scholarly journals Two-Point Velocity Measurements in Turbulent Round Jets

2020 ◽  
Author(s):  
Milad Samie ◽  
Philippe Lavoie ◽  
Andrew Pollard
Keyword(s):  
Velocity Measurements ◽  
Round Jets ◽  
Point Velocity

Estimating discharge in rivers through the combined use of dimensionless isovels and point velocity measurements

2017 ◽  
Vol 48 (3) ◽  
pp. 616-633 ◽  
Author(s):  
G. Farina ◽  
S. Alvisi ◽  
M. Franchini
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Accurate Estimation ◽  
Velocity Measurements ◽  
Combined Use ◽  
Point Velocity ◽  
New Formulation ◽  
The Relationship ◽  
River Cross Section

This paper presents a procedure for estimating discharge in a river cross-section based on the combined use of dimensionless isovels and point velocity measurements. Specifically, taking the Biot–Savart law on the magnetic field induced by an electric current in a wire as their basis as already done by other researchers, the authors propose a new formulation of the relationship characterizing the effect of the wetted perimeter on the range of velocities in a cross-section in order to take explicit account of roughness, expressed by means of Manning's coefficient. Once appropriately nondimensionalized, the isoeffect contours can be read as dimensionless isovels. Assuming in situ velocity measurements are available, discharge at a cross-section can be computed using two different methods. The proposed procedure was applied to six case studies characterized by river cross-sections which differed greatly from one another. The results show that the two methods proposed for estimating discharge lead to equivalent outcomes, and in all the cases the procedure as a whole enables a sufficiently accurate estimation of discharge, even when it is based on a limited number of velocity measurements or on the measurement of maximum surface-water velocity alone.

On using experimentally estimated wall shear stresses to validate numerically predicted results

2003 ◽  
Vol 217 (2) ◽  
pp. 77-90 ◽  
Author(s):  
M Walsh ◽  
T McGloughlin ◽  
D W Liepsch ◽  
T O'Brien ◽  
L Morris ◽  
...  
Keyword(s):  
Shear Rate ◽  
Laser Doppler Anemometry ◽  
Numerical Models ◽  
Wall Shear Rate ◽  
Shear Stresses ◽  
Velocity Measurements ◽  
Curve Fit ◽  
Wall Shear ◽  
Point Velocity ◽  
Curve Fitting Method

The objective of this investigation was to assess the use of experimentally estimated wall shear stresses to validate numerically predicted results. The most commonly cited haemodynamic factor implicated in the disease initiation and proliferation processes at graft/artery junctions is wall shear stress (WSS). WSS can be determined from the product of the viscosity of the fluid and the wall shear rate. Numerically, the wall shear rate is predicted using velocity values stored in the computational cell near the wall and assuming zero velocity at the wall. Experimentally, the wall shear rate is estimated by applying a curve-fit to near-wall velocity measurements and evaluating the shear rate at a specific distance from the wall. When estimating the wall shear rate from the laser Doppler anemometry (LDA) point velocity measurements, large differences between the experimentally estimated and numerically predicted WSSs were introduced. It was found that the estimated WSS distributions from the experimental results are highly dependent on the curve-fitting method used to calculate the wall shear rate. However, the velocity profiles for both the experimental and numerical investigations show extremely good comparison. It is concluded that numerical models should be validated using unprocessed LDA point velocity measurement and not estimated WSS values.

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Ground Water ◽  
2015 ◽  
Vol 54 (3) ◽  
pp. 394-405 ◽  
Author(s):  
P.C. Schillig ◽  
J.F. Devlin ◽  
D. Rudolph
Keyword(s):  
Velocity Measurements ◽  
Glacial Outwash ◽  
Point Velocity

scholarly journals Laser-Doppler measurements on a round turbulent jet in dilute polymer solutions

1973 ◽  
Vol 60 (4) ◽  
pp. 721-731 ◽  
Author(s):  
Steven J. Barker
Keyword(s):  
Polymer Solutions ◽  
Initial Conditions ◽  
Laser Doppler ◽  
Turbulent Jet ◽  
Laser Doppler Velocimeter ◽  
Doppler Velocity ◽  
Velocity Measurements ◽  
Convergent Nozzle ◽  
Round Jets ◽  
Dilute Polymer Solutions

A laser-Doppler velocimeter suitable for the measurement of mean and fluctuating flow velocities in water is described. Results of a study using this system in an axisymmetric turbulent jet of water and dilute polymer solutions are given. The laser-Doppler technique is better suited for such measurements than either Pitot tubes or heat-transfer gauges because the Doppler velocity measurements are independent of the physical properties of the fluid. Previous velocity measurements in polymer jets have suffered from the effects of the additives upon the sensors.Turbulent round jets with Reynolds numbers between 5000 and 50000 were studied. For a jet issuing from a convergent nozzle the additives were found to have no effect upon the mean axial velocity or turbulence intensity at any point in the jet. However, for a jet issuing from a long length of circular pipe, the additives reduced the centre-line velocity and increased the turbulence level in the early part of the jet. Thus the principal effect of a polymer additive upon the jet appears to result from its effect upon the initial conditions.

Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence

1983 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
J. C. McDaniel ◽  
B. Hiller ◽  
R. K. Hanson
Keyword(s):  
Multiple Point ◽  
Velocity Measurements ◽  
Point Velocity

Measurements of the velocity field of a wing-tip vortex, wandering in grid turbulence

2008 ◽  
Vol 601 ◽  
pp. 281-315 ◽  
Author(s):  
S. C. C. BAILEY ◽  
S. TAVOULARIS
Keyword(s):  
Free Stream ◽  
Tip Vortex ◽  
Grid Turbulence ◽  
Velocity Measurements ◽  
Free Stream Turbulence ◽  
Normal Probability ◽  
Rate Of Decay ◽  
Wing Tip Vortex ◽  
Point Velocity ◽  
Wing Tip

Velocity measurements were performed in a wing-tip vortex wandering in free-stream turbulence using two four-wire hot-wire probes. Vortex wandering was well represented by a bi-normal probability density with increasing free-stream turbulence resulting in increased amplitude of wandering. The most dominant wavelength of wandering was found to remain unaffected by free-stream conditions. Two-point velocity measurements were used to reconstruct the vortex velocity profile in a frame of reference wandering with the vortex. Increasing turbulence intensity was found to increase the rate of decay of the vortex peak circumferential velocity while the radial location of this peak velocity remained unchanged. These results are consistent with several possible vortex decay mechanisms, including the stripping of vorticity by azimuthally aligned vortical structures, transfer of angular momentum from the vortex to these structures during their formation and the deformation and breakup of the vortex by strong free-stream eddies.

Study on Multi-Point Velocity Measurements of Laser Doppler Velocimetry Based on Dual-Core Photonic Crystal Fiber

2015 ◽  
Vol 35 (11) ◽  
pp. 1112003
Author(s):  
黄雪峰 Huang Xuefeng ◽  
赵冠军 Zhao Guanjun ◽  
李盛姬 Li Shengji ◽  
郭枫 Guo Feng ◽  
郑光华 Zheng Guanghua ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystal Fiber ◽  
Laser Doppler Velocimetry ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Velocity Measurements ◽  
Crystal Fiber ◽  
Point Velocity ◽  
Dual Core
Sign in / Sign up

Export Citation Format

Share Document