Essentials of Fluid Mechanics for CFD - NAFEMS · PDF fileEssentials of Fluid Mechanics for CFD Webinar November 16, 2011November 16, 2011 NAFEMS - The International Association for

Essentials of Fluid Mechanics for CFD

Webinar November 16, 2011November 16, 2011

NAFEMS - The International Association for the Engineering Analysis CommunityInfoMec - CFD Training & Consultancy www.infomec.cc

Essentials of Fluid Mechanics for CFD Webinar V1.0 Page 1

AgendaAgendaW l & I t d tiWelcome & Introduction

David Quinn, NAFEMSEssentials of Fluid Mechanics for CFD

Kamran Fouladi, InfoMecQ & A Session



ONE AssociationONE Association

The one independent association d di d h i idedicated to the engineering

analysis communityanalysis community



ONE AssociationONE AssociationTh l i ti ld id d di t d t i i i l ti d• The only association worldwide dedicated to engineering simulation and analysis

• Offering vital ‘best practice’ information for FEA, CFD and CAE

• Providing industry-recognised training programs independent events andProviding industry recognised training programs, independent events and acclaimed publications



ONE VisionONE VisionNAFEMS i t f fit i ti ith l i iNAFEMS is a not-for-profit organisation with one clear vision:

the safe and reliable use of analysis and simulationanalysis and simulation

technologygy



ONE VisionONE VisionO th l t 25 NAFEMS’ i i h b tOver the last 25 years NAFEMS’ mission has been to:

• Facilitate industry academic and government• Facilitate industry, academic and government collaboration

• Improve product and process simulationp p p

D i i t i lit f t• Drive improvement in quality, safety, profitability and schedules



ONE CommunityONE Community

OverOver 1000 member companies

worldwide making a community of thousands of individualsthousands of individuals



ONE CommunityONE CommunityM b t th tMembers come together to:

• Share engineering experiencesg g p

• Build long lasting relationships

• Gain a genuine insight into the real-life uses simulation



NAFEMS Member IndustriesNAFEMS Member IndustriesEncompassing many

AerospaceOther5%

industries…

15% Automotive15%

Civil & Construction

8%Process

Research & Technology 6%

5%

8%Consumer Goods

5%

Defence7%

Power & Energy13%

Manufacturing5%

7%Design Engineering

6%Hardware

4%Marine

6%

Oil and Offshore5%

13%



NAFEMS Member SectorsNAFEMS Member SectorsAcross four sectors…

ConsultantsConsultants19%

Vendors17%

Industrial Users50%

17%

Academia50% Academia14%



NAFEMS Member RegionsNAFEMS Member RegionsIn over 50 countries…

DACH17% Nordic 8%North

America15%

17% Nordic 8%Iberia 3%

France 8%

UK & Ireland

Italy 3%Europe (other)

25%(other)11%

India4%Other

4%

Asia (other)

4%



2%

11

Wh J i NAFEMS?Why Join NAFEMS?



Why join NAFEMS?Why join NAFEMS?

“NAFEMS M b hi i“NAFEMS Membership is a must for all those truly involvedmust for all those truly involved with numerical analysis, for continuous improvement andcontinuous improvement and learning, and sharing of experience.”

- Insituto technologico de aragon




“By joining NAFEMS, Prospect reinforces itsProspect reinforces its commitment tocommitment to excellence in numerical i l ti ”simulation.”

- Prospect




“Nokia joined NAFEMS in order to expand and enhance our FEA knowledge and toour FEA knowledge, and to train and attract new analysts i thi ”in this area.”

- Nokia




“As a member of NAFEMS, we can actively participatewe can actively participate and contribute to the FEA

it duser community, and expose our clients to theexpose our clients to the latest developments in FEA.”- Epsilon Structural Analysis



Membership OptionsMembership Options




NAFEMS offers four options to suit the different needs of the engineeringthe different needs of the engineering analysis community:

Small Company MembershipCost effective membership for small to medium sized enterprisesp p

Site MembershipOffering a full range of benefits for larger corporations based at one locationOffering a full range of benefits for larger corporations based at one location




Corporate MembershipTailored membership for large companies with multiple locationsp g p p

Academic MembershipOffering the same benefits of site membership to recognised academicOffering the same benefits of site membership to recognised academic institutions



Benefits of MembershipBenefits of Membership




PublicationsC f• Complementary publication library of your chosen cutting edge NAFEMS textbooks, reports, how-to guides and benchmarks

• Copies of all new publications as they are produced

• Significant discounts on other publicationsSignificant discounts on other publications

• Subscription to ‘benchmark’ magazine




Seminar Credits

• Credits towards NAFEMS seminars which are held regularly and internationally each yeary y

