Velocity Profile Measurements in Bubbly Flow Using Multi-Wave Ultrasound Technique

Abstract

Velocity profile measurements in bubbly flows have been performed by using the ultrasonic velocity profile technique, which can measure velocity distributions along a measuring line. To obtain the liquid and gas velocity distributions simultaneously, a new technique for separating liquid and gas velocity data is developed. The technique employs a unique ultrasonic transducer (TDX) referred to as a multi-wave transducer. The multi-wave TDX consists of two kinds of ultrasonic piezoelectric elements that are concentrically set and have different resonant frequencies. The central element of 3 mm diameter has a basic frequency of 8 MHz for liquid-phase measurements, and the outer element has a basic frequency of 2 MHz for bubble-phase measurements in two-phase bubbly flows. The multi-wave TDX can emit the two ultrasonic frequencies independently. First, the multi-wave TDX is used together with an ultrasonic velocity profiler (UVP) based on the ultrasonic pulse repetition method. The effects due to volume, liquid velocity, and bubble rising velocity measurements are obtained by the UVP in two-phase bubbly flows. However, the velocity distribution of bubbles measured by the UVP includes errors induced by tracer particles suspended in the liquid. The ultrasonic velocity profile technique requires tracer particles as ultrasonic reflectors. Then to improve the accuracy of the bubble rising velocity distribution, the ultrasound time domain correlation (UTDC) method is applied. Comparing the intensities of echo signals from 2 MHz and 8 MHz ultrasounds, bubble and liquid velocity distributions were obtained. The velocity distributions measured by the UTDC are in good agreement with those measured by the UVP. This technique can be utilized for many industrial applications.

Experimental determination of maximum effective hydrodynamic stress in multiphase flow using shear sensitive aggregates

“…A large‐eddy PIV method was applied to compensate for low resolution of the PIV technique allowing an estimation of the turbulent dissipation rate . Several other experimental techniques such as Positron Emission Particle Tracking (PEPT), computer‐automated radioactive particle tracking computer tomography (CARPT), and multiwave ultrasound technique have been used to characterize the local gas volume fraction in stirred tanks. However, due to their low spatial and temporal resolution they are not suitable to characterize the small scale turbulence structures including highest local values.…”

Relation between oil–water flow and extraction performance in liquid–liquid countercurrent centrifugal extractors with Taylor vortices

“…Researchers have applied the UVP method to clarify the flow of single-phase structures of not only water flows, but also magnetic flows [17][18][19]. There has also been research on two-phase flow mea-surement using UVP, but most studies have examined bubbly flows [20][21][22][23][24][25], and there are few measurement studies on oil-water multiphase flows [26]. Although UVP measurements are applicable in many cases, certain difficulties and problems with this method are yet to be overcome.…”

Velocity measurement on two-phase air bubble column flow using array ultrasonic velocity profiler

“…Echo signals of the ultrasonic beam reflected by bubbles are stronger than those reflected by tracer particles. The velocity measured by the multi-wave transducer in two-phase bubbly flow has validated by comparing with High-Speed Camera measurement by Kikura et al [5].…”