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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? Air Velocity 10 micron Particles

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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 Import Geometry Sequence Choose Materials (Air) Set Inlet & Outlet B.C.’s Mesh Solve Next: Add Particle Tracing Finally: Results Statistics Air Velocity 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 Door P = 0 V=0.15 Hallway Office Hallway

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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 Next: Add Particle Tracing Add 2 nd 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 Air Velocity 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 = 1Refinement factor = 2

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Density Based Particle Release (Inlet Node) Expression = 1Expression = 1/(x 2 +y 2 )

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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 DONE: Add Particle Tracing Finally: Results Statistics Duplicate Results Dataset (2x) Add Selections – Office Add Selections – Window Calculate Transmission Probability Air Velocity 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 Mesh & Solve DONE: Add Particle Tracing Particle Properties Forces on Particles Inlets / Outlets Solve with Transient Finally: Results Statistics Transmission Probability Air Velocity 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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Capture the Concept TM 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 U 0 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” P 0 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 Concept TM 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: 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: 1 st 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: 2 nd 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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