This work is concerned with the interaction between condensing aerosol dynamics and hydrodynamic mixing within ow configurations in which aerosol particles form (nucleate) from a supersaturated vapor and supersaturation is induced by the mixing of two streams (a saturated stream and a cold one). Two canonical hydrodynamic configurations are proposed for the investigation. The First is the steady one-dimensional opposed-ow configuration. The setup consists of the two (saturated and cold) streams owing from opposite nozzles. A mixing layer is established across a stagnation plane in the center where nucleation and other aerosol dynamics are triggered. The second is homogeneous isotropic turbulence in a three-dimensional periodic domain. Patches of a hot saturated gas mix with patches of a cold one. A mixing layer forms across the growing interface where the aerosol dynamics of interest occur. In both configurations, a unique analogy is observed. The results reveal a complex response to variations in the mixing rates. Depending on the mixing rate, the response of the number density falls into one of two regimes. For fast mixing rates, the maximum reached number density of the condensing droplets increases with the hydrodynamic time. We refer to this as the nucleation regime. On the contrary, for low mixing rates, the maximum reached number density decreases with the hydrodynamic time. We refer to this as the consumption regime. It is shown that vapor scavenging by the aerosol phase is key to explaining the transition between these two regimes.

Open-channel flows are ubiquitous in nature and play a central role in many hydraulic engineering problems. This flow type occurs almost exclusively under fully-rough turbulent conditions and it is not uncommon for the relative submergence of these flows to be low. Despite this, most theory has so far been developed for smooth wall flows or rough-bed flows at high submergence while its applicability at low relative submergence remains questionable. This thesis therefore aims to contribute towards an improved understanding of turbulence structure in rough-bed open-channel flow at low to intermediate relative submergence. Experiments were conducted to collect turbulent velocity field data for nine different flow scenarios, covering roughness Reynolds numbers between 175 and 900, and relative submergence between 2.5 and 7.5. Each flow scenario was measured independently using particle image velocimetry (PIV) in five distinct configurations. The PIV system was first configured to make two-component velocity measurements with a very wide field of view (up to twenty flow depths) along the channel centreline in a streamwise-wall-normal plane. These measurements were supplemented with three-component stereoscopic PIV recordings along the same plane albeit with a shorter field of view. The third, fourth and fifth set ups involved stereoscopic PIV in three separate transverse-wall-normal planes and thus ensured the complete lateral coverage of the flow field from the sidewall to the centreline. The four-camera arrangement of each of the present stereoscopic PIV configurations was exploited to obtain velocity field statistics with significantly reduced contributions from measurement noise. The thesis reports distributions of bulk velocity statistics and spectra of all three velocity components. In addition, characteristic large scale features of the instantaneous flow are examined using velocity field visualisation, two-point velocity correlations and premultiplied velocity spectra. Further analysis is carried out on the time-averaged flow field to visualise secondary current patterns and to study their lateral extent.

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published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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