Effects of Surface Roughness on the Flow Characteristics in PDMS Microchannels

2005 ◽  
Author(s):  
Young-Min Kim ◽  
Woo-Seung Kim ◽  
Sang-Hoon Lee ◽  
Ju-Yeoul Baek
Keyword(s):  
Surface Roughness ◽  
Flow Characteristics

Impact of Print Parameters on Pressure Drop in Turbulent Flow Through 3-D Printed Pipes

2020 ◽  
Author(s):  
Thomas G. Shepard ◽  
John Wentz ◽  
Tucker Bender ◽  
Derek Olmschenk ◽  
Alex Gutenberg
Keyword(s):  
Surface Roughness ◽  
Additive Manufacturing ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Acrylonitrile Butadiene Styrene ◽  
Industrial Applications ◽  
Relative Pressure ◽  
Fused Filament Fabrication ◽  
Pressure Drops ◽  
Flow Through

Abstract Flow conduits made via additive manufacturing, commonly referred to as 3-D printing, are of increasing interest for a variety of industrial applications due to the ability to create unique and conformal flow paths that would not be possible with other fabrication techniques. Fused filament fabrication (FFF) is an additive manufacturing technique that is seeing new interest in the creation of internal flow channels with its ability to print high-temperature polymers and soluble supports. Printing parameter choices in the FFF printing process result in surfaces that can have significant profile differences that may significantly impact the flow characteristics within the conduits. In this study, two print parameters were experimentally studied for turbulent water flow through circular pipes created by fused filament fabrication out of acrylonitrile butadiene styrene (ABS). The print layer orientation relative to the flow was investigated for printing layers parallel, perpendicular, and at 45 degrees from the flow axis. Layer thickness were varied from 0.254 mm to 0.330 mm and all channels were created using soluble support structures. Pressure drops were measured for fully developed flow through pipes with an inside diameter of 5 mm and Reynolds numbers up to 62,000. Results are presented in terms of relative pressure drops as well as the wall surface roughness that would lead to such impacts. These flow-determined grain surface roughnesses are then compared against measurements of print surface roughness.

Induced Separation and Vorticity Using Roughness in VIV of Circular Cylinders at 8×103 < Re < 2.0×105

2008 ◽  
Author(s):  
Michael M. Bernitsas ◽  
Kamaldev Raghavan ◽  
G. Duchene
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Fluid Flow ◽  
Circular Cylinder ◽  
Passive Control ◽  
Flow Characteristics ◽  
Grit Size ◽  
Strip Width ◽  
Circular Cylinders ◽  
Flow Past

Results of an experimental investigation on fluid flow past an elastically mounted circular cylinder with rectangular surface roughness strips are presented. Flow characteristics change depending on the strip width, roughness grit size, and location. Roughness size and distribution can be designed to enhance or reduce/suppress VIV amplitude and increase or reduce the range of synchronization, respectively. To the authors’ knowledge this is the first study in passive control of VIV using properly distributed roughness.

Effects of Trees on Wind Flow Variability and Turbulence

1990 ◽  
Vol 112 (4) ◽  
pp. 320-325
Author(s):  
D. L. Elliott ◽  
J. C. Barnard
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Power Output ◽  
Flow Characteristics ◽  
Wind Flow ◽  
Considerable Decrease ◽  
Flow Variability ◽  
Mean Wind Speed ◽  
Variable Power ◽  
The Mean

This paper describes the results of a field experiment at the Goodnoe Hills, Wash. site to examine the effects of trees on wind flow variability and turbulence. Although vegetation at the site consisted primarily of grass, scattered areas of trees that penetrated the site provided an excellent opportunity to evaluate the effects of surface roughness changes on the wind flow characteristics. Wind data collected at nine towers across the site revealed that surface roughness changes in the upwind fetch caused pronounced variations in the wind flow over site. At two towers that were frequently 200 m to 300 m downwind of a grove of 10-m to 18-m trees, 20–30 percent reductions in wind speed and a factor of two to three increase in turbulence were measured at a height of 32 m. A substantial increase in the magnitude of the wind gusts, as well as a considerable decrease in the mean wind speed, was observed when a tower was downwind of the trees. Implications for a wind turbine located downwind of the trees, with a hub height near 30 m, would be reduced power output, more variable power output, more start/stop cycles, and increased stress caused by the tree-induced turbulence. The effects of the trees on the wind flow characteristics were considerably reduced at heights of 60 m and at distances greater than 500 m.

