Simultaneous measurements of the solid particles velocity and concentration profiles in two phase flow by pulsed ultrasonic doppler velocimetry

Abstract

In this experimental study, the pulsed ultrasonic Doppler velocimetry was used to measure simultaneously the local velocity and the local concentration in a flow of solid-liquid suspension in a horizontal pipe. In order to distinguish between the Doppler signals coming from the continuous phase, water and those of the glass bead particles larger than the Kolmogorov length scale and the wavelength of the ultrasonic wave, a threshold is imposed on the integral of the power spectral density of the Doppler signal. The new approach measurement of the local concentration was used. It consists of counting a number NP of the Doppler signals of the solid particles crossing the measurement volume and a number NPt of the Doppler signals of the solid particles crossing the control volume. The concentration profile is then represented by the ration NP / NPt. The results obtained show that the suspension of fine particles, which represents a tracer, behaves as a homogenous fluid. For large particles, we confirmed the existence of the slip velocity and the effects of both concentration and size particle on the turbulence. The use of two distinct measurement volumes allows the direct determination of the turbulent length scales. The results show that the turbulence characteristics of the carried fluid are modified by the presence of the solid particles.