scholarly journals LIMITING MAXIMUM DRAG REDUCTION ASYMPTOTE FOR THE MOMENT COEFFICIENT OF AN ENCLOSED ROTATING DISK WITH FINE SPIRAL GROOVES

2010 ◽  
Vol 11 (2) ◽  
Author(s):  
Budiarso . ◽  
Keizo Watanabe ◽  
Satoshi Ogata
Keyword(s):  
Drag Reduction ◽  
Rotating Disk ◽  
Moment Coefficient ◽  
Maximum Drag Reduction ◽  
The Moment ◽  
Spiral Grooves

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.

Friction Drag on Bladed Disks in Housings as a Function of Reynolds Number, Axial and Radial Clearance, and Blade Aspect Ratio and Solidity

1961 ◽  
Vol 83 (4) ◽  
pp. 719-723 ◽  
Author(s):  
Robert W. Mann ◽  
Charles H. Marston
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Rotating Disk ◽  
Radial Clearance ◽  
Disk Radius ◽  
Moment Coefficient ◽  
Aspect Ratios ◽  
Direct Measurements ◽  
Partial Admission ◽  
The Moment

Extra losses from partial admission operation of a gas turbine occur both in the nozzle flow arc and away from it. The latter have been related to the theory of fluid flow over a rotating disk expressing a dimensionless moment coefficient as a function of Reynolds number. By direct measurements of drag torque, the moment coefficient has been determined over a range of Reynolds number from 2.0 × 104 to 4.5 × 106 for several aspect ratios, axial and radial shroud clearances, and solidities. Losses increase with increasing aspect ratio. Small increases from minimum practical clearance have little effect, but blade pumping losses become severe at radial and axial clearances of the order of half the disk radius. Typical changes in solidity have only small effects on losses.

scholarly journals Drag Reduction of an Enclosed Rotating Disk with Fine Spiral Grooves

2005 ◽  
Vol 71 (712) ◽  
pp. 2849-2855 ◽  
Author(s):  
Keizo WATANABE ◽  
Budiarso ◽  
Satoshi OGATA ◽  
Keigo UEMURA
Keyword(s):  
Drag Reduction ◽  
Rotating Disk ◽  
Spiral Grooves

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 Drag Reduction of an Enclosed Rotating Disk with Fine Spiral Grooves

2007 ◽  
Vol 2 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Keizo WATANABE ◽  
BUDIARSO ◽  
Satoshi OGATA ◽  
Keigo UEMURA
Keyword(s):  
Drag Reduction ◽  
Rotating Disk ◽  
Spiral Grooves

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.

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