On using acoustic profiling to study bottom boundary layer flow dynamics in unsteady sediment-laden open-channel flow

摘要

Measurement and analysis of physical and chemical characteristics of sea water are necessary and important in many applications. ANZALI is an active and noisy port located in south west of the Caspian Sea. There are limited published data about physical and underwater acoustical characteristics of the port. In February and May 2007, measurement of underwater acoustical noise and Transmission loss in that zone, accomplished using two boats and some measurement equipments. A hydrophone array system and an acoustical projector were designed, constructed, and calibrated for use in these measurements. Some related quantities as, temperature profile; wind and water flow direction and magnitude were measured. Also before that time, water temperature measurement had been done in some different successive seasonal conditions. Water depth of the zone changes slowly from 100 to 200 meter. After preprocessing of measured data, Power Spectrum (PS) and Probability Density Function (PDF) estimation algorithms had applied to data using MATLAB software. We recognize a significant increase in PS levels below 200Hz in different weather conditions and industrial activities. Using seasonal temperature measured data; we conclude that water temperature, between surface and depth of 50 meter, decrease sharply from 27 to 8 centigrade at summer and slowly from 10 to 8 centigrade at winter. In depths below 50 meter, water temperature is not affected by air temperature and varies slowly from 8 to 7. Also in shallow regions we found, Transmission Loss model similar to spherical model that is reasonable regarding temperature profile and sea bed materials