Substantial drag reduction in turbulent flow using liquid-infused surfaces

2017 ◽  
Vol 827 ◽  
pp. 448-456 ◽  
Author(s):  
Tyler Van Buren ◽  
Alexander J. Smits
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Couette Flow ◽  
Viscosity Ratio ◽  
Area Fraction ◽  
Groove Width ◽  
Test Surface ◽  
Test Liquid ◽  
Turbulent Drag

Experiments are presented that demonstrate how liquid-infused surfaces can reduce turbulent drag significantly in Taylor–Couette flow. The test liquid was water, and the test surface was composed of square microscopic grooves measuring $100~\unicode[STIX]{x03BC}\text{m}$ to $800~\unicode[STIX]{x03BC}\text{m}$, filled with alkane liquids with viscosities from 0.3 to 1.4 times that of water. We achieve drag reduction exceeding 35 %, four times higher than previously reported for liquid-infused surfaces in turbulent flow. The level of drag reduction increased with viscosity ratio, groove width, fluid area fraction and Reynolds number. The optimum groove width was given by $w^{+}\approx 35$.

scholarly journals Fibre-induced drag reduction

2008 ◽  
Vol 602 ◽  
pp. 209-218 ◽  
Author(s):  
J. J. J. GILLISSEN ◽  
B. J. BOERSMA ◽  
P. H. MORTENSEN ◽  
H. I. ANDERSSON
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Reduction ◽  
Elastic Layer ◽  
Turbulent Drag Reduction ◽  
Rigid Polymer ◽  
Fibre Concentration ◽  
Induced Drag ◽  
Turbulent Drag

We use direct numerical simulation to study turbulent drag reduction by rigid polymer additives, referred to as fibres. The simulations agree with experimental data from the literature in terms of friction factor dependence on Reynolds number and fibre concentration. An expression for drag reduction is derived by adopting the concept of the elastic layer.

Common features between the Newtonian laminar–turbulent transition and the viscoelastic drag-reducing turbulence

2019 ◽  
Vol 877 ◽  
pp. 405-428 ◽  
Author(s):  
Anselmo S. Pereira ◽  
Roney L. Thompson ◽  
Gilmar Mompean
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Turbulent Flows ◽  
Temporal Dynamics ◽  
Homoclinic Orbits ◽  
Theoretical Development ◽  
Transitional Flows ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition

The transition from laminar to turbulent flows has challenged the scientific community since the seminal work of Reynolds (Phil. Trans. R. Soc. Lond. A, vol. 174, 1883, pp. 935–982). Recently, experimental and numerical investigations on this matter have demonstrated that the spatio-temporal dynamics that are associated with transitional flows belong to the directed percolation class. In the present work, we explore the analysis of laminar–turbulent transition from the perspective of the recent theoretical development that concerns viscoelastic turbulence, i.e. the drag-reducing turbulent flow obtained from adding polymers to a Newtonian fluid. We found remarkable fingerprints of the variety of states that are present in both types of flows, as captured by a series of features that are known to be present in drag-reducing viscoelastic turbulence. In particular, when compared to a Newtonian fully turbulent flow, the universal nature of these flows includes: (i) the statistical dynamics of the alternation between active and hibernating turbulence; (ii) the weakening of elliptical and hyperbolic structures; (iii) the existence of high and low drag reduction regimes with the same boundary; (iv) the relative enhancement of the streamwise-normal stress; and (v) the slope of the energy spectrum decay with respect to the wavenumber. The maximum drag reduction profile was attained in a Newtonian flow with a Reynolds number near the boundary of the laminar regime and in a hibernating state. It is generally conjectured that, as the Reynolds number increases, the dynamics of the intermittency that characterises transitional flows migrate from a situation where heteroclinic connections between the upper and the lower branches of solutions are more frequent to another where homoclinic orbits around the upper solution become the general rule.

scholarly journals Microbubbly drag reduction in Taylor–Couette flow in the wavy vortex regime

2008 ◽  
Vol 608 ◽  
pp. 21-41 ◽  
Author(s):  
KAZUYASU SUGIYAMA ◽  
ENRICO CALZAVARINI ◽  
DETLEF LOHSE
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Couette Flow ◽  
Physical Mechanism ◽  
Dilute Suspensions ◽  
Fluid Coupling ◽  
Taylor Couette ◽  
The Individual ◽  
Reynolds Number Dependence ◽  
Taylor Couette Flow

