Modeling sediment transport depends on several parameters, such as suspended sediment concentration （SSC）, shear stress, and settling velocity. To assess the ability of Pulse-Coherent Acoustic Doppler Profiling （PC...Modeling sediment transport depends on several parameters, such as suspended sediment concentration （SSC）, shear stress, and settling velocity. To assess the ability of Pulse-Coherent Acoustic Doppler Profiling （PC-ADP） to non-intrusively quantify spatial and temporal SSC and settling velocity at seabed, a field experiment was conducted in the Beibu Gulf （Tonkin Gulf）, in the South China Sea. The spatial profiles and temporal variations in SSC at 1 m above bottom were derived from PC-ADP acoustic backscatter intensity determinations after being calibrated with the optical backscatter sensor （OBS） measurements at the same elevation. The PC-ADP and OBS results agreed well. The temporal settling velocity obtained from Rouse profiles agreed well with the Soulsby formula based on size information by LISST （laser in situ scattering and transmissometry）. Tides and tidal currents are diurnal in the gulf. SSC increased with increasing ebb and flood flow, and it rapidly decreased with the increase of distance from the seabed. The maximum SSC at 0.16 m and 1.3 m above bottom reached 816 mg/L and 490 mg/L during spring tides, respectively. The sediments consisted of mineral particles 23-162 μm in diameter and 0.05-2.04 crn/s in settling velocity. Generally, both the SSC and settling velocity followed variations in the bottom friction. Results suggest that PC-ADP is able to provide reasonable SSC and settling velocity measurements of both profiles and time series for a long study period.展开更多
Mean and fluctuating velocities were measured by use of a pulse coherent acoustic Doppler profiler （PC-ADP） and an acoustic Doppler velocimeter in the tidal bottom boundary layer of the Pearl River Estuary. The bed ...Mean and fluctuating velocities were measured by use of a pulse coherent acoustic Doppler profiler （PC-ADP） and an acoustic Doppler velocimeter in the tidal bottom boundary layer of the Pearl River Estuary. The bed shear stresses were estimated by four different methods： log profile （LP）, eddy correlation （EC）, turbulent kinetic energy （TKE）, and inertial dissipation （ID）. The results show that （a） all four methods for estimating bed stresses have advantages and disadvantages, and they should be applied simultaneously to obtain reliable frictional velocity and to identify potential sources of errors; （b） the LP method was found to be the most suitable to estimate the bed stresses in non-stratified, quasi-steady, and homogeneous flows; and （c） in the estuary where the semi-diurnal tidal current is dominant, bed shear stresses exhibit a strong quarter-diurnal variation.展开更多
基金Supported by Major Programs of the Chinese Academy of Sciences (No. H42032602)the National Natural Science Foundation of China (No. 470776061)
文摘Modeling sediment transport depends on several parameters, such as suspended sediment concentration （SSC）, shear stress, and settling velocity. To assess the ability of Pulse-Coherent Acoustic Doppler Profiling （PC-ADP） to non-intrusively quantify spatial and temporal SSC and settling velocity at seabed, a field experiment was conducted in the Beibu Gulf （Tonkin Gulf）, in the South China Sea. The spatial profiles and temporal variations in SSC at 1 m above bottom were derived from PC-ADP acoustic backscatter intensity determinations after being calibrated with the optical backscatter sensor （OBS） measurements at the same elevation. The PC-ADP and OBS results agreed well. The temporal settling velocity obtained from Rouse profiles agreed well with the Soulsby formula based on size information by LISST （laser in situ scattering and transmissometry）. Tides and tidal currents are diurnal in the gulf. SSC increased with increasing ebb and flood flow, and it rapidly decreased with the increase of distance from the seabed. The maximum SSC at 0.16 m and 1.3 m above bottom reached 816 mg/L and 490 mg/L during spring tides, respectively. The sediments consisted of mineral particles 23-162 μm in diameter and 0.05-2.04 crn/s in settling velocity. Generally, both the SSC and settling velocity followed variations in the bottom friction. Results suggest that PC-ADP is able to provide reasonable SSC and settling velocity measurements of both profiles and time series for a long study period.
基金financially supported by the National Basic Research and Development Program of China(Grant No.2013CB956502)the National Natural Science Foundation of China(Grant Nos.41276079 and 41176067)the Open Research Foundation of Pearl River Hydraulic Research Institute(Grant No.2013KJ07)
文摘Mean and fluctuating velocities were measured by use of a pulse coherent acoustic Doppler profiler （PC-ADP） and an acoustic Doppler velocimeter in the tidal bottom boundary layer of the Pearl River Estuary. The bed shear stresses were estimated by four different methods： log profile （LP）, eddy correlation （EC）, turbulent kinetic energy （TKE）, and inertial dissipation （ID）. The results show that （a） all four methods for estimating bed stresses have advantages and disadvantages, and they should be applied simultaneously to obtain reliable frictional velocity and to identify potential sources of errors; （b） the LP method was found to be the most suitable to estimate the bed stresses in non-stratified, quasi-steady, and homogeneous flows; and （c） in the estuary where the semi-diurnal tidal current is dominant, bed shear stresses exhibit a strong quarter-diurnal variation.
