Drag Reduction by Polymer Diffusion at High Reynolds Numbers

1978 ◽  
Vol 12 (3) ◽  
pp. 134-136 ◽  
Author(s):  
J. Wu ◽  
D.H. Fruman ◽  
M.P. Tulin
Keyword(s):  
Drag Reduction ◽  
Reynolds Numbers ◽  
Polymer Diffusion ◽  
High Reynolds Numbers ◽  
High Reynolds

Drag reduction of a circular cylinder at high Reynolds numbers

1997 ◽  
Author(s):  
A. Krothapalli ◽  
C. Shih ◽  
L. Lourenco ◽  
S. Walker ◽  
P. Moriarty ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

The Effects of Polymer Solution Preparation and Injection on Drag Reduction

2005 ◽  
Vol 127 (3) ◽  
pp. 536-549 ◽  
Author(s):  
R. Sun Chee Fore ◽  
J. Szwalek ◽  
A. I. Sirviente
Keyword(s):  
Drag Reduction ◽  
Polymer Solution ◽  
Mass Production ◽  
Polymer Solutions ◽  
Cost Effective ◽  
Reynolds Numbers ◽  
Polymer Flow ◽  
High Reynolds Numbers ◽  
Solution Preparation ◽  
High Reynolds

The understanding of drag reduction by injection of polymer solutions requires an adequate and accurate polymer solution preparation process as well as a thorough understanding of the effects that the delivery system might have on the polymer flow. Mass production of polymer solutions for engineering applications could be more cost effective if large batches of highly concentrated polymer solutions are prepared and then diluted to the final concentrations of interest. However, as shown in this study, depending on the type of polymer used this procedure might be more or less adequate. This study also corroborates that the presence of macro-molecular polymer structures induced by injecting highly concentrated polymer solutions into a shear flow translates into a drag increase and substantial degradation endurance especially at high Reynolds numbers in comparison to homogeneous polymer solutions.

scholarly journals The effect of Reynolds number on turbulent drag reduction by streamwise travelling waves

2014 ◽  
Vol 759 ◽  
pp. 28-55 ◽  
Author(s):  
Edward Hurst ◽  
Qiang Yang ◽  
Yongmann M. Chung
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Flow Control ◽  
Travelling Waves ◽  
Reynolds Numbers ◽  
Travelling Wave ◽  
Control Parameters ◽  
Scaling Parameter ◽  
High Reynolds Numbers ◽  
High Reynolds

AbstractThis paper exploits the turbulent flow control method using streamwise travelling waves (Quadrio et al. J. Fluid Mech., vol. 627, 2009, pp. 161–178) to study the effect of Reynolds number on turbulent skin-friction drag reduction. Direct numerical simulations (DNS) of a turbulent channel flow subjected to the streamwise travelling waves of spanwise wall velocity have been performed at Reynolds numbers ranging from $\mathit{Re}_{{\it\tau}}=200$ to 1600. To the best of the authors’ knowledge, this is the highest Reynolds number attempted with DNS for this type of flow control. The present DNS results confirm that the effectiveness of drag reduction deteriorates, and the maximum drag reduction achieved by travelling waves decreases significantly as the Reynolds number increases. The intensity of both the drag reduction and drag increase is reduced with the Reynolds number. Another important finding is that the value of the optimal control parameters changes, even in wall units, when the Reynolds number is increased. This trend is observed for the wall oscillation, stationary wave, and streamwise travelling wave cases. This implies that, when the control parameters used are close to optimal values found at a lower Reynolds number, the drag reduction deteriorates rapidly with increased Reynolds number. In this study, the effect of Reynolds number for the travelling wave is quantified using a scaling in the form $\mathit{Re}_{{\it\tau}}^{-{\it\alpha}}$. No universal constant is found for the scaling parameter ${\it\alpha}$. Instead, the scaling parameter ${\it\alpha}$ has a wide range of values depending on the flow control conditions. Further Reynolds number scaling issues are discussed. Turbulent statistics are analysed to explain a weaker drag reduction observed at high Reynolds numbers. The changes in the Stokes layer and also the mean and root-mean-squared (r.m.s.) velocity with the Reynolds number are also reported. The Reynolds shear stress analysis suggests an interesting possibility of a finite drag reduction at very high Reynolds numbers.

Diffusion of a Tangential Drag-Reducing Polymer Injection on a Flat Plate at High Reynolds Numbers

1976 ◽  
Vol 20 (03) ◽  
pp. 171-180 ◽  
Author(s):  
Daniel H. Fruman ◽  
Marshall P Tulin
Keyword(s):  
Drag Reduction ◽  
Flat Plate ◽  
Concentration Distribution ◽  
Reynolds Numbers ◽  
Polymer Injection ◽  
High Reynolds Numbers ◽  
Pure Solvent ◽  
Reduction Effect ◽  
High Reynolds ◽  
Drag Reducing Polymer

The diffusion of a thin tangential jet of an aqueous solution of drag-reducing polymer injected into the water-turbulent boundary layer of a flat plate at a freestream Reynolds number, 3.6 × 107, and the accompanying drag reduction are investigated for a variety of initial concentrations and ratios of injection to freestream velocities. The concentration distribution along the wall is found to be mainly represented by two regions. In the first region the wall concentration is practically constant and equal to the injected one; in the second region the concentration varies approximately as the inverse of the distance from the injection slit. The length of the first region is significantly increased by the polymer solution injection as compared with the pure solvent injection. The drag-reduction effect associated with the polymer injection depends on the trailing-edge concentration achieved as a result of the diffusion process.

Drag Reduction Via Spanwise Transversal Surface Waves at High Reynolds Numbers

2015 ◽  
Vol 95 (1) ◽  
pp. 169-190 ◽  
Author(s):  
Seong Ryong Koh ◽  
Pascal Meysonnat ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Drag Reduction ◽  
Surface Waves ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds
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