Experimental investigation on inversion of ADVP measurement for suspended sediment concentration, a case study

To obtain vertical velocity profile and related suspended sediment concentration (SSC) simultaneously with little interference as far as possible is always of hydraulic researchers' interest. For this purpose, the experiments with suspended sediment of silica sand were carried out in water vessel in order to investigate the inversion of acoustic backscatter intensity for SSC distribution in acoustic Doppler velocimeter measurement. A Nortek Vectrino Profiler (ADVP) was used in the experiments. The influences of the sediment diameter, the average concentration and the instrument parameter setting on acoustic backscatter signal (AMP) were tested. The results show that AMP values of middle layer are larger than those of the other layers and they have similar logarithmic relationship with SSC as in ADV measurement inversion. The relationship was found to depend on the particle sizes and the sampling cell configuration. The more layered in a same sampling section, the weaker the backscattered intensity and the larger the intensity difference between the middle layer and the other layers. When certain amendment is given to the AMP values on each layer, the ADVP measurements can still be transferred into SSC by using the simple logarithmic relationship. Through the experiments, the acoustic inversion approaches are suggested and the involved formula for sediment concentration profile for the case is established.