Extended Short-Time Fourier Transform for Ultrasonic Velocity Profiler on Two-Phase Bubbly Flow Using a Single Resonant Frequency

Wongsakorn Wongsaroj,Hiroshige Kikura,Natee Thong-Un,Ari Hamdani,Hideharu Takahashi

doi:10.3390/app9010050

Abstract

This study introduces a measurement technique for simultaneous phase-separated velocity in two-phase bubbly flow. The non-invasive technique, based on an Ultrasonic Velocity Profiler (UVP), is used in order to obtain an instantaneous, separate velocity profile for both liquid and bubble. The aim of this paper is to measure each phase velocity at the same time and position it using only a single resonant frequency. To achieve this aim, extended signal processing of the Short-Time Fourier Transform (STFT) is proposed, combining with amplitude classification to analyze Doppler signal influenced from the bubbly flow. The use of developed algorithms allows the instantaneous separation of liquid and bubble velocity profiles. In this work, the developed technique is used to measure the velocity profile of bubbly flow in the vertical pipe, demonstrating the classification of liquid and bubble velocity. To confirm the accuracy of each velocity profile phase, the Particle Image Velocimetry (PIV) method is used for comparison. The results clarify that the proposed method is in good agreement with the PIV measurement. Finally, the effect of void fraction against velocity measurement of both phases was demonstrated.

Highlights

Two-phase bubbly flow is a common phenomenon in many industrial processes such as chemical production, thermal power plants, and nuclear reactors
This study proposes a measurement technique for obtaining the velocity profile of two-phase bubbly flow using the Ultrasonic Velocity Profiler (UVP) method with a single resonant frequency
The velocity distributions measured by Developed-UVP, Particle Image Velocimetry (PIV), and Original-UVP, were almost in agreement

Summary

Introduction

Two-phase bubbly flow is a common phenomenon in many industrial processes such as chemical production, thermal power plants, and nuclear reactors. To understand the characteristics of this phenomenon, multi-scale modeling has been developed to analyze and predict the characteristic of two-phase bubbly flow [1,2]. It employs many empirical correlations and consecutive equations such as bubble and liquid velocity, bubble size distribution, slip ratio, and so on. To provide a reliable database for two-phase flow models, the interaction between two phases and its behavior must be clarified by experimental work, in particular, velocity distribution of liquid and bubble. Several intrusive measurement techniques have been used to measure the velocity profile in two-phase bubbly flow such as hot-film anemometry [3]

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