Aeroelasticity in MSC.Nastran

Transcription

1 Aeroelasticity in MSC.Nastran Hybrid Static Aeroelasticity new capabilities - CFD data management Presented By: Fausto Gill Di Vincenzo

2 Hybrid Static Aeroelastic Solution with CFD data 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 Mathematical algorithm to convert CFD pressure into DMIJ cards (Nastran input) (PYTHON language) 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 6/5/2012 2

3 Hybrid Static Aeroelasticity Solution with CFD data 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) 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 Mathematicalprocedure developedin pythonautomaticallyconvertscfd pressuresintodmij Nastrantransformspressureloadtoforcesat AEGRIDsand mapsthemon the structure(spline6/spline7cards) CFD Aerodynamic Mesh extracted from CFD code (AEGRID, AEQUAD..) Rigid AerodynamicMesh with mapped FORCEs NASTRAN Target FE model with mapped FORCEs Aerodynamic Mesh AEPRESS SPLINE 6/7 DMIJ Fringe of Nodad forces Nastrantransforms Pressures in Forces on aerodynamic Grids Load Mapping Structural Model Load mapped on user-defined structural grids CFD Results Static Pressure Field on the Wing 6/5/2012 3

4 Hybrid Static Aeroelasticity Solution with CFD data Application Test Case - UAV TRIM Analysis Sol144 Yacovlev Yak112 UAV Model 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 CAD Model - Ortho View Tuned NASTRAN model - Ortho View FE Model Optimization by Sol 200 Nastran Structural Model Static Pressure field evaluated by CFD and UVLM codes 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) 6/5/2012 4

5 MD Nastran Structural Model Nastran FE Structural Model Side View Front View Ortho View The UAV structural model consists of: Plate for Fuselage, Wings, Fin, Rudder, Tail, Elevator, Spar Beam for Wing Braces Lumped mass for Engine System Wing Area m 2 Full Span 2.36 m Chord m Weight N Cruise Velocity 25 m/s 6/5/2012 5

6 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 The error function to be minimized is defined as: 4 ( ) 2 num ex f i fi 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 e = i= 1 TheMODAL TRACKING allows to follow each natural frequency in the different optimization cycles. Modal Assurance Criterion is internally used to do it 6/5/2012 6

7 Structural Modal Tuning - Sol200 IFASD AEROELASTIC SYSTEM IDENTIFICATION OF A FLYING UAV IN OPERATIVE CONDITIONS Modal tuning of the structural model via SOL 200 -Modal tracking Correlated Structural Modes - Frequencies Modal Assurance Criterion (MAC) 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

8 Hybrid Static Aeroelasticity Solution with CFD data 1 CFD Analysis performed with Fluent Air flowingoverthe LeftWingofthe UAV Freestreem velocity is 25 m/s AOA [ 0 8 ] Sea level values for the freestream properties(inviscid flow) Mesh - Computational Domain Symmetry Boundary Condition Static Pressure field Wall Far Field Ortho View Cutting Plane Three different flight conditions have been performed to create the Rigid Wing Aerodynamic data base AOA = 0 AOA = 4 AOA = 8 Wetted element pressures from CFD Python code Nastran DMIJ (Vector and Matrices operation Algorithm) 6/5/2012 8

9 Hybrid Static Aeroelasticity Solution with CFD data CFD Model Structural Model & CFD Model From CFD code OUTPUT FLUENT Matrix/Vector operation on Pressure Normal vectors on Nodes Getting all Cp Component Aerodynamic Matrix (DMIJ) Nastran input to Nastran Structural Solver Undeformed Aerodynamic Mesh with CFD Aerodynamic load Aerodynamic load mapped on structure SPLINE 6 AEGRID/AEQUAD4 FE 6/5/2012 9

10 From CFD pressure to DMIJ Input of CFD Aerodynamic Pressure on Rigid Aerodynamic Mesh - Validation case (0 Degrees AOA) Fluent- Wetted elements wall Fluent- Coefficient pressure field Fluent- Force report MIN = = N 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 (Direct Matrix Input at js-set of the Rigid Aero Mesh) Nastran- Rigid Aerodynamic Mesh Nastran-Cpon AEGRID (DMIJ) MAX = Nastran- Aero monitor point AEGRID/AEQUAD4 Z - COMPONENT Right Aerodynamic pressure distrubution got by Nastran Automatic process developed in python (SimXpert Customization..) = N 6/5/

11 From CFD pressure to DMIJ CFD Nastran Load Mapping check for 4-8 Monitor Point Application Aerodynamic Pressure mapping - 4 degrees of Angle of Attack Fluent Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Pressure mapping - 8 degrees of Angle of Attack Fluent Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Load is well mapped on the Aero Mesh 6/5/

12 Hybrid Static Aeroelasticity Solution with CFD data RIGID/Flexible Mesh Concepts 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 AEGRID/AEQUAD4 Aerodynamics database given by Fluent Analysis Aero Boxes CAERO1 Cards Aerodynamics given by DLM AOA 0 8 First run Subsequent run Rigid Aerodynamic Loads + Aeroelastic Increment Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data 6/5/

13 Rigid Aerodynamic TRIM with CFD pressure Data NastranSolution( Rigid Aerodynamic data base given by Fluent at [0 4 8 ]) TRIM Variables identified- AOA & Elevator Deflection AOA α The Aircraft is in level flights at 25 m/s with an AOA of about and Elevator deflection of about Aerodynamic Load -Aero Monitor Point on the Left Wing Rigid Aerodynamic database N Fluent Solution Aerodynamic Load - CFD Solution (α ) N Thickness and positive camber effect NastranAerodynamic Load is in good accordance with CFD Solution! 6/5/

