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

The drag reduction properties of a turbulent channel flow modified byspanwise sinusoidal oscillations of the walls are investigated by directnumerical simulations. The work is based on the linear relation between thedrag reduction and the parameter $S$, function of the maximum wall velocity andthe period of the oscillation. This quantity has been found through physicalarguments pertaining to the action of the oscillating Stokes layer on thenear-wall turbulence dynamics. The predictive potential of the scalingparameter is exploited to gain insight into the drag-reducing effects of theoscillating wall technique. The period of oscillation which guarantees themaximum drag reduction for a given maximum wall displacement is studied for thefirst time. The issue of the minimum intensity of wall forcing required toproduce a non-zero drag reduction effect and the dependence of the dragreduction on the Reynolds number are also addressed. The drag reduction dataavailable in the literature are compared with the prediction given by thescaling parameter, thus attaining a comprehensive view of the state of the art.

Wall-oscillation conditions for drag reduction in turbulent channel flow