Numerical Characterization of the Solid Particle Accumulation in a Turbulent Flow through Curved Pipes by Means of Stokes Numbers

Abstract

The accumulation of particles in a turbulent flow of incompressible air with mono-dispersed solid particles inside a 90° pipe bend was simulated using ANSYS® Fluent (CFD), taking into account the effect of gravity, drag force and a bidirectional fluid-particle coupling. An analysis of the geometrical parameters and the structures of the secondary flow generated in a curved pipe (Dean vortices) was developed, thus determining the characteristic time scales of the flow. Four Stokes numbers (Stk) were formulated, whose values are calculated and studied from the numerical simulations performed. Two different particle sizes (d1 = 50 μm y d2 = 150 μm), at two different flow conditions (Re1 = 61,500 y Re2 = 173,972), and for three curvature ratios Rc/R = 1, 4 and 8 were studied. The flow was solved using a Eulerian–Lagrangian approach with a RNG k-ε turbulence model. Once the multiphase flow was solved and validated, the distribution and maximum particle concentration inside the 90° bend were presented. Additionally, the Stk numbers were calculated to estimate the possible particle concentration level for the different system configurations (dp, Re and Rc/R). It is concluded that, if all Stk numbers are less than one, relative concentration levels reach a minimum, while for Stk numbers larger than one, an increase in the maximum concentration inside the pipe bend was noticed.

Rheology and Hydrodynamics of Iron Ore Mineral Pulps during a Bioleaching Process in a Continuous Stirred‐Tank Reactor

“…(S11) is N js = 341.7 rpm. Stokes numbers St based on the Kolmogorov time scale maps 20 are reported in the Supporting Information (Fig. S9).…”

“…Furthermore, mass and linear momentum balances are solved using the Galerkin finite‐element method with the stationary frozen‐rotor approach for the impeller rotation, in which the impeller system was kept static in space and the rotations are generated by the inclusion of centrifugal and Coriolis forces. The tolerance for convergence criteria is 0.001; dimensionless power consumption, apparent viscosity 14, Stokes number 20, suspended critical velocity N js 21, velocity fields, streamlines, the governing equations 22, and the rheological equations of state 14 are included in the Supporting Information (Sects. S1.2, S1.4–S1.6).…”

A combined CFD-based simulation and experimental study of particle dispersion in a high-concentration airtight space under unorganized airflow

“…A particle with a low Stokes number follows fluid streamlines (perfect advection), while a particle with a large Stokes number is dominated by its inertia and continues along its initial trajectory. 29,30 In the case of Stokes flow, 31 which is when the particle (or droplet) Reynolds number is less than unity, the particle drag coefficient is inversely proportional to the Reynolds number itself. 32 In that case, the characteristic time of the particle can be written as 33 :…”

“…A particle with a low Stokes number follows fluid streamlines (perfect advection), while a particle with a large Stokes number is dominated by its inertia and continues along its initial trajectory. 29,30…”