Re-evaluation of Nikuradse's experimental data for rough pipes.

Tani, Itirô

doi:10.2183/pjab.65.133

Cited by 2 publications

(2 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The same tendency in P was obtained by decreasing the flow rate without the hysteresis effect, demonstrating clear evidence for turbulence modification by the structured surface and not due to the laminar to turbulence transition. Similar findings were reported by Toms (1977) from early experiments on turbulent drag reduction by high polymers and additionally by Tani (1989), who re-evaluated Nikuradze's (1933) experiments performed in rough pipes.…”

Section: Turbulent Drag Reduction At Low Reynolds Numberssupporting

confidence: 85%

“…A variety of riblet patterns aligned in the flow direction were investigated, both experimentally and numerically, but they produced only a modest drag reduction effect, DR < 10 % (Walsh 1980;Choi, Moin & Kim 1993;Bechert et al 2000). Additional evidence emerged from re-examination of early measurements made in pipes covered with sand-grained roughness (Nikuradze 1933;Tani 1989) and experiments carried out in a plane channel consisting of walls covered with distributed arrow-shaped structures (Sirovich & Karlsson 1997), surface-embedded grooves (Frohnapfel, Jovanović & Delgado 2007b) or shallow dimples (Lienhart, Breuer & Köksoy 2008;Tay, Khoo & Chew 2015).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Toward design of the antiturbulence surface exhibiting maximum drag reduction effect

et al. 2018

View full text Add to dashboard Cite

The flow development in a groove-modified channel consisting of flat and grooved walls was investigated by direct numerical simulations based on the Navier–Stokes equations at a Reynolds number of $5\times 10^{3}$ based on the full channel height and the bulk velocity. Simulations were performed for highly disturbed initial flow conditions leading to the almost instantaneous appearance of turbulence in channels with flat walls. The surface morphology was designed in the form of profiled grooves aligned with the flow direction and embedded in the wall. Such grooves are presumed to allow development of only the statistically axisymmetric disturbances. In contrast to the rapid production of turbulence along a flat wall, it was found that such development was suppressed over a grooved wall for a remarkably long period of time. Owing to the difference in the flow structure, friction drag over the grooved wall was more than 60 % lower than that over the flat wall. Anisotropy-invariant mapping supports the conclusion, emerging from analytic considerations, that persistence of the laminar regime is due to statistical axisymmetry in the velocity fluctuations. Complementary investigations of turbulent drag reduction in grooved channels demonstrated that promotion of such a state across the entire wetted surface is required to stabilize flow and prevent transition and breakdown to turbulence. To support the results of numerical investigations, measurements in groove-modified channel flow were performed. Comparisons of the pressure differentials measured along flat and groove-modified channels reveal a skin-friction reduction as large as $\text{DR}\approx 50\,\%$ owing to the extended persistence of the laminar flow compared with flow development in a flat channel. These experiments demonstrate that early stabilization of the laminar boundary layer development with a grooved surface promotes drag reduction in a fully turbulent flow with a preserving magnitude as the Reynolds number increases.

show abstract

Section: Turbulent Drag Reduction At Low Reynolds Numberssupporting

confidence: 85%