SonTek SL3G Side-Looking Doppler Current Meter application in Complex Flow Conditions

Abstract:

The SonTek Argonaut SL Side-Looking Doppler Current Meters are well established products in the measurement of real-time water velocity in open channels. With the development of acoustic doppler technology the decision was made to incorporate latest technology in the Argonaut SL and hence the SonTek SL3G was born.

The SonTek SL3G Acoustic Doppler instrument incorporates a number of innovations that improves velocity measurements and quality assurance of data for Side-Looking Doppler Current Meters. SmartPulseHD was originally introduced with the launch of the SonTek M9/S5 RiverSurveyor Acoustic Doppler Instruments and the increased accuracy and resolution of velocity measurements made it obvious to include into the new SL3G instruments. SmartPulseHD continuously tracks the water conditions and selects the optimum processing configuration required using multiple ping types and processing techniques. The new SL3G design makes it the smallest Side Looking Acoustic Doppler Velocity Meter on the market reducing flow disturbance caused by the instrument and the distance of first measurement cell from boundary.

The application of the SL3G Acoustic Doppler instrument is designed for complex flow conditions where the use of conventional stage-discharge relationships is economically not viable and therefore requires the use of velocity index methodology. The case-study presented in this paper is situated in the Colorado River downstream of Imperial Dam affected by controlled releases, drainage from adjacent irrigation areas and backwater from a weir situated downstream of the monitoring site.  The paper analyses the relationship between measured mean velocity and index velocity and if additional variables such as stage and or Y-velocity need to be incorporated in the development of the index velocity rating.  In addition, to determine the variables impacting on the index velocity rating, the index velocity applied will be evaluated by the best linear relationship between the multi-cell and integrated cell index velocities and measured mean velocities.

The data presented in this paper shows that the physical design and features of the new SonTek SL3G instrument enables the user to accurately measure real time discharge information in complex flow conditions based on index velocity rating principles.