The University of Texas at Austin Spring 2013CAEE Department

Course: Modeling of Air and Pollutant Flows in Buildings

Instructor: Dr. Atila Novoselac Office: ECJ, 5.422 Phone: (512) 475-8175 e-mail: atila@mail.utexas.eduhttp://www.ce.utexas.edu/prof/Novoselac

Office Hours: Tuesday and Thursday 11:00 a.m.–12:00 p.m.

• Discuss the Syllabus• Describe scope of the course• Introduce the course themes• Answer your question • Fluid dynamics review

Today’s Lecture Objectives:

Introduce Yourself

• Name • Background

- academic program and status• Professional interests• Reason(s) for taking this course

Motivation for Modeling of Indoor Air Distribution using CFD:

• Major exposure to contaminant is in indoor environment

• Ventilation system provides contaminant dilution Controlled airflow (ventilation) can considerably improve the IAQ and reduce the ventilation air requirement

• Air-flow transports pollutants – gaseous and particulate

• Contaminant concentration in the space is more or less non-uniform – It affects: emission, filtration, reactions, exposure

Why to Care About Indoor Airflow Distribution ?

Pollutant concentration is very often non-uniform

- Exposure depends on dispersion

Perfect mixing

SinksSourcesdtdC

SinksSources

zCD

yCD

xCD

zCV

yCV

xCV

tC

zyx 2

2

2

2

2

2

We can control exposure by controlling the flow field

Examples of Exposure Control by Ventilation Systems

1) Control Exhaust

2) Control Supply

Supplydiffusers

Heater (radiator)

Example of Buoyancy Driven Flow:Airflow in a Stairwell

Example of Force Convection Contaminant Concentration in a Kitchen

Example Particle Dispersion

Fluid DynamicsContinuity:

Momentum:

Numerical Methods

Simulation Software (CFD)

Simulation SoftwareIf Garbage IN

ThenGarbage OUT

Input Output

• Recognize the physics behind various numerical tools used for solving airflow problems.

• Employ basic numerical methods for solving Navier-Stokes Equations.

• Apply CFD for airflow simulations in buildings and use these tools in design and research.

• Evaluate the thermal comfort and indoor air quality (IAQ) with different ventilation systems.

• Assess human exposure to different pollutant types.

• Critically analyze and evaluate CFD results.

Course Objectives

Topics:

1. Course Introduction and Background 1 wk2. Fundamentals of fluid dynamics 2 wks3. Turbulence models 1.5 wks

4. Numerical methods and parameters 2 wks5. CFD modeling parameters 1.5 wks6. Introduction to CFD software 1 wk

7. Application of CFD for building airflows 1 wk8. Simulation of IAQ parameters 1 wk9. Simulation of thermal comfort parameters 1 wk10. Modeling of aerosols 1 wk11. Air and pollutant flows in the vicinity of occupants 1 wk12. Accuracy and validation of building airflow simulations 1 wk

30%

30%

40%

Prerequisites

- Fluid Dynamics

Knowledge of the following is useful but not necessary:

- HVAC systems- Numerical analysis- Programming

Textbook1) An Introduction to Computational Fluid Dynamics,

Versteeg, H.K. and Malalasekera, W.

References: 2) Computational Fluid Dynamics –The Basics With

ApplicationsAnderson

3) Turbulence Modeling for CFD Wilcox

Handouts

• Copies of appropriate book sectionsAn Introduction to Computational Fluid Dynamics I will mark important sections

• Disadvantage - different nomenclature• I will point-out terms nomenclature and terminology

differences

• Journal papers and CFD software manual• Related to application of airflow simulation programs

Energy simulation software

Airpark Fluent

There is a large availability of CFD software !

- Star CD We have it and you will use it

- Phoenics- CFX - Flow Vent

Star CD Software – Air Quality in the Airplane Cabin

TENTATIVE COURSE SCHEDULE

TENTATIVE COURSE SCHEDULEContinues from previous page

Test 25%Homework Assignments 30%Midterm Project 10%Final Project & Presentation 30%Classroom Participation 5%

100%

Grading

Participation 5%

• Based on my assessment of your participation in the class

• How to get participation points• Come to class• Submit all assignments/projects on time• Participate in class discussions• Come to see me in my office

Homework 30% (each 10%)

Total 3

• HW1Problems related to fluid dynamic

• HW2Problem related to turbulence modeling

• HW3 Problem related numeric

Midterm Exam 25%

• Out -class exam (90 minutes)

