Laser Velocimeter Measurements in a Model Propeller Flowfield

1988 ◽  
Vol 110 (4) ◽  
pp. 350-354 ◽  
Author(s):  
J. Lepicovsky
Keyword(s):  
Data Acquisition ◽  
Data Reduction ◽  
Velocity Measurements ◽  
Simple Experiment ◽  
Reversed Flow ◽  
Mean Velocity ◽  
Blade Height ◽  
Reduction Techniques ◽  
The Mean ◽  
Set Up

The objective of this work was to demonstrate the usability of a laser velocimeter data acquisition and reduction techniques for ensemble-averaged velocity measurements near and between rotating propeller or fan blades. A relatively simple experiment was set up to measure the flowfield of a two-bladed model propeller operating at static (non-flight) conditions to verify the data reduction procedures. The mean velocity and ensemble-averaged blade-to-blade velocity distributions were acquired. The experimental results, plotted in a novel consise form, showed separated and reversed flow regions on a rotating static propeller. The flowfield distortion along the blade height in the vicinity of the propeller disc was also observed.

scholarly journals Improved Data Reduction Techniques for the ESO CES Plus Reticon Spectra

1988 ◽  
Vol 132 ◽  
pp. 355-360
Author(s):  
B. H. Foing ◽  
L. Crivellari
Keyword(s):  
Radial Velocity ◽  
Data Reduction ◽  
Equivalent Width ◽  
Optimal Recovery ◽  
Special Care ◽  
Velocity Measurements ◽  
Reduction Techniques ◽  
Dark Counts ◽  
Improved Data Reduction

We developed routines for intensity, equivalent width, and radial velocity measurements on CES plus reticon spectra obtained with the ESO 1.4m telescope. In order to achieve the optimal recovery of the signal, the noise has to be minimized by removing any parasitical effect. Special care has been devoted to the correction for remanence effects in the reticon dark counts. Typical results are presented and discussed.

An effective, low-cost method to improve the movement velocity measurement of a smartphone app during the bench press exercise

2021 ◽  
pp. 175433712110580
Author(s):  
Wladymir Külkamp ◽  
Jairo L Rosa-Junior ◽  
Jonathan Ache-Dias ◽  
Lorival J Carminatti
Keyword(s):  
Older Adults ◽  
Velocity Measurement ◽  
Bench Press ◽  
Low Cost ◽  
Reference Method ◽  
Velocity Measurements ◽  
Range Of Movement ◽  
Mean Velocity ◽  
Movement Velocity ◽  
The Mean

Some studies have reported considerable errors in the movement velocity measurement when using the My Lift app. This study aimed to investigate whether these errors may be related to the use of a range of movement (ROM) statically measured prior to the movement (ROMMYLIFT) instead of ROM dynamically monitored. Ten young adults performed two repetitions of the bench press exercise on a Smith machine with loads that allowed two velocity conditions (above and below 0.6 m s−1). The exercises were monitored by the My Lift app, a magnet and a rotary encoder. After, 15 older adults performed the same exercise at different percentages of 1RM, monitored by the My Lift app and a magnet. The results revealed that ROM dynamically obtained by encoder (reference method) with the mean velocity above (0.497 ± 0.069 m) and below (0.450 ± 0.056 m) 0.6 m s−1 were quite different ( p < 0.05; large effect) from the ROMMYLIFT (0.385 ± 0.040 m). These errors provided highly biased and heteroscedastic mean velocity measurements (mean errors approximately 22%). The errors observed in adults were also observed in the older participants, except for loads equal to 85% of 1RM. The magnet method proved to be valid, presenting measurements very close to the encoder (mean errors approximately 1.7%; r > 0.99). In conclusion, the use of ROMMYLIFT is inadequate, as the higher the movement velocity, the higher the errors, both for young and older adults. Thus, to improve the measurement of the My Lift app, it is recommended that the magnet method be used in conjunction with the app to more accurately determine the ROM.

Entry flow in a curved pipe

1975 ◽  
Vol 67 (1) ◽  
pp. 177-196 ◽  
Author(s):  
L.-S. Yao ◽  
S. A. Berger
Keyword(s):  
Fluid Flows ◽  
Resistance Coefficient ◽  
Straight Pipe ◽  
Mean Velocity ◽  
Dimensional Parameter ◽  
Fully Developed Flow ◽  
Curved Pipe ◽  
Entry Length ◽  
The Mean ◽  
Set Up

