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**Contaminate Plume in an Office**

John Dunec, Ph.D. COMSOL 4.2a

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**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

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**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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**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

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**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

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**COMSOL Products Used – This Tutorial**

Navier-Stokes from COMSOL Multiphysics (Turbulence would require CFD or Heat Xfer or Chem Rx Engrg) Particle Tracing Module

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**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

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**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

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**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

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**A Few COMSOL GUI Pointers**

Everything you do is recorded in the Model Builder When in doubt … Right Click!

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**Step by Steps in COMSOL …**

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**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

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**Simulation Should be Done Now!**

Takes ~ 60 seconds on my desktop

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**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

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**Step by Steps Using COMSOL …**

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**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

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**Particle Release Options**

Release on Boundary Mesh based Boundary Area based Boundary Grid based Release in Volume Coordinate-based

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**Mesh Based Particle Release (Inlet Node)**

Refinement factor = 1 Refinement factor = 2

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**Density Based Particle Release (Inlet Node)**

Expression = 1 Expression = 1/(x2+y2)

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**Projected Plane Grid (Inlet Node)**

Aligns with x – y – z coordinate axes

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**Grid Based (Release from Grid)**

Distributed over Domain

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**Simulation Should be Done Now!**

Takes ~ 65 seconds on my desktop

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**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

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**Step by Steps Using COMSOL …**

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**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

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**To Get More Information …**

Attend a Free Seminar Includes 2-week trial of COMSOL Attend our Webinars Contact Your Local COMSOL Office Attend our Annual Conference

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**Addendum Step-by-Step Instructions**

Capture the ConceptTM Addendum Step-by-Step Instructions

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**Start by Solving for Airflow**

Choose File > New Select “3D” Select “Fluid Flow” > “Single Phase Flow” > “Laminar Flow” Choose “Stationary”

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**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

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**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)

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**Material: Air Rt Click on “Materials” Choose “Material Browser”**

Expand “Built-in” Choose “Air” Be sure “All Domains” are selected

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**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”

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**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”

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**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

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**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.

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**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

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**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.

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**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

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**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

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**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”

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**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

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**Walls – Change Condition to “Bounce”**

Under “Particle Tracing for Fluid Flow” Highlight “Wall 1” Node Change “Freeze” to “Bounce”

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**Assign Stationary Solver to Flow only**

Expand “Study 1” Highlight “Step 1: Stationary” In the “Physics Selection”: Deselect “Particle Tracing for Fluid”

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**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

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**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

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**Add Particle Path Lines**

Under Results: Expand “Particle Trajectories” Highlight “Particle Trajectories 1” Change “Line style” from “None” to “Line”

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**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%)

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Capture the ConceptTM Geometry Steps

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**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

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**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

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**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

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**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

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**2D Floorplan: Union Hallway Rectangles**

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

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**3D Geometry: Extrude Room and Hallway**

Rt Click on “Workplane 1” Choose “Extrude” Set Distance as 8 [ft] Build

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**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

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**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

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**3D Geometry: Extrude Doorway**

Rt Click on “Workplane 2” Choose “Extrude” Set Distance as 0.5 [ft] Build

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**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

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**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

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**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

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**Build 3D Geometry to Add Windows**

Highlight “Geometry 1” in model builder Choose “Build all” button

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