international modefrontier users’ meeting 2010

International modeFRONTIER

Users’

Meeting 2010Applications of modeFRONTIER

on Aeronautical

Problems: an overview of experiences at the German Aerospace Centre (DLR)

Joël

Brezillon*, Frederic Guntzer Institute of Aerodynamics and Flow Technology

*Head of MDO group -

Braunschweig

J. Brezillon > UM10 > Mai 2010 > Folie 2

1.

General presentation2.

Optimisation of an Aircraft in Take-Off Configuration

3.

Optimal Noise Abatement Flight Procedures4.

Design of a Small Size Super-Sonic Aircraft

5.

Conclusion

Outline


Institute of Aerodynamics and Flow Technology (AS)

Braunschweig / Göttingen

C.-C. Rossow / A. Dillmann


Köln-Porz

Göttingen

~ 270 Employees

Braunschweig: ~ 135 Employees

Braunschweig

Göttingen / Köln: ~ 135 Employees

Site Locations


Covering the complete regime of flow speeds

Research Areas


Scientific Core Competencies

Multidisciplinary Numerical Simulation and Optimization

Measurement Technologies and Experimental Validation

Conceptual Design and Configuration Analysis

Aerodynamic Design and Analysis

Aeroacoustic

Prediction and Noise Reduction

Aerothermodynamic

Design and Analysis

Flow Technology


Identification and development of high-fidelity technologies needed in MDO contextin aerodynamics, structure and acousticsin optimisation strategies and architectures

Set up of MDO environment based on mixed high/low fidelities methodsApplication on realistic design configurationsDevelopment of fit purpose optimisation processes and strategies

Multi-Disciplinary Optimisation Process Group

2004: first license of modeFRONTIER (V3.0.2) and application on academicals cases2005: support ESTECO on the design of interface for the use of external gradient2006: first application of NLPQLP with external gradient capability on 2D CFD problem2007: same application on 3D CFD problem2008-09: Multi-objective optimisation of a supersonic business jet 2009: search to the optimal noise abatement flight procedures2010: successful use of krigging approach to solve multi-objectives problem

Mainly used on problems with limited number of variables (~ 20), on multi-objective optimisation problems or on multi-modal design spaces

modeFRONTIER

at DLR-AS

Flap and slat setting optimisation of an aircraft in take-off configuration


Aircraft in take-off configuration

>1.5VS>1.23VS

>1.13VS

1.13VS

>1.25VS

1.2VS

Airbus A319 with high-lift devices deployed

TAKE-OFF PERFORMANCE

REGULATIONS

min. climb angles

over speed related to VS

engine failure

max. touch-down speed

fast climb to cruise flight level

high altitude at overflow noise point


Aircraft in take-off configuration

Airbus A319 with high-lift devices deployed

TAKE-OFF PERFORMANCE

REGULATIONS

min. climb angles

over speed related to VS

engine failure

max. touch-down speed

fast climb to cruise flight level

high altitude at overflow noise point

Question: what is the optimal position of the high-lift devices to meet the required performance ?


Aerodynamic flow around a wing in take-off configuration

Flow is viscous and compressibleComputational Fluid Dynamics (CFD) based on Reynolds-Average Navier-Stokes solver recommended


Test case specification

Configuration

DLR-F11 geometry in take-off configuration

Objective and constraints

Maximization of

CL > CLinitial

Penalty to limit the deployment of the flap and slat (constraints from the kinematics of the high-lift system)

To complete the optimisation within 2 weeks turn-around time

Flow conditions

M

=0.2 ; Re=20x106 ; =8 º

2

3

33

D

D

CDCLOBJ


Design parameter Objective

Aerodynamic optimisation process

based on CFD solver

Optimiser

Parametrisation

Mesh process

Analysis

Drag 102 Lift 1.23Moment -0.542

CFD solver


F

Gap

-O/L

O/L

O/LGap

S

O/L

DoFDoF

Flap & slat position and deflection, constant along spanParametrisation of the geometry with ICEM-CFD (new position and intersection lines between body and slat/flap)

Parametrisation


Mesh Procedure

Smooth meshto capture the wakes

Mesh generated with ICEM-HexaAbout 2.5 Millions pts in totalSmooth mesh to capture wakes73 pts above the main wing for the wake49 pts between main wing and flat