A secondary flow is set up when a fluid flows through a stationary curved pipe. The fluid in the middle of the pipe moves outwards and that near the wall inwards. Dean showed that the dynamical similarity of this fully developed flow depends on a non-dimensional parameter $D = 2(a/R)^{\frac{1}{2}}(a\overline{W}/\nu) $, where $\overline{W} $ is the mean velocity along the pipe, v is the coefficient of kinematic viscosity and a is the radius of the pipe, which is bent into a coil of radius R. Dean's analysis was limited to small values of D. Later, Barua developed an asymptotic boundary-layer theory for large values of D and showed for these values of D that the resistance coefficient γc is much larger than that for the corresponding straight pipe. The present work deals with the flow in a curved pipe as it develops from a uniformly distributed velocity at the entrance to a fully developed profile. Barua's results for the fully developed flow are adopted as downstream conditions in the present work. The ratio of the entry lengths of the curved ipe and the corresponding straight one is shown to be proportional to D−1/2 when D is large. Thus, the entry length for a curved pipe is much shorter than that for the corresponding straight pipe.

Turbulent flow over large-amplitude wavy surfaces

1984 ◽  
Vol 140 ◽  
pp. 27-44 ◽  
Author(s):  
Jeffrey Buckles ◽  
Thomas J. Hanratty ◽  
Ronald J. Adrian
Keyword(s):  
Boundary Layer ◽  
Turbulent Flow ◽  
Velocity Fields ◽  
Laser Doppler Velocimeter ◽  
Free Shear Layer ◽  
Wave Surface ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Wavy Surfaces ◽  
The Mean

The laser-Doppler velocimeter is used to measure the mean and the fluctuating velocity for turbulent flow over a solid sinusoidal wave surface having a wavelength λ of 50.8 mm and a wave amplitude of 5.08 mm. For this flow, a large separated region exists, extending from x/λ = 0.14 to 0.69. From the mean velocity measurements, the time-averaged streamlines and therefore the extent of the separated region are calculated. Three flow elements are identified: the separated region, an attached boundary layer, and a free shear layer formed by the detachment of the boundary layer from the wave surface. The characteristics of these flow elements are discussed in terms of the properties of the mean and fluctuating velocity fields.

Designing of Velocity Measuring System of Initiating Explosive Devices Based on Photoelectric Method

2011 ◽  
Vol 346 ◽  
pp. 533-538
Author(s):  
Shi Meng Li ◽  
Jun Wang ◽  
Lin Yang
Keyword(s):  
Measuring System ◽  
Velocity Measurements ◽  
Photoelectric Conversion ◽  
Photoelectric Method ◽  
Mean Velocity ◽  
Muzzle Velocity ◽  
Spacing Interval ◽  
The Mean ◽  
Velocity Measuring ◽  
Explosive Devices

This paper introduced a new method of designing on the velocity measuring system of initiating explosive devices. We designed multiple selectable targets using the principle of photoelectric conversion. When the object passed through the targets, two pulses would generate separately. Through counting the spacing interval of the two pulses, we could calculate the mean velocity of the object passing through the targets, and revise it into the muzzle velocity. This paper designed the structure of photoelectric targets and circuits of the measuring system, also processed revising and error analysis of the measurement result. The system designed in this paper has the features of simple, reliable, high accuracy, good dynamic response, easy to disassemble and maintain, and is suitable for various environment with the reducing of the errors and inconvenience of traditional velocity measurements.

Comparison Between a Slot Jet and Round Jets Impinging a Curved Wall

2003 ◽  
Author(s):  
V. Gilard ◽  
L.-E. Brizzi
Keyword(s):  
Data Processing ◽  
Flow Structure ◽  
Statistical Data ◽  
Velocity Fields ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Statistical Data Processing ◽  
Round Jets ◽  
The Mean

Velocity measurements by PIV are realized in order to compare a slot jet and round jets impinging a curved surface. A statistical data processing allows us to obtain the mean velocity fields and the Reynolds stresses. For the two jet geometries, the flow structure is described. Some velocity distributions according to different axis are extracted of the mean velocity fields and are also described.

Slot Jet Impinging a Curved Wall

2002 ◽  
Author(s):  
V. Gilard ◽  
L.-E. Brizzi
Keyword(s):  
Data Processing ◽  
Statistical Data ◽  
Velocity Fields ◽  
Pressure Measurements ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Concave Wall ◽  
Wall Flow ◽  
The Mean

In order to study the aerodynamics of a slot jet impinging a concave wall, flow visualisations, velocity measurements by PIV and pressure measurements are carried out. A statistical data processing allows us to obtain the mean velocity fields and the Reynolds stresses. Among the studied parameters, the effect of the relative curvature of the wall is studied in particular because of a jet beating phenomenon observed for a low relative curvature. Three flow modes are then described.

