Numerical simulation of particle trapping in laminar and turbulent t-junction flows

This paper describes the mechanism of particle trapping in flows in models related T-junction type bifurcations. For validation of CFD calculations, a T-junction model with one inlet pipe and two outlet pipes creating a symmetric bifurcation at 90^o is analyzed. Navier-Stokes (RANS) equations are solved for single phase laminar flow using the commercial CFD software ANSYS Fluent. After validation, Eulerian simulations are performed by using the Discrete Phase Model (DPM) for two-phase flow with particles injected in different bifurcation models with bifurcation angle of an outlet pipe varying from 80^o to 100^o w.r.t the centerline of the inlet pipe (90^o being the bifurcation angle of T-junction). By changing the average Reynolds number of the flow and the injected particle diameters, the mechanism of particle trapping is investigated in laminar flow. The contours of velocity magnitude, pressure and wall shear stress are obtained and analyzed. Detailed simulations show that in certain range of Reynolds numbers, permanent particle trapping probability is positively correlated with the initial particle position in the inlet pipe and bifurcation angle. It is found that the particle trapping increases as the bifurcation angle decreases from 90^o and becomes negligible as the bifurcation angle increases above 90^o . This is a very important result which has never been reported in the previous literature. In addition, turbulent flow computations for T-junction flow are performed using the Reynolds-Averaged Navier-Stokes (RANS) equations with SST k-ω and Wray-Agarwal (WA) turbulence models.