A depth-of-field limited particle image velocimetry technique applied to oscillatory boundary layer flow over a porous bed

2002 ◽  
Vol 33 (1) ◽  
pp. 47-53 ◽  
Author(s):  
J. Lara ◽  
E. Cowen ◽  
I. Sou
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Boundary Layer Flow ◽  
Particle Image ◽  
Depth Of Field ◽  
Particle Image Velocimetry Technique ◽  
Porous Bed ◽  
Oscillatory Boundary Layer ◽  
Image Velocimetry ◽  
Layer Flow

Investigation of the Boundary Layer Flow Under Engine-Like Conditions Using Particle Image Velocimetry

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Daming Liu ◽  
Tianyou Wang ◽  
Ming Jia ◽  
Wei Li ◽  
Zhen Lu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Boundary Layer Flow ◽  
Particle Image ◽  
Viscous Sublayer ◽  
Wall Jet ◽  
Image Velocimetry ◽  
Layer Flow

The turbulent boundary layer flow in internal combustion (IC) engines has a significant effect on the in-cylinder flow and the wall heat transfer. A detailed analysis of the in-cylinder near-wall flow was carried out on an optical steady flow test bench by using high-resolution particle image velocimetry (PIV) in order to characterize the in-cylinder boundary layer flow in this study. The difference between the in-cylinder boundary layer and the canonical turbulent boundary layer was analyzed. The experimental results show that small-scale vortices with a length scale of about 1–2 mm in the instantaneous flow fields appeared in the wall jet region due to the entrainment of the free jet in the outer region of the wall jet. The viscous sublayer thickness decreased from 0.5 mm to 0.3 mm as the valve lift increased from 2.32 mm to 7.975 mm and the pressure drop from 0.5 kPa to 1 kPa. The dimensionless velocity profile is in good agreement with the law of the wall in the viscous sublayer. However, no obvious logarithmic law distribution region was observed in the logarithmic layer. The distribution of the Reynolds stress and the turbulent kinetic energy is similar to that of the canonical turbulent boundary layer. But the Reynolds stress had a much larger magnitude because the turbulent velocity measured in this boundary layer included not only the turbulence generated by wall shear but also the large-scale turbulent vortices caused by the wall jet.

scholarly journals THE EFFECT OF BED PERMEABILITY ON OSCILLATORY BOUNDARY LAYER FLOW

2012 ◽  
Vol 1 (33) ◽  
pp. 26 ◽  
Author(s):  
Kathryn Sparrow ◽  
Dubravka Pokrajac ◽  
Dominic A Van der A
Keyword(s):  
Boundary Layer ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Boundary Layer Flow ◽  
Particle Image ◽  
Velocity Measurements ◽  
Phase Lead ◽  
Oscillatory Boundary Layer ◽  
Image Velocimetry ◽  
Layer Flow

This experimental study consists of a series of full-scale experiments involving oscillatory boundary layer flow over an impermeable bed and a permeable bed. Velocity measurements have been obtained through particle image velocimetry, and the effect of bed permeability on the velocity profile, phase lead, boundary layer thickness, bed shear stress (as estimated by fitting the log law), and finally the resulting friction factor is presented. For our rough turbulent flows over a permeable bed it has been found that the friction factor is increased by up to 36% and that the friction factor also demonstrates a dependence on Reynolds number.

Characteristics of a separated flow past a semicircular leading-edge airfoil model under different imposed pressure gradient

2021 ◽  
pp. 095441002110212
Author(s):  
K Anand ◽  
KT Ganesh
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Pressure Gradient ◽  
Particle Image ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Field Measurements ◽  
Bench Mark ◽  
Image Velocimetry

The effect of pressure gradient on a separated boundary layer past the leading edge of an airfoil model is studied experimentally using electronically scanned pressure (ESP) and particle image velocimetry (PIV) for a Reynolds number ( Re) of 25,000, based on leading-edge diameter ( D). The features of the boundary layer in the region of separation and its development past the reattachment location are examined for three cases of β (−30°, 0°, and +30°). The bubble parameters such as the onset of separation and transition and the reattachment location are identified from the averaged data obtained from pressure and velocity measurements. Surface pressure measurements obtained from ESP show a surge in wall static pressure for β = −30° (flap deflected up), while it goes down for β = +30° (flap deflected down) compared to the fundamental case, β = 0°. Particle image velocimetry results show that the roll up of the shear layer past the onset of separation is early for β = +30°, owing to higher amplification of background disturbances compared to β = 0° and −30°. Downstream to transition location, the instantaneous field measurements reveal a stretched, disoriented, and at instances bigger vortices for β = +30°, whereas a regular, periodically shed vortices, keeping their identity past the reattachment location, is observed for β = 0° and −30°. Above all, this study presents a new insight on the features of a separation bubble receiving a disturbance from the downstream end of the model, and these results may serve as a bench mark for future studies over an airfoil under similar environment.

Analysis of local velocity gradients in rapid mixer using particle image velocimetry technique

2002 ◽  
Vol 2 (5-6) ◽  
pp. 47-55
Author(s):  
N.-S. Park ◽  
H. Park
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Velocity Fields ◽  
Local Velocity ◽  
Mixing Condition ◽  
Particle Image Velocimetry Technique ◽  
Velocity Gradients ◽  
Image Velocimetry ◽  
Current Design ◽  
G Value

Recognizing the significance of factual velocity fields in a rapid mixer, this study focuses on analyzing local velocity gradients in various mixer geometries with particle image velocimetry (PIV) and comparing the results of the analysis with the conventional G-value, for reviewing the roles of G-value in the current design and operation practices. The results of this study clearly show that many arguments and doubts are possible about the scientific correctness of G-value, and its current use. This is because the G-value attempts to represent the turbulent and complicated factual velocity field in a jar. Also, the results suggest that it is still a good index for representing some aspects of mixing condition, at least, mixing intensity. However, it cannot represent the distribution of velocity gradients in a jar, which is an important factor for mixing. This study as a result suggests developing another index for representing the distribution to be used with the G-value.

scholarly journals A New Particle Image Velocimetry Technique for Turbomachinery Applications

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Sayantan Bhattacharya ◽  
Reid A. Berdanier ◽  
Pavlos P. Vlachos ◽  
Nicole L. Key
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Laser Sheet ◽  
Measurement Techniques ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Particle Image Velocimetry Technique ◽  
Optical Access ◽  
Tip Leakage ◽  
Image Velocimetry

Nonintrusive measurement techniques such as particle image velocimetry (PIV) are growing in both capability and utility for turbomachinery applications. However, the restrictive optical access afforded by multistage research compressors typically requires the use of a periscope probe to introduce the laser sheet for measurements in a rotor passage. This paper demonstrates the capability to perform three-dimensional PIV in a multistage compressor without the need for intrusive optical probes and requiring only line-of-sight optical access. The results collected from the embedded second stage of a three-stage axial compressor highlight the rotor tip leakage flow, and PIV measurements are qualitatively compared with high-frequency response piezoresistive pressure measurements to assess the tip leakage flow identification.

Sign in / Sign up

Export Citation Format

Share Document