14 Hybrid Aeroelastic TRIM with CFD Pressure Data Sol144 TRIM Results Overview - Comparison Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by CFD Flexible increment given by DLM) AOA α 4.44 Standard DLM Approach-(Rigid Aerodynamic given by DLM Flexible increment given by DLM) AOA α 5.86 Trim solution evaluated by using CFD data pressure leads to a value of the AOA lower then that one given by DLM approach Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to the Rigid Aerodynamic database 6/5/

15 Hybrid Static Aeroelasticity Solution with CFD data 2 CFD Analysis performed with XFlow Air flowingoverthe LeftWingofthe UAV Freestreem velocity is 25 m/s AOA [ 0 8 ] Sea level values for the freestream properties(inviscid flow) Computational Domain Boundary Condition Static Pressure at α=0 Wall Far Field Ortho View Cutting Plane Three different flight conditions have been performed to create the Rigid Wing Aerodynamic data base AOA = 0 AOA = 4 AOA = 8 Vertex coefficient pressures from CFD Python code Nastran DMIJ (Vector and Matrices operation Algorithm) 6/5/

16 From CFD Coefficient pressure to DMIJ Input of CFD Coefficient Pressure on Rigid Aerodynamic Mesh - Validation case (0 Degrees AOA) FE Model XFlow- STL Geometry XFlow- Pressure Coefficient field CQUAD4& CTRIA3 Vertex & Polygons From CAD to FE Model (CQUAD4& CTRIA3) via SimXpert or Patran From FEM to STL Geometry (Vertex & Polygons) and Aero Mesh (AEGRID..) CFD simulation and Cp field extracted from Xflow on Vertex From XFlowCp to DMIJ -Python code Aerodynamic Monitor point to check the mapped Aerodynamic load Nastran- Rigid Aerodynamic Mesh Nastran-Cpon AEGRID (DMIJ) XFlow XFlow Force in Z direction = N Nastran- Aero monitor point AEGRID/AEQUAD4 Z -Component = N Aerodynamic pressure is quite well mapped on the Rigid Aerodynamic Mesh.. To be improved by increasing Resolved Scale and Geometry quality

17 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 XFlow Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Pressure mapping - 8 degrees of Angle of Attack XFlow Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Load is quite well mapped on the structure To be improved by increasing Resolved Scale and Geometry quality 6/5/

18 Hybrid Static Aeroelasticity Solution with CFD data RIGID/Flexible Mesh Concepts 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 AEGRID/AEQUAD4 Aerodynamics database given by XFlow Analysis Aero Boxes CAERO1 Cards Aerodynamics given by DLM AOA 0 8 First run Subsequent run Rigid Aerodynamic Loads + Aeroelastic Increment Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data 6/5/

19 Hybrid Aeroelastic TRIM with CFD Pressure Data Sol144 TRIM Results Overview Comparison Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by CFD Flexible increment given by DLM) AOA α 4.31 Standard DLM Approach-(Rigid Aerodynamic given by DLM Flexible increment given by DLM) AOA α 5.86 Trim solution evaluated by using CFD data pressure leads to a value of the AOA lower then that one given by DLM approach Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to the Rigid Aerodynamic database 6/5/

20 Hybrid Static Aeroelasticity Solution with CFD data 3 Aerodynamics performed with UVLM Air flowingoverthe theentiremodelofthe UAV Freestreem velocity is 25 m/s AOA [ 0 8 ] Sea level values for the freestream properties(inviscid flow) UVLM Aerodynamic Model Static Pressure distriutionat α=0 Vortices shed Free vortex wake Ortho View Wetted Panels - Ortho View Rigid Aerodynamic Mesh Wetted Panels - Side View Rigid Aerodynamic Mesh Pressure Data export AOA = 0 AOA = 4 AOA = 8 Free wake formation 6/5/

21 From CFD pressure to DMIJ CFD Nastran Load Mapping check for 0-4 Monitor Point Application Aerodynamic Pressure mapping - 4 degrees of Angle of Attack UVLM Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Pressure mapping - 8 degrees of Angle of Attack UVLM Simulation - Force in Z direction Nastran Rigid Trim Analysis - Monitor Point N N Aerodynamic Load is well mapped on the structure 6/5/

22 Hybrid Static Aeroelasticity Solution with CFD data RIGID/Flexible Mesh Concepts 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 AEGRID/AEQUAD4 Aerodynamics database given by UVLM Analysis Aero Boxes CAERO1 Cards Aerodynamics given by DLM AOA 0 8 First run Subsequent run Rigid Aerodynamic Loads + Aeroelastic Increment Hybrid Static Aeroelasticity Solution (Sol144) with CFD Pressure data 6/5/

23 Hybrid Aeroelastic TRIM with UVLM Pressure Data Sol144 TRIM Results Overview Comparison Hybrid Rigid-Flexible Mesh Approach (Rigid Aerodynamic given by UVLM Flexible increment given by DLM) AOA α 4.28 Standard DLM Approach-(Rigid Aerodynamic given by DLM Flexible increment given by DLM) AOA α 5.86 Trim solution evaluated by using UVLM data pressure leads to a value of the AOA lower then that one given by DLM approach Static Aerodynamic effect due to Airfoil geometry (Camber, thickness) taken into account tanks to the Rigid Aerodynamic database 6/5/

24 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: 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 6/5/