An Examination of the Application of Acoustic Doppler Current Profiler Measurements in a Wide Channel of Uniform Depth for Turbulence Calculations

Acoustic Doppler Current Profilers (ADCPs) have been used for measuring river discharges for over twenty years. To determine the discharge of a channel, the ADCP rapidly gathers a large amount of velocity data and this data can be used to provide useful information about the flow distribution in a channel. But since the acoustic beams from the ADCP diverge and sample different locations in the channel, the process for determining turbulence parameters is unlike that used for point measurements where velocity readings are taken at specific locations in the channel. In order to assess the measurement capabilities of the ADCP for turbulence parameters, a side-by-side comparison was made between an ADCP and an Acoustic Doppler Velocimeter (ADV). Tests were performed in a long, straight channel with a relatively uniform depth profile and a constant discharge. The three components of the channel velocity (streamwise, transverse, and vertical) were concurrently recorded by both instruments from a boat secured parallel to the direction of streamwise flow. Using the velocity data gathered with the acoustic instruments, turbulence parameters such as turbulent kinetic energy, Reynolds stresses, and root-mean-square (rms) velocities were calculated. A comparison of these parameters as determined by each instrument and a discussion of the overall performance of the ADCP are given.