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 minutes duration
Short Q&A at end
Upcoming Tutorials:
Gate Valve
Positive Displacement Pump
One-Way Flapper Valve

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

4. COMSOL Multiphysics Multiphysics – Everything can link to everything.
Flexible – You can model just about anything.
Usable – You can keep your sanity doing it.
Extensible – If its not specifically there…add it!
Trusted by 80,000+ Users Worldwide

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 First: Setup and Solve AirFlow Choose Physics
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 DONE: Setup and Solve AirFlow
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 DONE: Setup and Solve AirFlow
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 Setup and Solve AirFlow Geometry & Materials Inlets/Outlets
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

26. To Get More Information …
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30. Addendum Step-by-Step Instructions
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%)

51. Capture the ConceptTM
Geometry Steps

52. Set up Geometry – Floor plan Workplane
Choose Geometry
Change “Units” to “Feet”
Right click on Geometry
Choose “Workplane”
Select “Quick plane” “xy-plane”
Choose the “Show Workplane” button

53. 2D Floorplan Geometry: Main Room
Right click on Geometry (under Workplane 1)
Choose: Rectangle
Width: 15
Height: 10
Position: Corner
X: 0
Y: 0
Build

54. 2D Floorplan Geometry: Hallway
Right click on Geometry (under Workplane 1)
Choose: Rectangle
Width: 20
Height: 4
Position: Corner
X: -5
Y: -4.5
Build

55. 2D Floorplan Geometry: Jog in Hallway
Right click on Geometry (under Workplane 1)
Choose: Rectangle
Width: 3
Height: 10
Position: Corner
X: 12
Y: -14.5
Build

56. 2D Floorplan: Union Hallway Rectangles
Right click on Geometry
Choose: Boolean Operations > Union
Deselect “Keep Interior Boundaries”
Choose the two Hallway Rectangles
Build

57. 3D Geometry: Extrude Room and Hallway
Rt Click on “Workplane 1”
Choose “Extrude”
Set Distance as 8 [ft]
Build

58. 3D Geometry– Doorway Workplane
Right click on Geometry
Choose “Workplane”
Select “Face Parallel”
Choose the Room wall that is closest to the hallway
Choose the “Show Workplane” button

59. 2D Door Outline: Door Rectangle
Right click on Geometry (under Workplane 2)
Choose: Rectangle
Width: 3
Height: 6.5
Position: Corner
X: 3
Y: -2.5
Build

60. 3D Geometry: Extrude Doorway
Rt Click on “Workplane 2”
Choose “Extrude”
Set Distance as 0.5 [ft]
Build

61. 3D Geometry– Window Workplane
Right click on Geometry
Choose “Workplane”
Select “Face Parallel”
Choose the Room wall that is farthest from hallway, but parallel to hallway
Choose the “Show Workplane” button

62. 2D Door Outline: 1st Window
Right click on Geometry (under Workplane 3)
Choose: Rectangle
Width: 3
Height: 4
Position: Corner
X: -5
Y: -2
Build

63. 2D Door Outline: 2nd Window
Right click on Geometry (under Workplane 3)
Choose: Rectangle
Width: 3
Height: 4
Position: Corner
X: 2
Y: -2
Build

64. Build 3D Geometry to Add Windows
Highlight “Geometry 1” in model builder
Choose “Build all” button