1. Computational Fluid Dynamics
By:-
Thombare A.S.

2. 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 result of CFD analyses is relevant engineering data used in:
conceptual studies of new designs
detailed product development
troubleshooting
redesign
CFD analysis complements testing and experimentation.
Reduces the total effort required in the laboratory.

3. Base of the CFD
The fundamental basis of almost all CFD problems are the Navier-Stokes Equations ,which defines any single phase fluid flow.
By some simplifications equation becomes :-

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

5. Where is CFD used? Aerospacee Automotive Biomedical
Chemical Processing
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Chemical Processing
Polymerization reactor vessel - prediction of flow separation and residence time effects.
Hydraulics

6. Flow of lubricating mud over drill bit Flow around cooling towers
Where is CFD used?
Aerospace
Automotive
Biomedical
Chemical Processing
HVAC
Hydraulics
Marine
Oil & Gas
Power Generation
Sports
Sports
Marine (movie)
Oil & Gas
Power Generation
Flow of lubricating mud over drill bit
Flow around cooling towers

7. Domain for bottle filling problem.
CFD - How It Works
Filling Nozzle
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/or boundary conditions for the problem.
Bottle
Domain for bottle filling problem.

8. Mesh for bottle filling problem.
CFD applies numerical methods (called discretization) to develop approximations of the governing equations of fluid mechanics and the fluid region to be studied.
Governing differential equations  algebraic
The collection of cells is called the grid or mesh.
The set of approximating 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, heat transfer, separation points, pressure loss, etc.).
Mesh for bottle filling problem.

9. An Example: Water flow over a tube bank
Goal
compute average pressure drop, heat transfer per tube row
Assumptions
flow is two-dimensional, laminar, incompressible
flow approaching tube bank is steady with a known velocity
body forces due to gravity are negligible
flow is translationally periodic (i.e. geometry repeats itself)
Physical System can be modeled with repeating geometry.

10. Mesh Generation
Geometry created or imported into preprocessor for meshing.
Mesh is generated for the fluid region (and/or solid region for conduction).
A fine structured mesh is placed around cylinders to help resolve boundary layer flow.
Unstructured mesh is used for remaining fluid areas.
Identify interfaces to which boundary conditions will be applied.
cylindrical walls
inlet and outlets
symmetry and periodic faces
Section of mesh for tube bank problem

11. 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
CFD provides the ability to theoretically simulate any physical condition

12. 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.

13. 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.

14. Fully Developed Inlet Profile
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.
Computational Domain
Fully Developed Inlet Profile
Computational Domain
Uniform Inlet Profile
poor
better

15. 2. CFD for Dryers:-
CFD models are applied to determine optimum equipment configuration and process settings.
Drying equipment is usually large and expensive. As a result, efficiency is an important factor that influences production and operation cost.
CFD is applied to examine configuration changes and thus minimize risk and avoid unnecessary downtime during testing.

16. Spray Dryer

17. Summary
Computational Fluid Dynamics is a powerful way of modeling fluid flow, heat transfer, and related processes for a wide range of important scientific and engineering problems.
The cost of doing CFD has decreased dramatically in recent years, and will continue to do so as computers become more and more powerful.

18. References Websites :- www.leads.ac.uk/cfd www.wikipedia.com
Journal :-
Chemical Engg. Education (CEE)

19. Thank you !!