• Previous seminars have included:• Concrete under Fire: High Temperature Effects on Concrete• Concrete under Fire: High Temperature Effects on Concrete• Die Integration von Strömungsberechnungen (CFD) in den

Produktentwicklungsprozes• High Performance Computing• Analyses non linéaires et conception des structures



Benefits of Membership

f

Benefits of Membership

Access to ‘Members Area’ of NAFEMS orgNAFEMS.org

• PDF versions of NAFEMS documents• Presentations from previous seminars• ‘benchmark’ magazine article archive• benchmark magazine article archive• Jargon guides• Discounted member prices on all events and publications

NAFEMS’ bi hi• NAFEMS’ webinar archive• All of NAFEMS events and news• Publish your events and press releases to promote your company




Attend NAFEMS events at members rates

• NAFEMS provides as many as thirty seminars, courses, workshops and open forums throughout the world each yearyear

• Events are widely held to encompass the broadest and• Events are widely held to encompass the broadest and most accurate view of the community available

• NAFEMS members receive significant discounts



Benefits of MembershipBenefits of Membershipt di t d tat discounted rates

• NAFEMS is focussed on providing quality and worthwhile trainingp g q y g

• NAFEMS Training offers several analysis and simulation training courses

• Members receive discounts on all courses – including e-learning



About



Q litQuality• All courses are fully NAFEMS accredited

C l d b t i d d t d i i d t d t i i• Courses led by most experienced and respected in industry and training

VarietyVariety• FEA and CFD• Basic to Advanced• Basic to Advanced• Courses added regularly

Flexibility• Classroom based training



g• e-Learning

CoursesCoursesNAFEMS T i i ff i t f l b dNAFEMS Training offers a variety of classroom based including:

• Practical Introduction to FEA• Practical CFD Analysis• Praktische Einfuehrung in FEMPraktische Einfuehrung in FEM• FEM Basic 1• Praxisorientierte Grundlagen für CFD-Berechnungen

I d i C l l d S El Fi i l• Introduction au Calcul de Structures, aux Elements Finis et a la Simulation Numerique

• Advanced Non-linear FE Analysis



e Learning Coursese-Learning CoursesNAFEMS T i i l ff id i t f L iNAFEMS Training also offers a wide variety of e-Learning courses including:

• Basic FE Analysis• Composite FE Analysis• Dynamic FE AnalysisDynamic FE Analysis• Fatigue and Fracture Mechanics in FE Analysis• Non-Linear Analysis

S l O i i i i FE A l i• Structural Optimisation in FE Analysis• Introduction to CFD• Essential Fluid Dynamics for CFDy

and more…..



FeedbackFeedback“G d f l ti l ti l t ’ d t d li t f l t“Good course, useful practical tips, lecturer’s anecdotes and lists useful to pass on”

“An excellent and comprehensive course - well worth the money. The tutor has a very clear and concise teaching manner”

“Extremely helpful and informative”

“This course did everything right From organisation to presentation toThis course did everything right. From organisation to presentation to interaction - this is a good model for what online training should be”



Contact NAFEMSContact NAFEMST l 44 1355 22 56 88Tel: +44 1355 22 56 88Fax: +44 1698 82 33 11

SpringwoodBooths Park

Chelford RoadKnutsford

Cheshire WA16 8QZUnited Kingdom

www.nafems.orgone@nafems [email protected]



E ti l f Fl id M h i f CFDEssentials of Fluid Mechanics for CFD

Webinar November 16 2011November 16, 2011

Kamran Fouladi, Ph.D., P.E.InfoMec ConsultingInfoMec Consulting



MotivationMotivationProliferation of commercial CFD software

Effective CFD Need Fluid Mechanics

Knowledge

Proliferation of commercial CFD software Deep knowledge of math and computer science

g

More organizations andMore organizations and newer analysts would embark on using CFD

Essential understanding of fluid dynamics

g

Growing use of CFD for complex problems



Course RoadmapCourse RoadmapFluid Dynamics Fluid Dynamics Fluid Dynamicsy

Definitions, Properties,

Challenges & Approaches

Fluid Dynamics Important

Phenomena & Concept

Fluid Dynamics Governing

Theories & Flow ClassificationsApproachesp

Introduction to Turbulence

Introduction to CFD

Managers Needing CFDUnderstanding of Fluid

New CFD analysts needing fluid

dynamics

Needing CFD

Case Studies

U de sta d g o u dDynamics for using

CFD on real-life applications



yrefresher

pp

The Need for CFD

Pressure contours on a pump impeller



Governing PrinciplesGoverning PrinciplesWhy do we need

CFD?CFD?

