Modeling particle capturing and filtration
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Spherical micro-particles filtration by micro-sized pillar structures. Evaluate the filtration efficiency/capacity of different filter structures.
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Modeling particle capturing and filtration
- 1. Fa-Gung Fan Modeling Particle Capturing/Filtration 4/6/2012 Fa-Gung Fan fagung@gmail.com
- 2. Fa-Gung Fan Objectives • Model and simulate rigid, spherical micro- particles filtration by micro-sized pillar structures. • Evaluate the filtration efficiency/capacity of different filter structures. • Evaluate the pressure drop vs. time.
- 3. Fa-Gung Fan
- 4. Fa-Gung Fan Physics • Laminar flow • Particle motion • Flow blockage and momentum exchange • Particle-particle and particle-wall collisions • Particle deposition and buildup
- 5. Fa-Gung Fan Fluent Macro-Particle Model (MPM) • Flow simulation is carried out with Fluent software. • MPM is a module attached to standard Fluent code. • Particle motion, particle-particle/particle-wall collisions, particle buildup are handled by MPM module. • Filter structure is modeled with body-fitted mesh (in Fluent), whereas particles are modeled with immersed-boundary method (in MPM).
- 6. Fa-Gung Fan Fluent Macro-Particle Model (MPM) Account for: • Flow blockage and momentum exchange • Drag and torque on particles • Particle-particle and particle-wall collision and friction dynamics • Particle deposition and buildup
- 7. Fa-Gung Fan MPM Technical Approach
- 8. Fa-Gung Fan • Fluent/MPM provides the most comprehensive capability with respect to the modeling needs. • However, MPM was originally developed for oil/gas industry. Had not been used in micro- filtration application before. • Collision detection algorithm was not optimized for micro-scale features. • Had to worked with Fluent developer for about two months to improve the algorithm. • ANSYS/Fluent extended the software license for 2.5 months to compensate for the lost time. Software Choice
- 9. Fa-Gung Fan z x d rz rx Design x z rx rz d Ov1 184 60 50 25 20 Ov2 184 100 50 25 20 Ov3 240 100 50 25 20 Designs (Ov1, Ov2, Ov3, Ov4)
- 10. Fa-Gung Fan • Ov4 is a case of narrow channel, truncated from Ov3 by taking only a single oval-shaped structure. Ov3 Ov4 Ov1 These are actually ovals (like those in Ov1). The figures do not preserve aspect ratio so they look like circles. Ov1
- 11. Fa-Gung Fan Ov1 design Unit Cell
- 12. Fa-Gung Fan Ov1 Reached stationary state. # of particles captured in one unit cell Ov1 Design: unit cell area 184umx120um, captures 150 particle per unit cell Total 4060 particles injected. Capture Efficiency / Capture Capacity
- 13. Fa-Gung Fan Ov3 # of particles captured in one unit cell Reached stationary state. Ov3 Design: unit cell area 240umx200um, captures 150 particles per unit cell
- 14. Fa-Gung Fan Pressure Drop Comparison Ov3 Ov4Ov1
- 15. Fa-Gung Fan 10mm 10mm A 10mmx10mm chip can fit – 54x83 Ov1 unit cells. Total capture capacity: 672300 particles/chip 54x50 Ov2 unit cells. Total capture capacity: 432000 particles/chip 41x50 Ov3 unit cells. Total capture capacity: 307500 particles/chip
- 16. Fa-Gung Fan Particle number density profile Unit Cell Depending on the capture efficiency of the unit cells, the speed of propagation varies. z Propagation of Density Profiles A uniform density profile propagates down a series of 50 unit cells (each 0.2mm length in the z direction). The following animation shows the propagations of the profiles (corresponding to 40% solid loadings) for unit cell capture capacities of 0, 150, 550, and 3000 particles and a fluid flow speed of 0.05m/s. It can be seen that, when the unit cell does not capture particle at all, the propagation of the density profile is fastest. As the unit cell capture capacity increases, the propagation speed decreases. At the limit of very large capture capacity, the wave does not propagate down the unit cells, which means that all the particles are captured by the first unit cell.
- 17. Fa-Gung Fan Ov1 Ov2 Ov3 Density profiles (correspond to 40% solid loadings) at t=0.2 sec
- 18. Fa-Gung Fan Particle Loading Sensitivity Ov3 (inject 5 particles every 8.e-5 sec) Ov3 Design: unit cell area 240umx200um, captures 150 particles per unit cell
- 19. Fa-Gung Fan Ov3 (inject 10 particles every 8.e-5 sec) Ov3 Design: unit cell area 240umx200um, captures 150 particles per unit cell Total 5810 particle injected. Note: This animation runs fast.
- 20. Fa-Gung Fan Ov3 (inject 20 particles every 8.e-5 sec) Ov3 Design: unit cell area 240umx200um, captures 175 particles per unit cell
- 21. Fa-Gung Fan Conclusions • Direct simulations of filtration of rigid, spherical micro-particles by micro- filter structures have been carried out. • The simulations provide information about filtration/capturing efficiency, capturing capability, and pressure drop. • Several filter structures were evaluated and their capturing/filtration effects and pressure drops were compared.
- 22. Fa-Gung Fan • Sensitivity to particle loading was also studied. The result indicates that simulations need to be carried out at actual particle loadings. • Fluent/MPM platform provides the most comprehensive capability for the work.