Application of Short Time Fourier Transform in Ultrasonic Velocity Profiler on Bubbly Flow

Abstract

Two-phase bubbly flow is a common phenomenon in many industrial processes. To understand its characteristic, the velocity profile of liquid and bubble are necessary to be known accurately. The ultrasonic velocity profile (UVP) method has been known as a nonintrusive measurement method that can measure velocity profiles of fluid. Although the original UVP can measure velocity profile of two phase bubbly flow, it cannot distinguish liquid and bubble velocity. Therefore, the separation technique is used to overcome this limitation. The aim of this study was to develop signal processing of UVP method to measure liquid and bubble velocity profiles separately. Short Time Fourier Transform (STFT) was proposed to be applied in this case, and it was paralleled with other signal processing techniques. The experiment was conducted on vertical pipe flow apparatus. The velocity profile measurement in two-phase bubbly flow was performed. Separation of liquid and bubble velocity was demonstrated. Moreover, the method was compared with other techniques experimentally.