Date post: | 28-Apr-2015 |
Category: |
Documents |
Upload: | muhammad-aamir |
View: | 200 times |
Download: | 9 times |
1
Aeroelastic Analysis of a Reference
Aircraft Wing for Investigation of Structural Stability using ANSYS®
Student: Advisor : S/L Nadeem
Muhammad Amir Co-Advisor : S/L Kashif
Pak No. 71008
SCOPE
A Reference Aircraft Wing shallbe Investigated for its StructuralStability by Performing Fluid-Structure Interaction Studies,using ANSYS as ComputationalPlatform.
3
MILESTONES
Two-Way FSI in ANSYS Workbench
Static Aeroelastic Analysis to Compute
Divergence Speed
Dynamic Aeroelastic Analysis and
Calculating Flutter Boundary
Validation of Divergence Speed
and Flutter Boundary
4
METHODOLOGY
Literature Review and Software Learning
Demonstration of Two-way FSI
Material Properties and Flow Characteristics
Discretization of Structural and Aerodynamic domains
Static Aeroelastic Analysis
5
METHODOLOGY
6
Dynamic Aeroelastic Analysis
Results and Discussion on StabilityParameters
Conclusion
Recommendations
Aeroelasticity and ANSYS 13
7
A Coupled Field
– No flexibility, No Aeroelasticity
– Max Wingtip Displacement of Boeing 747=24 ft
Serious Threat to Flight Safety
Aeroelasticity
8
Aeroelasticity
9
Static Aeroelastic Phenomena• Wing Divergence
• Control Reversal
Dynamic Aeroelastic phenomena• Flutter
• Limit Cycle Oscillation
• Gust Response
Flutter
Highly Non-linear Phenomena
Experimental Tests are Destructive
Analytical Results not Possible
Best Option is Finite Element Method
10
ANSYS 13
ANSYS 13 Capabilities....
Flow Analysis: CFX/Fluent
Meshing: ICEM CFD
Two Way FSI: Multi-field Solver
11
ANSYS 13
One Way FSI
ANSYS MECHANICAL-
FLUENT/CFX
Two Way FSI
ANSYS MECHANICAL-
CFX
12
TWO WAY FSI
13
DEMONSTRATION OF TWO WAY FSI
Model: 2D Plate
Material: Structural Steel
Element Type: Solid 186
Initial Disturbance and Left Free
14
COUPLING
Transient Structural and CFX
15
Tip Displacement
16
TWO-WAY FSI
1st Time-step
17
Results
Damping Motion Shows Transfer of Loads
between Fields
18
STATIC AEROELASTIC ANALYSIS
19
STATIC AEROELASTIC ANALYSIS
Model Selection : NASA Wind-Tunnel
Experiments on Divergence of Forward
Swept Wing(Aug 1980)
20
Model Specification
MODEL 1 MODEL 2
SWEEP -30˚ -15˚
TAPER 1 1
AR 4 4
TRANSITION STRIP NO.46 CARBORANDUM
GRIT
NO 46 CARBORANDUM
GRIT
MODEL MOUNT CANTILEVER CANTILEVER
AOA .1˚ .1˚
21
Experimental Results
MODEL 1(-30 Sweep) MODEL 2(-15 Sweep)
DIVERGENCE
SPEED(m/s)
51 73.41
22
Ref: Wind-Tunnel Experiments on Divergence of Forward-Swept Wings,
NASA Technical Paper 1685
MODEL 1 = -30˚
23
MODEL 1: -30˚
Model
Transition Strip is not Modelled
24
Monitor Point
25
Velocity = 45m/s
Divergence Speed(-30˚ Sweep)
26
V= 48 m/s V= 45 m/s
Divergence Speed ≈ 46.5 m/s
DEFORMATION
27
Velocity = 48 m/s
MODEL 2 = -15˚
28
Wingtip Displacement
Velocity = 75 m/s
29
Velocity = 80 m/s
30
Wingtip Displacement
Divergence Speed(-15˚ Sweep)
31
V= 80 m/s V= 78 m/s
Divergence Speed≈ 79 m/s
RESULTS
32
Divergence Speed
ANSYS
(m/s)
EXPERIMENTAL
(m/s)
Error
MODEL 1 46.5 51 8.8%
MODEL 2 79 73 8.2%
RESULTS
Divergence Dynamic Pressure
33
CONCLUSION
Divergence Results are in Good
Agreement with the Experimental Results
Difference in Results is due to Simplified
Model
Divergence Speed Increase as Wing
Sweep Back Increases
34
DYNAMIC AEROELATIC STUDY
35
Methodology
Model Selection = AGARD 445.6
Geometric ModellingMode Shape and Modal Frequency
Matching
Flutter Boundary Calculation of AGARD
