.

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