The Powerpoint presentation discusses about the Introduction to CFD and its Applications in various fields as an Introductory topic for Mechanical Engg. Students in General.

1. SRES’s Sanjivani College of Engineering,
KOPARGAON
Content Beyond Syllabus (CBS)
on
COMPUTATIONAL FLUID DYNAMICS (CFD)
& ITS APPLICATIONS
Subject: FLUID MECHANICS
Class: S.E. (Mech)
FACULTY: PROF. Y. H. AHIRE

2. FLUID DYNAMICS
 Fluid dynamics is the science of fluid motion.
 Fluid flow is commonly studied in one of three ways:
• Experimental fluid dynamics.
• Theoretical fluid dynamics.
• Numerically: computational fluid dynamics (CFD).
CFD nicely and synergistically complements the other two approaches but
will never replace either of the two.

3. WHAT IS CFD?
 Computational fluid dynamics (CFD) is the science of predicting fluid flow,
heat transfer, mass transfer, chemical reactions, and related phenomena
by solving the mathematical equations which govern these processes
using a numerical process.
 The governing equations are based on conservation of mass, momentum,
energy, chemical species etc.
 The result of CFD analyses is relevant engineering data used in:
• Conceptual studies of new designs
• Detailed product development
• Troubleshooting
• Redesign

4. WHY USE CFD?
 CFD is an alternative to experiments that are expensive, time-consuming,
difficult, dangerous or impossible and also to theoretical methods which
can tackle only simplied cases.
 CFD complements experiments and theory.
 CFD is used for design & development, for research and in education.
 The use of CFD has steadily increased in design; currently upto 40%.

5. APPLICATIONS OF CFD
. Where is CFD used?
• Aerospace
• Automotive
• Biomedical
• Chemical
Processing
• HVAC
• Hydraulics
• Marine
• Oil & Gas
• Power Generation
• Sports
F18 Store Separation
Temperature and natural
convection currents in the eye
following laser heating.
Aerospace
Automotive
Biomedical

6. APPLICATIONS…
.
Polymerization reactor vessel - prediction
of flow separation and residence time
effects.
Streamlines for workstation
ventilation
 Where is CFD used?
• Aerospacee
• Automotive
• Biomedical
• Chemical Processing
• HVAC
• Hydraulics
• Marine
• Oil & Gas
• Power Generation
• Sports
HVAC
Chemical Processing
Hydraulics

7. APPLICATIONS…
. Where is CFD used?
• Aerospace
• Automotive
• Biomedical
• Chemical Processing
• HVAC
• Hydraulics
• Marine
• Oil & Gas
• Power Generation
• Sports
Flow of lubricating
mud over drill bit
Flow around cooling towers
Marine
Oil & Gas
Sports
Power Generation

8. CFD - how it works ?
 Analysis begins with a mathematical
model of a physical problem.
 Conservation of matter, momentum,
and energy must be satisfied
throughout the region of interest.
 Fluid properties are modeled
empirically.
 Simplifying assumptions are made in
order to make the problem tractable
(e.g., steady-state, incompressible,
inviscid, two-dimensional).
 Provide appropriate initial and
boundary conditions for the problem.
Domain for bottle filling
problem.
Filling
Nozzle
Bottle

9. CFD - how it works…
 CFD applies numerical methods (called
discretization) to develop approximations of
the governing equations of fluid mechanics in
the fluid region of interest.
• Governing differential equations: algebraic.
• The collection of cells is called the grid.
• The set of algebraic equations are solved
numerically (on a computer) for the flow
field variables at each node or cell.
• System of equations are solved
simultaneously to provide solution.
 The solution is post-processed to extract
quantities of interest (e.g. lift, drag, torque,
heat transfer, separation, pressure loss, etc.). Mesh for bottle filling
problem.

