Fabio Kasper Comparison Between Numerical & PIV Experimental Results for Gas-Solid Flow in Ducts Rodrigo Decker, Oscar Sgrott Jr., Henry F. Meier Waldir Martignoni
Agenda Introduction The Test Bench Case Studies Mesh Studies Grid Convergence Index Assessment Results Conclusions
Introduction There are many processes from different industries containing particulate flows Object of study of many groups Different variables change flow characteristics and is difficult to study Studies are typically conducted with Experiments and/or Numerical Simulation Objectives of this work Present an experimental measure of Particle Solid Velocity component in two duct sessions, with a Particle Image Velocimetry device (PIV) Assess numerically this particular gas-solid flow with CAE software STAR-CCM+
The Test Bench Facility located at Regional University of Blumenau (FURB).
L = 1.18m The Test Bench (cont d) Overview of measured stations. L = 2.1m L/D = 10.3 L/D = 5.8 L/D = 1.8 D = 100mm
Case Studies Physical properties Gas Density: 1.18 kg/m 3 Dynamic Viscosity: 1.85e -5 Pa.s Solid Density: 1,845 kg/m 3 Mean diameter: 56.7 µm Operating conditions Volume Flow Rate: 140 m g3 /h Mass Load Ratio: 40 g s /m 3 g Re g : 28,000 (Reynolds number) St: 0.9 (Stokes number)
Case Studies (cont d) Overview of physics and numerical setup Eulerian Multiphase (EMP): 2 phases Interphase momentum transfer through Drag Force Isothermal and incompressible RANS approach 1 st order Implicit Unsteady with a time step of 5e -4 s; CFL ave ~ 1.0 and CFL max ~ 3.0 (Grid 1) 10 inner iterations URFs: 0.6 for Pressure; 0.9 for all others Advection schemes 2 nd order for momentum 1 st order for everything else Total physical time: 3s Corresponds to 3 flows through Mean variables collected after 1.5s Simulations carried out in STAR-CCM+ v9.02
Case Studies (cont d) It was chosen to evaluate two closures for the Solid phase Inviscid (µ s 0) Kinetic Theory of Granular Materials (KTGF) Known as Granular Pressure in STAR-CCM+ (Transport Equation Model) Particle Kinetic Viscosity by Syamlal Friction Regime by Schaeffer With two different High-Re turbulence models for the Gas phase Standard k- Reynolds Stress Model with Quadratic Pressure Strain (RSM SSG) Drag Force correlation was tied to Solid phase stresses closure Inviscid: Schiller-Naumann KTGF: Gidaspow Free-slip walls were considered for the Solid phase
Mesh Studies Grids overview 100% hexahedron cells Very high quality O-Grid topology with Directed Meshing Aspect ratio adjusted accordingly Grid Process was automated with a refinement factor of 1.5 based on the area of the cells at inlet Best grid for each refinement was obtained with HEEDS Cell Count Grid 1 5.8M Grid 2 2.8M Grid 3 1.8M Grid Convergence Index Based on the approach proposed by Patrick J. Roache Richardson extrapolation of successive refined grids Process was automated in STAR-CCM+ Safety factor used: 1.25 Case studies were simulated on Grid 1
Mesh Studies (cont d) Best grid for each mesh refinement found by SHERPA (HEEDS)
Mesh Studies (cont d) Grid 1 overview and inlet detail
Grid Convergence Index Assessment Vertical profiles on mean Solid axial velocity (Inviscid k- )
Grid Convergence Index Assessment (cont d) Horizontal profiles on mean Solid axial velocity (Inviscid k- )
Results Solid Velocity magnitude on first curvature Inviscid k- Inviscid RSM SSG KTGF k- KTGF RSM SSG Discontinuities
Results (cont d) Solid Velocity magnitude on second curvature KTGF RSM SSG KTGF k- Inviscid RSM SSG Inviscid k-
Results (cont d) Vertical profiles on mean Solid axial velocity
Results (cont d) Horizontal profiles on mean Solid axial velocity
Conclusions Overall good agreement was obtained between the numerical and experimental results Best predictions given at developed flow sessions Inviscid approach provides a cheap and valid strategy of modeling these diluted regimes transported gas-solid flows Grid Convergence Index is a valuable methodology to assess uncertainties over consistently refined meshes Some discontinuities highlighted with the KTGF closure will be investigated
Obrigado!