essentials of fluid mechanics for cfd
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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
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ONE AssociationONE Association
The one independent association d di d h i idedicated to the engineering
analysis communityanalysis community
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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
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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
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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
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ONE CommunityONE Community
OverOver 1000 member companies
worldwide making a community of thousands of individualsthousands of individuals
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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
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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%
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NAFEMS Member SectorsNAFEMS Member SectorsAcross four sectors…
ConsultantsConsultants19%
Vendors17%
Industrial Users50%
17%
Academia50% Academia14%
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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%
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2%
11
Wh J i NAFEMS?Why Join NAFEMS?
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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
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Why join NAFEMS?Why join NAFEMS?
“By joining NAFEMS, Prospect reinforces itsProspect reinforces its commitment tocommitment to excellence in numerical i l ti ”simulation.”
- Prospect
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Why join NAFEMS?Why join NAFEMS?
“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
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Why join NAFEMS?Why join NAFEMS?
“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
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Membership OptionsMembership Options
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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
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Membership OptionsMembership Options
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
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Benefits of MembershipBenefits of Membership
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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
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Benefits of MembershipBenefits of Membership
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
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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
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Benefits of MembershipBenefits of Membership
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
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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
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About
NAFEMS - The International Association for the Engineering Analysis CommunityInfoMec - CFD Training & Consultancy www.infomec.cc
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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
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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
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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…..
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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”
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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 orgone@nafems.org
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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
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 32
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
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 33
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
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Essentials of Fluid Mechanics for CFD Webinar V1.0 Page 34
yrefresher
pp
The Need for CFD
Pressure contours on a pump impeller
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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
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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
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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
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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
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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
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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?
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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.
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Essentials of Fluid Mechanics for CFD Webinar V1.0 Page 42
Flow ClassificationFlow ClassificationFluid Dynamics & Heat Transfer
Steady Transient/Unsteady
Inviscid FluidViscous FluidHeat Transfer
LaminarConduction Radiation Turbulent
Convection
Incompressible CompressibleFluid
Incompressible CompressibleNatural
Forced
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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
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Shock
Important Concepts & PhenomenaBoundary layer
Balance of Forces
Acceleration
Vortices
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• 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
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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
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Turbulent Flows
Fl ith H t T fFlows with Heat Transfer
Multiphase FlowsMultiphase Flows
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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
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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
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Grid
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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
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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
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qconduction
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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)
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56
Internal Flows
E t l flExternal flows
TurbomachinaryTurbomachinary
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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
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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
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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
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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.
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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
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Introduction to CFDNAFEMS Course: Practical
Introduction to CFD
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CFD ProcessBuild model
CFD Processpre-process
Mesh
Set flow & boundary conditions
Visualize
conditionsAnalyze
post-process
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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
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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
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monitor solution Post-process
CFD Post ProcessingCFD Post ProcessingContours
St liStreamline
Velocity vector plotsAnimations
Velocity vector plotsXY plots
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Questions
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