wing
36
AGARD 445.6 WING
37
Holes are Drilled to Reduce Stiffness
Number of Holes are Unknown
Modelling Holes Creates Extra Surfaces
that Increase Processing Time
Problems
Structural Properties are not Well Defined
Modal Matching Requires an Iterative
Process
Dynamic Pressure Matching Requires
Iterative Process
38
Model
39
Mesh
40
Modal Frequency Matching
Density is Tuned to 390 kg/m3 to Match
Modes
41
Mode ANSYS EXPERIMENTAL ERROR
1 9.61 9.6 .1%
2 40.098 38.10 5.2%
3 50.4 50.7 .5%
4 96.63 98.5 1.8%
Mode Shapes
42
Mode 1 Mode 2
Mode Shapes
43
Mode 3 Mode 4
Flutter Analysis
44
Flutter Analysis
General Solution Methods• Time Domain Method
• Frequency Domain Method
Flutter Solution is Mostly Found using
Frequency Domain Method• Simple Technique, Quick Solution
ANSYS uses Time-Domain Method• Average Time per Run ≈ 72 hour
45
Flutter Analysis
46
Setting Desired Mach
Number
Varying Dynamic Pressure
Checking Time
History of Motion
FFT of Time-
History of Motion
Flutter Analysis
Flutter Analysis is Performed at only one
Mach# due to Unbearably Large Solution
Time
Solution Time for one Flutter Test is >72Hr
Dynamic Pressure is Changed at Constant
Mach Number till Flutter is Achieved
47
Result
48
Mach = .9
Dynamic Pressure = 4520 Pa
Flutter Boundary at Mach=.9
(Flutter Dynamic Pressure)
ANSYS
• 4520 Pa
Experimental
• 4500 Pa
49
Flutter Frequency
Error in Tip-Displacement Plot due to Data
Corruption
50
Flutter Frequency
51
Neglecting the First Jump,
Computed Experimental %age Error
Flutter
Frequency(Hz)
17 20.35 16%
Flutter in ANSYS Workbench
The First time, Flutter is Performed in
ANSYS WB.
Flutter Frequency Can be Improved by
making the Mesh more Fine– Adds Solution Time
52
Additional Work
53
Two-way FSI (APDL + FLOTRAN)
54
Two-way FSI
Multi-field Solver(ANSYS
Workbench)
Physics File-Based Procedure
Two-way FSI (APDL + Flotran)
Multi-field Solver(ANSYS Workbench) • Allows FSI of only 3D Geometry
• Element Selection is not Allowed
Physics File-Based Procedure(APDL+Flotran)
• Requires Node to Node Matching Mesh of
Structural and Fluid part
• Problematic in 3D
55
Two-way FSI (APDL + Flotran)
56
Methodology
Modelling Geometry
Element Selection
Defining Morphing Region
Flow Solution
Reading Pressure into a File
Applying Pressure Loads on Structure
Two-way FSI (APDL + Flotran)
Methodology
Send Deformation to Fluid Physics
Morph The Mesh
Solve Fluid Physics
Read Pressure Loads
Apply Pressure on Structure
57
Geometry
58
Results
Tip Motion
59
Results
Streamlines
60
Results
Von-Mises Stress
61
1st Time-Step
Results
Von-Mises Stress
62
Last Time-Step
Conclusion
Significant Changes in Stress if
Deformation is Considered
Accurate Prediction of Lift if Deformation is
Considered
All the Milestones Successfully Achieved
Extra Task of Doing Two-way FSI in APDL
achieved
63
References
Wind-Tunnel Experiments on Divergence of Forward-Swept Wings, NASA Technical
Paper 1685
AGARD Standard Aeroelastic Configurations for Dynamic Response. Candidate
Configuration I.-Wing 445.6, NASA TM-100492
Time and Frequency Domain Flutter Solutions for The AGARD 445.6 Wing
by Ryan J. Beaubien, Fred Nitzsche, and Daniel Feszty
Static Aeroelastic Analysis of the Arw-2 Wing Including Correlation with Experiment
By Joseph P. Hepp
(Department of Mechanical Engineering and Material Science Duke University)
AGARD Report 765, Dynamic Aeroelastic Analysis of AGARD 445.6 Wing
64
Thank You
65
Questions
66