We investigate the effect of microbubbles on Taylor–Couette flow by means of direct numerical simulations. We employ an Eulerian–Lagrangian approach with a gas–fluid coupling based on the point-force approximation. Added mass, drag, lift and gravity are taken into account in the modelling of the motion of the individual bubble. We find that very dilute suspensions of small non-deformable bubbles (volume void fraction below 1%, zero Weber number and bubble Reynolds number ≲10) induce a robust statistically steady drag reduction (up to 20%) in the wavy vortex flow regime (Re=600–2500). The Reynolds number dependence of the normalized torque (the so-called torque reduction ratio (TRR) which corresponds to the drag reduction) is consistent with a recent series of experimental measurements performed by Murai et al. (J. Phys. Conf. Ser. vol. 14, 2005, p. 143). Our analysis suggests that the physical mechanism for the torque reduction in this regime is due to the local axial forcing, induced by rising bubbles, that is able to break the highly dissipative Taylor wavy vortices in the system. We finally show that the lift force acting on the bubble is crucial in this process. When it is neglected, the bubbles preferentially accumulate near the inner cylinder and the bulk flow is less efficiently modified. Movies are available with the online version of the paper.

scholarly journals Study on the Law of Pseudo-Cavitation on Superhydrophobic Surface in Turbulent Flow Field of Backward-Facing Step

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 200
Author(s):  
Xuecheng Lv ◽  
Wei-Tao Wu ◽  
Jizu Lv ◽  
Ke Mao ◽  
Linsong Gao ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Large Bubble ◽  
Backward Facing Step ◽  
Bubble Generation ◽  
Turbulent Flow Field ◽  
Flow Drag

Superhydrophobic surface is regarded as important topic in the field of thermal fluids today due to its unique features on flow drag reduction and heat transfer enhancement. In this study, the pseudo-cavitation phenomenon on the superhydrophobic surface in the backward-facing step turbulent flow field is observed through experiments. The underlying reason for this phenomenon is studied with experimental observation and analysis, and the time variant mechanisms of this phenomenon with various Reynolds number is summarized. The research results indicate that the superhydrophobic surface and the backward-facing step provide the material basis and dynamic condition for the generation of pseudo-cavitation. The pseudo-cavitation induces a large bubble on the superhydrophobic surface below the backward-facing step. The size, position, shape, oscillation amplitude, detachment, and splitting of the large bubble show regularity with the changes of Reynolds number. Meanwhile, the bubble growth, oscillation, detachment, split, and regeneration over time also show regularity. The study of bubble generation and development laws can be used to better control the perturbation of the flow field. Importantly, the present study has meaning in better understanding the flow mechanisms and gas coverage of superhydrophobic surface under condition of backward-facing step, paving the way for studying the flow drag reduction effect of superhydrophobic surface.

scholarly journals An energy-efficient pathway to turbulent drag reduction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ivan Marusic ◽  
Dileep Chandran ◽  
Amirreza Rouhi ◽  
Matt K. Fu ◽  
David Wine ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Small Scale ◽  
Power Cost ◽  
Turbulent Fluid Flow ◽  
Low Reynolds Numbers ◽  
Turbulent Drag ◽  
Direct Measurements

AbstractSimulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased by oscillatory motion in the surface, with the amount of drag reduction predicted to decline with increasing Reynolds number. Here, we report direct measurements of substantial drag reduction achieved by using spanwise surface oscillations at high friction Reynolds numbers ($${{{\mathrm{Re}}}_{\tau }}$$ Re τ ) up to 12,800. The drag reduction occurs via two distinct physical pathways. The first pathway, as studied previously, involves actuating the surface at frequencies comparable to those of the small-scale eddies that dominate turbulence near the surface. We show that this strategy leads to drag reduction levels up to 25% at $${{{{{{{{\mathrm{Re}}}}}}}}}_{\tau }$$ Re τ = 6,000, but with a power cost that exceeds any drag-reduction savings. The second pathway is new, and it involves actuation at frequencies comparable to those of the large-scale eddies farther from the surface. This alternate pathway produces drag reduction of 13% at $${{{{{{{{\mathrm{Re}}}}}}}}}_{\tau }$$ Re τ = 12,800. It requires significantly less power and the drag reduction grows with Reynolds number, thereby opening up potential new avenues for reducing fuel consumption by transport vehicles and increasing power generation by wind turbines.

