Particle Image Velocimetry Based Measurement of Entropy Production With Free Convection Heat Transfer

2005 ◽  
Vol 127 (6) ◽  
pp. 614-623 ◽  
Author(s):  
O. B. Adeyinka ◽  
G. F. Naterer
Keyword(s):  
Particle Image Velocimetry ◽  
Free Convection ◽  
Entropy Production ◽  
Particle Image ◽  
Control Volume ◽  
Temperature Fields ◽  
Element Formulation ◽  
Measured Velocity ◽  
Numerical Predictions ◽  
Image Velocimetry

Local entropy production rates are determined from a numerical and experimental study of natural convection in an enclosure. Numerical predictions are obtained from a control-volume-based finite element formulation of the conservation equations and the Second Law. The experimental procedure combines methods of particle image velocimetry and planar laser induced fluorescence for measured velocity and temperature fields in the enclosure. An entropy based conversion algorithm in the measurement procedure is developed and compared with numerical predictions of free convection in the cavity. The predicted and measured results show close agreement. A measurement uncertainty analysis suggests that the algorithm postprocesses velocities (accurate within ±0.5%) to give entropy production data, which is accurate within ±8.77% near the wall. Results are reported for free convection of air and water in a square cavity at various Rayleigh numbers. The results provide measured data for tracking spatial variations of friction irreversibility and local exergy losses.

Aerodynamic load characterisation of a low speed aerofoil using particle image velocimetry

2008 ◽  
Vol 112 (1130) ◽  
pp. 197-205 ◽  
Author(s):  
B. W. van Oudheusden ◽  
E. W. F. Casimiri ◽  
F. Scarano
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Control Volume ◽  
Flow Simulation ◽  
Momentum Equation ◽  
Aerodynamic Load ◽  
Surface Pressure Distribution ◽  
Velocity Statistics ◽  
Image Velocimetry ◽  
Standard Pressure

AbstractParticle image velocimetry (PIV) measurements of the flow around a wing section are employed as a basis for non-intrusive aerodynamic mean loads characterisation, providing sectional lift, drag and pitching moment. The technique relies upon the application of control-volume approaches in combination with the deduction of the pressure from the PIV experimental data through application of the momentum equation. The treatment can also be applied when the flow is unsteady; in that case time-mean loads are obtained from velocity statistics, through the use of Reynolds-averaged formulation of the governing equations. The procedure was applied in the experimental investigation of a NACA 642A015 aerofoil, in which the PIV approach is validated against standard pressure-based methods (surface pressure distribution and wake rake). The chord Reynolds number considered in the investigation ranges between 1 – 7 × 105. In addition, the consistency and potential performance of the method was assessed by means of synthetic velocity field data obtained from a numerical flow simulation.

Validation of Analytical Solution for Depth-of-Correlation in Microscopic Particle Image Velocimetry

2003 ◽  
Author(s):  
Christopher J. Bourdon ◽  
Michael G. Olsen ◽  
Allen D. Gorby
Keyword(s):  
Particle Image Velocimetry ◽  
Correlation Function ◽  
Analytical Model ◽  
Particle Image ◽  
Object Plane ◽  
Measured Velocity ◽  
Microscopic Particle ◽  
Relative Contribution ◽  
Physical Experiments ◽  
Image Velocimetry

Because the entire flowfield is generally illuminated in microscopic particle image velocimetry (microPIV), determining the depth over which particles will contribute to the measured velocity is more difficult than in traditional, light-sheet PIV. This paper experimentally and computationally measures the influence that volume illumination, optical parameters, and particle size have on the depth of correlation for typical microPIV system. First, it is demonstrated mathematically that the relative contribution to the measured velocity at a given distance from the object plane is proportional to the curvature of the local cross-correlation function at the distance. The depth of correlation is then determined in both the physical experiments and in computational simulations by directly measuring the relative contribution to the correlation function of particles located at a known separation from the object plane. These results are then compared with a previously derived analytical model that predicts the depth of correlation from the basic properties of the imaging sytem and seed particles used for the microPIV measurements. Excellent agreement was obtained between the analytical model and both computational and physical experiments, verifying the accuracy of the previously derived analytical model.

Experimental and Numerical Analysis of the Cavitating Part Load Vortex Dynamics of Low-Head Hydraulic Turbines

2011 ◽  
Author(s):  
Se´bastien Houde ◽  
Monica S. Iliescu ◽  
Richard Fraser ◽  
Se´bastien Lemay ◽  
Gabriel D. Ciocan ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Draft Tube ◽  
Experimental Methodology ◽  
Flow Measurements ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Vortex Rope ◽  
Part Load ◽  
Image Velocimetry

The draft tube flow is a two-sided challenge for the operation of a hydraulic turbine. On one side, it is an important component for the performance of low to medium head turbines, where it can provide up to 40% of the extracted energy from the flow. On the other side, being a diffuser with a complex vorticity distribution at the inlet, vortex breakdown instability can occur at part load and generate a corkscrewed precessing vortex that can be associated with cavitation. The cavitating vortex rope, may generate undesired power output fluctuation and/or structural vibration. Therefore, draft tubes are much studied components but hard to tackle both numerically and experimentally. Within the framework of the AxialT project, the flow in the draft tube of a propeller turbine model operating at part load was studied using a combination of two-phase Particle Image Velocimetry (PIV) measurements and Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations. The paper main focus is on the experimental methodology and results. It explains how Particle Image Velocimetry measurements were implemented, validated and post-treated to provide flow measurements in the draft tube cone at part load in the cavitating and non-cavitating regimes. It also describes various image processing techniques used to extract the velocity field around the cavitating vortex rope and to estimate the location of the water-vapour interface of the cavitating region. In the spirit of feeding experimental data to numerical simulations, an analysis of measured velocity profiles just under the runner is presented. Comparison between PIV measurements and preliminary URANS simulations is also illustrated.

Development of Combined Particle Image Velocimetry and Particle Image Thermography for Air Flows

2010 ◽  
Author(s):  
Daniel Schmeling ◽  
Marek Czapp ◽  
Johannes Bosbach ◽  
Claus Wagner
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Developmental Process ◽  
Temperature Fields ◽  
Special Focus ◽  
Thermal Plumes ◽  
Tracer Particles ◽  
Image Velocimetry ◽  
Cubical Enclosure ◽  
Air Flows

Simultaneous measurements of instantaneous velocity and temperature fields of air flows by means of Particle Image Velocimetry (PIV) and Particle Image Thermography (PIT) enables highly demanded studies on thermal plumes, their dynamics and the resulting heat transfer for Pr ≈ 0.7. Thereby, small particles of thermochromic liquid crystals (TLCs), which reveal temperature depending reflection properties are used as tracer particles for combined PIT and PIV. The feasibility of the method is demonstrated in a Rayleigh-Be´nard convection experiment in a cubical enclosure. Furthermore, a new particle generator being able to produce continuously very small monodisperse droplets of TLCs has been designed. The improvement of the developmental process for mixed and Rayleig-Be´nard convection studies is discussed. Thereby, special focus is laid on the production process of small TLCs, the generation of monodisperse acetone-TLC droplets and the temperature depending colour play of the produced particles.

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