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Basic Fluid Mechanics
Dr. Peter J. Disimile
“Dr.D”
Department of Aerospace [email protected]
Chapter 1 Introduction 14/16/2018
Chapter 1A: Introduction
Why Study Fluid Mechanics?
It impacts every aspect of our life from weather to transportation, the environment to physiology, from sports and recreation, etc. Some examples follow:
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Weather & Climate
Tornado
Hurricane
Global Climate
Thunderstorm
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4/16/2018 Chapter 1 Introduction 4
Vehicles
Aircraft
SubmarinesHigh-speed rail
Surface ships
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4/16/2018 Chapter 1 Introduction 5
EnvironmentMan made Air Pollution
Volcanic Eruption
River Hydraulics
4/16/2018 Chapter 1 Introduction 6
Physiology and Medicine
Blood pump
Ventricular assist device
Waste Fluid Flow
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4/16/2018 Chapter 1 Introduction 7
Sports & Recreation
Water sports
Auto racing
Offshore racingCycling
Surfing
Chapter 1A: Introduction
(AFD)(EFD)(CFD)
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Chapter 1A: Solution Methods
Analytical FD - The mathematical solution of fluid mechanics problems using control volume and differential analysis:
- Exact solutions only exist for simple geometries and boundary conditions.
- Approximate solutions exist for linear problems and those which utilize empirical correlations obtained from experiments.
Chapter 1 Introduction 94/16/2018
Analytical Fluid Dynamics
Laminar pipe flow - simplify the momentum equation, integrate, and apply boundary conditions.
Exact solution :
2 21( ) ( )( )4
pu r R rx
Assume:
xgy
u
x
u
x
p
Dt
Du
2
2
2
2
0
00
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Experimental FD - Using experimental methods and procedures to solve fluid mechanic phenomena on both small scale models and full scale systems.
• This requires the use of measurement systems, uncertainty analysis, and similarity.
• Measurement systems require calibrated sensors and data acquisition systems.
Experimental Fluid Dynamics
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Experimental Fluid Dynamics
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Flow with particles
d (known)
Velocity = distance/time
t (measured)
Signal
Time
LaserBraggCell backscattered light
measuring volume
Detector
Processor
Laser Doppler Anemometry (LDA)
Experimental Fluid Dynamics
Chapter 1 Introduction 134/16/2018
Flow is seeded with micron sized particles, scattered laser light is collected, and velocity calculated.
Experimental Fluid Dynamics
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Velocity Profile 2.5cm Upstream of Inlet Cone
0
5
10
15
20
25
0 20 40 60 80 100 120
Distance across the pipe diameter (mm)
Me
an
Ve
loc
ity
(m
/s)
Blue component Green Component
Experimental Fluid Dynamics
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Computational FD - Using computational methods the governing equations and boundary conditions are solved numerically.
This involves the use of equation solvers and grid generation techniques.
Computational Fluid Dynamics
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Viscous Model
Boundary Conditions
Initial Conditions
Convergent Limit
Contours
Precisions(single/double)
Numerical Scheme
Vectors
StreamlinesVerification
Geometry
Select Geometry
Geometry Parameters
Physics Mesh Solve Post-Processing
CompressibleON/OFF
Flow properties
Unstructured(automatic/
manual)
Steady/Unsteady
Forces Report(lift/drag, shear stress, etc)
XY Plot
Domain Shape and Size
Heat Transfer ON/OFF
Structured(automatic/
manual)
Iterations/Steps
Validation
Reports
Computational Fluid Dynamics
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Vulcan Geometry, Grid, and Location of Planes
CoreInlet Pipe
Detailed view of planes 3 and 4
3 4
Z
Y
X
Computational Fluid Dynamics
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Example of Grid Used by CFD-ACE
Start of coreexpansion
Constant axialgrid slice
End of nacelle expansion, andend of core expansion
Start of nacelleexpansion
Constant circumferentialgrid slice
Computational Fluid Dynamics
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Measurement Plane 2
Velocity(m/s)
He
ight
(m)
0 5 10 15 20¦0.15
¦0.1
¦0.05
0
0.05
0.1
0.15
VULCANaxialVULCANverticalVULCAN lateralCFD¦ACEaxialCFD¦ACEverticalCFD¦ACElateral
Plane of Results
Computational Fluid Dynamics
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Axial Velocity
U: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Computational Fluid Dynamics
VULCAN Axial
Velocity
CFD-ACE Axial
Velocity
Chapter 1 Introduction 214/16/2018