scholarly journals Maximum Drag Reduction Asymptote for Moment Coefficient of a Rotating Disk in Drag-Reducing Solutions

2000 ◽  
Vol 2000 (0) ◽  
pp. 175
Author(s):  
Satoshi OGATA ◽  
Keizo WATANABE
Keyword(s):  
Drag Reduction ◽  
Rotating Disk ◽  
Moment Coefficient ◽  
Maximum Drag Reduction

Limiting maximum drag-reduction asymptote for the moment coefficient of a rotating disk in drag-reducing surfactant solution

2002 ◽  
Vol 457 ◽  
pp. 325-337 ◽  
Author(s):  
SATOSHI OGATA ◽  
KEIZO WATANABE
Keyword(s):  
Drag Reduction ◽  
Surfactant Solution ◽  
Rotating Disk ◽  
Turbulent Pipe Flow ◽  
Experimental Results ◽  
Flow Angle ◽  
Moment Coefficient ◽  
Maximum Drag Reduction ◽  
The Moment ◽  
Momentum Integral

In this study, the limiting maximum drag-reduction asymptote for the moment coefficient of a rotating disk in a surfactant solution was obtained analytically. The analysis, which was based on the logarithmic velocity profile of turbulent pipe flow in the surfactant solution, was carried out using momentum integral equations of the boundary layer, and the moment coefficient results agreed with experimental results for maximum drag reduction in surfactant solution. Additionally, flow visualization was performed using the tracer and the tuft techniques, which revealed that the direction of flow of surfactant solution on the disk was turned towards the circumferential direction and the amplitude of the circular vortex on the rotating disk was reduced by addition of surfactant solution. The experimental results for flow angle on a rotating disk can be explained well with the analytical results.

Drag Reduction of Surfactant Solutions for an Enclosed Rotating Disk

1999 ◽  
Author(s):  
Satoshi Ogata ◽  
Keizo Watanabe
Keyword(s):  
Drag Reduction ◽  
Pipe Flow ◽  
Transition Point ◽  
Rotating Disk ◽  
Torque Measurement ◽  
Rotating Disks ◽  
Rotating Shaft ◽  
Surfactant Solutions ◽  
Circular Pipe Flow ◽  
Maximum Drag Reduction

Abstract Recently, many studies on surfactant solutions have been conducted for drag reduction in a circular pipe flow. However, currently there are very few studies on rotating disks in the solutions. In this study, drag reduction for an enclosed rotating disk in surfactant solutions was clarified experimentally. Experiments were carried out to measure the torque acting on one side of a rotating disk, using a torque measurement device located at the top of the rotating shaft. Test surfactant solutions were Ethoquad O/12 at concentrations of 50, 100 and 200ppm. The temperatures of solutions were 18°C and 28°C. The clearances between the disk and the stator were 10mm and 20mm. It was shown that the Reynolds number at the transition point increased with increasing concentration and temperature of these solutions. The maximum drag reduction ratio was about 41% in 200ppm Ethoquad O/12 solution at 28°C.

Use of Electrochemical Methods for the Study of Mass Transfer and Drag Reduction in Polymer Solutions Close to a Wall

1979 ◽  
Vol 101 (1) ◽  
pp. 121-127 ◽  
Author(s):  
C. Deslouis ◽  
I. Epelboin ◽  
B. Tribollet ◽  
L. Viet
Keyword(s):  
Mass Transfer ◽  
Drag Reduction ◽  
Electrochemical Method ◽  
Friction Velocity ◽  
Rotating Disk ◽  
Ring Electrode ◽  
Transfer Rates ◽  
Thin Ring ◽  
Maximum Drag Reduction ◽  
Drag Reducing Polymer

Mass transfer to the surface of a rotating disk in the presence of a drag reducing polymer (PEO) has been studied by an electrochemical method. Mass transfer rates were predicted and measured for different electrode geometries: (i) thin ring, (ii) circular microelectrode, and (iii) the disk. A relation for friction velocity available up to maximum drag reduction conditions where the average flow is laminarized at the scale of the diffusion layer, has been proposed from the analysis of the experimental data on circular microelectrode and ring electrode. The comparison of these data with disk electrode measurements substantiated a sharp thickening of the diffusion sublayer at the lowest polymer concentrations.

scholarly journals Enhanced Drag Reduction Performance of Nanocomposites: The Effects of Surface Modification of Nano Silica

2017 ◽  
Vol 26 (4) ◽  
pp. 096369351702600 ◽  
Author(s):  
Xiaodong Dai ◽  
Guicai Zhang ◽  
Bing Li ◽  
Jijiang Ge ◽  
Xuewu Wang ◽  
...  
Keyword(s):  
Surface Modification ◽  
Drag Reduction ◽  
Rotating Disk ◽  
Shear Resistance ◽  
Test Results ◽  
Nano Silica ◽  
Surface Hydroxyl ◽  
Adsorption Analysis ◽  
Oil Adsorption ◽  
Loop 2

In this paper, nanocomposite was synthesized with nano silica and poly-α-olefin, and the effects of surface modification to the nano silica on its drag reduction performance were investigated. The dosage coupling agent, Y-aminopropyltriethoxysilane, and the modification temperature were studied intensively through surface hydroxyl and oil adsorption analysis. The test results indicated that the hydroxyl number of the silica was decreased by Y-aminopropyltriethoxysilane modification, with improved lipophilicity and oil adsorption. At 50°C, the optimum Y-aminopropyltriethoxysilane dosages were 15% for Nano-Si-10, 5% for Nano-Si-20, and 10% for Degussa-R972. The modification significantly changed the nano silica surface properties and enhanced the interaction with poly-α-olefin. Through drag reduction and shear resistance tests by rotating disk 40 mins degradation and testing loop 2 times shearing, it was shown that the nanocomposite possessed good drag reduction and excellent shear resistance properties.