Fluid dynamics problems are difficult to solve:

System of PDEsIrregular boundariesNonlinearity Coupled equations

Only limited number of problems can be solved analytically

Ph i l t ti i tl d ti i



Physical testing is costly and time consuming

CFD for EngineeringCFD for Engineering To include CFD in product design, CFD

must show real benefitsbecome an integral part of designbecome an integral part of designbe practical - cost and time feasible

We will provide a brief introduction to CFD

Effective use of CFD needs :Fluid Engineering knowledge

Familiarity with practical CFD

Fluid Mechanics

Software training

Attention to best practices



Attention to best practices

Engineering Knowledge

Fundamental Understanding ExperienceFundamental Understanding Experience

DefinitionsConceptsGoverning principles

Forces acting on fluid in motionSources contributing to fluid’s energyAcceleration,Diffusiong p p

Important ConceptsImportant phenomena…..

Pressure loss/recoveryBoundary layersTransition and turbulenceFlow separation

… WakesJetsVorticesBuoyancy



Shock waves

Navier-Stokes EquationsNavier Stokes EquationsDifferential Form

uuupuuuu 222

Assuming: constant density & viscosity; Newtonian fluid x-direction only

xgzu

yu

xu

xp

zuw

yuv

xuu

tu

)( 222

localacceleration

advective acceleration

pressuregradient diffusion body forces

We will present some simple forms of N-S equations &

Discuss importance of each term in those equation



Fluid PropertiesFluid Properties

Important concepts and properties encountered in fluid analysis Dynamic y

Static Pressure, P

Stagnation Pressure, Pstag

yPressure

V2/2

ContinuumNewtonian fluidsLagrangian & Eulerian descriptions

VLagrangian & Eulerian descriptionsDensity – ideal gas vs. real gasViscosity - no slip conditionScalar properties (density pressure temperature )

Stagnation point

Scalar properties (density, pressure, temperature, ..) Vector properties (velocity, acceleration, …)….. Atmospheric pressure

Absolute Pressure



Gage pressure

Dimensional AnalysisDimensional AnalysisNon DimensionalizationNon-Dimensionalization

For model testing to be useful, model & prototype must be similar

G t i i il itGeometric similarity

Kinematic similarity

Dynamic similarity

=

Dynamic similarity

Scaled Models Full Scale Prototypes?



Scaled Models Full Scale Prototypes

Dimensionless Parameters Used to Classify Flow Problems

uLReReynolds No.

Prandtl No.

kcpPrTurbulentMach No.

Rayleigh No

kLhNu L i

Turbulent Rayleigh No.

Nusselt No.

S Laminar Compressible

Strouhal No.

Cavitation No.

auM /

p

Incompressible Richardson No.

Grashof No.



Flow ClassificationFlow ClassificationFluid Dynamics & Heat Transfer

Steady Transient/Unsteady

Inviscid FluidViscous FluidHeat Transfer

LaminarConduction Radiation Turbulent

Convection

Incompressible CompressibleFluid

Incompressible CompressibleNatural

Forced



Internal ExternalForced

Flow ClassificationFlow ClassificationLaminar Turbulent

Laminar flows are orderly and smooth – They can be described by continuity and momentum equations

Turbulent flows are random & chaotic with eddies at higher Reynolds numbers (inertia forces>> viscous forces)

TurbulentLaminar

Incompressible Compressible

This classification is based on variation of densityLiquids are essentially incompressible substancesGases are considered incompressible at Mach Number <0.3Major differences between compressible & incompressible flows



Shock

Important Concepts & PhenomenaBoundary layer

Balance of Forces

Acceleration

Vortices



• Adverse pressure gradient is where static i i fl di ti

dp/dx<0 dp/dx=0 dp/dx>0

Adverse Pressure Gradient

pressure increases in flow direction

• Adverse pressure gradient has more significant effect on flow (slower) in the boundary layer

• Adverse pressure gradient can lead to flow separation and wakes

backflowbrought to rest

Flow Separation is a process in which flow in

Wakes & Flow Separation

boundary layer can no longer stay attached to the surface & separates from the surface

Wake is the region of flow trailing a body whereWake is the region of flow trailing a body where effect of that body is felt on velocity field

Flow separation results in energy loss and drag



Flow separation results in energy loss and drag

StreamliningStreamliningStreamlining reduces drag by reducing Pressure Drag, at the cost of increasing wetted surface area and Friction Dragg

Goals:•Eliminate flow separation and•Eliminate flow separation and minimize total drag•Improves structural acoustics -separation and vortex shedding

it t t l dcan excite structural modes



Turbulent Flows

Fl ith H t T fFlows with Heat Transfer

Multiphase FlowsMultiphase Flows



TurbulenceTurbulenceIn Engineering applications, laminar flows are exception, not the rule

S ll di i hi h i itiSmall dimensions, high viscosities

Most flows in nature & in engineering applications are turbulentplume of smokestack boundary layer over aircraft wing flow of water in riversplume of smokestack, boundary layer over aircraft wing, flow of water in rivers,

most combustion processes, chemical mixing, etc.

