Flow Structure in a Radial Flow Pumping System Using High-Image-Density Particle Image Velocimetry

1994 ◽  
Vol 116 (3) ◽  
pp. 538-544 ◽  
Author(s):  
O. Akin ◽  
D. Rockwell
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Substantial Reduction ◽  
Source Terms ◽  
Ensemble Averaging ◽  
Pressure Source ◽  
Pumping System ◽  
Image Velocimetry ◽  
Image Density ◽  
Instantaneous Pressure

Use of high-image-density particle image velocimetry (PIV) allows characterization of the instantaneous structure of wake and wake-blade interactions in a simulated rotating machine. The distribution of vorticity over an entire plane within the pumping system is related to the instantaneous pressure source terms in the wake of the impeller. Comparison of instantaneous and ensemble-averaged vorticity contours shows that limited ensemble-averaging can produce a substantial reduction in vorticity levels associated with the instantaneous pressure source terms. When the wake from the impeller interacts with a stationary diffuser blade, the instantaneous processes of flow separation and reattachment can be effectively characterized using combinations of instantaneous streamline patterns and contours of constant vorticity. Moreover, active control of the inflow into the pumping system allows substantial modification of these vorticity distributions.

Effect of inlet port on the flow in the cylinder of an internal combustion engine

2006 ◽  
Vol 220 (1) ◽  
pp. 73-82 ◽  
Author(s):  
A Yasar ◽  
B Sahin ◽  
H Akilli ◽  
K Aydin
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Distribution ◽  
Particle Image ◽  
Combustion Engine ◽  
Flow Characteristics ◽  
Intake Port ◽  
Intake Valve ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Image Density

In this study, the characteristics of flow emerging from the inlet of the intake port in the cylinder were investigated experimentally. A particle image velocimetry (PIV) technique was used to measure the velocity distribution in order to observe and analyse the flow behaviour. High-image-density PIV provided acquisition of patterns of instantaneous and averaged vorticity and velocity, revealing the detail of the flow characteristics in the cylinder cavity. With this measuring technique, it is possible to study the effect of intake valve geometry on the flow behaviours. The results showed that the flow structure changed substantially along the cylinder stroke due to the geometry of the intake valve port.

Flow Structures in a U-Shaped Fuel Cell Flow Channel: Quantitative Visualization Using Particle Image Velocimetry

2004 ◽  
Vol 2 (1) ◽  
pp. 70-80 ◽  
Author(s):  
J. Martin ◽  
P. Oshkai ◽  
N. Djilali
Keyword(s):  
Particle Image Velocimetry ◽  
Fuel Cell ◽  
Cross Sections ◽  
Particle Image ◽  
Fluid Dynamic ◽  
Vortex Formation ◽  
Image Velocimetry ◽  
Quantitative Visualization ◽  
Image Density ◽  
Transport Channels

Flow through an experimental model of a U-shaped fuel cell channel is used to investigate the fluid dynamic phenomena that occur within serpentine reactant transport channels of fuel cells. Achieving effective mixing within these channels can significantly improve the performance of the fuel cell and proper understanding and characterization of the underlying fluid dynamics is required. Classes of vortex formation within a U-shaped channel of square cross section are characterized using high-image-density particle image velocimetry. A range of Reynolds numbers, 109⩽Re⩽872, corresponding to flow rates encountered in a fuel cell operating at low to medium current densities is investigated. The flow fields corresponding to two perpendicular cross sections of the channel are characterized in terms of the instantaneous and time-averaged representations of the velocity, streamline topology, and vorticity contours. The critical Reynolds number necessary for the onset of instability is determined, and the two perpendicular flow planes are compared in terms of absolute and averaged velocity values as well as Reynolds stress correlations. Generally, the flow undergoes a transition to a different regime when two recirculation zones, which originally develop in the U-bend region, merge into one separation region. This transition corresponds to generation of additional vortices in the secondary flow plane.

scholarly journals Analysis of the Cavitating Draft Tube Vortex in a Francis Turbine Using Particle Image Velocimetry Measurements in Two-Phase Flow

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Monica Sanda Iliescu ◽  
Gabriel Dan Ciocan ◽  
François Avellan
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Francis Turbine ◽  
Ensemble Averaging ◽  
Two Phase ◽  
Physical Knowledge ◽  
Image Velocimetry ◽  
Constant Pitch ◽  
Turbine Runner ◽  
Complex Phenomena

Partial flow rate operation of hydroturbines with constant pitch blades causes complex unstable cavitating flow in the diffuser cone. A particle image velocimetry (PIV) system allows investigating the flow velocity field in the case of a developing cavitation vortex, the so-called vortex rope, at the outlet of a Francis turbine runner. The synchronization of the PIV flow survey with the rope precession allows applying the ensemble averaging by phase technique to extract both the periodic velocity components and the rope shape. The influence of the turbine setting level on the volume of the cavity rope and its centerline is investigated, providing a physical knowledge about the hydrodynamic complex phenomena involved in the development of the cavitation rope in Francis turbine operating regimes.

High image-density particle image velocimetry using laser scanning techniques

1993 ◽  
Vol 14 (3) ◽  
pp. 181-192 ◽  
Author(s):  
D. Rockwell ◽  
C. Magness ◽  
J. Towfighi ◽  
O. Akin ◽  
T. Corcoran
Keyword(s):  
Particle Image Velocimetry ◽  
Laser Scanning ◽  
Particle Image ◽  
Image Velocimetry ◽  
Image Density

scholarly journals Motion blur treatment utilizing deep learning for time-resolved particle image velocimetry

2021 ◽  
Vol 62 (11) ◽  
Author(s):  
Jeong Suk Oh ◽  
Hoonsang Lee ◽  
Wontae Hwang
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Substantial Reduction ◽  
Motion Blur ◽  
Synthetic Jet ◽  
Worst Case ◽  
Time Resolved ◽  
Displacement Error ◽  
Image Velocimetry ◽  
Synthetic Images

Abstract A new method is hereby presented to reduce motion blur induced error of time-resolved particle image velocimetry. The Monte-Carlo method (MCM) was applied to synthetic images to quantify the error due to blurred particle images. As the size of the streaks grew, it caused large errors in estimating displacements and increased the frequency of outliers beyond 20% for some cases. The mean displacement error was also about 0.2 – 0.55 px, which is larger than the nominally accepted PIV uncertainty of 0.1 px. A novel deblur filter (i.e., the generator) using a generative adversarial network (GAN) was developed, using 1 million synthetic images. The generator was verified using unlearned data from the MCM. The frequency of outliers, which was originally higher than 20% for the worst case, decreased to about 6%, and the displacement error was reduced to less than 0.3 px. The generator was applied to actual experimental images of a synthetic jet that had image blur and resulted in a substantial reduction of outliers. We also checked the performance of the generator in a uniform channel flow, and found that the deblurred images resulted in less PIV velocity error, and was closer to the results from the sharp images than those from the blurry images. Graphic abstract

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