Turbulent flow around convex curved tandem cylinders DOI Creative Commons
Tale E. Aasland, Bjørnar Pettersen, Helge I. Andersson

и другие.

Journal of Fluid Mechanics, Год журнала: 2024, Номер 997

Опубликована: Окт. 17, 2024

Turbulent flow around curved tandem cylinders has been studied for the first time, by means of direct numerical simulation. The convex configuration was used, with a nominal gap ratio $L/D = 3$ and Reynolds number 3900. Along span, regimes vary from alternating overshoot/reattachment to co-shedding. Three distinct Strouhal numbers coexist in that are tied directly different cylinder regimes. This result differs substantially at transitional number, where only single dominant frequency is found. All exhibit some degree instability, so can be considered multistable. A mode switch symmetric reattachment Complex interactions observed between primary shear layer instability alterations. As opposed previous investigations straight subcritical regime, our results indicate there may feedback instability. downdraft region exhibits slow meandering, travel upstream amplify causing early transition layer. governed modulations vortex formation lower gap, meaning dynamics this indirectly influence higher up gap.

Язык: Английский

Combined effect of diameter ratio and spacing ratio on flow around two tandem circular cylinders at a moderate Reynolds number (Re) DOI
Di Zhang,

Yizhen Qi,

Dongfang Liang

и другие.

Physics of Fluids, Год журнала: 2024, Номер 36(8)

Опубликована: Авг. 1, 2024

In order to ascertain the combined effect of diameter ratio (d/D) and spacing (L/D) on flow around two tandem circular cylinders, a total 43 research cases are numerically simulated using large eddy simulation model in this study, including d/D = 0.2 (L/D 0.80–6.00), 0.4 0.6 0.90–6.00) at Re 3900. By systematically analyzing instantaneous/time-averaged spanwise vorticity contours, three-dimensional time-averaged Q-criterion iso-surfaces, periodicity within gap, Strouhal number (St), eight sub-flow regimes can be identified, namely, non-periodic reattachment-(1), small-scale periodic reattachment, large-scale reattachment-(2), bi-stable flow, intermittent lock-in co-shedding, subharmonic co-shedding no co-shedding. The occurrence these depends combination L/D. Besides, with regard larger downstream cylinder (DC), there three possible dominant St values for DC instantaneous drag coefficient (i.e. StCD-D1, StCD-D2, StCD-D3). It is quite clear that StCD-D1 has almost same value as StCL-D1, StCD-D2 roughly equal 2StCL-D1, StCD-D3 approximately summation StCL-D1 StCL-D2, where StCL-D2 denote primary secondary lift coefficient, respectively. Additionally, various statistical parameters obtained compared different combinations L/D, such velocity, vorticity, value, periodicity, force base pressure reattachment angle, separation angle.

Язык: Английский

Процитировано

4
Turbulent flow and heat transfer of superhydrophobic cylinders with measured slip length DOI
Mohammad Saadatbakhsh, Mohammad Jadidi

Physics of Fluids, Год журнала: 2025, Номер 37(2)

Опубликована: Фев. 1, 2025

This study investigates the impact of surface-engineered wall slip on flow dynamics and heat transfer in tandem cylinder configurations at a subcritical Reynolds number (Re = 3900). Utilizing large eddy simulation (LES) with experimentally calibrated lengths, research examines how conditions modify boundary layer behavior, wake structures, turbulence characteristics, overall thermal performance. LES predictions reveal significant modifications physics characteristics. Slip lead to thinner layers both cylinders delayed separation. modification enhances aerodynamic performance by reducing drag lift forces, particularly for upstream cylinder. The wakes become narrower more elongated, increasing vortex-shedding frequencies while attenuating energy associated vortex shedding. Furthermore, implementation significantly alters characteristics toward one-component “cigar-shaped” Lumley triangle. Both spatial temporal scales undergo substantial modifications, integral length typically reducing. Heat quantified through Nusselt distributions exhibits nuanced response conditions. While consistently shows enhanced transfer, downstream cylinder's strongly depends center-to-center ratio. highlights potential optimizing strategic application slip, opening new avenues innovation various engineering applications, including exchangers management systems.

Язык: Английский

Процитировано

0
Turbulent flow around convex curved tandem cylinders DOI Creative Commons
Tale E. Aasland, Bjørnar Pettersen, Helge I. Andersson

и другие.

Journal of Fluid Mechanics, Год журнала: 2024, Номер 997

Опубликована: Окт. 17, 2024

Turbulent flow around curved tandem cylinders has been studied for the first time, by means of direct numerical simulation. The convex configuration was used, with a nominal gap ratio $L/D = 3$ and Reynolds number 3900. Along span, regimes vary from alternating overshoot/reattachment to co-shedding. Three distinct Strouhal numbers coexist in that are tied directly different cylinder regimes. This result differs substantially at transitional number, where only single dominant frequency is found. All exhibit some degree instability, so can be considered multistable. A mode switch symmetric reattachment Complex interactions observed between primary shear layer instability alterations. As opposed previous investigations straight subcritical regime, our results indicate there may feedback instability. downdraft region exhibits slow meandering, travel upstream amplify causing early transition layer. governed modulations vortex formation lower gap, meaning dynamics this indirectly influence higher up gap.

Язык: Английский

Процитировано

1