• At the the end of March - we will arrange the exact time

• Problems based on topics cover in the first two parts of the course

Midterm Project 10%• Individual project

• Use of CFD program for air and pollutant flow analysis

• Primary goal is to get familiar with the CFD software

Final Project 30%

• Use of CFD for detail airflow, thermal and IAQ analyses

• Different projects topics– Real engineering an/or research problems

• Final presentation (10-15 minutes)

Previous Course projects -Human Exposure to toxins

Previous Course projects- Surface Boundary Layer

Previous Course Projects - Hydro-Jet Screen

Previous Course projects - Natural Ventilation

• Design of ventilation system

• Smoke management

• Natural ventilation

• Human exposure to various pollutants

• Your suggestion

More CFD Final Project:

Grading

> 93 A 90-93 A-86-90 B+

83-86 B 80-83 B-

< 80 C-, C, C+

Course Website All course information:http://www.ce.utexas.edu/prof/Novoselac/Classes/ARE372/

• Except your grades and HW solutionsGrades and progress on the Blackboard

• On the course website • Look at Assignments sections• Review class material ahead of time

use posted class notes

My Issues

• Please try to use office hours for questions problems and other reasons for visitTuesday and Thursday morning reserved - Class preparation

• Please don’t use e-mail to ask me questions which require long explanations• Come to see me or call me

• Suggestions are welcome• The more specific the better

Fluid Dynamics

Review

Conservation equations

Important operations

kz

jy

ix

grad

zV

yV

xVVdiv zyx

zV

yV

xV

DD

zyx

Vector and scalar operators:

)()()()()( zzyyxxzyxzyx VUVUVUkVjViVkUjUiUVU

Total derivative for fluid particle which is moving:

x

z

y

vector

scalar

V

any scalar

Continuity equation -conservation of mass

0

flow

0

zw

yv

xu

ibleIncompresszw

yv

xu

Mass flow in and out of fluid element

Change of density in volume == Σ(Mass in) - Σ(Mass out)

……………….……………….

Volume V = δxδyδz Infinitely small volume

Volume sides: Ax = δyδz Ay = δxδz Az = δxδy

Shear and Normal stress

τyx

Momentum equation –Newton’s second law

Stress components in x direction

DDv

DDv

DDv

zyx particle fluid of for volume and DDvaFor

Fam Fam Fam :or Fam

zyx

zzyyxx

zyx fff

totalderivative

forcesper unit of volume in direction x

………………..…………………………….

dimensions of fluid particle

DDvx

xf

Momentum equation

Sum of all forces in x direction

xzyx Sz

Vy

Vx

V

zyxxp)vvvv( zxyxxxxxxx

xS

zyxx

pDDv zxyxxxx

xx Sf

zyxx

p zxyxxx

Internal source

yzyx Sz

Vy

Vx

V

zyxyp)

vvvv( zyyyxyyyyy

zzyx Sz

Vy

Vx

V

zyxzp)vvvv( zzyzxzzzzz

x direction

y direction

z direction

Newtonian fluids• Viscous stress are proportional to the rate of deformation (e)

zv e ,

yv

e , xve z

zzy

yyx

xx

yv

zv

21ee ,

xv

zv

21ee ,

xv

yv

21ee zy

zyyzzx

zxxzyx

yxxy

Elongation:

Shearing deformation:

Viscous stress:

)(xv2 x

xx zV

yV

xV zyx

yv

zv

, xv

zv ,

xv

yv zy

zyyzzx

zxxzyx

yxxy

zv 2 ,

yv

2 , xv2 z

zzy

yyx

xx

0

For incompressible flow

viscosity

Momentum equations for Newtonian fluids

yzyx Sz

Vy

Vx

V

zyvμ

yv

μxy

vμzv

yv

xv

yp)

vvvv( z

2

2y

2x

2

2y

2

2y

2

2y

2yyyy

xz

2y

2

2x

2

2x

2

2x

2

2x

2x

zx

yx

xx S

zxvμ

yxv

μxvμ

zvμ

yvμ

xvμ

xp)

zvV

yvV

xvV

τvρ(

x direction:

y direction:

z direction:

zzyx Sz

Vy

Vx

V

2z

2y

2x

2

2z

2

2z

2

2z

2zzzz

zvμ

yzv

μxz

vμzv

yv

xv

zp)vvvv(

After substitution: