Transcript CFD Pre-Lab 2Simulation of TurbulentFlowaround an

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Overview of Flow Around Airfoil
CFD Process
Workbench Geometry
Physics
Mesh
Solution
Results
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Simulation of flow around airfoil will be
conducted for this lab
Computational fluid dynamics (CFD)
results for drag and lift coefficients,
coefficient of pressure around the
airfoil will be compared to experimental
fluid dynamics (EFD)
This lab will cover concept of boundary
layer and flow separation
Flow visualization around airfoil
(starts at 5:34)
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Boundary Layer
◦ Defined by Ludwig Prandtl
◦ Generated by viscosity near wall
◦ Cause of lift and drag forces
◦ Inviscid vs. viscous flow
◦ Flow separation
Note: Refer to Chapter 9 of your
book for more details
Flow visualization of boundary layer
(Start at 3:21)
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The overall procedure for simulation of flow around airfoil is shown
on chart below
Although we will be making the mesh before we define the physics
you have to know the physics to design appropriate mesh.
Physics
Mesh
Solution
Results
Airfoil (ANSYS
Design Modeler)
General (ANSYS
Fluent - Setup)
Structured (ANSYS
Mesh)
Solution Methods
(ANSYS Fluent Solution)
Plots (ANSYS
Fluent- Results)
C-Domain (ANSYS
Design Modeler)
Model (ANSYS
Fluent - Setup)
Geometry
Non-uniform
O-Domain (ANSYS
Design Modeler)
Boundary
Conditions (ANSYS
Fluent -Setup)
(ANSYS Mesh)
Monitors (ANSYS
Fluent - Solution)
Reference Values
(ANSYS Fluent Setup)
Turbulent
Solution
Initialization
(ANSYS Fluent Solution)
Solution Controls
(ANSYS Fluent Solution)
Solution
Initialization
(ANSYS Fluent Solution)
Run Calculation
(ANSYS Fluent Solution)
Graphics and
Animations (ANSYS
Fluent- Results)
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Import Clark-Y airfoil geometry
Split O-type domain into four pieces
Parameter
Value
Chord length, c
0.3048 m
Radius of domain, Rc
12.0 m
Angle of attack, α
0, 16
Wall – No slip BC
Inlet – Velocity inlet BC
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Outlet – Pressure outlet BC
Inviscid and viscous models
Air properties based on experimental temperature measurements
Boundary Conditions (BC)
𝑑𝑝
◦ No-slip: velocities are zero (𝑢, 𝑣 = 0), pressure gradient ( 𝑑𝑟 = 0) is zero
◦ Inlet velocity: extracted from experimental data
◦ Outlet: (gauge) pressure is imposed to the boundary (𝑝 = 0)
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Fine mesh at the boundary layer region to resolve large velocity gradients
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If you have problems with solution convergence reduce
Under-Relaxation Factors. This issue is more likely to
occur for large angle of attack cases.
Also you may need to increase the number of iterations
0.300
1.200
Benchmark Data
Benchmark Data
Wake Velocity Profile Pitot
0.250
Pressure Distribution Measurement
1.000
Load Cell Measurement
Load Cell Measurement
CFD
Wake Velocity Profile Hot-wire
0.200
CFD
Cd
Cl
0.800
0.150
0.600
0.400
0.100
0.200
0.050
0.000
0.000
0
4
8
AoA
12
16
0
20
4
8
AoA
12
16
20
Coefficent of Drag (Cd) Distribution
Coefficent of Lift (Cl) Distribution
Benchmark Data
1.500000
Experimental2013
Experimental2010
1.50000
0.50000
0.500000
Cp
1.00000
Cp
1.000000
Benchmark Data
Experimental-2013
Experimental-2012
experimental-2010
CFD
0.00000
-20
0
20
40
60
80
100
0.000000
-20
0
-0.500000
-0.50000
-1.000000
-1.00000
-1.500000
-1.50000
-2.000000
-2.00000
-2.500000
-2.50000
X/Chord
Coefficent of Pressure (Cp ) Distribution at 0 AOA
20
40
60
80
100
X/Chord
Coefficent of Pressure (Cp ) Distribution at
16 AOA
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Pressure distribution around airfoil
Velocity vectors near wall and boundary
layer development
Stream lines around airfoil