Computational Fluid Dynamics [käm·pyə′tā·shən·əl ′flü·əd dī′nam·iks]

Archimedes(C. 287-212 BC)

Newton(1642-1727)

Leibniz(1646-1716)

Euler(1707-1783)

Navier(1785-1836)

Stokes(1819-1903)

Reynolds(1842-1912)

Prandtl(1875-1953)

Bernoulli(1667-1748)

Taylor(1886-1975)

Experimental Fluid Dynamics(EFD)

Analytical Fluid Dynamics(AFD)

Computational Fluid Dynamics(CFD)

Fluid Dynamics Study Approach

Computational Fluid Dynamics is the science of predicting fluid flow, heat transfer, mass transfer, chemical reaction and related phenomena by solving mathematical equations which govern these processes using numerical methods (i.e. on a computer).

Why CFD…?? Growth in complexity of unsolved engineering problem. Need for quick solutions of moderate accuracy. Absence of analytical solutions. The prohibitive cost involved in performing even scaled

laboratory experiments. Efficient solution algorithms. Developments in computers in terms of speed and

storage. Serial/parallel/web computing. Sophisticated pre and post processing facilities.

Inside the CFD Process :CFD Process Flow :Pre-processing

Geometry Creation Geometry Clean-up Mesh Generation Boundary conditions

Solver Problem Specification Additional Models Numerical Computations

Post-processing Understanding flow with color,

contour etc. plots. Line and Contour Data Average Values (Drag, lift, heat

transfer coefficient) Report Generation

Pre-processing

Solver

Post-processing

Inside the CFD process …

Analysis Begins with the mathematical model of a physical problem.

• Conservation of Mass, momentum and energy conservation must be satisfied throughout the region of interest.

• Simplifying assumptions are made to make the problem more tractable (e.g. steady state, incompressible, inviscid, two-dimensional etc.)

• Provide appropriate boundary and initial conditions for the problem.

Domain of interest : Area between two fins Half thickness of fin

First Thing First…

Commercial Fin-tube Heat Exchanger

CFD applies Numerical methods (called discretization) to develop algebraic equations to approximate the governing differential equations of fluid mechanics in the domain to be studied.

Entire domain should be divided into small cells or volume.

The collection of cells is called the grid or mesh.

Meshing your way into it …

Inside the CFD process …

Mesh Generation

Inside the CFD process …Solver …Inside the CFD process … System of algebraic equations are

solved numerically (on a computer) for the flow field variables at each node or cell.

The final solution is post-processed to extract quantities of interest (e.g. lift, drag, heat transfer, separation points, pressure loss, etc.)

What will I do with all this data …?

TemperatureContours

Discretization

Governing Equations:

Conservation Of MassMomentum

ConservationEnergy Conservation

Two different forms of equations: Conservation form Non-Conservation form

Inviscid & Viscid Equations Navier-Stokes Equation

Euler Equations

Advantages of CFD: Low Cost:- 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 short period of

time.- Quick turnaround means engineering data be

introduced early in 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.- CFD provides the ability to theoretically simulate any

physical condition.

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 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.

Limitations of CFD: Physical Models: - CFD solutions rely upon physical models of real

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 approximates 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.

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

ApplicationAerospace

Automobile and Engine

HVAC

Application

EnvironmentalAspects

Bio-Medical

Electronics

More Application

Process Engineering

Glass Industry

Nuclear Power Plants

Trains

Commercial Packages Available For CFD analysis and VisualizationSoftware Company Website TypeANSYS CFX Ansys Inc. http://www.ansys.com/Products/Simulation+Technology/Fluid+

Dynamics/Fluid+Dynamics+Products/ANSYS+CFX

CFD Code

FLUENT Ansys Inc. http://www.ansys.com/Products/Simulation+Technology/Fluid+Dynamics/Fluid+Dynamics+Products/ANSYS+Fluent

CFD Code

OPENFLOWER http://sourceforge.net/projects/openflower CFD Code

COMSOL MULTIPHYSICS COMSOL http://www.comsol.com/products/multiphysics CFD Code

FLOW3D Flow Science, Inc. http://www.flow3d.com/ CFD Code

OPEN FOAM OpenCFD Ltd. http://www.openfoam.com/ Open Source CFD Code

GADGET http://www.mpa-garching.mpg.de/~volker/gadget CFD Code

CFD++ Metacomp Technologies http://www.metacomptech.com/index.php/products/cfd CFD Code

ANSYS ICEM CFD Ansys Inc. http://www.ansys.com/Products/Other+Products/ANSYS+ICEM+CFD

CFD Code

FLO++ Softflo http://homepage.usask.ca/~ijm451/finite/fe_resources/node545.html

CFD Code

FLASH http://flash.uchicago.edu/ CFD Code

TECHPLOT Amtec Engineering, Inc. http://www.tecplot.com/ Visualization

STAR-CD CD-adapco http://www.cd-adapco.com/ CFD Code

MATLAB Mathworks http://www.mathworks.com/ Symbolic Math Package

Ravi Choudhary, Mechanical, 3rd YearRoll: 120970104037E-mail: ravi4582@outlook.comContact: 7895121440TOPIC: Introduction to CFD and its application