Drag Reduction of the Flow Past a Circular Cylinder in Surfactant Solution

2001 ◽  
Author(s):  
Satoshi Ogata ◽  
Keizo Watanabe
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Sodium Salicylate ◽  
Tap Water ◽  
Pressure Coefficient ◽  
Surfactant Solution ◽  
Reduction Ratio ◽  
Number Range ◽  
Surfactant Solutions ◽  
Maximum Drag Reduction

Abstract The flow around a circular cylinder in surfactant solution was investigated experimentally by measurement of the pressure and velocity profiles in the Reynolds number range 6000 < Re < 50000. The test surfactant solutions were aqueous solutions of Ethoquad O/12 (Lion Co.) at concentrations of 50, 100 and 200 ppm, and sodium salicylate was added as a counterion. It was clarified that the pressure coefficient of surfactant solutions in the range of 10000 < Re < 50000 at the behind of the separation point was larger than that of tap water, and the separation angle increased with concentration of the surfactant solution. The velocity defect in surfactant solutions behind a circular cylinder was smaller than those in tap water. The drag coefficients of a circular cylinder in surfactant solutions were smaller than those of tap water in the range 10000 < Re < 50000, and no drag reduction occurred at Re = 6000. The drag reduction ratio increased with increasing concentration of surfactant solution. The maximum drag reduction ratio was approximately 35%.

scholarly journals Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit

2019 ◽  
Vol 874 ◽  
pp. 699-719 ◽  
Author(s):  
Jose M. Lopez ◽  
George H. Choueiri ◽  
Björn Hof
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows ◽  
Pipe Flow ◽  
Domain Size ◽  
Reynolds Numbers ◽  
Weissenberg Number ◽  
Pipe Length ◽  
Low Reynolds Numbers ◽  
Maximum Drag Reduction ◽  
Low Reynolds

Polymer additives can substantially reduce the drag of turbulent flows and the upper limit, the so-called state of ‘maximum drag reduction’ (MDR), is to a good approximation independent of the type of polymer and solvent used. Until recently, the consensus was that, in this limit, flows are in a marginal state where only a minimal level of turbulence activity persists. Observations in direct numerical simulations at low Reynolds numbers ($Re$) using minimal sized channels appeared to support this view and reported long ‘hibernation’ periods where turbulence is marginalized. In simulations of pipe flow at $Re$ near transition we find that, indeed, with increasing Weissenberg number ($Wi$), turbulence expresses long periods of hibernation if the domain size is small. However, with increasing pipe length, the temporal hibernation continuously alters to spatio-temporal intermittency and here the flow consists of turbulent puffs surrounded by laminar flow. Moreover, upon an increase in $Wi$, the flow fully relaminarizes, in agreement with recent experiments. At even larger $Wi$, a different instability is encountered causing a drag increase towards MDR. Our findings hence link earlier minimal flow unit simulations with recent experiments and confirm that the addition of polymers initially suppresses Newtonian turbulence and leads to a reverse transition. The MDR state on the other hand results at these low$Re$ from a separate instability and the underlying dynamics corresponds to the recently proposed state of elasto-inertial turbulence.

Maximum Drag Reduction Asymptote of Polymeric Fluid Flow in Coiled Tubing

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Subhash N. Shah ◽  
Yunxu Zhou
Keyword(s):  
Drag Reduction ◽  
Oil And Gas ◽  
Guar Gum ◽  
Oil And Gas Industry ◽  
Flow Loop ◽  
Polymeric Fluids ◽  
Curvature Ratio ◽  
Coiled Tubing ◽  
Industry Applications ◽  
Maximum Drag Reduction

This study experimentally investigates the drag reduction characteristics of the most commonly used polymer fluids in coiled tubing applications. The flow loop employed consists of 12.7mm straight and coiled tubing sections. The curvature ratio (a∕R, where a and R are the radii of the tubing and the reel drum, respectively) investigated is from 0.01 to 0.076, which covers the typical curvature ratio range encountered in the oil and gas industry applications. Fluids tested include xanthan gum, guar gum, and hydroxypropyl guar at various polymer concentrations. It is found that the drag reduction in coiled tubing is significantly lower than that in straight tubing, probably due to the effect of secondary flow in curved geometry. The onset of drag reduction is also found to be delayed as the curvature ratio was increased. A correlation for the maximum drag reduction (MDR) asymptote in coiled tubing is developed. When the curvature ratio is set to zero, the new correlation reduces to the well-known Virk’s MDR asymptote for dilute polymer solutions in straight pipes. A new drag reduction envelope is proposed for the analysis of drag reduction behavior of polymeric fluids in coiled tubing. Application of the new drag reduction envelope is also discussed.

The drag reduction and degradation characteristics of poly α olefin in diesel via rotating disk apparatus

2018 ◽  
Vol 36 (13) ◽  
pp. 981-986
Author(s):  
Xiaodong Dai ◽  
Lei Li ◽  
Shuming Yin ◽  
Guicai Zhang ◽  
Jijiang Ge
Keyword(s):  
Drag Reduction ◽  
Rotating Disk

Drag Reduction on a Rotating Disk Using a Polymer Additive

1969 ◽  
pp. 251-263 ◽  
Author(s):  
C. Gorman Gilbert ◽  
John F. Ripken
Keyword(s):  
Drag Reduction ◽  
Rotating Disk ◽  
Polymer Additive
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