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Copyright © ESI Group, 2015. All rights reserved.
www.esi-group.com
Copyright © ESI Group, 2015. All rights reserved.
Wind characterization around
offshore platform for real-time
helicopter simulator
Stefano Scala
Aeronautical Engineer – TXT NEXT
October 19 – 21 – Stuttgart, Germany
2www.esi-group.com
Copyright © ESI Group, 2015. All rights reserved.
Introduction
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
TXT NEXT is a valuable partner that can support aircraft manufacturers in the development of the state-of-the-art training and operational solutions
AgustaWestland is committed to be a worldwide leader in the rotary wing industry by delivering best-in-class products and services and focusing on customer satisfaction, sustainable business, integrity and value creation.
Training Helicopter Support System Department
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Copyright © ESI Group, 2015. All rights reserved.
Flight Simulation Training Devices
Introduction
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• Development of Full Flight Simulators Lev. D Devices
• Devices that re-create aircraft flight and the environment for pilot training
• Each Full Flight Simulator performances are analyzed against aircraft flight data to ensure that its handling characteristics are representative of real helicopter
• Flight Simulator allow training of critical – emergency conditions in a safe, but yet realistic environment
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Aerodynamic effects in ground proximity operations
Introduction
• Atmospheric conditions can compromise mission effectiveness
• Atmospheric phenomena may vary according to ground obstacles
• Ground proximity operations are among the most dangerous flight phases
• The correct modeling of atmospheric conditions is crucial to allow the trainee pilot to exercise for these critical and complex maneuvers in a cost-effective and safe way
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Our approach
Introduction
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• 3d moving models from Visual System
• CFD computation
• Local velocity tables in grid points
• Run-time query to extract data
• Airwake model algorithm
• Local velocity in hc control points
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Copyright © ESI Group, 2015. All rights reserved.
3D model
CFD Computation
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
Oilrig Landable Ship
• 4 oil rigs models
• 2 ships models
• Models provided in Stereolithography (STL) format
• Mesh generation using snappyHexMesh
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OpenFoam analysis
CFD Computation
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
Boundary conditions
• 36 wind directions (every 10°) obtained rotating the 3D model
• 5 intensity of wind (5,15,25,35,45 knots)
• 180 standalone simulations for each model
Turbulence model
• SimpleFOAM with a stationary incompressible k-ԑ turbulence RANS model
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Copyright © ESI Group, 2015. All rights reserved.
Mesh parameters
CFD Computation
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
External domain:
200 x 1150 x 150 meters
60 x 230 x 30 cells
Refinement domain:
100 x 150 x 70 meters
Total 1.3x106 cells
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Copyright © ESI Group, 2015. All rights reserved.
Results
CFD Computation
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• Velocity components stored in a table of about 35Mb
• Time required for a single run of about 2h.
• Total time for a 3D model: 6 Gb and 15 days.
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Results
CFD Computation
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• Stream tracer on the backside of
the oilrig with 0° and 45 knots
• Stream tracer of a vortex generated
on the oil rig with 0° and 45 knots
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Copyright © ESI Group, 2015. All rights reserved.
Requirements
Integration
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• The goal.
‣ Provide run-time local wind to flight model
• The challenge.
‣ Real time environment (120 Hz frequency).
‣ Select right CFD computation depending on boundary conditions
‣ Manage such a big amount of data
‣ Local wind velocities in grid points only
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Database extraction (1)
Integration
• Database to store all the bulk of data produced by CFD.
• Algorithm for DB data extraction depending on
‣ Asymptotic wind speed
‣ Asymptotic wind direction
‣ 3Dmodel – HC distance
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
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Copyright © ESI Group, 2015. All rights reserved.
Database extraction (2)
Integration
• Extraction of portion of points
‣ Nearest to helicopter
‣ Depending on helicopter attitude and airspeed
‣ Less points means faster query
• New query when hc is about to leave the portion obtained with previous query
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
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Helicopter control points
Integration
• 95 HC control points
‣ 81 Main rotor
‣ 9 Tail rotor
‣ 2 Horizontal stab
‣ 1 Tail fin
‣ 1 Fuselage
‣ 1 Pitot tube
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
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Run-time algorithm
Integration
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
For each helicopter control point:
• Evaluate distance between hc point and grid points
• Identify the 8 grid points closest to hc point and extract wind components on these points
• Calculate wind components in hc point using a linear interpolation weighted on distance of the 8 points previously selected
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Copyright © ESI Group, 2015. All rights reserved.
Unsteady effects
Integration
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• Stationary CFD approach:
‣ Best trade-off between run-time requirements and our goal of improving fidelity of simulation during takeoff, approach and landing
‣ Unsuitable to reproduce unsteady micro-instabilities typical of flight in these conditions
• Our solution:
‣ Run-time evaluation of statistical indicators of velocity components in 95 hc control points
‣ Development of an algorithm on the basis of statistical indicators to add different intensities of turbulence to the flight model
‣ Turbulence is obtained by passing band-limited white noise though appropriate forming filters, according to military specification MIL-F-8785C
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Results and Validation
Conclusions
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
• OpenFOAM range of features provide us all the capabilities to obtainthe best compromise between fidelity level and simulation real-timerequirements
• OpenFOAM allows us to perform about 1000 CFD computation in anacceptable timeframe
• Successfully integration within Full Flight Simulator real-time software
• Very positive pilots’ evaluation during all takeoff\landing\approachesnear oil rigs and ships
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Copyright © ESI Group, 2015. All rights reserved.
Future applications
Conclusions
ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
New challenge: urban environments
• Stereolithography (STL) format models generation of a wider area
• Higher computational effort
• Trade-off between grid discretization and run-time environment
• Validation of results by test pilots
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Copyright © ESI Group, 2015. All rights reserved. ESI OpenFOAM User Conference 2015 – October 19 – 21 in Stuttgart, Germany
THANK YOU FOR YOUR ATTENTION
Wind characterization around offshore platform for real-time
helicopter simulator
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