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: [email protected]://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
SinksSourcesdt
dC
SinksSourcesz
CD
y
CD
x
CD
z
CV
y
CV
x
CV
t
Czyx 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
Textbook
1) 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 sections
An 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 SCHEDULE
Continues 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 visit
Tuesday 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
z
V
y
V
x
VVdiv zyx
zV
yV
xV
D
Dzyx
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
z
w
y
v
x
u
ibleIncompress
z
w
y
v
x
u
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
D
Dv
D
Dv
D
Dv
zyx particle fluid of for volume and D
DvaFor
Fam Fam Fam :or Fam
zyx
zzyyxx
zyx fff
totalderivative
forcesper unit of volume in direction x
………………..…………………………….
dimensions of fluid particle
D
Dvxxf
Momentum equation
Sum of all forces in x direction
xzyx Sz
Vy
Vx
V
zyxx
p)
vvvv( zxyxxxxxxx
xS
zyxx
p
D
Dv zxyxxxx
xx Sf
zyxx
p zxyxxx
Internal source
yzyx Sz
Vy
Vx
V
zyxy
p)
vvvv( zyyyxyyyyy
zzyx Sz
Vy
Vx
V
zyxz
p)
vvvv( zzyzxzzzzz
x direction
y direction
z direction
Newtonian fluids• Viscous stress are proportional to the rate of deformation (e)
z
v e ,
y
v e ,
x
ve z
zzy
yyx
xx
y
v
z
v
2
1ee ,
x
v
z
v
2
1ee ,
x
v
y
v
2
1ee zy
zyyzzx
zxxzyx
yxxy
Elongation:
Shearing deformation:
Viscous stress:
)(x
v2 x
xx z
V
y
V
x
V zyx
y
v
z
v ,
x
v
z
v ,
x
v
y
v zyzyyz
zxzxxz
yxyxxy
z
v 2 ,
y
v 2 ,
x
v2 z
zzy
yyx
xx
0
For incompressible flow
viscosity
Momentum equations for Newtonian fluids
yzyx Sz
Vy
Vx
V
zy
vμ
y
vμ
xy
vμ
z
v
y
v
x
v
y
p)
vvvv( z
2
2
y2
x2
2
y2
2
y2
2
y2
yyyy
xz
2y
2
2x
2
2x
2
2x
2
2x
2x
zx
yx
xx S
zx
vμ
yx
vμ
x
vμ
z
vμ
y
vμ
x
vμ
x
p)
z
vV
y
vV
x
vV
τ
vρ(
x direction:
y direction:
z direction:
zzyx Sz
Vy
Vx
V
2z
2y
2
x2
2z
2
2z
2
2z
2zzzz
z
vμ
yz
vμ
xz
vμ
z
v
y
v
x
v
z
p)
vvvv(
After substitution: