Particle field clustering and dynamics experiments with holographic imaging
de Jong, Jeremy Christopher
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Collision and coagulation processes of inertial particles suspended in turbulence are of considerable significance in a wide variety of both natural and industrial flows. Due to the complex nature of these processes, they are typically studied through the use of direct numerical simulations (DNS). However, these exists a pressing need to experimentally validate the DNS results. In this regard, we utilize digital particle holography to study a dynamic particle field in a stationary, homogenous and isotropic turbulent flow and evaluate important collision parameters such as the radial distribution function (RDF) and the radial relative velocity probability density function (PDF). We compare the experimental results with those obtain by DNS under similar flow and particle conditions and define correction factors that must be applied to the DNS to account for limitations and uncertainties inherent in experimental measurements. These factors include correction for the limited experimental volume, a polydisperse particle size distribution, lower dimensional measurements and uncertainties in the measured particle locations. Additionally, we defined a particle signature function that enhances the ability to distinguish real particles from noise in numerically reconstructed digital holograms and developed a method the uses inertial range fitting of the second order velocity structure function determine the dissipation rate inside a stationary turbulence chamber that allows complete characterization of the flow.