Instantaneous flow vector measurement by a pair of ultrasound doppler instruments

Ultrasound Doppler velocity profiling is an effective method for instantaneous fluid velocity measurement along a measurement line. However, measuring vector components in multiple dimensions requires the development of multiple transducers, with the exact number depending on numbers of required cross-sections. This study provides a technique to extract two-dimensional velocity data along the bisector between two transducers by using a reasonable correction of the time lag or progress between the transducers. The observed time differences arise from geometry of the set-up and depend on the distance from the crossing point, intersection angle, and representative velocity in the main flow direction. The developed methodology is applied to the measurement of a quartz-particle-laden turbidity current produced in a lock-gate flume. After opening the gate, the suspension intrudes into the ambient water and is transported downstream according to a density difference. A convex-shape velocity distribution in the direction of stream flow and the vertically generated instabilities along the interface with ambient water are observed using this simple and convenient velocity measurement technique, which can characterize flow structure and aid statistical analyses of parameters such as vorticity.