A New Particle Image Velocimetry Technique for Turbomachinery Applications

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.

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

Water Science & Technology Water Supply ◽

10.2166/ws.2002.0149 ◽

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.

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Out-of-Plane Motion Effects in Microscopic Particle Image Velocimetry

Journal of Fluids Engineering ◽

10.1115/1.1598989 ◽

2003 ◽

Vol 125 (5) ◽

pp. 895-901 ◽

Cited By ~ 34

Author(s):

Michael G. Olsen ◽

Chris J. Bourdon

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Laser Sheet ◽

Plane Motion ◽

Entire Volume ◽

Measurement Volume ◽

Microscopic Particle ◽

Image Velocimetry ◽

Out Of Plane ◽

Signal Peak

In microscopic particle image velocimetry (microPIV) experiments, the entire volume of a flowfield is illuminated, resulting in all of the particles in the field of view contributing to the image. Unlike in light-sheet PIV, where the depth of the measurement volume is simply the thickness of the laser sheet, in microPIV, the measurement volume depth is a function of the image forming optics of the microscope. In a flowfield with out-of-plane motion, the measurement volume (called the depth of correlation) is also a function of the magnitude of the out-of-plane motion within the measurement volume. Equations are presented describing the depth of correlation and its dependence on out-of-plane motion. The consequences of this dependence and suggestions for limiting its significance are also presented. Another result of the out-of-plane motion is that the height of the PIV signal peak in the correlation plane will decrease. Because the height of the noise peaks will not be affected by the out-of-plane motion, this could lead to erroneous velocity measurements. An equation is introduced that describes the effect of the out-of-plane motion on the signal peak height, and its implications are discussed. Finally, the derived analytical equations are compared to results calculated using synthetic PIV images, and the agreement between the two is seen to be excellent.

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Abstract 14952: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV)

Circulation ◽

10.1161/circ.130.suppl_2.14952 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Ahmad Falahatpisheh ◽

Arash Kheradvar

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Contrast Echocardiography ◽

Ultrasound Contrast Agent ◽

Three Dimensions ◽

Small Scale ◽

High Temporal Resolution ◽

Two Dimensional ◽

Particle Image Velocimetry Technique ◽

Image Velocimetry

Introduction: The two-dimensional (2D) echocardiographic particle image velocimetry technique that was introduced in 2010 received much attention in clinical cardiology. Cardiac flow visualization based on contrast echocardiography results in images with high temporal resolution that are obtainable at relatively low cost. This makes it an ideal diagnostic and follow-up tool for routine clinical use. However, cardiac flow in a cardiac cycle is multidirectional with a tendency to spin in three dimensions rather than two-dimensional curl. Here, for the first time, we introduce a volumetric echocardiographic particle image velocimetry technique that robustly acquires the flow in three spatial dimensions and in time: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV). Methods: V-Echo-PIV technique utilizes matrix array 3D ultrasound probes to capture the flow seeded with an ultrasound contrast agent (Definity). For this feasibility study, we used a pulse duplicator with a silicone ventricular sac along with bioprosthetic heart valves at the inlet and outlet. GE Vivid E9 system with an Active Matrix 4D Volume Phased Array probe at 30 Hz was used to capture the flow data (Figure 1). Results: The 3D particle field was obtained with excellent spatial resolution without significant noise (Figure 1). 3D velocity field was successfully captured for multiple cardiac cycles. Flow features are shown in Figure 2 where the velocity vectors in two selected slices and some streamlines in 3D space are depicted. Conclusions: We report successful completion of the feasibility studies for volumetric echocardiographic PIV in an LV phantom. The small-scale features of flow in the LV phantom were revealed by this technique. Validation and human studies are currently in progress.

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Simultaneous Measurement of Free Surface Elevation and Three-Component Velocity Field Around a Translating Surface-Piercing Foil

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4038586 ◽

2018 ◽

Vol 140 (3) ◽

Author(s):

James Schock ◽

Jason Dahl

Keyword(s):

Particle Image Velocimetry ◽

Free Surface ◽

Velocity Field ◽

Numerical Methods ◽

Flow Field ◽

Particle Image ◽

Laser Sheet ◽

Three Dimensional ◽

Dynamic Mode ◽

Image Velocimetry

Two methods are investigated to simultaneously obtain both three-dimensional (3D) velocity field and free surface elevations (FSEs) measurements near a surface piercing foil, while limiting the equipment. The combined velocity field and FSE measurements are obtained specifically for the validation of numerical methods requiring simultaneous field data and free surface measurements for a slender body shape. Both methods use stereo particle image velocimetry (SPIV) to measure three component velocities in the flow field and both methods use an off the shelf digital camera with a laser intersection line to measure FSEs. The first method is performed using a vertical laser sheet oriented parallel to the foil chord line. Through repetition of experiments with repositioning of the laser, a statistical representation of the three-dimensional flow field and surface elevations is obtained. The second method orients the vertical laser sheet such that the foil chord line is orthogonal to the laser sheet. A single experiment is performed with this method to measure the three-dimensional three component (3D3C) flow field and free surface, assuming steady flow conditions, such that the time dimension is used to expand the flow field in 3D space. The two methods are compared using dynamic mode decomposition and found to be comparable in the primary mode. Utilizing these methods produces results that are acceptable for use in numerical methods verification, at a fraction of the capital and computing cost associated with two plane or tomographic particle image velocimetry (PIV).

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