Aeroelasticity in MSC.Nastran

Hybrid Static Aeroelasticity new capabilities - CFD data management

Presented By: Fausto Gill Di Vincenzo04-06-2012

MSC.Nastran 2010 new capabilities into Static Aeroelasticity - Sol144

• Input of CFD Aerodynamic Pressures on a Rigid Aerodynamic Mesh

AEPRESS/DMIJ & AEGRID/AEQUAD4/AETRIA3 Cards

• New 6 DOF Load Mapping Technology

SPLINE 6/7 Cards

Automatic Procedure developed for Hybrid Static Aeroelastic Simulation

Hybrid Static Aeroelastic Solution with CFD data

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Steady 1-g Load (TRIM analysis) using external Aerodynamic Pressure

• By carrying out a CFD simulation (covered in this presentation)

• By using Wind Tunnel Test data

Automatic Procedure developed for Hybrid Static Aeroelastic Simulation

• Mathematical algorithm to convert CFD pressure into DMIJ cards (Nastran input)

(PYTHON language)

• An aerodynamic mesh is to be created in terms of AEGRID, AEQUAD4/AETRIA3 Cards

• Aerodynamic Pressure applied at the aerodynamic grid points AEGRID by using AEPRESS/DMIJ Cards

• Mathematical procedure developed in python automatically converts CFD pressures into DMIJ

Use of pressures which come from an external source (CFD analysis / Wind Tunnel Tests)

(Only available in Static Aeroelasticity Sol144 or Sol200 with ANALYSIS=SAERO option)

Nastran transforms pressure load to forces at AEGRIDs and maps them on the structure (SPLINE6/SPLINE7 Cards)

Aerodynamic Mesh extracted from

CFD code (AEGRID, AEQUAD..)

CFD

NASTRAN

Hybrid Static Aeroelasticity Solution with CFD data

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Static Pressure Field on the Wing

Target FE model with

mapped FORCEs Rigid Aerodynamic Mesh with

mapped FORCEs

Aerodynamic Mesh extracted from

CFD code (AEGRID, AEQUAD..)

SPLINE 6/7

Load Mapping

AEPRESS

DMIJ

CFD Results

Aerodynamic Mesh

Nastran transforms Pressures in

Forces on aerodynamic Grids

NASTRAN

Fringe of Nodad forces Structural Model

Load mapped on user-defined

structural grids

Application Test Case - UAV TRIM Analysis Sol144Yacovlev Yak112 – UAV Model

CAD Model - Ortho View

Flight condition parametres

• M=0.07 Sea Level• Straight and level case under 1g loading• Flight velocity 25 m/s � q=382 Pa

Free trim variables

• Angle of attack• Angle of Elevator

FE Model

Tuned NASTRAN model - Ortho View

Nastran

Hybrid Static Aeroelasticity Solution with CFD data

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Optimization by Sol 200

NastranStructural Model

• 1. Aerodynamic Pressures by Fluent mesh-based CFD code - Only left Wings (Tail & Elevator by UVLM)

• 2. Aerodynamic Pressures by Xflow meshless CFD code - Only left Wings (Tail & Elevator by UVLM)

• 3. Aerodynamic Pressures by UVLM code (ZONA Technology) - Wings, Tail & Elevator (beta testing)

Static Pressure field evaluated by CFD and UVLM cod es

MD Nastran Structural Model

Side View

Nastran FE Structural Model

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The UAV structural model consists of:

Plate for Fuselage, Wings, Fin, Rudder, Tail, Elevator, Spar

Beam for Wing Braces

Lumped mass for Engine System

Front View Ortho View

• Wing Area 0.948 m2

• Full Span 2.36 m

• Chord 0.402 m

• Weight 134.394 N

• Cruise Velocity 25 m/s

Validation - Modal tuning through Sol 200

Modal tuning of the structural model via SOL 200

• An internal OPTIMIZATION TOOL of MD Nastran has been used to built a

numerical finite element model that accurately represents the structural

dynamic behavior of the experimantal model

• SOL 200 has been exploited to perform the modal optimization

• An error function based on the lowest four natural frequencies of the structure has

been defined as objective function

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been defined as objective function

• The error function to be minimized is defined as:

• The chosen design variables are the elastic parameters of the orthotropic material

• Density has been kept constant in order to obtain the actual mass of the UAV

• The MODAL TRACKING allows to follow each natural frequency in the

different optimization cycles.

