English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The motivation for this study is to investigate the abilities and limitationsof a Nortek Signature1000 acoustic Doppler current profiler (ADCP) regardingfine-scale turbulence measurements. Current profilers offer the advantage ofgaining more coherent measurement data than available with point acousticmeasurements, and it is desirable to exploit this property in laboratory andfield applications. The ADCP was tested in a towing tank, where turbulence wasgenerated from a grid towed under controlled conditions. Grid-inducedturbulence is a well-studied phenomenon and a good approximation for isotropicturbulence. Several previous experiments are available for comparison and thereare developed theories within the topic. In the present experiments, anacoustic Doppler velocimeter (ADV), which is an established instrument forturbulence measurements, was applied to validate the ADCP. It was found thatthe mean flow measured with the ADCP was accurate within 4% of the ADV. Theturbulent variance was reasonably well resolved by the ADCP when large gridbars were towed at a high speed, but largely overestimated for lower towingspeed and smaller grid bars. The effective cutoff frequency and turbulent eddysize were characterized experimentally, which provides detailed guidelines forwhen the ADCP data can be trusted and will allow future experimentalists todecide a priori if the Nortek Signature can be used in their setup. We concludethat the ADCP is not suitable for resolving turbulent spectra in a small-scalegrid-induced flow due to the intrinsic Doppler noise and the low spatial andtemporal sample resolution relative to the turbulent scales.

Grid turbulence measurements with an acoustic Doppler current profiler