scholarly journals Experimental work on the Low Reynolds Number Behaviour of 2-Hole Offset Probes

2020 ◽  
Vol 9 (5) ◽  
pp. 449-454
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Experimental Work ◽  
Air Flow ◽  
Reynolds Numbers ◽  
Pitot Tube ◽  
Velocity Range ◽  
Efficient Performance ◽  
Flow Through ◽  
Simulated Wind

Whenever a dusty or slurry air passes through the L-type pitot tube its impurities struck at 900 bend, resulting in the partially choking of the air flow through this device. And eventually its accuracy is decreased with the passage of time. Alternatively, such type of obstruction of the air flow can be avoided by using S-type pitot tube. Keeping this in mind, in the present work we had used S-type pitot tube of diameters ranging from 1.23 mm to 9.54 mm to test against the standard (L-type) pitot tube to control the accuracy of S-type pitot tube co-efficient. An experimental work has been carried out in a simulated wind tunnel environment. The results of the present work showed that there a slight dip over a velocity range of 3 to 14 m/s. Further, it is observed that for higher Reynolds numbers or at higher velocities of the air (more than 14 m/s) the co-efficient performance of S-pitot tube is found almost constant.

Power Augmentation of a HAWT by Mie-type Tip Vanes, considering Wind Tunnel Flow Visualisation, Blade-Aspect Ratios and Reynolds Number

2003 ◽  
Vol 27 (3) ◽  
pp. 183-194 ◽  
Author(s):  
Yukimaru Shimizu ◽  
Edmond Ismaili ◽  
Yasunari Kamada ◽  
Takao Maeda
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Reynolds Numbers ◽  
Flow Visualisation ◽  
Velocity Measurements ◽  
Horizontal Axis Wind Turbine ◽  
Aspect Ratios ◽  
Detailed Surface ◽  
Blade Tips

Wind tunnel results are reported concerning the effects of blade aspect ratio and Reynolds number on the performance of a horizontal axis wind turbine (HAWT) with Mie-type1 tip attachments. The flow behaviour around the blade tips and the Mie-type tip vanes is presented. Detailed surface oil film visualization and velocity measurements around the blade tips, with and without Mie vanes, were obtained with the two-dimensional, Laser-Doppler Velocimetry method. Experiments were performed with rotors having blades with different aspect ratio and operating at different Reynolds numbers. The properties of the vortices generated by the Mie vanes and the blade tips were carefully studied. It was found that increased power augmentation by Mie vanes is achieved with blades having smaller aspect ratio and smaller Reynolds number.

Effect of Surface Roughness on Gaseous Flow Through Microchannels

2000 ◽  
Author(s):  
Stephen E. Turner ◽  
Hongwei Sun ◽  
Mohammad Faghri ◽  
Otto J. Gregory
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Helium Flow ◽  
Local Pressure ◽  
Aspect Ratios ◽  
Corrugated Surfaces ◽  
Flow Through ◽  
Effect Of Surface

Abstract This paper presents an experimental investigation on nitrogen and helium flow through microchannels etched in silicon with hydraulic diameters between 10 and 40 microns, and Reynolds numbers ranging from 0.3 to 600. The objectives of this research are (1) to fabricate microchannels with uniform surface roughness and local pressure measurement; (2) to determine the friction factor within the locally fully developed region of the microchannel; and (3) to evaluate the effect of surface roughness on momentum transfer by comparison with smooth microchannels. The friction factor results are presented as the product of friction factor and Reynolds number plotted against Reynolds number. The following conclusions have been reached in the present investigation: (1) microchannels with uniform corrugated surfaces can be fabricated using standard photolithographic processes; and (2) surface features with low aspect ratios of height to width have little effect on the friction factor for laminar flow in microchannels.

Strut Interference Effects on Pitot Tube Velocity Measurements

2007 ◽  
Author(s):  
Sandra K. S. Boetcher ◽  
Ephraim M. Sparrow
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Body ◽  
Pitot Tube ◽  
Velocity Measurements ◽  
Measuring Device ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Velocity Measuring ◽  
The Impact

The possible impact of the presence of the strut portion of a Pitot tube on the efficacy of the tube as a velocity-measuring device has been evaluated by numerical simulation. At sufficiently low Reynolds numbers, there is a possibility that the precursive effects of the strut could alter the flow field adjacent to the static taps on the body of the Pitot tube and might even affect the impact pressure measured at the nose. The simulations were performed in dimensionless form with the Reynolds number being the only prescribed parameter, but the dimensions were taken from a short-shanked Pitot tube. Over the Reynolds number range from 1500 to 4000, a slight effect of the strut was identified. However, the variation due to the presence of the shank of the velocity measured by the Pitot tube operating in that range of Reynolds numbers was only 1.5%.

Effects of the Divergence Angle on the Onset of Asymmetric Flow Through a Planar Diffuser

2009 ◽  
Author(s):  
Majid Nabavi ◽  
Luc Mongeau
Keyword(s):  
Reynolds Number ◽  
Flow Regime ◽  
Critical Reynolds Number ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Asymmetric Flow ◽  
Symmetric Flow ◽  
Turbulent Flow Regime ◽  
Flow Through ◽  
Gradual Expansion

In this study, two-dimensional laminar incompressible and turbulent compressible flow through the planar diffuser (gradual expansion) for different divergence half angles of the diffuser (θ), and different Reynolds numbers (Re) was numerically studied. The effects of θ on the critical Reynolds number at which the onset of asymmetric flow is observed, were investigated. In the laminar flow regime, it was observed that for every values of θ, there is a critical Re beyond which the flow is asymmetric. However, in the turbulent flow regime, for θ ≥ 20°, even at low Reynolds number the flow is asymmetric. Only for θ ≤ 10°, symmetric flow was observed below a critical Re.

