Drag reduction promoted by repetitive bubble injection in turbulent channel flows

2018 ◽  
Vol 2018 (0) ◽  
pp. OS3-7
Author(s):  
Hyun Jin PARK
Keyword(s):  
Drag Reduction ◽  
Channel Flows ◽  
Turbulent Channel Flows

Drag Reduction Due to Streamwise Grooves in Turbulent Channel Flow

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
C. T. DeGroot ◽  
C. Wang ◽  
J. M. Floryan
Keyword(s):  
Shear Stress ◽  
Drag Reduction ◽  
Turbulent Channel Flow ◽  
Surface Modifications ◽  
Channel Flows ◽  
Wave Number ◽  
Stress Profile ◽  
Bulk Fluid ◽  
Geometry Model ◽  
Turbulent Channel Flows

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.

scholarly journals Effect of finite Weissenberg number on turbulent channel flows of an elastoviscoplastic fluid

2021 ◽  
Vol 927 ◽  
Author(s):  
Daulet Izbassarov ◽  
Marco E. Rosti ◽  
Luca Brandt ◽  
Outi Tammisola
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Weissenberg Number ◽  
Channel Flows ◽  
Viscoplastic Flow ◽  
Turbulent Structures ◽  
Turbulent Dissipation ◽  
Flow Equations ◽  
Turbulent Channel Flows ◽  
Nonlinear Elastic

Direct numerical simulations are carried out to study the effect of finite Weissenberg number up to $Wi=16$ on laminar and turbulent channel flows of an elastoviscoplastic (EVP) fluid, at a fixed bulk Reynolds number of $2800$ . The incompressible flow equations are coupled with the evolution equation for the EVP stress tensor by a modified Saramito model that extends both the Bingham viscoplastic and the finite extensible nonlinear elastic-Peterlin (FENE-P) viscoelastic models. In turbulent flow, we find that drag decreases with both the Bingham and Weissenberg numbers, until the flow laminarises at high enough elastic and yield stresses. Hence, a higher drag reduction is achieved than in the viscoelastic flow at the same Weissenberg number. The drag reduction persists at Bingham numbers up to 20, in contrast to viscoplastic flow, where the drag increases in the laminar regime compared with a Newtonian flow. Moreover, elasticity affects the laminarisation of an EVP flow in a non-monotonic fashion, delaying it at lower and promoting it at higher Weissenberg numbers. A hibernation phenomenon is observed in the EVP flow, leading to large changes in the unyielded regions. Finally, plasticity is observed to affect both low- and high-speed streaks equally, attenuating the turbulent dissipation and the fragmentation of turbulent structures.

Frictional drag reduction promoted by generating void waves in high-speed turbulent channel flows

2019 ◽  
Vol 2019.24 (0) ◽  
pp. A122
Author(s):  
Taiji TANAKA ◽  
Hyun Jin PARK ◽  
Yuji TASAKA ◽  
Yuichi MURAI ◽  
Chiharu KAWAKITA
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Channel Flows ◽  
Frictional Drag ◽  
Turbulent Channel Flows

Drag reduction promoted by repetitive bubble injection in turbulent channel flows

2015 ◽  
Vol 75 ◽  
pp. 12-25 ◽  
Author(s):  
Hyun Jin Park ◽  
Yuji Tasaka ◽  
Yoshihiko Oishi ◽  
Yuichi Murai
Keyword(s):  
Drag Reduction ◽  
Channel Flows ◽  
Turbulent Channel Flows

Repetitive bubble injection promoting frictional drag reduction in high-speed horizontal turbulent channel flows

2021 ◽  
Vol 239 ◽  
pp. 109909
Author(s):  
Taiji Tanaka ◽  
Yoshihiko Oishi ◽  
Hyun Jin Park ◽  
Yuji Tasaka ◽  
Yuichi Murai ◽  
...  
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Channel Flows ◽  
Frictional Drag ◽  
Turbulent Channel Flows

Drag reduction of turbulent channel flows over an anisotropic porous wall with reduced spanwise permeability

2019 ◽  
Vol 40 (7) ◽  
pp. 1041-1052 ◽  
Author(s):  
Qingxiang Li ◽  
Ming Pan ◽  
Quan Zhou ◽  
Yuhong Dong
Keyword(s):  
Drag Reduction ◽  
Porous Wall ◽  
Channel Flows ◽  
Turbulent Channel Flows

Drag reduction in turbulent channel flows by a spanwise traveling wave of wall blowing and suction

2021 ◽  
Vol 33 (9) ◽  
pp. 095111
Author(s):  
Yi Huang ◽  
Liang Wang ◽  
Song Fu
Keyword(s):  
Drag Reduction ◽  
Traveling Wave ◽  
Channel Flows ◽  
Turbulent Channel Flows

scholarly journals Active and passive in-plane wall fluctuations in turbulent channel flows

2019 ◽  
Vol 866 ◽  
pp. 689-720 ◽  
Author(s):  
T. I. Józsa ◽  
E. Balaras ◽  
M. Kashtalyan ◽  
A. G. L. Borthwick ◽  
I. M. Viola
Keyword(s):  
Drag Reduction ◽  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Channel Flows ◽  
Small Scale ◽  
Shear Stresses ◽  
Friction Drag ◽  
Turbulent Friction ◽  
Turbulent Channel Flows ◽  
Compliant Surfaces

Compliant walls offer the tantalising possibility of passive flow control. This paper examines the mechanics of compliant surfaces driven by wall shear stresses, with solely in-plane velocity response. We present direct numerical simulations of turbulent channel flows at low ($Re_{\unicode[STIX]{x1D70F}}\approx 180$) and intermediate ($Re_{\unicode[STIX]{x1D70F}}\approx 1000$) Reynolds numbers. In-plane spanwise and streamwise active controls proposed by Choi et al. (J. Fluid Mech., vol. 262, 1994, pp. 75–110) are revisited in order to characterise beneficial wall fluctuations. An analytical framework is then used to map the parameter space of the proposed compliant surfaces. The direct numerical simulations show that large-scale passive streamwise wall fluctuations can reduce friction drag by at least $3.7\pm 1\,\%$, whereas even small-scale passive spanwise wall motions lead to considerable drag penalty. It is found that a well-designed compliant wall can theoretically exploit the drag-reduction mechanism of an active control; this may help advance the development of practical active and passive control strategies for turbulent friction drag reduction.

scholarly journals Drag reduction by polymers in turbulent channel flows: Energy redistribution between invariant empirical modes

2003 ◽  
Vol 67 (5) ◽  
Author(s):  
Elisabetta De Angelis ◽  
Carlo M. Casciola ◽  
Victor S. L’vov ◽  
Renzo Piva ◽  
Itamar Procaccia
Keyword(s):  
Drag Reduction ◽  
Channel Flows ◽  
Energy Redistribution ◽  
Turbulent Channel Flows
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