Contaminate Plume in an Office John Dunec, Ph.D. COMSOL 4.2a

1. Contaminate Plume in an Office John Dunec, Ph.D. COMSOL 4.2a

2. Welcome to the Lunch-Time Tutorials! • Solve One Problem Using COMSOL Multiphysics • This Tutorial: Contamination Plume in an Office • About 30-35 minutes duration • Short Q&A at end Upcoming Tutorials: • Gate Valve • Positive Displacement Pump • One-Way Flapper Valve www.comsol.com/events

3. Multiphysics: Multiple Interacting Phenomena Could be simple: • Heat convected by Flow Could be complex: • Local temperature sets reaction rates • Multiple exothermic reactions • Convected by flow in pipes and porous media • Viscosity strongly temperature dependent

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5. Contaminate Plume in an Office • Convection Dominated diffusion lead to numerical instabilities • Use Particle Tracing Module instead • Particle Release in Hallway • How much gets into office? 10 micron Particles Air Velocity

6. COMSOL Products Used – This Tutorial • Navier-Stokes from COMSOL Multiphysics • (Turbulence would require CFD or Heat Xfer or Chem Rx Engrg) • Particle Tracing Module

7. Tutorial Roadmap Air Velocity First: Setup and Solve AirFlow • Choose Physics • Import Geometry Sequence • Choose Materials (Air) • Set Inlet & Outlet B.C.’s • Mesh • Solve Next: Add Particle Tracing Finally: Results Statistics 10 micron Particles

8. Flow Boundary Conditions • 10’ x 10’ Office • Office Door Wide Open • Both Office Windows Open • Light Breeze Down Hallway. V = 0.15 m/s P=0 P=0 Office Door Hallway Hallway P = 0 V=0.15

9. Disclaimer! This Flow is Actually Turbulent • Checking the Reynolds number – This should be turbulent flow The Problem Size gets much bigger • Turbulence requires a much denser mesh • Turbulence introduces more variables to calculate For this example we will ignore this(It’s a classroom example!) • Want a quick solution • Want small memory requirements • Will show at conclusion of problem how to solve with turbulence

10. A Few COMSOL GUI Pointers • Everything you do is recorded in the Model Builder • When in doubt … Right Click!

11. Step by Steps in COMSOL …

12. While it’s Solving … What about Turbulence? Requires either the CFD or Heat Transfer or Chem Rx Engr’g Module • k-epsilon • Low Re k-epsilon • k-omega • Spalart-Allmaras

13. Simulation Should be Done Now! • Takes ~ 60 seconds on my desktop

14. Tutorial Roadmap Air Velocity DONE: Setup and Solve AirFlow Next: Add Particle Tracing • Add 2nd Physics • Set Particle Properties • Add Particle Forces (Drag) • Define Inlets & Outlets • Set What to do at Walls • Add Transient Study • 2-Step Solution Finally: Results Statistics 10 micron Particles

15. Step by Steps Using COMSOL …

16. While it’s Solving … What about Turbulence? Requires either the CFD or Heat Transfer or Chem Rx Eng’g Module • k-epsilon • Select Turbulent Disp. in Force Window • Link to Turbulence Model in Flow • Generates random-normal forces on particle to include forces from turbulent eddies

17. Particle Release Options Release on Boundary • Mesh based • Boundary Area based • Boundary Grid based Release in Volume • Coordinate-based

18. Mesh Based Particle Release (Inlet Node) Refinement factor = 1 Refinement factor = 2

19. Density Based Particle Release (Inlet Node) Expression = 1 Expression = 1/(x2+y2)

20. Projected Plane Grid (Inlet Node) • Aligns with x – y – z coordinate axes

21. Grid Based (Release from Grid) Distributed over Domain

22. Simulation Should be Done Now! • Takes ~ 65 seconds on my desktop

23. Tutorial Roadmap Air Velocity DONE: Setup and Solve AirFlow DONE: Add Particle Tracing Finally: Results Statistics • Duplicate Results Dataset (2x) • Add Selections – Office • Add Selections – Window • Calculate Transmission Probability 10 micron Particles

24. Step by Steps Using COMSOL …

25. Review Air Velocity Setup and Solve AirFlow • Geometry & Materials • Inlets/Outlets • Mesh & Solve DONE: Add Particle Tracing • Particle Properties • Forces on Particles • Inlets / Outlets • Solve with Transient Finally: Results Statistics • Transmission Probability 10 micron Particles

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29. www.comsol.com

30. Capture the ConceptTM Addendum Step-by-Step Instructions

31. Start by Solving for Airflow • Choose File > New • Select “3D” • Select “Fluid Flow” > “Single Phase Flow” > “Laminar Flow” • Choose “Stationary”