Turbulent flows exhibit disorderly & complex motions



Turbulent flows exhibit disorderly & complex motions

Origin of TurbulenceOrigin of Turbulence• Many factors can cause transition to turbulent

Factors influencing transition* Free stream turbulence ar

y la

yer

Free stream turbulence* Heat transfer (cooling or heating)* Pressure gradient

Bou

nda

* Surface roughness* Surface curvature

Categories of Turbulent flows ear l

ayer

g* Boundary layer* Shear layer* Grid Generated

She

d* Grid-Generatedd

Gen

erat

ed



Grid



Turbulence ModelingModels are semi-empirical mathematical

Di t N i l Si l ti

ode s a e se e p ca at e at carelations to predict the effect of turbulence

Direct Numerical Simulationresolving (not modeling) all eddies - most accurate

Eddy Simulation resolvingsome of the “significant” eddies (large) and modeling the rest(large) and modeling the rest (small eddies) - more accurate

Averaged Navier-StokesAveraged Navier Stokes Simulation modeling all eddies - least accurate



Heat Transfer• Conduction - Transfer of thermal energy due to temperature gradient• Convection - Transfer of thermal energy by moving fluid• Radiation - Transfer of thermal energy by electromagnetic waves

between surfaces with different temperatures

qconvection

qradiation



qconduction



Multiphase FlowsMultiphase FlowsMultiphase flow is simultaneous flow of:Multiphase flow is simultaneous flow of:

Materials with different states or phases (i.e. gas, liquid or solid). Materials with different chemical properties but in the same state or phase (i.e. liquid-liquid systems such as oil droplets in water)





56

Internal Flows

E t l flExternal flows

TurbomachinaryTurbomachinary



I t l FlInternal Flows

No-slip condition causes shear stress and friction on the fluid along the pipe wallsthe fluid along the pipe walls

Shear Stress t b l t > Shear Stress L iShear Stress turbulent > Shear Stress Laminar



Entrance & Fully Developed FlowsEntrance & Fully Developed Flowsgrowing boundary layerdeveloping

velocity boundary layers merge

yprofile

fully developed

inviscid core

y pvelocity profile

pressureLe= entrance length

entrance length pressure drop

linear pressure drop in fully developed

g

in fully developed region



xLe0

E t l FlExternal FlowsLift & drag forces are function to geometry density & velocityLift & drag forces are function to geometry, density, & velocity

lift coefficient drag coefficient

CD = 1.0, A = 25 ft2, CDA = 25ft2 CD = 0.28, A = 10 ft2, CDA = 2.8ft2



D , , D D , , D

TurbomachinaryTurbomachinary• Pump: adds energy to

a fluid, resulting in an increase in pressure across the pump.

• Turbine: extracts energy from the fluid, resulting in a gdecrease in pressure across the turbine.



PumpsPumps

Net Head: Change in Bernoulli head from inlet to outlet

Water horsepower: Useful power actually deliveredy

Brake horsepower: External power supplied to the pumpsupplied to the pump

Pump efficiency: Ratio of useful power to supplied powerto supplied power



Introduction to CFDNAFEMS Course: Practical

Introduction to CFD



CFD ProcessBuild model

CFD Processpre-process

Mesh

Set flow & boundary conditions

Visualize

conditionsAnalyze

post-process



CFD Pre-ProcessingCFD Pre-ProcessingCFD solvers solve flow physics within the flow domain

Grid Generation

C so e s so e o p ys cs t t e o do a

Model & Flow DomainFlow domain must be established

Domain includes geometry & region of interest Grid Generation is discretization of

the flow domain

Grid Generation isGrid Generation is discretization of the flow

domain

Model

Region of interest



CFD Solution Iterative ProcessCFD Solution Iterative Processinitialize / update Grid

B d ditiinitialize / update properties

Boundary conditionsMaterial properties

solve continuity, momentum, energy equations simultaneously

solve turbulence & scalar equationsq

converged stopNO YESconverged stop

monitor solution



monitor solution Post-process

CFD Post ProcessingCFD Post ProcessingContours

St liStreamline

Velocity vector plotsAnimations

Velocity vector plotsXY plots



Questions



Documents

Essentials of Fluid Mechanics for CFD - NAFEMS · PDF fileEssentials of Fluid Mechanics for CFD Webinar November 16, 2011November 16, 2011 NAFEMS - The International Association for