10. Modeling (governing equations)
 Navier-Stokes equations (3D in Cartesian coordinates)






∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
−=
∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
2
2
2
2
2
2
ˆ
z
u
y
u
x
u
x
p
z
u
w
y
u
v
x
u
u
t
u
µρρρρ






∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
−=
∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
2
2
2
2
2
2
ˆ
z
v
y
v
x
v
y
p
z
v
w
y
v
v
x
v
u
t
v
µρρρρ
( ) ( ) ( ) 0=
∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
z
w
y
v
x
u
t
ρρρρ
RTp ρ=
Convection Piezometric pressure gradient Viscous termsLocal
acceleration
Continuity equation
Equation of state






∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
−=
∂
∂
+
∂
∂
+
∂
∂
+
∂
∂
2
2
2
2
2
2
ˆ
z
w
y
w
x
w
z
p
z
w
w
y
w
v
x
w
u
t
w
µρρρρ

11. Types of CFD codes
 Commercial CFD code: FLUENT, Star-CD,
PHOENICS, CFDRC, CFX/AEA, etc.
 Research CFD code: CFDSHIP-IOWA
 Public domain software: (PHI3D, HYDRO, and
WinpipeD, etc.)
 Grid generation software: (e.g. Gridgen, Gambit,
TGrid)
 Flow visualization software: (e.g. Tecplot,
FieldView)
CFDSHIPIOWA

12. How Does a CFD Code Work?
Geometry MESH
Fluid Props.
Model/App.
Bound Conds.
PRE-Processor SOLVER
Finite Diff.
Finite Vol.
Finite Elem.
POST-Processor
Contours
Line Plot
Vel. Vectors
Par. Track
Animations
CBA
A. Pre-Processor
 Geometry definition or computational domain
 Generate mesh / grid or subdivisions
 Definitions of fluid properties
 Definition of physical or chemical phenomena to be modeled
 Specifications of boundary and initial conditions

13. How Does a CFD Code Work…
B. SOLVER
 This is the heart of the code
 Involves applications of the discretized equation to each of the CV
 Basically 3 Steps are Involved : -
• Approximation of the unknown flow variables
• Discretization – Substitution of approximation into governing flow
equations and subsequent manipulations
• Solution of Algebraic Equation For Each Node
 3 Methodologies are used : Finite Difference, Finite Volume, Finite Element
 Most Commercial Code use FV e.g. FLUENT, CFX, PHOENICS

14. For example, for general fluids motion – the PDE is called the
Navier Stokes equations

15. How Does a CFD Code Work …
C. Post-Processor
 Tabular/Graphical Display of the Output Results
 E.g. Contours, Line Plot, Vector Plot, Surface Plot, Particle Track

16. CFD analysis using GAMBIT & FLUENT
GAMBIT
Geometry MESH
Fluid Props
Model/App
Bound Cond
PRE-Processor SOLVER
Finite Diff
Finite Vol
Finite Elem
POST-Processor
Contours
Line Plot
Vel Vectors
Par Track
Animations
CBA
FLUENT

21. Tri/Tet vs. Quad/Hex meshes
 For simple geometries, quad/hex
meshes can provide high-quality
solutions with fewer cells than a
comparable tri/tet mesh.
 For complex geometries, quad/hex
meshes show no numerical
advantage, and you can save
meshing effort by using a tri/tet
mesh.

22. Hybrid mesh example
 Valve port grid.
 Specific regions can be meshed
with different cell types.
 Both efficiency and accuracy are
enhanced relative to a hexahedral
or tetrahedral mesh alone.
Hybrid mesh for
an IC engine
valve port
Tet.
mesh
Hex.
mesh
Wedge mesh

23. Dinosaur mesh example

27. Tools to Examine the Results
 Graphical tools
– Grid, contour, and vector plots
– Pathlines and particle trajectory plots
– XY plots
– Animations
 Numerical reporting tools
– Flux balances
– Surface and volume integrals and averages
– Forces and moments

28. Velocity vectors around a dinosaur

29. Velocity magnitude (0-6 m/s) on a dinosaur

31. ADVANTAGES OF CFD
 Relatively low cost
– Using physical experiments and tests to get essential engineering data
for design can be expensive.
– CFD simulations are relatively inexpensive, and costs are likely to
decrease as computers become more powerful.
 Speed
– CFD simulations can be executed in a short period of time.
– Quick turnaround means engineering data can be introduced early in
the design process.
 Ability to simulate real conditions
– Many flow and heat transfer processes can not be (easily) tested, e.g.
hypersonic flow.
– CFD provides the ability to theoretically simulate any physical
condition.

