Methodology

Ultrasound Velocity Profiling (UVP) is a technique originally developed for studying blood flow in humans. This method was extended in the mid 1980’s to include measurements also in general fluids and has since become an important tool within research and fluid engineering.

UVP, which is sometimes also called Pulsed Ultrasound Velocimentry is a method to measure an instantaneous velocity profile in a liquid flow by echography.

With Ultrasound Velocity Profiling (UVP), pulses of ultrasound are transmitted through the pipe where the liquid flows. When the ultrasound hits the fluid, or particles in the fluid, it is echoed back and the returning pulse is measured using a sensor. In this process, when the pulse is reflected by a scattering particle suspended in the fluid, the signal frequency is altered. In other words, there is a slight difference in frequency/time between the pulse sent out and the pulse coming back. This small difference can then be analyzed and related to the local fluid velocity by detecting the Doppler shift information.

The measurement is unidimensional (1D) providing a velocity profile projected along the probing axis. Since the majority of the small scattering particles are assumed to travel at a velocity equal to that of the continuous phase the true velocity distribution along the probing axis is obtained.

UVP measurements can be combined with simultanous Pressure Difference (PD) measurments over a fixed length of a pipe. This novel method for in-line rheometry, commonly known as UVP+PD, has been developed and optimised at SIK - The Swedish Institute for Food and Biotechnology and Cape Peninsula University of Technology (CPUT). The method is a multi-point version of the traditional single point tube viscometer concept. It allows real-time measurements of radial velocity profiles, volume flow rate, Solid Fat Content (SFC) as well as acoustic and rheological properties directly in-line while under true dynamic process conditions. It has advantages over commercially available process viscometers and and off-line rheometers instruments in being non-invasive, applicable to opaque and concentrated suspensions, having small sensors dimensions and relatively low cost.