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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 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

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

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

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

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

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

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

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

To Get More Information …

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

Addendum Step-by-Step Instructions

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

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.

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

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

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

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