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.

Local and overall mass transfer rates to a rotating disk in turbulent and transition flows

1980 ◽  
Vol 25 (8) ◽  
pp. 1027-1032 ◽  
Author(s):  
C. Deslouis ◽  
B. Tribollet ◽  
L. Viet
Keyword(s):  
Mass Transfer ◽  
Rotating Disk ◽  
Transfer Rates

scholarly journals Control of Wall Turbulence by Spinning Discs

2013 ◽  
Vol 745 ◽  
pp. 135-143
Author(s):  
Pierre Ricco ◽  
Stanislav Hahn
Keyword(s):  
Drag Reduction ◽  
Friction Velocity ◽  
Wall Turbulence ◽  
Channel Height ◽  
Friction Drag ◽  
Disc Rotation ◽  
Maximum Drag Reduction ◽  
Friction Drag Reduction ◽  
Stress Term ◽  
Active Technique

This article is an extension to a previous paper of ours. It summarizes the main findingsand complements flow visualisations. An active technique for friction drag reduction in a turbulentchannel flow is studied by direct numerical simulations. The flow is modified by the steady rotationof rigid flush-mounted discs, located next to one another on the walls. The effect of the disc motionon the friction drag is investigated at a Reynolds number of Rτ =180, based on the friction velocity ofthe stationary-wall case and the half channel height. We compute a maximum drag reduction of 23%and a maximum net power saved of 10%, calculated by taking into account the power needed to rotatethe discs. The new Reynolds stress term induced by the disc rotation and generated by the velocitycomponents of the time averaged flow is shown to be instrumental for drag reduction.

scholarly journals A note to further explain the mechanism of turbulent flow drag reduction by polymer from chemistry view

2021 ◽  
Author(s):  
Xin Zhang ◽  
Xiaodong Dai ◽  
Jishi Zhao ◽  
Dengwei Jing ◽  
Fei Liu ◽  
...  
Keyword(s):  
Fourier Series ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Phase Angle ◽  
Linear Polymers ◽  
Flexible Polymers ◽  
Viscoelastic Theory ◽  
Maximum Drag Reduction ◽  
Flow Drag ◽  
Drag Reducing Polymer

In our previous work regarding the mechanism of drag reduction and degradation by flexible linear polymers, we proposed a correlation based on the Fourier series to predict the drag reduction and its degradation, where a phase angle was involved, but the physical meaning for the correlation especially of the employed phase angle was not clear, which is however important for reasonable explanation of the drag reduction mechanism over flexible linear polymers. This letter aims to clarify this issue. We use several steps of deduction from the viscoelastic theory, and conclude that the Fourier series employed to predict the drag reduction and its degradation is due to viscoelastic property of drag-reducing polymer solution, and the phase angle represents the hysteresis of polymer in turbulent flow. Besides, our new view of drag reduction by flexible polymers can also explain why a maximum drag reduction in rotational flow appears before degradation happens.

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.

Heat and Mass Transfer From a Rotating Disk

1959 ◽  
Vol 81 (2) ◽  
pp. 95-103 ◽  
Author(s):  
F. Kreith ◽  
J. H. Taylor ◽  
J. P. Chong
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Rotating Disk ◽  
Heat Transfer Process ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Turbulent Vortex ◽  
Heat Transfer Coefficients ◽  
Adiabatic Surface ◽  
Measured Mass

The analogy between heat, mass, and momentum transfer is applied to a rotating disk. Experimentally measured mass-transfer rates from a disk rotating in an infinite environment under laminar and turbulent conditions are related to the corresponding heat-transfer process by means of an analogy method. The experimental analog is shown to eliminate difficulties associated with accurate measurements of heat-transfer coefficients. Experimental data on the effect of an adiabatic surface placed at various distances parallel to the disk on the transfer rate from the disk are presented. Observations of some unusual flow patterns resulting from Goertler type vortexes in the transition regime and from some as yet unexplained turbulent vortex phenomena are also reported.

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.

The Torque and Turbulent Boundary Layer of Rotating Disks with Smooth and Rough Surfaces, and in Drag-Reducing Polymer Solutions

1973 ◽  
Vol 17 (04) ◽  
pp. 181-195
Author(s):  
Paul S. Granville
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Polymer Solutions ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Rotating Disks ◽  
Dimensional Boundary ◽  
Maximum Drag Reduction ◽  
Drag Reducing Polymer ◽  
Unbounded Fluid

The resisting torque of disks rotating in an unbounded fluid is analyzed on the basis of three-dimensional boundary-layer theory. Smooth and rough surfaces in ordinary fluids and in drag-reducing polymer solutions are considered. A general logarithmic relation is derived for the torque as a function of Reynolds number for arbitrary roughness and arbitrary drag reduction. Special formulas are obtained for smooth surfaces, fully rough surfaces, polymer solutions with a linear logarithmic drag-reduction characterization, and polymer solutions with maximum drag reduction. Relations are also obtained for boundary-layer parameters such as thickness and wall shearing stress. The computed results are in excellent agreement with experimental data available in the literature.

Mass and Heat Transfer From an Enclosed Rotating Disk With and Without Source Flow

1963 ◽  
Vol 85 (2) ◽  
pp. 153-162 ◽  
Author(s):  
Frank Kreith ◽  
E. Doughman ◽  
H. Kozlowski
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Correlation Equation ◽  
Rotating Disks ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Smoke Visualization ◽  
Source Flow

The heat-transfer characteristics of a partially enclosed rotating disk have been investigated experimentally by means of a mass-transfer analog. Mass-transfer rates to air from naphthalene coated disks of 4 and 8 in. diameter were measured at speeds between zero and 10,000 rpm and the influence of the spacing between the rotating disk and its housing was investigated with and without source flow. From the experimental results a dimensionless correlation equation suitable for predicting average heat and mass-transfer coefficients for rotating disks with source flow in turbulent flow at rotational Reynolds numbers up to 4 × 105 was deduced. The flow pattern was investigated by means of a hot wire, a smoke visualization technique, and the china clay method.

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