CFD solverHybrid solver DLR-TAU2nd order accurate methodsfully parallel solversPreconditioning for low Mach numberViscous computation with Spalart-Allmaras-Edwards turb. modeladjoint capability (for fast computation of sensitivities)


Computation of the sensitivity using adjoint

approach

Good agreement between central finite differences and adjoint computations

2

3

)grad(CDCL

OBJ


Process in modeFRONTIER


modeFRONTIER

4.0NLPQLP for fast convergence12 cycles, 13 Aero. evaluations, 2*12 adjoint computationsComputation of the aerodynamic flow on a Linux cluster with 32 proc.Computation of the adjoint flows (CD and CL) on 2 Linux clusters with 16 proc. each3 hours for CFD, 2 hours for AdjointFull optimisation in less than ~ 3 days of computations

Optimisation Strategies


Synthesis

Leading edge slat Trailing edge flap

Final slat and flap positions for a given span position


ConclusionDLR developed a computational chain to predict the aerodynamic performance of aircraft in take-off configuration.The time for each simulation is of about 3 hours wall clock time.To complete the optimisation within a reasonable turn around time, the use of gradient based strategy is advisable. In combination of efficient gradient computations (like the adjoint approach in CFD), the procedure is highly efficient and permit to cut down the simulation time.The NLPQLP optimisation combined with the possibility to read the gradient in modeFRONTIER has permitted to reach this goal.

Reference: Numerical Aerodynamic Optimisation of 3D High-Lift Configurations J. Brezillon, R.P. Dwight, J. Wild 26th International Congress of The Aeronautical Sciences, Sept. 2008 Anchorage, USA

Optimal Noise Abatement Flight Procedures of an EC-135

From Frédéric Guntzer, Pierre Spiegel, Markus Lummer and presented at the 35th European Rotorcraft Forum,

September 22-25, 2009, Hamburg, Germany


Noise Abatement Flight Procedure

Flight path

noise directivities on hemisphere

Ground

EC135 at landing phase

Objective: Finding a feasible flight path that produces the minimum noise at the ground

Problem: Finding a feasible flight path that produces the minimum noise at the ground


Requirements of the simulation

Cover all noise sources of an helicopter: main rotor, tail rotor, engine, interaction and installation effects.Able to simulate arbitrary procedure noise footprint.Wind effects taken into account:

On flight conditionsOn noise propagation

Ensure flyable procedureCheck criterion on comfortable flightGuarantee safe flight manoeuvre: check avoidance of Vortex Ring State and ensure compatibility with safety requirement in case of engine failure, ensure marging to autorotation….


Noise propagated on ground including atmospheric/ground

effects

1. Generation of flight path and velocity evolution using cubic splines

2. Flight dynamics calculation of flight conditions (PmAlpha, RmCT, RmMu) and source attitude

using HOST code.

3. HEMISPHERE 2

At each selected steps do step 2 & 3

1

n

t1.1t1.m

tn.m

Control points with velocity at these points

The SELENE noise computation chain of arbitrary flights (Sound Exposure Level starting from the Emitted Noise Evaluation)

DATA BASE of noise directivities on

hemisphere from flight test conducted in 2004


SELENE and optimization loop flowchart overview

Conditions for Noise Abatement Flight Procedure (Input)

Ensure Flyable procedure generation

Noise on ground simulation

HEMISPHERE 2

Optimizer: ModeFrontier


Procedure optimization parameters

Final conditions fixed: landing point position and zero velocity

Flight path within a vertical plane

Control of the flight path with 4 free control points : 4 x 2 coordinates + 4 velocity/ground magnitudes = 12 DoF

For some optimizations initial velocity and/or initial height were set free: up to 14 degrees of freedom (DoF) ‏

Optimiser: Multi-Objective Genetic Algorithm (MOGA II)Generations from 50 to up to 500 individualsSimultaneous evaluation on Linux Cluster with up to 32 processors80.000 iterations within 2 days wall clock time


Verification of the optimised flight procedure Flights test campaign in 2008

Microphones layout in Cochstedt

Reference flight procedure

Tip path plane

Real path of the helicopter

Horizontal velocity

Optimised flight procedure

Ideal path of the helicopter


Verification of the optimised flight procedure Flights test campaign in 2008

Tip path plane

Horizontal velocity

Optimised flight procedure

Reference flight procedure

Noise Footprint (dBA) at the ground measured with 33 microphonesResults assembled from

