Experimental Study of the Multifrequency Acoustic Backscatter System using Field Sediment

摘要

Measurements of suspended sediment concentration (SSC) and particle size (PS) are very significant in the study of sediment transport in estuarine and coastal areas. The multifrequency acoustic backscatter system (ABS) can be applied to measure the boundary layer SSC and PS profiles using backscatter strength data. The experiments in this study were conducted using an ABS equipped with sensors at multiple frequencies (0.5, 1, 2, and 4 MHz) in a test tank system in the laboratory. The fine sediment (average particle size < 20 μm) and coarse sediment (average particle size > 100 μm) used in the experiment were obtained from the Changjiang Estuary. The results were as follows: A linear relationship between the time-averaged strength of the backscatter measured by the ABS and the square root of SSC was detected; Different inverse models used to calculate SSC (IASC, IAMC, EASC) and PS (IAMP) from ABS data exhibited different patterns, and appropriate calibration or regression approaches should be used to obtain reliable results; The SSC and PS results for the field sediment indicate that the ABS is potentially applicable in coastal and estuarine areas, especially in the fine sediment environment. Further experiments are required to model sediment suspension in different environments, particularly with regard to the uncertainty of various PSs in the water column.