Ari Hamdani

Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using Fast Fourier Transform (FFT) Technique

In two-phase bubbly flow, measurement of liquid and bubble velocity is a necessity to understand fluid characteristic. The conventional ultrasonic velocity profiler (UVP), which has been known as a nonintrusive measurement technique, can measure velocity profile of liquid and bubble simultaneously by applying a separation technique for both phases (liquid and bubble) and transparent test section is unnecessary. The aim of this study was to develop a new technique for separating liquid and bubble velocity data in UVP method to measure liquid and bubble velocity profiles separately. The technique employs only single resonant frequency transducer and a simple UVP system. An extra equipment is not required. Fast Fourier Transform (FFT) based frequency estimator paralleled with other signal processing techniques, which is called as proposed technique, was proposed to measure liquid and bubble velocity separately. The experimental facility of two-phase bubbly flow in the vertical pipe was constructed. Firstly, the Doppler frequency estimation by using the FFT technique was evaluated in single-phase liquid flow. Results showed that FFT technique showed a good agreement with autocorrelation and maximum likelihood estimator. Then, separation of liquid and bubble velocity was demonstrated experimentally in the two-phase bubbly flow. The proposed technique confirmed that liquid and bubble velocity could be measured efficiently.

Two-Phase Flow Studies in Boiling Single Channel Flow Using Wire Mesh Tomography (WMT) and Ultrasound Velocity Profile (UVP)

The objective of this work is to investigate characteristics of co-current boiling flow in a circular pipe with an inner diameter of 52 mm by using wire mesh tomography (WMT) and ultrasonic velocity profile (UVP). The inner wall of pipe is modified by adding fins on the inner pipe’s wall. This modification is intended to change the flow behavior into swirling flow in boiling flow. Firstly, the effect of wall modification on flow behavior is investigated by numerical calculation. Secondly, two-phase flow is investigated experimentally using UVP and WMT. In experiments, local time-average void fraction is measured using WMT and velocity profile is measured using UVP. Furthermore, these measured data, both void fraction and velocity profile, will give information about changing in flow pattern caused by modified inner pipe’s wall.Copyright