# COMPUTATIONAL FLUID DYNAMICS swen WHAT IS CFD COMPUTATIONAL

Document Sample

```					swen
WHAT IS CFD ?
COMPUTATIONAL FLUID DYNAMICS OR “CFD” IS
THE ANALYSIS OF SYSTEMS INVOLVING FLUID
FLOW , HEAT TRANSFER AND ASSOCIATED
PHENOMINA SUCH AS CHEMICAL REACTIONS
BY MEANS OF COMPUTER BASED NUMERICAL
APPROACH .

IN THIS CFD APPROACH , THE EQUATIONS
( USUALLY PARTIAL DIFFERENTIAL EQUATIONS )
THAT GOVERN A PROCESS OF INTEREST ARE
SOLVED NUMERICALLY.
swen
TYPES OF FLUID FLOWS

   VISCOUS OR INVISCID FLOWS

   INCOMPRESSIBLE OR COMPRESSIBLE FLOWS IN
PIPES OR OPEN CHANNELS

   FLOWS IN PIPES AND TURBINES

   WATER WAVES

swen
HOW CAN A FLUID FLOW
PROBLEM BE ANALYSED?

EXPERIMENTAL

THEORETICAL

COMPUTATIONAL

swen
COMPARISON OF APPROACHES

1. CAPABLE OF    1 .EQUIPMENT
BEING MOST   REQUIRED
REALISTIC    2 SCALING PROBLEMS
EXPERIMENTAL                    3 .TUNNEL CORRECTIONS
4. MEASUREMENT
DIFFICULTIES
5. OPERATING COSTS

1.CLEAN GENERAL 1.RESTRICTED TO SIMPLE
INFORMATION     GEOMETRY AND
WHICH IS        PHYSICS
THEORETICAL      USUALLY       2.USUALLY RESTRICTED
IN FORMULA       TO LINEAR PROBLEMS
FORM
swen
Start

Initial thinking                       conceptual mistake
no
Mesh generation                        poor mesh?
yes                     no
Flow specification                     incorrect flow specification
yes
Calculate numerical
Solution

Analyze results
results not ok
stop

swen
COMPARISON OF APPROACHES

1.NO RESTRICTION
1.TRUNCATION
TO LINEARITY
ERRORS
2.COMPLICATED
PHYSICS CAN
2. ROUND OFF ERROR
COMPUTATIONAL      BE TREATED.
3. TIME EVOLUTION
OF FLOW CAN
BE OBTAINED
3.COMPUTER COSTS

swen
NUMERICAL METHODS FOR FLUID
FLOWS
Velocity and pressure
distribution by Nevier-
stokes equations and
equation of continuity

GOVERNING EQUATIONS
A 2D,laminar,
incompressible flow
with constant viscosity is
described by,
X-momentum=(2u/  x2 +  2u/  y2) _  p/  x

y-momentum=  ( 2v/  x2 +  2v/  y2) _  p/  y
swen
BUILDING A MESH
BASIC PARTS FROM
WHICH MESHES ARE
BUILD:
   POINTS,SOMETIMES
CALLED NODES.
   VOLUMES,ALSO KNOWN
AS CELLS IN
SOME DOCUMENTATION.
   ELEMENTS.

GEOMETRICALLY SPEAKING
A MESH MAY BE 2D OR
3D.SOME COMMON
EXAMPLES ARE
AL,FOUR
NODEDTETRAHEDRON,
SIX NODED PRISM          swen
BASIC APPROACH IN SOLVING A
PROBLEM BY CFD TECHNIQUE

GRID POINTS
(KNOWN TEMP.)

GRID POINTS
(UNKNOWN TEMP.)

IT IS A 4*4 GRID FOR COMPUTATION OF2D STEADY
STATE HEAT CONDUCTION IN A SQUARE PLATE
swen
MESH GENERATED AROUND AN AEROFOIL

swen
HOW DOES A CFD CODE WORKS

ALL CODES CONTAIN THREE ELEMENTS

 A PRE-PROCESSOR

A SOLVER

A POST-PROCESSOR

swen
HOW DOES A CFD WORKS

CFD CODES ARE STRUCTURED AROUND THE
NUMERICAL ALGORITHMS

ALL COMMERCIAL CFD SOFTWARES SUCH AS
FLUENT , CFX SOLUTIONS ETC , INCLUDE
SOPHISTICATED USER INTERFACES TO INPUT
PROBLEM PARAMETERS AND EXAMINE THE
RESULTS

swen
PRE-PROCESSOR :
DEFENITION OF GEOMETRY & REGION OF
INTEREST: THE COMPUTATIONAL DOMAIN

GRID GENERATION THE SUBDIVISION OF THE
DOMAIN INTO NUMBER OF SMALLER ,
NON-OVERLAPPING SUBDOMAINS : GRID POINTS

SELECTION OF PHYSICAL AND CHEMICAL
PHENOMENA THAT NEEDED TO BE MODELLED

DEFINATION OF FLUID PARTICLES

SPECIFICATION OF APPROPRIATE BOUNDARY
CONDITIONS AT THE DOMAIN BOUNDARY
swen
POST-PROCESSOR

POST PROCESSING MEANS ANALYSIS OF RESULTS

THIS INCLUDES :

VECTOR PLOTS

2D AND 3D SURFACE PLOTS ETC

swen
FLUENT

FLUENT IS A COMMERCIAL CFD SOFTWARE
DEVELOPED IN „C‟ LANGUAGE

IT‟S A CONTROL VOLUME APPROACH

FLUENT IS THE BEST CFD TOOLFOR THE
ANALYSIS OF FLOW AND HEAT TRANFER
PROBLEMS ESPECIALLY IN PROCESS
INDUSTRIES

swen
ANALYSIS OF CFD OUTPUT DATA

CHECKING A SOLUTION

FLOW SHOULD LOOK QUALITATIVELY CORRECT
RESULTS SHOULD SHOW A VELOCITY CHANGE
THAT RESEMBLES THAT IN THE BOUNDARY LAYER
MASS CONSERVATION

REFINING A COMPUTER MODEL

INCREASE THE DENSITY OF MESH POINTS
IMPROVING THE PHYSICS OF THE MODEL

swen
SOME IMPORTANT APPLICATION
APPLICATION AREAS . . .
AERODYNAMICS OF AIRCRAFT AND VEHICLES:
LIFT AND DRAG

HYDRODYNAMICS OF SHIPS

POWER PLANT : COMBUSTION IN IC ENGINES AND
GAS TURBINES

TURBO MACHINERY : FLOW INSIDE ROTATING
PASSAGES , DIFFUSERS ETC

ELECTRICAL AND ELECTRONIC ENGINEERING :
COOLING OF EQUIPMENT INCLUDING MICROCIRCUIT
swen
CONCLUSION

CFD MAKES MODELING PROCESS FASTER AND
CHEAPER

INCREASES FLEXIBILITY IN DESIGN

MAY NOT BE A PERFECT SOLUTION ALWAYS

swen
QUESTIONS?

EXAMPLE FOR A HYBRID MESH
swen
THANK YOU

swen

```
DOCUMENT INFO
Categories:
Stats:
 views: 44 posted: 1/5/2011 language: English pages: 21
How are you planning on using Docstoc?