Evaluation of an Extended Autocorrelation Phase Estimator for Ultrasonic Velocity Profiles Using Nondestructive...

Area of Science:

• Fluid dynamics
• Ultrasonic measurement techniques
• Signal processing

Background:

• Autocorrelation method (ACM) is widely used for ultrasonic velocity profiling but limited by phase aliasing at higher velocities.
• Cross-correlation method (CCM) overcomes phase aliasing but requires significant computational resources.
• Extended autocorrelation method (EAM) is a recent technique combining ACM and CCM advantages.

Purpose of the Study:

• Evaluate and compare ACM, CCM, and EAM for ultrasonic velocity estimation.
• Assess performance below and beyond the Nyquist limit.
• Investigate EAM's computational efficiency and accuracy.

Main Methods:

• Comparison of three velocity estimators: ACM, CCM, and EAM.
• Utilized a nondestructive ultrasonic device on a controlled rotating cylinder flow.
• Evaluated performance using root-mean-square deviation variation coefficient (CVRMSD).

Main Results:

• EAM accurately measures velocities below the Nyquist limit with <2% CVRMSD.
• EAM and CCM effectively measure velocities beyond the Nyquist limit.
• EAM is computationally 15 times faster than CCM.

Conclusions:

• EAM provides accurate and efficient ultrasonic velocity measurements beyond the Nyquist limit.
• The study validates EAM for NDT applications, overcoming ACM limitations.
• Velocities up to six times the Nyquist limit are measurable with EAM and CCM under specific parameters.