Natural Convection Heat Transfer With Horizontal Rectangular Fin Array Using Straight Knurling Patterns on Fins: An Experimental Study

2018 ◽  
Author(s):  
R. C. Chikurde ◽  
B. S. Kothavale ◽  
N. K. Sane
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Flow Characteristics ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Heat Transfer Augmentation

Natural Convection heat transfer from horizontal rectangular fin array with various knurling patterns is studied experimentally to find the effect of varying surface roughness on the heat transfer rate. The experimental parametric study is performed to investigate the effect of knurl produced surface roughness of fin on heat transfer rate. The parameters like knurling height from base, knurling depth and fin spacing might affect the flow characteristics and hence it is investigated to find the effect on heat transfer coefficient. The knurling is usually accomplished using one or more very hard rollers that contain the reverse of the pattern to be imposed. The result of this study shows that there are some important geometric factors related to knurling affecting the design of fin arrays and also heat transfer augmentation of natural convection heat transfer is observed.

scholarly journals Effect of Size and Surface Roughness of Cylindrical Weirs on Over Flow Characteristics

2011 ◽  
Vol 19 (2) ◽  
pp. 77-89
Author(s):  
Ibrahim A. I. Al-Hafith ◽  
Tahssen A. Chilmeran ◽  
Khalil I. Othman
Keyword(s):  
Surface Roughness ◽  
Flow Characteristics

Influence of Additional Leading-Edge Surface Roughness on Performances in Highly Loaded Compressor Cascade

2015 ◽  
Vol 32 (2) ◽  
Author(s):  
Shaowen Chen ◽  
Hao Xu ◽  
Shijun Sun ◽  
Longxin Zhang ◽  
Songtao Wang
Keyword(s):  
Surface Roughness ◽  
Flow Characteristics ◽  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Local Area ◽  
Compressor Cascade ◽  
Edge Surface ◽  
Aerodynamic Parameters ◽  
Highly Loaded

AbstractExperimental research has been carried out at low speed to investigate the effect of additional leading-edge surface roughness on a highly-loaded axial compressor cascade. A 5-hole aerodynamic probe has been traversed across one pitch to obtain the distribution of total pressure loss coefficient, secondary flow vector, flow angles and other aerodynamic parameters at the exit section. Meanwhile, ink-trace flow visualization has been used to measure the flow fields on the walls of cascades and a detailed topology structure of the flow on the walls has been obtained. Aerodynamic parameters and flow characteristics are compared by arranging different levels of roughness on various parts of the leading edge. The results show that adding surface roughness at the leading edge and on the suction side obviously influences cascade performance. Aggravated 3-D flow separation significantly increases the loss in cascades, and the loss increases till 60% when the level of emery paper is 80 mm. Even there is the potential to improve cascade performance in local area of cascade passage. The influence of the length of surface roughness on cascade performance is not always adverse, and which depends on the position of surface roughness.

Effect of Surface Roughness and Inlet Turbulence Intensity on a Turbine Nozzle Guide Vane External Heat Transfer: Experimental Investigation on a Literature Test Case

2020 ◽  
Author(s):  
T. Bacci ◽  
A. Picchi ◽  
T. Lenzi ◽  
B. Facchini ◽  
L. Innocenti
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Turbulence Intensity ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Sample Surface ◽  
Surface Finishing ◽  
Cfd Modelling ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Surface roughness is well known to significantly influence turbine aerodynamics and heat transfer; different studies have been undertaken in the last decades, in order to precisely characterize its effects and pursue a reliable and unified CFD modelling approach. Despite the effort, further research is still required to completely fulfill the goal, due to the complexity of the considered environment, with many other aspects and flow characteristics factoring into the final behavior. In this work an experimental campaign was carried out to evaluate the heat transfer coefficient on a linear nozzle guide vane geometry. The adopted geometry has been developed and tested, at different inlet turbulence intensity, Reynolds and Mach number, at Von Karman Institute. The results achieved on a test article with smooth surface were made available. In the present work the effect of increased turbulence level and surface roughness were taken into account, respectively using passive grids and conditioning the test sample surface finishing. Experiments were conducted using a transient technique by measuring the surface temperature evolution by IR thermography. The collected results integrate the existing database available in the open literature in order to support development and benchmarking of numerical approaches aimed at a reliable characterization of these aspects.

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