CFD simulace usazování malých částic

Abstract

The present work focused to find optimal time steps and model setup for the CFD simulation of sedimentation of small particles and performed analysis on real lamella geometry to observe effectiveness for different factors, like inclination angles and velocity magnitudes. The work of this thesis has been conducted by CFD analysis in ANSYS Fluent software. The preliminary analyses ran with the Euler-Granular and DDPM-KTGF models. The obtained data have been compared for various time steps and their error rates % to reduce the analysis time by calculating the grid convergence index. The similarity analysis has been done and compared with real-sized particle experiment data so that bigger-sized particles could be used to decrease computational requirements. The effect of different inclination angles and velocity magnitudes for laminar and turbulent regimes on the lamella geometry was observed for bigger-sized particles. The sedimentation effectiveness of the lamella geometry according to the ratio of particles leaving the outlet was evaluated. The critical velocities have been calculated for specific effectiveness, 99 %. The study can be improved by widening the number of analyses to find the optimum inclination angle and velocity for the desired design of a lamella clarifier. The lamella clarifier process can be faster by using a two-step lamella clarifier. The first clarifier tank can have a higher velocity magnitude to reduce the number of particles faster during the first step and the second clarifier tank can have the optimal velocity to obtain higher effectiveness for the device.

The present work focused to find optimal time steps and model setup for the CFD simulation of sedimentation of small particles and performed analysis on real lamella geometry to observe effectiveness for different factors, like inclination angles and velocity magnitudes. The work of this thesis has been conducted by CFD analysis in ANSYS Fluent software. The preliminary analyses ran with the Euler-Granular and DDPM-KTGF models. The obtained data have been compared for various time steps and their error rates % to reduce the analysis time by calculating the grid convergence index. The similarity analysis has been done and compared with real-sized particle experiment data so that bigger-sized particles could be used to decrease computational requirements. The effect of different inclination angles and velocity magnitudes for laminar and turbulent regimes on the lamella geometry was observed for bigger-sized particles. The sedimentation effectiveness of the lamella geometry according to the ratio of particles leaving the outlet was evaluated. The critical velocities have been calculated for specific effectiveness, 99 %. The study can be improved by widening the number of analyses to find the optimum inclination angle and velocity for the desired design of a lamella clarifier. The lamella clarifier process can be faster by using a two-step lamella clarifier. The first clarifier tank can have a higher velocity magnitude to reduce the number of particles faster during the first step and the second clarifier tank can have the optimal velocity to obtain higher effectiveness for the device.