aerodynamic modeling and simulation

8/6/2019 Aerodynamic Modeling and Simulation

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PRESENTED BY:-Prem Ranjan SinghGET 2006, 81929Batch C


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INTRODUCTION TO AERODYNAMICS

Aerodynamics is a branch of fluid dynamics concerned with the study

of forces acting on objects moving through the air.

T he solution of an aerodynamic problem normally involves calculating

for various properties of the flow, such as velocity, pressure, density,

and temperature, as a function of space and time.


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AERODYNAMIC DRAG

W hen a O bject moves, the air exerts a force on the object that resistsits motion. T his force is the aerodynamic drag .

Aerodynamic drag w 1/2 D x A x V 2

D rag = 1/391 x Cd x A x V 2 (For Real Body Shape)

Coefficient of drag (Cd) : T his is a number that is a measure of anobjects resistance to the fluid it passes through.lower numbersmeaning the object has greater aerodynamic properties.

In case of automobile this number should be as low as possible.


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COMPONENTS OF DRAGA erodynamic drag has two components.Form or pressure drag . P ressure drag is almost 80% responsible for the total aerodynamic drag

Skin friction drag : T he skin friction drag is caused by the shear forces acting on the sides of vehicle and contributes only 20% of thetotal aerodynamic drag.


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AERODYNAMIC FORCES ON PLANE


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CLASSIFICATION OF AERODYNAMICS

AERODYNAMICS

F low E nvironment F low S peed F low Viscosity

E xternal

aerodynamicsInternal

aerodynamics S upersonicaerodynamics

T ransonicaerodynamics

S ubsonicaerodynamics

HypersonicA erodynamics

Inviscid F low

Viscous F low


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APPLICATION OF AERODYNAMICS

A erospace engineering.In structural engineering to calculate wind loads in the design of large

buildings and bridges.I t is a significant factor in any type of vehicle design, includingautomobiles.P rediction of forces and moments in sailing.T he field of environmental aerodynamics studies the ways atmosphericcirculation and flight mechanics affects ecosystems.T he aerodynamics of internal passages is important inheating/ventilation, gas piping, and in automotive engines.


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FORCE CALCULATION

T wo W ays to calculate these forces :-

1. Experimental testing of any object by using wind tunnel test.- F abricate the object.- measure all flow parameters in flowing fluid


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CONTINUED

2. AERO DYN AMIC MO D ELI NG AND SIMULATIO N

B y M odeling of that object in 3 D solid modeling software like

PRO - E and CATIA and then A nalysis of that object by using anyCFD (computational fluid dynamics) software like FLUENT .- G eometrical and M aterial specification.- M ake a 3 D solid model of object.- A nalysis in CFD software.


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AIRODYNAMIC SIMULATION

COMPUTATIO N AL FLUI D DYN AMICSCFD is a tool to analyze fluid flow. CFD is meant for engineers

designing products that relate to the flow of gases or liquids, heattransfer and fluid forces on solids .

Advantage of using CF D simulation :-

- C osts incurred in time and resources are much less than experimentaltesting.

- T his cost advantage comes with no compromise on the accuracy of the results.

- A nother advantage of CFD is that it need not wait for the design to becomplete. CFD analysis is done on a parallel basis along with thedesign phase and hence further timesavings.

- A ll information can be used in future.


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STEPS IN VOL VED IN CFD SIMULATION

T he geometry (physical bounds) of the problem is defined.

T he volume occupied by the fluid is divided into discrete cells (the

mesh).T he physical modelling is defined.

B oundary conditions are defined. T his involves specifying the fluid

behaviour and properties at the boundaries of the problem. F or

transient problems, the initial conditions are also defined.T he equations are solved iteratively as a steady - state or transient.

A nalysis and visualization of the resulting solution.


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MES HING AND SIMULATION


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A ssumptions M ade In A erodynamics Continuity Assumption: properties such as density, pressure, temperature,and velocity are taken to be well - defined at infinitely small points, and areassumed to vary continuously from one point to another. T he discrete,molecular nature of a gas is ignored.

Conservation laws:

Conservation of mass: M atter is not created or destroyed. If a certain massof fluid enters a volume, it must either exit the volume or increase the mass

inside the volume.Conservation of momentum: A lso called N ewton's second law of motion

Conservation of energy : A lthough it can be converted from one form toanother, the total energy in a given system remains constant


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AUTOMOTI VE AERODYNAMICS

Automotive aerodynamics is the study of the aerodynamics of road

vehicles. A utomotive aerodynamics differs from aircraft aerodynamicsF irst the characteristic shape of a road vehicle is bluff , compared to an

aircraft. S econd, the vehicle operates very close to the ground, rather than

in free air. T hird, the operating speeds are lower.

Concerns of automotive aerodynamics :- How to reduce drag ?

- How to reduce wind noise?

- How to P revent undesired lift forces at high speeds?

- T o produce desirable downwards aerodynamic forces to improve

traction and thus cornering abilities in racing cars.


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TRUCK AERODYNAMICS

The fuel cost is approx. 1/3 of the operational cost


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What is the challenge?


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Airflow pattern around an Unaerodynamic truck


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M ain D evelopment A reas

C ab shape.

C ab details.A ir deflectors.

S un visor, R ear view mirrors.

C hassis details.

S ide skirts.W heel deflectors, floor panels.


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What is the solution to reduce drag?

Tractor Aerodynamics:- B y using roof fairings (an integrated air deflector mounted on the top of

the cab).- C ab extenders (known as gap seals, which reduce the gap between the

tractor and the trailer)- S ide fairings.- A nd a front bumper air dam (to reduce air flow beneath the truck)Trailer Aerodynamics :

- R educing trailer gap from 45 to 25 inches could improve fuel economy asmuch as 2 percent.

- B y using side skirts can improve fuel economy by up to 5 percent.- R educe drag by arranging cargo as low and smooth as possible.


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R educing D rag by using streamline flow


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By

R educing

Frontal

Area

Aerodynamic drag w 1/2 D x A x V 2

T ype of vehicles

T ypical frontal area(m2)

T ypical wind - averagedcoefficients

R igid 8.75 0.7

A rticulated 9.5 0.85


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B y using N osecone

N osecone smoothes airflow over the whole pan by reducing turbulence anddrag at sides and rear.

Side Forces without nosecone Side Forces with nosecone


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Position

Of

Load


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B y using C oncept T ruck

T hese trucks are designed by the scania motor for future application . Inthis truck drag coefficient will be very low.


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Development

?


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W here W e (Ashok Leyland)Stand .???


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REFERENCES

http : //www.scania.co.uk/technology ( S cania L td).

http : //www.cfdrc.com ( CFD R esearch C orporation).

http:

//www.wikipedia.org (O

nlineE

ncyclopedia).http : //www.howstuffworks.comhttp : //www.nosecone.com.au ( N osecone the winddeflector).http : //www.epa.gov/smartway ( U .S .A E nvironmental

P rotection A gency).http : //www.nasa.govhttp : //www.volvo.comhttp : //www.google.com


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aerodynamic modeling and simulation

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