Particle image velocimetry (PIV) is used to make volume-flow-rate measurements at the exit of a turbulent, planar nozzle. The objective of this report is to assess a range of data acquisition and processing parameters. Data is acquired for volume flow rates of Reynolds numbers between 10,000 and 100,000 for both two-component (2C) and stereo PIV. The parameters are systematically changed one at a time and evaluated using differences in uncertainty, calculation time, and volume- flow-rate deviation. Data acquisition parameters follow the trends of previous work. A multitude of processing parameters were varied for several PIV processing methods. Recommendations for each method are developed and listed with potential drawbacks. 2C PIV was found to underestimate volume-flow-rate by 3-4% depending on the integration scheme and stereo PIV underestimated volume-flow-rate by 2%.

Particle Image Velocimetry (PIV) is an optical fluid measurement technique used to obtain velocity measurements. Two PIV systems were used to capture data simultaneously and measurement error for the MS PIV system is calculated. An investigation of error distribution is performed to determine when uncertainty estimations fail for the CS PIV-UQ method. Investigation of when results from multi pass PIV processing are achieve were performed so that reliable uncertainty estimations are produced with the CS method. An investigation was also performed which determined that error distributions in PIV systems are correlated with flow shear and particle seeding density. Correlation of random errors in space was also performed at the jet core and shear regions of the flow. It was found that in flow regions with large shear that error distributions were non-Gaussian. It was also found in regions of large shear that CS uncertainty results did not match the error. For multi-pass PIV processing with 50% and 75% IW overlap it was found that 4 and 6 passes should be used, respectively, in order for CS uncertainty estimations to be reliable. It was also found that the correlation of random errors in space is much larger in shear regions of the jet flow than in the jet core.

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This work analyzes the solid flow dynamics of gas-solid downer fluidized bed reactor in co-current and, particularly, in counter-current mode. This reactor is potentially interesting for catalytic applications where very short (sub second) and precise contact times are required between the solid catalyst and the gaseous reactants-products. To this aim, a 1.5 m and 36 mm ID downer reactor setup was built to replicate the conditions in a real unit in cold flow and using materials that enable the observation of the solid particle dynamics. Specifically, two state-of-the-art techniques have been used: Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA). Three types of particles have been used: two commercial fluidized catalytic cracking (FCC) particles (ρp = 1300 kg/m3, dp = 75 and 56 μm) and sand (ρp=2600 kg/m3, dp= 370 μm). High-speed cameras were positioned in two axial positions: 70 and 140 cm from the top, to reveal the flow behavior across the reactor. It was found that the solid flow initially was segregated because of the solid feeding design. Thus, 3D printed re-distributer was used to even the solid flow. The solid particles in the counter-current downer was approaching the plug-flow behavior with 23% variation in the velocity gradient across the radial direction, compared with 40% for the co-current counterpart. A method to estimate solid hold-up based on images was developed, yielding values in a good agreement with literature. Keywords: Hydrodynamics, counter-current, downer, PIV, DIA, Solid hold-up

In urban areas, discharging wastewater into rivers is a common way to dispose of contaminants, and it is usually the most economical. Accurate information about how effluents are distributed in the receiving water body is desirable when designing industrial plants. Flow structures will be influenced by an effluent’s dilution processes during the mixing. Meanwhile, the cross-stream motions resulting from the streamline curvature can redistribute both the velocity and the shear stress, which favors the mixing behavior compared to a straight channel. However, the interactions between jet mixing behavior and the bend flow requires further investigation. In the present study, jets with different densities were discharged horizontally into a laboratory flume with a 135-degree open channel bend, and both the main and secondary flow behaviors in the bend were observed after the introduction of effluents. The acquired three- dimensional velocity data were used to validate numerical models of the effluent-bend flow. Numerical turbulence models such as the standard k-ε eddy viscosity model, non-linear k-ε model (Shih quadratic k-ε), and the k-ω SST (shear stress transport) model were employed to evaluate their accuracy. OpenFOAM was selected in the analysis for proposing better numerical models since it gives high-quality results to individualized complex fluid flows, and as an open source CFD software it can be beneficial to further develop and maintain. The first part of this study presents the implementation of the physical modelling of the proposed problems. Detailed descriptions of the experimental process were elaborated. Specifically, the three velocity components at four cross-sectional planes in the bend section were measured with and without saltwater jets by using the stereo Particle Image Velocimetry (PIV) ii technique in the laboratory flume. The experimental results show that the more pronounced effects with the jets were found at the beginning and exit of the bend. Although the jets had little effect on the maximum streamwise velocity, it was found that the occurrence of the negatively buoyant jets would affect the patterns and properties of the secondary flow in the bend. The second part of this study investigated the mechanisms underlying the two cells system, particularly when interacting with a discharged effluent jet. Detailed experimental data were used in interpreting the large center-region cell as well as small structures in the 135-degree open channel bend. A term-by-term analysis of the downstream vorticity equation was executed to investigate the various mechanisms underlying these cross-stream flow motions considering the influence of the negatively buoyant jets. The results indicated the generation and the dissipation of the streamwise vorticity with the effective terms of the vorticity equation. The third part of this study evaluated the performance of three different turbulence models with the experimental measurements. It can be concluded that fully 3D numerical models are capable of simulating the primary flow pattern in a strongly curved channel with the presence of a negatively buoyant jet. The comparison also shows that, although the outer bank cell was not predicted, the k-omega SST model can satisfactorily predict some of the smaller flow features in bend flow, such as the inner bank circulation cell and the overall form of the vorticity distributions. The results enable more reliable predictions for the characteristics and development of jets in a bend.

The flow over a set of tandem cylinders at a moderate Reynolds numbers (Re), and with different separation lengths has been studied. Two dimensional (2D) and three-dimensional (3D) plasma actuators were used to control the flow over the leading cylinder to change the vortex shedding, and subsequently the flow on the second cylinder. The 3D plasma actuator was segmented along the length of the cylinder with a spacing of λ = 4 while the 2D actuator simply ran straight down the span of the cylinder. Particle image velocimetry (PIV) measurements were used to investigate the flow along the central plane in the wake of the cylinders. The image pairs were processed into velocity grids which were then averaged. Plots of the shear, vorticity, and turbulent kinetic energy were created. These plots are used to understand how the character of vortex shedding from the upstream cylinder changes the same from the downstream one.

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