Precise prediction of the drag reduction efficiency of polymer in turbulent flow considering diameter effect

2021 ◽  
Vol 33 (9) ◽  
pp. 095124
Author(s):  
Xin Zhang ◽  
Xiaodong Dai ◽  
Jishi Zhao ◽  
Dengwei Jing ◽  
Fei Liu ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Reduction Efficiency ◽  
Precise Prediction ◽  
Diameter Effect

Drag reduction for turbulent flow over a projectile. Part II

1994 ◽  
Vol 31 (1) ◽  
pp. 93-98 ◽  
Author(s):  
Shen-Min Liang ◽  
Jan-Kuang Fu
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction

Durability of a Drag Reducing Solution

2008 ◽  
Vol 18 (1) ◽  
pp. 12421-1-12421-5
Author(s):  
V. Mik ◽  
J. Myska ◽  
Z. Chara ◽  
P. Stern
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Turbulence Intensity ◽  
Surfactant Concentration ◽  
Surfactant Solution ◽  
Small Addition ◽  
Rheological Parameters ◽  
Aging Effects ◽  
Flow Disturbance ◽  
Solution Change

AbstractEffectiveness of drag reduction by small addition of a surfactant in the turbulent flow of water depends on the structure and concentration of the additive, temperature of the solution and turbulence intensity, possible flow disturbance by a mechanical obstacle and the content of ions in water, but also on the age of the surfactant solution. We show how important aging effects are in connection with total surfactant concentration, in particular how rheological parameters of the drag reducing solution change with time.

Turbulent flow over superhydrophobic surfaces with streamwise grooves

2014 ◽  
Vol 747 ◽  
pp. 186-217 ◽  
Author(s):  
S. Türk ◽  
G. Daschiel ◽  
A. Stroh ◽  
Y. Hasegawa ◽  
B. Frohnapfel
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Secondary Flow ◽  
Slip Length ◽  
Laminar Flows ◽  
Superhydrophobic Surfaces ◽  
Mean Velocity ◽  
Effective Slip Length ◽  
Effective Slip

AbstractWe investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. For a small spanwise periodicity of the streamwise grooves, the effective slip length in a turbulent flow agrees well with the analytical solution for laminar flows. Once the spanwise width of the free-slip area becomes larger than approximately 20 wall units, however, the effective slip length is significantly reduced from the laminar value due to the mixing caused by the underlying turbulence and secondary flow. Based on these results, we develop a simple model that allows estimating the gain due to a SHS in turbulent flows at practically high Reynolds numbers.

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.

Drag Reduction of Gas-Liquid Two-Phase Flow in Steel Pipes with Different Inclination Geometry

2012 ◽  
Vol 433-440 ◽  
pp. 463-470
Author(s):  
Lei Liu ◽  
Xin Feng Guo ◽  
Qiu Yue Guo ◽  
Hui Qing Fan ◽  
Zhu Hai Zhong
Keyword(s):  
Drag Reduction ◽  
Two Phase Flow ◽  
Vertical Section ◽  
High Energy ◽  
Phase Flow ◽  
Two Phase ◽  
Steel Pipes ◽  
Horizontal Pipes ◽  
Reduction Efficiency ◽  
Reduction Characteristics

It is significant to make researches on drag reduction in two-phase transport pipeline because two-phase flow has high energy dissipation. API X 52 steel pipe with diameter of 40mm is used in this paper to simulate pipeline with different inclination geometry including horizontal, up-inclined and vertical sections. The up-inclined section has an inclination angle of eight degree. Experiments and theoretical analysis are carried out to study the drag reduction characteristics of gas-liquid two-phase flow in these three sections. The drag reducing agents used here is polyacrylamide. It is found that two-phase drag reduction varies with pipe inclination geometry. The largest drag reduction efficiency occurs in horizontal pipes and which is up to seventy percent. Drag reduction efficiency in up-inclined section is up to sixty percent. Drag reduction in vertical section is the lowest and which can be up to about thirty percent. A mechanistic drag reduction model is proposed to predict drag reduction in gas-liquid two-phase flow. The results predicted are in good agreement with the experiment data.

Active control of turbulent flow over a model vehicle for drag reduction

2004 ◽  
Vol 5 ◽  
Author(s):  
Jeonglae Kim ◽  
Seonghyeon Hahn ◽  
Jinsung Kim ◽  
Dong-kon Lee ◽  
Jin Choi ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Active Control
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