| Though many prototypes of hydrodynamic separators have been developed to remove solids from wastewater and stormwater, to date, not much fundamental development on unit performance evaluation exists due to the complexity of the problem. Design specifications of commercial separators are derived from empirical or semi-empirical equations that are unique and proprietary to each manufacturer. In this research, experimental and theoretical investigations were conducted to examine the mechanisms of solid-liquid separation for a general vortex separator, thereby providing a fundamental approach for unit performance evaluation. The main achievements and findings obtained through the experimental investigation and theoretical study are as follows.;Experimental investigation with four physical vortex models, three with varying inlet pipe elevations and one with a lower chamber height, reveal that the impact of a changing inlet pipe elevation on particle removal efficiency is insignificant; while the effect of a changing chamber height on removal efficiency is significant and measurable.;In the theoretical development, three topics, namely, flow pattern, particle trajectory, and unit performance evaluation, were researched. Based on the Rankine combined vortex model, the law of conservation of momentum, and the boundary conditions for a confined vortex chamber, a simple formula for angular velocity was derived. By applying the Navier-Stokes governing equation coupled with the angular velocity derived in this study, a vortex flow pattern model was developed.;Based on the balance of forces acting on a particle, a new particle settling formula for natural sediment particles was proposed. Additionally, using the particle settling velocity and the flow pattern derived for the confined vortex chamber, the particle trajectory equations were derived in this study.;A new sizing equation for the confined vortex chamber was developed from the newly-derived particle trajectory. The new sizing equation was validated by laboratory measured particle removal efficiencies. The results generated from this dissertation research will help design, performance evaluation, as well as improvement of the hydrodynamic separators. |
