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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.

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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

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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

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METHODOLOGY

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Dynamic Aeroelastic Analysis

Results and Discussion on StabilityParameters

Conclusion

Recommendations

Aeroelasticity and ANSYS 13

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A Coupled Field

– No flexibility, No Aeroelasticity

– Max Wingtip Displacement of Boeing 747=24 ft

Serious Threat to Flight Safety

Aeroelasticity

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Aeroelasticity

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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

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ANSYS 13

ANSYS 13 Capabilities....

Flow Analysis: CFX/Fluent

Meshing: ICEM CFD

Two Way FSI: Multi-field Solver

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ANSYS 13

One Way FSI

ANSYS MECHANICAL-

FLUENT/CFX

Two Way FSI

ANSYS MECHANICAL-

CFX

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TWO WAY FSI

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DEMONSTRATION OF TWO WAY FSI

Model: 2D Plate

Material: Structural Steel

Element Type: Solid 186

Initial Disturbance and Left Free

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COUPLING

Transient Structural and CFX

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Tip Displacement

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TWO-WAY FSI

1st Time-step

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Results

Damping Motion Shows Transfer of Loads

between Fields

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STATIC AEROELASTIC ANALYSIS

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STATIC AEROELASTIC ANALYSIS

Model Selection : NASA Wind-Tunnel

Experiments on Divergence of Forward

Swept Wing(Aug 1980)

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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˚

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Experimental Results

MODEL 1(-30 Sweep) MODEL 2(-15 Sweep)

DIVERGENCE

SPEED(m/s)

51 73.41

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Ref: Wind-Tunnel Experiments on Divergence of Forward-Swept Wings,

NASA Technical Paper 1685

MODEL 1 = -30˚

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MODEL 1: -30˚

Model

Transition Strip is not Modelled

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Monitor Point

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Velocity = 45m/s

Divergence Speed(-30˚ Sweep)

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V= 48 m/s V= 45 m/s

Divergence Speed ≈ 46.5 m/s

DEFORMATION

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Velocity = 48 m/s

MODEL 2 = -15˚

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Wingtip Displacement

Velocity = 75 m/s

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Velocity = 80 m/s

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Wingtip Displacement

Divergence Speed(-15˚ Sweep)

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V= 80 m/s V= 78 m/s

Divergence Speed≈ 79 m/s

RESULTS

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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

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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

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DYNAMIC AEROELATIC STUDY

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Methodology

Model Selection = AGARD 445.6

Geometric ModellingMode Shape and Modal Frequency

Matching

Flutter Boundary Calculation of AGARD

wing

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AGARD 445.6 WING

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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

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Model

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Mesh

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Modal Frequency Matching

Density is Tuned to 390 kg/m3 to Match

Modes

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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

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Mode 1 Mode 2

Mode Shapes

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Mode 3 Mode 4

Flutter Analysis

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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

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Flutter Analysis

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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

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Result

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Mach = .9

Dynamic Pressure = 4520 Pa

Flutter Boundary at Mach=.9

(Flutter Dynamic Pressure)

ANSYS

• 4520 Pa

Experimental

• 4500 Pa

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Flutter Frequency

Error in Tip-Displacement Plot due to Data

Corruption

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Flutter Frequency

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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

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Additional Work

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Two-way FSI (APDL + FLOTRAN)

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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

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Two-way FSI (APDL + Flotran)

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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

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Geometry

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Results

Tip Motion

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Results

Streamlines

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Results

Von-Mises Stress

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1st Time-Step

Results

Von-Mises Stress

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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

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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

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Thank You

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Questions

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