Drag Reduction Due to Streamwise Grooves in Turbulent Channel Flow

Abstract

Drag reduction in turbulent channel flows has significant practical relevance for energy savings. Various methods have been proposed to reduce turbulent skin friction, including microscale surface modifications such as riblets or superhydrophobic surfaces. More recently, macroscale surface modifications in the form of longitudinal grooves have been shown to reduce drag in laminar channel flows. The purpose of this study is to show that these grooves also reduce drag in turbulent channel flows and to quantify the drag reduction as a function of the groove parameters. Results are obtained using computational fluid dynamics (CFD) simulations with turbulence modeled by the k–ω shear-stress transport (SST) model, which is first validated with direct numerical simulations (DNS). Based on the CFD results, a reduced geometry model is proposed which shows that the approximate drag reduction can be quantified by evaluating the drag reduction of the geometry given by the first Fourier mode of an arbitrary groove geometry. Results are presented to show the drag reducing potential of grooves as a function of Reynolds number as well as groove wave number, amplitude, and shape. The mechanism of drag reduction is discussed, which is found to be due to a rearrangement of the bulk fluid motion into high-velocity streamtubes in the widest portion of the channel opening, resulting in a change in the wall shear stress profile.

Direct numerical simulation of surfactant solution flow in the wide‐rib rectangular grooved channel

“…The existence of the secondary streamwise vortices found in this study means a control on the near-wall turbulence structures and a rearrangement of the bulk fluid motions. This phenomenon agrees with the analysis of the turbulent drag reduction mechanism reported by Kim, 6 Chen et al 23 and Degroot et al 24…”

“…This phenomenon agrees with the analysis of the turbulent drag reduction mechanism reported by Kim, 6 Chen et al 23 and Degroot et al 24 When the secondary streamwise vortices can occupy most space of the grooved valleys and then effectively prevent the smaller near-wall vortices from intruding into the grooved valley, the drag reduction enhancement occurs.…”

“…They also reported that the drag reduction performance of microgroove was related to its size and shape, and the optimal drag-reducing size of microgroove was about s 1 %16 and the drag reduction region was about s 1 <30. In the recent years, Chen et al 23 and Degroot et al 24 both performed the numerical investigations on the drag reduction of the longitudinal corrugated channels in the laminar and turbulent flows. They found that under the same pressure gradient, the grooves with suitable geometry could increase the discharge compared with in the smooth channel.…”

Evaluation of drag and lift in the internal flow field of a dual rotor spinning unit via CFD

“…Study on the behavior of drag and lift forces in the flows is a significant phenomenon that gives a comprehensive understanding of a given processes, which can help to improve the quality and handle costs efficiently. [3][4][5] Numerical studies in textile processing have tremendously risen in the past decade with authors focusing on finite element methods to study fiber processing techniques more comprehensively [6][7][8][9][10][11][12][13]. In all industrial rotor spinning machines, the opening of the fibers is performed by the opening roller, in which sliver is fed from a single point.…”

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

“…High-momentum fluid is recirculated from the impeller to the impeller inlet through the recirculation slot. [180] 2017 Recirculating slots CC − + + [180] 2017 Bleed slots CC 40% ±0% +10% + [181] 2017 Axial slots MC −0.7% +26.4% [182] 2017 Recirculating slots AC 0.27-0.38% ±0% + +20% [183] 2017 Injection nozzle CC 0-80% −1% +3% +40% [184] 2017 Injection nozzle AC + [185] 2017 Grooves HPT cascade 220,000 Max 4% reduction in total pressure loss [186] 2017 Injection nozzle HPT cascade 60,000 0.4% 20% reduction in total pressure loss [187] 2016 Grooves AC ±0% ±0% [188] 2016 Grooves Channel flow 2648-30,000 40% reduction in drag [171] 2016 Recirculating slots with vanes CC, Ns = 1.00 up to 20% −0.25%pt +25% +69% [171] 2016 Recirculating slots with vanes CC, Ns = 0.85 up to 20% −0.4%pt +30% +94% [189] 2016 Recirculating slots AC 0.47% ±0% +6.12% [190] 2016 Grooves AC +5.7% [191] 2016 Bleed chamber AC ±0% ±0% +3.5 . .…”