Turbulent Flow of Drag Reducing Fluids Between Concentric Rotating Cylinders

1972 ◽  
Vol 1 (1) ◽  
pp. 25-30 ◽  
Author(s):  
E. Bilgen ◽  
R. Boulos
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Polyethylene Oxide ◽  
Guar Gum ◽  
Rotating Cylinder ◽  
Large Reynolds Number ◽  
Reduction Mechanism ◽  
Dilute Solutions ◽  
Concentric Cylinders

The turbulent flow of drag reducing fluids between concentric cylinders, the inner cylinder rotating and the outer one at rest, has been studied experimentally. The drag reducing fluids were dilute solutions of polyethylene oxide, polyacrylamide and guar gum. The torques exerted by the inner rotating cylinder have been measured for various gap widths and over a relatively large Reynolds number. The results have been reduced in dimensionless parameters and correlated. The velocity profiles between the cylinders have also been measured and the drag reduction mechanism has been discussed briefly.

scholarly journals Turbulent channel flow of an elastoviscoplastic fluid

2018 ◽  
Vol 853 ◽  
pp. 488-514 ◽  
Author(s):  
Marco E. Rosti ◽  
Daulet Izbassarov ◽  
Outi Tammisola ◽  
Sarah Hormozi ◽  
Luca Brandt
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Channel Flow ◽  
Viscosity Ratio ◽  
Turbulent Channel Flow ◽  
Turbulent Regime ◽  
Bingham Number ◽  
Wide Range ◽  
Near Wall

We present numerical simulations of laminar and turbulent channel flow of an elastoviscoplastic fluid. The non-Newtonian flow is simulated by solving the full incompressible Navier–Stokes equations coupled with the evolution equation for the elastoviscoplastic stress tensor. The laminar simulations are carried out for a wide range of Reynolds numbers, Bingham numbers and ratios of the fluid and total viscosity, while the turbulent flow simulations are performed at a fixed bulk Reynolds number equal to 2800 and weak elasticity. We show that in the laminar flow regime the friction factor increases monotonically with the Bingham number (yield stress) and decreases with the viscosity ratio, while in the turbulent regime the friction factor is almost independent of the viscosity ratio and decreases with the Bingham number, until the flow eventually returns to a fully laminar condition for large enough yield stresses. Three main regimes are found in the turbulent case, depending on the Bingham number: for low values, the friction Reynolds number and the turbulent flow statistics only slightly differ from those of a Newtonian fluid; for intermediate values of the Bingham number, the fluctuations increase and the inertial equilibrium range is lost. Finally, for higher values the flow completely laminarizes. These different behaviours are associated with a progressive increases of the volume where the fluid is not yielded, growing from the centreline towards the walls as the Bingham number increases. The unyielded region interacts with the near-wall structures, forming preferentially above the high-speed streaks. In particular, the near-wall streaks and the associated quasi-streamwise vortices are strongly enhanced in an highly elastoviscoplastic fluid and the flow becomes more correlated in the streamwise direction.

scholarly journals Drag reduction in boiling Taylor–Couette turbulence

2019 ◽  
Vol 881 ◽  
pp. 104-118
Author(s):  
Rodrigo Ezeta ◽  
Dennis Bakhuis ◽  
Sander G. Huisman ◽  
Chao Sun ◽  
Detlef Lohse
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Drag Reduction ◽  
Couette Flow ◽  
Turbulent Flows ◽  
Vapour Bubble ◽  
Laboratory Environment ◽  
Global Result ◽  
Taylor Couette ◽  
Global And Local

We create a highly controlled laboratory environment – accessible to both global and local monitoring – to analyse turbulent boiling flows and in particular their shear stress in a statistically stationary state. By precisely monitoring the drag of strongly turbulent Taylor–Couette flow (the flow in between two coaxially rotating cylinders, Reynolds number $Re\approx 10^{6}$) during its transition from non-boiling to boiling, we show that the intuitive expectation, namely that a few volume per cent of vapour bubbles would correspondingly change the global drag by a few per cent, is wrong. Rather, we find that for these conditions a dramatic global drag reduction of up to 45 % occurs. We connect this global result to our local observations, showing that for major drag reduction the vapour bubble deformability is crucial, corresponding to Weber numbers larger than one. We compare our findings with those for turbulent flows with gas bubbles, which obey very different physics from those of vapour bubbles. Nonetheless, we find remarkable similarities and explain these.

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