32. Disclaimer! This Flow is Actually Turbulent • Checking the Reynolds number – This should be turbulent flow The Problem Size gets much bigger • Turbulence requires a much denser mesh • Turbulence introduces more variables to calculate For this example we will ignore this(It’s a classroom example!) • Want a quick solution • Want small memory requirements • Will show at conclusion of problem how to solve with turbulence

33. Set up Geometry – Import Sequence • Choose Geometry • Change “Units” to “Feet” • Right click on Geometry • Choose “Import Sequence from File” • Navigate to proper file location (probably on CD) • Choose “ContaminationPlume_GEOM_SEQUENCE” • Build All, Zoom Extents Or you can build it from scratch (instructions at end of presentation)

34. Material: Air • Rt Click on “Materials” • Choose “Material Browser” • Expand “Built-in” • Choose “Air” • Be sure “All Domains” are selected

35. Airflow: Inlet Boundary Conditions • Rt Click on “Laminar Flow” • Choose “Inlet” • Choose the end of the hallway near the door • Set to “Velocity” • Normal inflow velocity • U0 set to “0.15”

36. Airflow: Outlet Boundary Conditions • Rt Click on “Laminar Flow” • Choose “Outlet” • Choose the other end of the hallway • Choose both windows • Set to “Pressure, no viscous stress” • P0 set to “0”

37. Mesh: Physics-based Mesh • Highlight “Mesh” • Leave as “Physics-controlled mesh” • Set size as “Extra Coarse” • Build Note: This is way too coarse for accurate flow

38. Give the Nonlinear Solver more Iterations • Rt Click on “Study 1” • Select “Show default solver” • Expand everything under Study 1 • Highlight “Fully Coupled” • Change iterations from 25 to 50 Note: This controls max number of Newton iterations before giving up.

39. Solve for Flow • Rt Click on Study 1 • Hit “Compute” • Under Results: • Rt Click on “Velocity” • Choose “Slice” • Choose “Quick” • Choose “xy-plane” • Planes: “1” • Plot

40. Add Particle Tracing • Rt click on “Model 1” • Choose “Add Physics” • Choose “Fluid Flow” > “Particle Tracing for Fluid Flow” • Choose the blue “Next” arrow • Choose “Time Dependant” Note: You need an additional study since particle tracing is transient whereas the fluid flow was stationary.

41. Set Particle Properties • Open “Particle Tracing for Fluid Flow” • Highlight “Particle Properties 1” • Change to “Specify density & diameter” • Density: 2200 • Diameter: 10e-6 • Charge number: 0

42. Add Fluid Forces • Rt Click on “Particle Tracing for Fluid Flow” • Choose “Drag Force” • Select “All Domains” • Set “u” to “Velocity Field” Note: for Turbulent flows (typical for room dispersion) you must select “Turbulent dispersion” in the “Drag Force” section. Do not select this in this tutorial

43. BC: Particle Inlet • Rt Click on “Particle Tracing for Fluid Flow” • Choose “Inlet” • Select hall boundary near door • Change “Initial position” to “Density” • Set “N” to “1000” • Set density to “1” • Set Initial Velocity to “Velocity field”

44. BC: Particle Outlets • Rt Click on “Particle Tracing for Fluid Flow” • Choose “Outlet” • Choose the other end of the hallway • Choose both windows • Leave as “Freeze” Note: The other likely setting is “disappear” – but then we cannot do statistics on the particles later

45. Walls – Change Condition to “Bounce” • Under “Particle Tracing for Fluid Flow” • Highlight “Wall 1” Node • Change “Freeze” to “Bounce”

46. Assign Stationary Solver to Flow only • Expand “Study 1” • Highlight “Step 1: Stationary” • In the “Physics Selection”: • Deselect “Particle Tracing for Fluid”

47. Assign Transient Solver to Particle Tracing • Expand “Study 2” • Highlight “Step 1: Time Dependant” • In the “Physics Selection”: • Deselect “Laminar Flow” • Expand the “Values of Dependent Variables” section • Select “Values of variables not solve for” • Method: “Solution” • Study: “Study 1, Stationary” • Stationary: “Automatic” Note: This uses the flow solution obtained in study 1

48. Set Times and Solve • Highlight “Step 1: Time Dependant” • Choose the “Range” button • Start: “0” • Stop: “360” • Step: “2” • Rt Click on Study 2 • Hit Compute

49. Add Particle Path Lines Under Results: • Expand “Particle Trajectories” • Highlight “Particle Trajectories 1” • Change “Line style” from “None” to “Line”

50. Set up Transmission Probability • Expand “Data Sets” under “Results” • Rt Click on “Particle 1” > Select “Duplicate” • Rt Click on “Particle 2” > Rename as “Particle 2 – RoomOnly” • Rt Click on Particle 2 > Add Selection • Choose ONLY room domain • Rt Click on “Derived Values” > Choose “Global Evaluation” • Dataset: Particle 2 • Time Selection: Last • Select expression as “Transmission Probability” • Hit the “=“ sign to evaluate (27%)