Asymptotic turbulent friction in 2D rough-walled flows.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33514543.
- Also identified by DOI 10.1126/sciadv.abc6234 and PMC identifier 7846176.
- Licence recorded as CC BY-NC.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
The friction <i>f</i> is the property of wall-bounded flows that sets the pumping cost of a pipeline, the draining capacity of a river, and other variables of practical relevance. For highly turbulent rough-walled pipe flows, <i>f</i> depends solely on the roughness length scale <i>r</i>, and the <i>f</i> - <i>r</i> relation may be expressed by the Strickler empirical scaling <i>f</i> ∝ <i>r</i> <sup>1/3</sup> Here, we show experimentally that for soap film flows that are the two-dimensional (2D) equivalent of highly turbulent rough-walled pipe flows, <i>f</i> ∝ <i>r</i> and the <i>f</i> - <i>r</i> relation is not the same in 2D as in 3D. Our findings are beyond the purview of the standard theory of friction but consistent with a competing theory in which <i>f</i> is linked to the turbulent spectrum via the spectral exponent α: In 3D, α = 5/3 and the theory yields <i>f</i> ∝ <i>r</i> <sup>1/3</sup>; in 2D, α = 3 and the theory yields <i>f</i> ∝ <i>r</i>.