Synchronous measurements of the velocity and concentration in low density turbidity currents using an Acoustic Doppler Velocimeter

Abstract

Low density turbidity currents have been investigated in a laboratory flume. An Acoustic Doppler Velocimeter (ADV) was used to measure the velocity. The dimensionless velocity profiles were compared with previous studies to check the accuracy of acoustic measuring techniques for turbidity currents. Successful use of the ADV to measure the current velocity has led to interest in the technique of using acoustic sensors to estimate concentrations. Acoustic backscattering analyses are used for estimating the sediment concentration in turbidity currents. With this approach, concentration measurements can be reasonably well represented by a similarity profile. Using this technique, an accurate estimation of the concentration close to the bed, where obtaining reliable concentration data by sampling techniques is difficult, is possible. The results show that a power relation is a good estimate for the concentration distribution in this region, for which no reliable expressions have been provided previously. Successful estimation of the velocity and concentration, in the present experiments, indicates that this technique could be appropriate and useful for determining the flow structure in turbidity currents.