Velocity profiles assessment in natural channels during high floods

2011 ◽  
Vol 42 (2-3) ◽  
pp. 162-170 ◽  
Author(s):  
Tommaso Moramarco ◽  
Carla Saltalippi ◽  
Vijay P. Singh
Keyword(s):  
Flow Velocity ◽  
Maximum Flow ◽  
Velocity Profiles ◽  
Mean Flow ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Flow Area ◽  
The Mean ◽  
Logarithmic Law ◽  
Maximum Flow Velocity

The accuracy of three different approaches for velocity profiles assessment during high floods, when the velocity points sampling is carried out only in the upper portion of the flow area, has been investigated. The first two methods assume the classical logarithmic law with additional terms, to take account of the dip-phenomenon in the velocity profile. The third one is based on the entropy theory and uses the maximum flow velocity occurring in the flow area. A sample of velocity measurements carried out at Pontelagoscuro gauged section (Po River, Italy), has been considered for the analysis. Six flood events have been selected and the accuracy of the investigated methods has been evaluated in terms of mean error in estimating both the mean velocity along each sampled vertical and the mean flow velocity. For high floods, the logarithmic law and the entropic approach were found quite accurate; however, the ability of the latter in reproducing the velocity profiles only by sampling the maximum flow velocity has been shown. Therefore, a procedure for velocity measurements based on the entropic approach has been proposed. The procedure allows one to both to shorten remarkably the time of the velocity sampling and to quickly estimate the discharge.

Laser-Doppler anemometer measurements in drag-reducing channel flows

1975 ◽  
Vol 70 (2) ◽  
pp. 369-392 ◽  
Author(s):  
M. M. Reischman ◽  
W. G. Tiederman
Keyword(s):  
Velocity Profile ◽  
Streamwise Velocity ◽  
Laser Doppler Anemometer ◽  
Channel Flows ◽  
Two Dimensional ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Buffer Region ◽  
The Mean ◽  
Made In

The objective of this study was to make velocity measurements in drag-reducing flows which would be sufficient in scope and accuracy to test proposed models of drag-reducing flows and to yield new information about the mechanisms of drag reduction. Consequently, measurements of the mean and turbulence intensity of the streamwise velocity component were made in fully developed, turbulent, drag-reducing flow in a two-dimensional channel with a laser-Doppler anemometer. The anemometer was operated in the individual-realization mode and corrections were made to eliminate statistical biasing of the data. Two polyacrylamides and a polyethylene oxide were used to produce seven flows which had drag reductions ranging from 24 to 41 %. Measurements were also made in water to establish the standard characteristics of the flow channel.The data show that the drag-reducing mean velocity profile can be divided into three zones: a viscous sublayer, a buffer or interactive region and a logarithmic region. There is no evidence that the viscous sublayers of the drag-reducing channel flows are thicker than those in the solvent flows. In addition the normalized streamwise fluctuations are essentially the same in both the solvent and drag-reducing sublayers. The changes caused by the polymer addition occur in the buffer region. The drag-reducing buffer region is thicker and the velocity profile in the outer flow region adjusts in order to accommodate this buffer-region thickening. The measurements of the streamwise velocity fluctuations also show that the polymer additives redistribute the primary turbulent activity over a broadened buffer region. The normalized magnitude of these fluctuations is, however, considerably lower in these two-dimensional drag-reducing channel flows than in those previously reported by Rudd (1972), Logan (1972) and Kumor & Sylvester (1973). Moreover, the mean velocity profiles in the buffer region do not confirm the hypothesis of Virk, Mickley & Smith (1970) that the data will follow their proposed ‘ultimate profile’ when the drag reduction is less than that given by the maximum asymptote. The mean velocity measurements also show that the proposed methods for predicting the upward shift in the outer portion of the mean velocity profile are inconsistent and lack universality. However, these results do confirm the previous suggestions of Virk (1971), Tomita (1970) and Lumley (1973) that the buffer region is the area of importance and change in drag-reducing flows.

Spatial Filter Velocimetry Based on Time-Series Particle Images

2011 ◽  
Author(s):  
Shigeo Hosokawa ◽  
Hiroki Sakamoto ◽  
Akio Tomiyama
Keyword(s):  
Time Series ◽  
Turbulent Flows ◽  
Frequency Analysis ◽  
Spatial Filter ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
The Mean ◽  
Particle Images ◽  
Laminar And Turbulent Flows ◽  
Analysis Of Time Series

High spatial and temporal resolutions are required in velocity measurements for turbulent flows to examine turbulence characteristics accurately. In this study, we proposed a spatial filter velocimetry (SFV) based on a frequency analysis of time-series spatially-filtered particle images. Since this method can measure velocity from one particle in a measurement region, it enables us to measure the velocity with high spatial and temporal resolutions. We developed a SFV system and applied it to laminar and turbulent flows in a duct to examine its performance. Through comparisons between the velocities measured by SFV and LDV, we confirmed that SFV accurately measures the mean velocity and turbulent intensity with spatial and temporal resolutions as high as LDV.

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