1. Introduction to Computational Fluid Dynamics

2. What Is CFD?
CFD is to use computer codes to solve a wide range of problems in fluid flow and heat transfer.

3. What Is CFD?
CFD is a tool to investigate and research a wide range of problems in fluid flow and heat transfer.

4. Where is CFD used? Aerospace Where is CFD used? Appliances Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
F18 Store Separation
Hypersonic Launch Vehicle
Wing-Body Interaction

5. Appliances Appliances Where is CFD used? Aerospace Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Surface-heat-flux plots of the No-Frost refrigerator and freezer compartments helped BOSCH-SIEMENS engineers to optimize the location of air inlets.

6. Automotive Automotive Where is CFD used? Aerospace Appliances
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
External Aerodynamics
Undercarriage Aerodynamics
Interior Ventilation
Engine Cooling

7. Biomedical Biomedical Where is CFD used? Aerospace Appliances
Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Medtronic Blood Pump
Temperature and natural convection currents in the eye following laser heating.
Spinal Catheter

8. Twin-screw extruder modeling
Chemical Processing
Where is CFD used?
Aerospace
Appliances
Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Polymerization reactor vessel - prediction of flow separation and residence time effects.
Twin-screw extruder modeling
Shear rate distribution in twin-screw extruder simulation

9. HVAC&R HVAC&R Where is CFD used? Aerospace Appliances Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Particle traces of copier VOC emissions colored by concentration level fall behind the copier and then circulate through the room before exiting the exhaust.
Streamlines for workstation ventilation
Mean age of air contours indicate location of fresh supply air
Flow pathlines colored by pressure quantify head loss in ductwork

10. Hydraulics Hydraulics Where is CFD used? Aerospace Appliances
Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports

11. Marine Marine Where is CFD used? Aerospace Appliances Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports

12. Oil & Gas Oil & Gas Where is CFD used? Aerospace Appliances Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Volume fraction of gas
Volume fraction of oil
Flow vectors and pressure distribution on an offshore oil rig
Volume fraction of water
Analysis of multiphase separator
Flow of lubricating mud over drill bit

13. Flow around cooling towers Flow pattern through a water turbine.
Power Generation
Where is CFD used?
Aerospace
Appliances
Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Flow in a burner
Flow around cooling towers
Pathlines from the inlet colored by temperature during standard operating conditions
Flow pattern through a water turbine.

14. Sports Aerospace Sports Where is CFD used? Appliances Automotive
Biomedical
Chemical Processing
HVAC&R
Hydraulics
Marine
Oil & Gas
Power Generation
Sports

15. Important factors influencing CFD
Rapid growth in computing power;
Greatly improved numerical models;
More efficient numerical techniques;
Advanced visualisation tools.

16. Increasing Computing Power

17. Need of High-Performance Computing

18. Need of Highly-Reliable Models

19. Advantages of CFD Low Cost Speed Ability to Simulate Real Conditions
Using physical experiments and tests to get essential engineering data for design can be expensive.
Computational 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 at Mach 20, nuclear accident analysis.
CFD provides the ability to theoretically simulate any physical condition

20. Advantages of CFD (2) 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.

21. Limitations of CFD Physical Models Numerical Errors
CFD solutions rely upon physical models of real world processes (e.g. turbulence, compressibility, chemistry, multiphase flow, etc.).
The solutions that are obtained through CFD 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 - errors due to finite word size available on the computer
Truncation error - error due to approximations in the numerical models
Round-off errors will always exist (though they should be small in most cases)
Truncation errors will go to zero as the grid is refined - so mesh refinement is one way to deal with truncation error.

22. Fully Developed Inlet Profile
Limitations of CFD (2)
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.
Fully Developed Inlet Profile
Computational Domain
Computational Domain
Uniform Inlet Profile
poor
better
Computer Resources
Even with the advent of ever faster computers and larger storage media, simulation of complex engineering systems could still require more computer resources.

23. Geometric Model – Computing Power

24. Physics
CFD codes typically designed for resolution of certain flow phenomenon
viscous vs. inviscid (Re)
turbulent vs. laminar (Re)
incompressible vs. compressible (Ma)
single- vs. multi-phase (St)
thermal/density effects and energy equation (Nu, Pr, Gr)
free-surface flow and surface tension (Fr, We)
Chemical reactions and many constituents (C)
etc…
Modeling requirements depend upon which physical phenomenon are important

25. Physical Models
Transport Equations
Interactions

26. Modelling Air-Particle Flow
Studies of Drug Delivery Devices
To assess aerosol delivery to the smaller airways

27. Gas-Particle flow in Boiler
Flyash velocity and concentration distribution

28. Numerical Issues computational solution of the governing equations
method dependent upon the model equations and physics
several components to formulation
discretization and linearization
assembly of system of algebraic equations
solution of equations
unsteady 3D RANS equations have many issues

29. Faster numerical techniques
assembly/solution of algebraic system
build matrix equation by taking all points across boundary layer including boundary conditions
This is a special type of matrix equation known as a tridiagonal system which can be solved directly (as opposed to iterative solvers such as Guass-Seidel)
no-slip
edge velocity

30. Software CFD software Two types of available software
Built upon physics, modeling, numerics
Black box approach is dangerous. Knowledge is important since codes will have limited range of applicability.
Two types of available software
Commercial (e.g., Fluent, CFX, Star-CD)
Research (e.g., CFD codes in universities and institutes)
Software written in either C/C++ or Fortran90/95
Special coding for parallel computing

31. Post-processing Data reduction, analysis, and visualization
calculation of derived variables
vorticity,
wall shear stress,
calculation of integral parameters: forces, moments
Fourier analysis of unsteady flow
Visualization (again, usually with commercial software)
simple X-Y plots
simple 2D contours
3D contour carpet plots
vector plots and streamlines
animations

32. Research and Development (R&D)
Engineering
Experimental
Fluid Dynamics
(EFD)
Computational
Fluid Dynamics
(CFD)
Mathematics
Computer
Science
Model Development
& Validation

33. Research on engine flow
Physical process Existing models
Spray breakup KH-RT model
Droplet drag Droplet distortion model
Wall impingement Rebound-slide model
Turbulence RNG k- model
Ingition Shell autoignition model
Combustion Characteristic time model
Soot Nagle-Stricland model
NOx Extended Zeldovich model

34. Fluid-Structure Interaction
Coupling
Interaction
Fluid Modelling
(CFD)
Solid Modelling
(FE)
Turbulence
Pressure Waves
Fluctuations
Temperature
Vibration
Noise
Deformation
Stress
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Information

35. Computational Fluid Dynamics
Innovative CFD-CAD Optimisation
Computational Fluid Dynamics
(CFD)
Computer
Aid Design
(CAD)
Flow distribution
Efficiency
Performance
Thermal analysis
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Information
Geometric profile
Materials
Manufacturing
techniques
Optimised Designs

36. End of Lecture 1