2 flightsOptimised flight procedure has permitted to:

decrease maximum noise of about 5dBA

60% reduction of area with more than 80 dB


Conclusion

DLR developed a computational chain to model noise of arbitrary flight procedures (SELENE)

Coupled with optimisation strategies, the procedure is able to design optimal noise abatement flight procedure

The design space seems to be multi-modal and required robust and global optimisation strategy: the use of ARMOGA-II with simultaneous evaluation has demonstrated the capability to find good minimum in limited turn around time

The prediction of the noise abatement for the optimal flight procedure is confirmed by flight testing

Reference: Genetic Optimizations of EC-135 Noise Abatement Flight Procedures using an Aeroacoustic Database Frédéric Guntzer, Pierre Spiegel, Markus Lummer 35th European Rotorcraft Forum, September 22-25, 2009, Hamburg, Germany.

Design of a Small Size Super Sonic Aircraft


Motivation

The general objectives of the EU project HISAC (High Speed Aircraft project) was to assess the technical feasibility of environmental compliant supersonic small size transport aircraftsThe commercial characteristics are

Size of cabin for 8 to 16 passengersSpeed up to Mach 1.8Range up to 5000 nm

The DLR contribution was to evaluate the performance potential of given SuperSonic Bussiness Jet concepts using MDO process based on high-fidelity methods.

High-fidelity methods are the best candidate to correctly consider the complex multi-disciplinary interactions that occur on supersonic configuration.

High-fidelity methods (CFD, CSM, …) have reached a mature stage and are routinely used for analysis and assessment of aircraft configurations

DLR, NLR and Onera joint effort to set up such a MDO process


Realistic transport mission is modelledFour coupled disciplines:

AerodynamicStructureEngineFlight mechanic

High-Fidelity for aerodynamic (cruise) and structure (+2.5g load case)Low-Fidelity for engine, flight mechanic & other flight conditionsOptimisation strategy: MD Analyse driven by optimisation hierarchyNLR provides a core MDA processOnera provide module to compute sonic boom MDO process constructed and applied by DLR Baseline configuration: Low Sonic Boom concept

Multi-Disciplinary Analyse and Optimisation


Design of a Small Size SuperSonic

AircraftCommon process chain with NLR and Onera


MDO process operational at DLR

Global optimiser: ARMOGA

Global optimiser: ARMOGA

FEM solver:NASTRAN

FEM solver:NASTRAN

DLR flowsolver: FLOWer

DLR flowsolver: FLOWer

Mesh Generation:

ICEM-CFD

Mesh Generation:

ICEM-CFD


Process in modeFRONTIER


Objective:Wing planform optimisation of a low sonic boom supersonic business jet.

Strategy:Adaptive Range Multi-Objective Genetic Algorithm (ARMOGA) as global optimiser

Minimise the sonic boom impact at the groundMinimise the Maximum Take-Off Weight (MTOW)Maximise the range

Population with 50 individuals, initialised with LHS Each analysis takes 1 hour on cluster with 8 cpu

Parametrisation:13 geometrical parameters + MTOW (!) for the global optimiser201 internal wing structural elements supporting structural sizing

Design of a Small Size SuperSonic Aircraft


+ twist & thicknesses @ C1, C2, C3

Beam, spar and cover thicknesses

Local

(201)

Global (13)

Design variables


Results:40 generations (2.000 evaluations)200 hours wall clockDecrease MTOW by 1 TDecrease Noise level by 1.7 dBAIncrease range by 263 Nm.

Design of a Small Size SuperSonic Aircraft


Conclusion

modeFRONTIER has been successfully used at DLR-AS since 2004 for solving wide range of aeronautical problems: drag reduction of wing in cruise configuration, aerodynamic improvement of aircraft in take-off, multi-disciplinary design of small size supersonic aircraft, optimal noise abatement flight procedures of an EC-135, ….

modeFRONTIER offers a bright range of useful optimisation strategies, ranking from efficient gradient based approach (NLPQLP) to robust multi-objective strategies (ARMOGA, MOGA).

What’s next ?


Thank you ! for your attention

international modefrontier users’ meeting 2010

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