An Investigation Into the Performance of Two ISA Metering Nozzles of Finite and Zero Area Ratio

1965 ◽  
Vol 87 (2) ◽  
pp. 525-529 ◽  
Author(s):  
S. Soundranayagam
Keyword(s):  
Reynolds Number ◽  
Potential Flow ◽  
Discharge Coefficient ◽  
Flow Model ◽  
Reynolds Numbers ◽  
Area Ratio ◽  
Flow Through

The flow through two ISA nozzles of area ratio zero and 0.4 was investigated to determine the nature of the flow and its variation with Reynolds number. Separation occurs within the nozzle of zero area ratio, the size of the bubble increasing with decreasing Reynolds number. The predicted discharge coefficient based on a simplified flow model agrees with experiment for large Reynolds numbers. Upstream influences affect the performance of the nozzle of area ratio 0.4. The flows through the two nozzles are not comparable, and potential-flow results cannot be used to explain flow in venturis and nozzles in pipes. The discharge-coefficient curve for area ratio 0.4 shows a distinct hump when based on the head differential measured as for venturis, but no hump when based on the head differential across the corner taps.

Low Reynolds number heat transfer from a circular cylinder

1968 ◽  
Vol 32 (1) ◽  
pp. 21-28 ◽  
Author(s):  
C. A. Hieber ◽  
B. Gebhart
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Number Theory ◽  
Circular Cylinder ◽  
Prandtl Number ◽  
Experimental Work ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Theoretical Results

Theoretical results are obtained for forced heat convection from a circular cylinder at low Reynolds numbers. Consideration is given to the cases of a moderate and a large Prandtl number, the analysis in each case being based upon the method of matched asymptotic expansions. Comparison between the moderate Prandtl number theory and known experimental results indicates excellent agreement; no relevant experimental work has been found for comparison with the large Prandtl number theory.

Numerical Analysis of Vortex Dynamics in a Double Expansion

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Allan I. J. Love ◽  
Donald Giddings ◽  
Henry Power
Keyword(s):  
Reynolds Number ◽  
Vortex Dynamics ◽  
Experimental Studies ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
Reynolds Stress Model ◽  
Main Flow ◽  
Time Dependent ◽  
Ansys Fluent ◽  
Flow Through

The turbulent flow through a 3D diffuser featuring a double expansion is investigated using computational fluid dynamics. Time dependent simulations are reported using the stress omega Reynolds stress model available in ANSYS FLUENT 13.0. The flow topography and characteristics over a range of Reynolds numbers from 42,000 to 170,000 is reported, and its features are consistent with those investigated for other similar geometries. A transition from a chaotic separated flow to one featuring one large recirculation in one corner of the diffuser is predicted at a Reynolds number of 80,000. For a Reynolds number of 170,000 a precessing/flapping motion of the main flow field was identified, the frequency of which is consistent with other numerical and experimental studies.

Flow separation on a spheroid at incidence

1979 ◽  
Vol 92 (4) ◽  
pp. 643-657 ◽  
Author(s):  
Taeyoung Han ◽  
V. C. Patel
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Reynolds Numbers ◽  
Surface Flow ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Turbulent Separation

Surface streamline patterns on a spheroid have been examined at several angles of attack. Most of the tests were performed at low Reynolds numbers in a hydraulic flume using coloured dye to make the surface flow visible. A limited number of experiments was also carried out in a wind tunnel, using wool tufts, to study the influence of Reynolds number and turbulent separation. The study has verified some of the important qualitative features of three-dimensional separation criteria proposed earlier by Maskell, Wang and others. The observed locations of laminar separation lines on a spheroid at various incidences have been compared with the numerical solutions of Wang and show qualitative agreement. The quantitative differences are attributed largely to the significant viscous-inviscid flow interaction which is present, especially at large incidences.

The effect of mass ratio and tether length on the flow around a tethered cylinder

2007 ◽  
Vol 591 ◽  
pp. 117-144 ◽  
Author(s):  
K. RYAN ◽  
M. C. THOMPSON ◽  
K. HOURIGAN
Keyword(s):  
Reynolds Number ◽  
Experimental Work ◽  
Large Amplitude ◽  
Critical Mass ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Mass Ratio ◽  
Flow Past ◽  
Mass Ratios ◽  
Related Experimental Work

A tethered cylinder may be considered an extension of the widely studied problem of a hydro-elastically mounted cylinder. Here we numerically investigate the flow past a positively buoyant tethered cylinder for a range of mass ratios and tether length ratios at a Reynolds numberRe= 200. The results are found to be qualitatively similar to related experimental work performed at significantly higher Reynolds numbers. Two important findings are related in this paper. First, we find that the action of the tethered cylinder oscillating at an angle to the flow induces a mean lift coefficient. Second, a critical mass ratio (m*crit) is found below which large-amplitude oscillations are noted, similar to that previously reported for the case of a hydro-elastically mounted cylinder. For short tether lengths, (m*crit) is significantly greater than that found for a hydro-elastically mounted cylinder. As the tether length increases, the (m*crit) decreases and asymptotes to that of a hydro-elastically mounted cylinder as the tether length approaches infinity.

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