Solid-liquid flow in fluidic oscillator: Influence of solids on jet oscillations and residence time distribution

Wall attachment bistable fluidic oscillators (FOs) based on the Coanda effect have been studied and explored for various industrial applications. Recently, FOs have been effectively used for continuous crystallization. However, despite numerous studies on the fluid dynamics of FOs, adequate information on the influence of solids on the flow and mixing characteristics of FOs is not available. In this work, we have attempted to bridge this gap. We have computationally and experimentally investigated solid - liquid flow in FOs. The Eulerian - Eulerian approach was used for simulating solid - liquid flow in FO. The jet oscillation frequency and the velocity profiles in the FO were measured using the laser Doppler anemometer for the first time. The measured flow characteristics were used to evaluate and validate computational models. The validated computational model was then used for investigating the influence of solid volume fraction and particle size on flow characteristics of FO including jet oscillation frequency. The influence of particle size and solid loading on jet oscillation frequency and overall flow characteristics of FO was found to be insignificant over the considered range (up to 175 mu m paracetamol particles and up to 5 % solids loading). The backflow through limbs was found to enhance the residence time of smaller particles compared to the larger particles. The results presented in this work will be useful in extending applications of FO for process applications involving solid particles such as crystallisation.