32. ADVANTAGES...
 Ability to simulate ideal conditions
– CFD allows great control over the physical process, and provides the
ability to isolate specific phenomena for study.
– Example: a heat transfer process can be idealized with adiabatic,
constant heat flux, or constant temperature boundaries.
 Comprehensive information
– Experiments only permit data to be extracted at a limited number of
locations in the system (e.g. pressure and temperature probes, heat
flux gauges, LDV, etc.).
– CFD allows the analyst to examine a large number of locations in the
region of interest, and yields a comprehensive set of flow parameters
for examination.

33. LIMITATIONS OF CFD
 Physical models
– CFD solutions rely upon physical models of real world processes (e.g.
turbulence, compressibility, chemistry, multiphase flow, etc.).
– The CFD solutions can only be as accurate as the physical models on
which they are based.
 Numerical errors
– Solving equations on a computer invariably introduces numerical
errors.
– Round-off error: due to finite word size available on the computer.
Round-off errors will always exist (though they can be small in most
cases).
– Truncation error: due to approximations in the numerical models.
Truncation errors will go to zero as the grid is refined. Mesh
refinement is one way to deal with truncation error.

34. LIMITATIONS…
 Boundary conditions
– As with physical models, the accuracy of the CFD solution is only as
good as the initial/boundary conditions provided to the numerical
model.
– Example: flow in a duct with sudden expansion. If flow is supplied to
domain by a pipe, you should use a fully-developed profile for velocity
rather than assume uniform conditions.
poor better
Fully Developed Inlet
Profile
Computational
Domain
Computational
Domain
Uniform Inlet
Profile

35. SUMMARY
 CFD is a method to numerically calculate heat transfer and fluid flow.
 Currently, its main application is as an engineering method, to provide
data that is complementary to theoretical and experimental data. This is
mainly the domain of commercially available codes and in-house codes at
large companies.
 CFD can also be used for purely scientific studies, e.g. into the
fundamentals of turbulence. This is more common in academic
institutions and government research laboratories. Codes are usually
developed to specifically study a certain problem.

36. REFERENCES
 J D Anderson, Computational Fluid Dynamics-Basics and Applications,
TATA McGraw Hill.
 Fluent Inc.: Http://www.fluent.com
 Adapted from notes by: Tao Xing and Fred Stern, The University of Iowa.

37. Problems
1. CFD stands for: (a) Colourful Fluid Dynamics (b)
Computational Fluid Dynamics (c) Computational Fluid
Mechanics (d) Contour Fluid Dynamics.
2. Computations in CFD are done by (a) Human (b) Calculator
(c) Computer (d) None.
3. CFD can be used in: (a) Automobile (b) Biomedical (c)
Aerospace (d) All.
4. Navier-Stoke equation is manifestation of : (a) conservation
of mass (b) conservation of momentum (c) conservation of
energy (d) None of the above .
5. Navier-Stoke equation is : (a) ODE (b) PDE (c) Non-linear PDE
(d) Non-linear ODE.
6. CFD can’t be applied to complicated geometries.
(True/False).

38. Problems contd..
7. Pre-processing involves: (a) Mathematical modeling (b)
Analyzing data using contours (c) Solution of algebraic equations
(d) None.
8. Post-processing involves : (a) Mathematical modeling (b)
Analyzing data using contours (c) Solution of algebraic equations
(d) None.
9. Turbulent modeling can be done using : (a) LES (b) RANS (c)
DES (d) All.
10. Discretization methods are : (a) Finite difference method
(FDM) (b) Finite volume method (FVM) (c) Finite element
method (FEM) (d) All.
11. Videos/contours/plots can be made in CFD. True/False.