Data evaluation for acoustic Doppler current profiler measurements obtained at fixed locations in a natural river

摘要

[1] Methodologies are presented to (1) evaluate the effect of acoustic Doppler current profiler (ADCP) motion on velocity measurements, (2) assess the stationarity of velocity time series, and (3) ensure that a sample record is of sufficient length for measurements taken with an ADCP at a fixed location in a natural river. ADCP motion occurring on the timescale of an ensemble is investigated by comparing single-ping and multiping measurements obtained at the same location under the same flow conditions. Large-scale motion occurring over the course of the entire measurement is studied by first examining a set of indicators to determine if motion may have resulted in the ADCP measuring in regions of different flow characteristics and then dividing the record into segments representing the potentially different regions for comparison. If boat motion is significant, the ADCP record is edited accordingly. Stationarity is assessed using statistical trend tests with guidance provided for selecting parameters based on instrument physics and flow conditions. Mean streamwise and spanwise velocity profiles can be calculated after confirming the reliability of a measurement. A set of criteria are presented to evaluate the appropriateness of an assumption of the law of the wall for streamwise velocity profiles. The methodology is demonstrated using 67 fixed-vessel measurements obtained at two sites on the lower Roanoke River for two discharges. The results indicate that an appropriate procedure was used for securing the ADCP in the channel and that the sample records were sufficient to provide both accurate measurements of mean quantities and assess the stationarity of velocity.