Particle velocity detection and measurement in two-phase flow using combined electronic logic system and LDA technique

A new experimental method to measure the velocity and fluctuations of a solid–liquid suspension is proposed in this work. This method based on laser anemometry with Doppler effects consists of an association of laser velocimetry and an electronic logic circuit placed at the reception. This circuit was developed in order to distinguish between signals from the continuous phase (water) and those of the solid particles (glass beads) and therefore to detect the presence of large particles (larger than the laser wavelength) in the measurement volume. The present experimental method is limited to small volumetric concentrations lower than 2%. Indeed, when the value of 2% is exceeded, the suspension becomes a very diffusing medium and prevents the propagation of laser beams in the flow in an ascending vertical glass pipe. The results show that a fine particle suspension, which represents a tracer, behaves as a homogeneous fluid. For large particles, we confirmed the existence of a slip velocity and the effect of particle concentration on the turbulence intensity.