• Modal Assurance Criterion is internally used to do it

( )24

1∑

=

−=i

exi

numi ffe

Structural Modal Tuning - Sol200IFASD-2009-166 “AEROELASTIC SYSTEM IDENTIFICATION OF A FLYING UAV IN OPERATIVE CONDITIONS”

Modal Assurance Criterion (MAC)Correlated Structural Modes - Frequencies

• Modal tuning of the structural model via SOL 200 - Modal tracking

• Mode shape comparison

Correlated mode shapes - Num

Correlated mode shapes – Exp

After the optimization process the sequence of the numerical natural

frequencies is exactly the same than that one of the experimental ones

1°°°° CFD Analysis performed with Fluent

Boundary ConditionMesh - Computational Domain Static Pressure field

Far Field

Symmetry

Wall

• Air flowing over the Left Wing of the UAV

• Freestreem velocity is 25 m/s

• AOA [ 0°÷ 8°]

• Sea level values for the freestream properties (Inviscid flow)

Hybrid Static Aeroelasticity Solution with CFD data

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Cutting Plane

Ortho View

• AOA = 0°°°°

• AOA = 4°°°°

• AOA = 8°°°°

Three different flight conditions have been performed to create the “Rigid” Wing Aerodynamic data base

Wetted element pressures from CFD Python code Nastran DMIJ

(Vector and Matrices operation Algorithm)

Hybrid Static Aeroelasticity Solution with CFD data

From CFD code

Aerodynamic

Normal vectors on Nodes

Structural Model & CFD Model

Matrix/Vector

operation on Pressure

CFD Model

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AEGRID/AEQUAD4

Aerodynamic load mapped on structure

to Nastran Structural Solver

SPLINE 6

Undeformed Aerodynamic Mesh

with CFD Aerodynamic load

OUTPUT

FLUENT

Aerodynamic

Matrix (DMIJ)

Nastran input

Getting all Cp

Component

operation on Pressure

FE

Fluent - Coefficient pressure field

From CFD pressure to DMIJ

Fluent - Wetted elements wall Fluent - Force report

FZ = 14.167403 NMIN =- 0.597

Wetted elements transformed into AEGRID/AEQUAD4 - Rigid Aerodynamic Mesh

Input of CFD Aerodynamic Pressure on Rigid Aerodynamic Mesh - Validation case (0 Degrees AOA)

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Nastran - Cp on AEGRID (DMIJ)Nastran - Rigid Aerodynamic Mesh

AEGRID/AEQUAD4 Z - COMPONENT

Nastran - Aero monitor point

FZ = 14.17238 N

MAX = 0.596

Wetted elements transformed into AEGRID/AEQUAD4 - Rigid Aerodynamic Mesh

Pressures on wetted elements transformed into AEGRID Cp - DMIJ

Aerodynamic monitor point to check the mapped load on rigid aerodynamic mesh – Aero database

Right Aerodynamic pressure distrubution got by Nastran

(Direct Matrix Input at js-Set of the Rigid Aero Mesh)

Automatic process developed in python (SimXpert Customization..)

CFD ���� Nastran Load Mapping check for 4 °°°°- 8°°°°

Fluent Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

Monitor Point Application

• Aerodynamic Pressure mapping - 4 degrees of Angle of Attack

61.355213 N

61.29341 N

From CFD pressure to DMIJ

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Aerodynamic Load is well mapped on the Aero Mesh

Fluent Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

• Aerodynamic Pressure mapping - 8 degrees of Angle of Attack

106.68246 N

61.29341 N

106.5416 N

• Nastran support the ability to generate the rigid aerodynamic loads on one mesh while the aeroelastic

increment is generated from a second mesh. Separate Rigid and Flexible Aero Meshes needed.

