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 Tools annual

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 Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

In this work, we propose a new detector function based on wavelet transformto discriminate between turbulent and non-turbulent regions in an intermittentvelocity signal. The derivative-based detector function, which is commonly usedin intermittency calculation schemes, shows large fluctuations within turbulentparts of the signal and requires averaging over a certain ``smoothing period''to remove the fake drop-outs, introducing subjectivity in calculatingintermittency. The new detector function proposed here is obtained by averagingthe ``pre-multiplied wavelet energy'' over the entire frequency range,resulting in a function that is much smoother than the derivative-baseddetector and at the same time has a good discriminatory property. This makesthe choice of the smoothing period unnecessary and removes the subjectivityassociated with it. We demonstrate the effectiveness of the wavelet detectorwithin the framework of the widely-used method by Hedley and Keffer (1974, J.Fluid Mech., V64, pp625), for a range of velocity signals representing thedifferent stages of roughness-induced transition. The wavelet detector functionworks well in detecting the edge intermittency of a canonical turbulentboundary layer as well, thereby highlighting its generality. Our detector can,in principle, be used with any method of specifying threshold for obtaining anindicator function.

A wavelet-based detector function for characterizing intermittent velocity signals