Surface roughness effect on cylinder vortex-induced vibration at moderate Re regimes

2021 ◽  
Vol 224 ◽  
pp. 108690
Author(s):  
Xiangxi Han ◽  
Youhong Tang ◽  
Zhanbin Meng ◽  
Fei Fu ◽  
Ang Qiu ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Roughness Effect ◽  
Vortex Induced Vibration

scholarly journals Effects of Roughness on Stresses in an Oxide Scale Formed on a Superalloy Substrate

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 479
Author(s):  
Yang Zhao ◽  
Fan Sun ◽  
Peng Jiang ◽  
Yongle Sun
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Residual Stresses ◽  
Oxide Scale ◽  
Rough Surface ◽  
Alumina Scale ◽  
Growth Stress ◽  
Oxide Growth ◽  
Substrate Thickness ◽  
Roughness Effect

The effects of surface roughness on the stresses in an alumina scale formed on a Fecralloy substrate are investigated. Spherical indenters were used to create indents with different radii and depths to represent surface roughness and then the roughness effect was studied comprehensively. It was found that the residual stresses in the alumina scale formed around the rough surface are almost constant and they are dominated by the curvature rather than the depth of the roughness. Oxidation changes the surface roughness. The edge of the indent was sharpened after oxidation and the residual stress there was released presumably due to cracking. The residual stresses in the alumina scale decrease with increase in oxidation time, while the substrate thickness has little effect, given that the substrate is thicker than the alumina scale. Furthermore, the effect of roughness on the oxide growth stress is analysed. This work indicates that the surface roughness should be considered for evaluation of stresses in coatings.

Experimental Study on Roughness Effect for Laminar Micro-Channel Gas Flow

2001 ◽  
Author(s):  
Jih-Hsing Tu ◽  
Fangang Tseng ◽  
Ching-Chang Chieng
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Friction Factor ◽  
Gas Flow ◽  
Micro Channel ◽  
Micro Machining ◽  
Roughness Effect ◽  
Relative Roughness ◽  
Smooth Channel ◽  
Micro Channels

Abstract Present study investigates the roughness effect on laminar gas flow for microchannels ranging from 40 to 600 μm with various roughness heights (40–82 nm) by systematical experiments. The micro-channels are manufactured by micro-machining technology and KOH anisotropic etching is employed to achieve various roughness patterns. Experimental results shows that higher product levels of Reynolds number (Reh) and friction factor (f) are obtained for microchannels of larger size and smaller relative roughness and friction factor f approaches to laminar flow theory value f0 for very smooth channel but the ratio of (f/f0) decreases as the surface roughness increases.

Surface Roughness Effects on Circular Cylinders at High Reynolds Numbers

2002 ◽  
Author(s):  
M. Eaddy ◽  
W. H. Melbourne ◽  
J. Sheridan
Keyword(s):  
Surface Roughness ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Roughness Effects ◽  
Vortex Induced Vibration ◽  
Smooth Cylinder ◽  
Lift Forces ◽  
High Reynolds ◽  
Effect Of Surface

The problem of flow-induced vibration has been studied extensively. However, much of this research has focused on the smooth cylinder to gain an understanding of the mechanisms that cause vortex-induced vibration. In this paper results of an investigation of the effect of surface roughness on the cross-wind forces are presented. Measurements of the sectional RMS fluctuating lift forces and the axial correlation of the pressures for Reynolds numbers from 1 × 105 to 1.4 × 106 are given. It was found that surface roughness significantly increased the axial correlation of the pressures to similar values found at high subcritical Reynolds numbers. There was little effect of the surface roughness on the sectional lift forces. The improved correlation of the vortex shedding means rough cylinders will be subject to larger cross-wind forces and an increased possibility of vortex-induced vibration compared to smooth cylinders.

scholarly journals NUMERICAL INVESTIGATION OF ROUGNESS EFFECTS ON HYDERDYNMIC AND THERMAL PERFORMANCE OF COUNTER FLOW MICROCHANNEL HEAT EXCHANGER

2019 ◽  
Vol 11 (4) ◽  
pp. 426-445
Author(s):  
Ahmed A. Ali ◽  
Mushtaq I. Hasan ◽  
Ghassan Adnan
Keyword(s):  
Surface Roughness ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Substrate Material ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Counter Flow ◽  
Roughness Effect ◽  
Microchannel Heat Exchanger ◽  
Effect Of Surface

In this paper the effect of surface roughness on the performance of counter flow microchannel heat exchanger has been numerically investigated. The studied Microchannel heat exchanger is a square shape and made of aluminum as substrate material with different values of hydraulic diameters (20, 50, 110, 150 ) μm. The working fluid used is water  at constant properties. Roughness- viscosity model has been used to study the roughness effect with 0.14 ratio of roughness to hydraulic diameter.  The results obtained indicate that pressure drop of (CFMCHX) increased with increasing surface roughness and decrease hydraulic diameter also the results showed that there is a slight increasing in thermal performance with increasing the surface roughness.

scholarly journals Surface-roughness effect on capacitance and leakage current of an insulating film

1999 ◽  
Vol 60 (12) ◽  
pp. 9157-9164 ◽  
Author(s):  
Y.-P. Zhao ◽  
G.-C. Wang ◽  
T.-M. Lu ◽  
G. Palasantzas ◽  
J. Th. M. De Hosson
Keyword(s):  
Surface Roughness ◽  
Leakage Current ◽  
Roughness Effect
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