Rigid Aerodynamic Mesh Flexible Aerodynamic Mesh

Hybrid Static Aeroelasticity Solution with CFD dataRIGID/Flexible Mesh Concepts

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Rigid Aerodynamic Loads Aeroelastic Increment

First run Subsequent run

Aerodynamics given by DLM

+

AEGRID/AEQUAD4 Aero Boxes – CAERO1 Cards

AOA 0°÷ 8°

Aerodynamics database given by Fluent Analysis

Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data

TRIM Variables identified - AOA & Elevator Deflection

Aerodynamic Load - Aero Monitor Point on the Left Wing

AOA

Rigid Aerodynamic TRIM with CFD pressure Data• Nastran Solution (“Rigid” Aerodynamic data base given by Fluent at [0°4°8°])

The Aircraft is in level flights at 25 m/s with an AOA of about 4.285°and Elevator deflection of about 1.252°

α ≈ 4.185°°°°

Rigid Aerodynamic database

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FZ

Nastran Aerodynamic Load is in good accordance with CFD Solution!

FZ

Aerodynamic Load - CFD Solution (α ≈ 4.185°°°°)

• Fluent Solution

Thickness and positive camber effect

63.04 N

63.52 N

Sol144 TRIM Results Overview - Comparison

• Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by CFD – Flexible increment given by DLM)

AOA

α ≈ 4.44°°°°

Hybrid Aeroelastic TRIM with CFD Pressure Data

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• Standard DLM Approach - (Rigid Aerodynamic given by DLM – Flexible increment given by DLM)

Trim solution evaluated by using CFD data pressure leads to a value of the AOA lower

then that one given by DLM approach

AOA

α ≈ 5.86°°°°

Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to

the Rigid Aerodynamic database

2°°°° CFD Analysis performed with XFlow

Boundary ConditionComputational Domain Static Pressure at α=0°°°°

Far FieldWall

• Air flowing over the Left Wing of the UAV

• Freestreem velocity is 25 m/s

• AOA [ 0°÷ 8°]

• Sea level values for the freestream properties (Inviscid flow)

Hybrid Static Aeroelasticity Solution with CFD data

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Cutting Plane

Ortho View

• AOA = 0°°°°

• AOA = 4°°°°

• AOA = 8°°°°

“Vertex” coefficient pressures from CFD Python code Nastran DMIJ

(Vector and Matrices operation Algorithm)

Three different flight conditions have been performed to create the “Rigid” Wing Aerodynamic data base

FE Model XFlow - STL Geometry XFlow - Pressure Coefficient field

CQUAD4 & CTRIA3 Vertex & Polygons

From FEM to STL Geometry (Vertex & Polygons) and Aero Mesh (AEGRID..)

XFlow

From CAD to FE Model (CQUAD4 & CTRIA3) via SimXpert or Patran

From CFD Coefficient pressure to DMIJInput of CFD Coefficient Pressure on Rigid Aerodynamic Mesh - Validation case (0 Degrees AOA)

XFlow – Force in Z direction

FZ = 16.80 NFrom FEM to STL Geometry (Vertex & Polygons) and Aero Mesh (AEGRID..)

From XFlow Cp to DMIJ - Python code

Aerodynamic pressure is quite well mapped on the Rigid Aerodynamic Mesh..

CFD simulation and Cp field extracted from Xflow on Vertex

Z - Component

Nastran - Aero monitor pointNastran - Cp on AEGRID (DMIJ)

To be improved by increasing Resolved Scale and Geometry quality

Nastran - Rigid Aerodynamic Mesh

FZ = 16.80 N

FZ = 17.28 N

Aerodynamic Monitor point to check the mapped Aerodynamic load

AEGRID/AEQUAD4

XFlow Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

60.67 N

62.12 N

From CFD Coefficient pressure to DMIJ

CFD ���� Nastran Load Mapping check for 4 °°°°- 8°°°° Monitor Point Application

• Aerodynamic Pressure mapping - 4 degrees of Angle of Attack

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Aerodynamic Load is quite well mapped on the struct ure

XFlow Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

109.5 N

107.17 N

To be improved by increasing Resolved Scale and Geometry quality

• Aerodynamic Pressure mapping - 8 degrees of Angle of Attack

• Nastran support the ability to generate the rigid aerodynamic loads on one mesh while the aeroelastic

increment is generated from a second mesh. Separate Rigid and Flexible Aero Meshes needed.

