scholarly journals Closure to “Discussion of ‘Roughness Effects on Frictional Resistance of Enclosed Rotating Disks’” (1960, ASME J. Basic Eng., 82, p. 561)

1960 ◽  
Vol 82 (3) ◽  
pp. 561-562
Author(s):  
R. E. Nece ◽  
J. W. Daily
Keyword(s):  
Frictional Resistance ◽  
Rotating Disks ◽  
Roughness Effects

Roughness Effects on Frictional Resistance of Enclosed Rotating Disks

1960 ◽  
Vol 82 (3) ◽  
pp. 553-560 ◽  
Author(s):  
R. E. Nece ◽  
J. W. Daily
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Initial Point ◽  
Frictional Resistance ◽  
Reynolds Numbers ◽  
Tip Clearance ◽  
Rotating Disks ◽  
Roughness Effects ◽  
Disk Radius ◽  
Onset Of Turbulence

The effects of surface roughness on the frictional resistance of enclosed rotating disks have been studied experimentally. Torque data were obtained over the range of disk Reynolds numbers 4 × 103 to 6 × 106 for three different relative roughnesses a/k of 1000, 2000, and 3200 at three axial-clearance-to-disk-radius ratios s/a of 0.0227, 0.0609, and 0.112 for a constant, small, radial tip clearance. The existence of four possible basic flow regimes in the axial gap between the disk and casing wall was verified. Empirical expressions have been presented which predict the initial point of onset of turbulence in the flow within the boundary layer on the disk, the point at which the surface roughness becomes fully effective, and the magnitudes of the resistance coefficients in the zone of fully rough turbulent flow. The similarities and differences between smooth and rough-disk torque behavior, and to a limited extent boundary-layer behavior, have been noted.

scholarly journals The Frictional Resistance of Enclosed Rough Rotating Disks with Throughflow

1977 ◽  
Vol 43 (376) ◽  
pp. 4538-4549 ◽  
Author(s):  
Yutaka YAMADA ◽  
Motoyuki ITO ◽  
Yutaka SINODA
Keyword(s):  
Frictional Resistance ◽  
Rotating Disks

scholarly journals Numerical Validation of Frictional Coefficient for a Flat Plate with Various Anti-Fouling Coatings

2019 ◽  
Vol 8 (4) ◽  
pp. 12729-12736
Keyword(s):  
Flat Plate ◽  
Fuel Consumption ◽  
Frictional Coefficient ◽  
Frictional Resistance ◽  
Roughness Effects ◽  
Frictional Drag ◽  
Hull Form ◽  
Ship Hulls ◽  
Marine Coatings ◽  
Wetted Surface Area

Skin friction is responsible for approximately 60-70% of ship resistance. The fuel consumption and emission of the ship vary with the wetted surface, hull form and roughness. Reducing wetted surface area is not feasible and hence for reducing frictional resistance either the hull form should be optimized or the hull roughness function be made optimum. Most of the cases the hull form optimization of existing vessels are difficult and not economical. For these ships, the application of anti-fouling coating or air injection method below the bottom of the hull can be easily adapted to minimize the frictional resistance without any alteration on the vessel. The anti-fouling coating reduces the accumulation of marine growth and surface deterioration and hence limit the frictional drag. The selection of anti-fouling coating is also important since the resistance generated by the surrounded fluid on the ship increases with an increase in roughness function. This paper presents the numerical analysis and validation of frictional coefficient using CFD for different anti-fouling coating in the case of a flat plate. The roughness effects of different marine coatings are replicated and the frictional coefficient are compared with existing experimental data. The CFD results are agreeable with the published results. The work presented here could be applied to ship hulls to study the roughness effects due to various coatings or bio-fouling conditions to estimate the frictional drag and its effects in fuel consumption.

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