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

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

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

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Contaminate Plume in an Office

John Dunec, Ph.D.

COMSOL 4.2a

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

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
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

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

COMSOL Products Used – This Tutorial

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

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

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

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
A Few COMSOL GUI Pointers
• Everything you do is recorded in the Model Builder
• When in doubt … Right Click!
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
Simulation Should be Done Now!
• Takes ~ 60 seconds on my desktop

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

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
Particle Release Options

Release on Boundary

• Mesh based
• Boundary Area based
• Boundary Grid based

Release in Volume

• Coordinate-based
Mesh Based Particle Release (Inlet Node)

Refinement factor = 1

Refinement factor = 2

Density Based Particle Release (Inlet Node)

Expression = 1

Expression = 1/(x2+y2)

Projected Plane Grid (Inlet Node)
• Aligns with x – y – z coordinate axes
Grid Based (Release from Grid)

Distributed over Domain

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

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

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

Attend a Free Seminar

• Includes 2-week trial of COMSOL
• www.comsol.com/events

Attend our Webinars

• www.comsol.com/events/webinars/

Contact Your Local COMSOL Office

• www.comsol.com/contact

Attend our Annual Conference

• www.comsol.com/conference2012
Capture the ConceptTM

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

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

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.

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
• 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.

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
• 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

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”
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

Walls – Change Condition to “Bounce”
• Under “Particle Tracing for Fluid Flow”
• Highlight “Wall 1” Node
• Change “Freeze” to “Bounce”
Assign Stationary Solver to Flow only
• Expand “Study 1”
• Highlight “Step 1: Stationary”
• In the “Physics Selection”:
• Deselect “Particle Tracing for Fluid”
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

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
Add Particle Path Lines

Under Results:

• Expand “Particle Trajectories”
• Highlight “Particle Trajectories 1”
• Change “Line style” from “None” to “Line”
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%)
Capture the ConceptTM

Geometry Steps

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
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
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
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
2D Floorplan: Union Hallway Rectangles
• Right click on Geometry
• Choose: Boolean Operations > Union
• Deselect “Keep Interior Boundaries”
• Choose the two Hallway Rectangles
• Build
3D Geometry: Extrude Room and Hallway
• Rt Click on “Workplane 1”
• Choose “Extrude”
• Set Distance as 8 [ft]
• Build
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
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
3D Geometry: Extrude Doorway
• Rt Click on “Workplane 2”
• Choose “Extrude”
• Set Distance as 0.5 [ft]
• Build
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
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
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
Build 3D Geometry to Add Windows
• Highlight “Geometry 1” in model builder
• Choose “Build all” button