RIGID/Flexible Mesh Concepts

Rigid Aerodynamic Mesh Flexible Aerodynamic Mesh

Hybrid Static Aeroelasticity Solution with CFD data

6/5/2012 18

Rigid Aerodynamic Loads Aeroelastic Increment

First run Subsequent run

Aerodynamics given by DLM

+

AEGRID/AEQUAD4 Aero Boxes – CAERO1 Cards

AOA 0°÷ 8°

Aerodynamics database given by XFlow Analysis

Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data

Sol144 TRIM Results Overview – Comparison

AOA

α ≈ 4.31°°°°

Hybrid Aeroelastic TRIM with CFD Pressure Data

• Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by CFD – Flexible increment given by DLM)

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• Standard DLM Approach - (Rigid Aerodynamic given by DLM – Flexible increment given by DLM)

Trim solution evaluated by using CFD data pressure leads to a value of the AOA lower

then that one given by DLM approach

AOA

α ≈ 5.86°°°°

Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to

the Rigid Aerodynamic database

3°°°° Aerodynamics performed with UVLM

UVLM Aerodynamic Model Static Pressure distriutionat α=0°°°°

• Air flowing over the the entire model of the UAV

• Freestreem velocity is 25 m/s

• AOA [ 0°÷ 8°]

• Sea level values for the freestream properties (Inviscid flow)

Vortices shed

Free vortex wake

Hybrid Static Aeroelasticity Solution with CFD data

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Ortho View

Rigid Aerodynamic Mesh

Wetted Panels - Ortho View

• AOA = 0°°°°

• AOA = 4°°°°

• AOA = 8°°°°

Wetted Panels - Side View

Pressure Data export

Rigid Aerodynamic Mesh

Free wake formation

UVLM Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

21.3592 N

21.3583 N

CFD ���� Nastran Load Mapping check for 0 °°°°- 4°°°° Monitor Point Application

From CFD pressure to DMIJ

• Aerodynamic Pressure mapping - 4 degrees of Angle of Attack

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Aerodynamic Load is well mapped on the structure

UVLM Simulation - Force in Z direction Nastran “Rigid” Trim Analysis - Monitor Point

FZ

FZ

FZ 60.4669 N

21.3583 N

60.4681 N

• Aerodynamic Pressure mapping - 8 degrees of Angle of Attack

• Nastran support the ability to generate the rigid aerodynamic loads on one mesh while the aeroelastic

increment is generated from a second mesh. Separate Rigid and Flexible Aero Meshes needed.

Rigid Aerodynamic Mesh Flexible Aerodynamic Mesh

RIGID/Flexible Mesh Concepts

Hybrid Static Aeroelasticity Solution with CFD data

6/5/2012 22

Rigid Aerodynamic Loads Aeroelastic Increment

First run Subsequent run

Aerodynamics given by DLM

+

AEGRID/AEQUAD4 Aero Boxes – CAERO1 Cards

AOA 0°÷ 8°

Aerodynamics database given by UVLM Analysis

Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data

Sol144 TRIM Results Overview – Comparison

AOA

α ≈ 4.28°°°°

• Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by UVLM – Flexible increment given by DLM)

Hybrid Aeroelastic TRIM with UVLM Pressure Data

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• Standard DLM Approach - (Rigid Aerodynamic given by DLM – Flexible increment given by DLM)

Trim solution evaluated by using UVLM data pressure leads to a value of the AOA

lower then that one given by DLM approach

AOA

α ≈ 5.86°°°°

Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to

the Rigid Aerodynamic database

Concluding Remarks

• It is now possible to use Aerodynamic Pressure data evaluated by a general CFD

or UVLM code in Static Aeroelasticity Analysis Sol 144

• The SPLINE6/7 load mapping technology transfers correctly the aerodynamic load

to the structure

• Monitor point is an important and essensial tool to check the Aero Load Mapping

• A new procedure able to use “external” aerodynamic pressure in Static

Aeroelasticity has been verified for:

6/5/2012 24

• a commercial CFD “mesh-based” code - Fluent

• a commercial CFD “meshless” code - Xflow MSC.Software

• an UVLM code “panel method” - Zona Technology

• A Mathematical algorithm to automatically convert pressures into DMIJ matrix

has been developed by using python programming language

• Possible future applications:

• Customize all the automatic procedure into SimXpert (python..)

• Load mapping of the entire Aircraft