Simulation of the V-22 Tiltrotor Aircraft in High-Speed Cruise
Investigator: R. Meakin, Army AFDD (AMCOM)
Application Overview
The V-22 tiltrotor aircraft is strategically significant in both a defense and civil sense. The present simulation corresponds to a high-speed cruise condition for which flight data exists. A future wind-tunnel experiment is scheduled that includes this case as a data point. The specific case corresponds to a full-span tiltrotor at Mach 0.445, 4.3 degrees angle-of-attack, flying at an altitude of 14,930 feet and -2.8 degrees Celsius. The rotor-blade collective pitch angle is 45.1 degrees at 75% radius. The rotor speed is 333 rpm.
Methodology
Overset structured grids are used to discretize the V-22 geometry. The approach is well suited to analysis of such applications. Grid components conform to the shape of the V-22, facilitating resolution of the viscous boundary layer and important off body aerodynamics. The near-body portion of the V-22 geometry is decomposed into 118 components and approximately 8 million points. The default off-body grid system includes 150 components and 19.8 million points, for a total of 268 components at 27.8 million points in all. The simulation is carried out on 65-nodes of the IBM-SP (pandion) at the DoD MSRC located at CEWES. Preliminary results of the simulations are available in AIAA Paper 99-3302-CP. The simulation includes the full-span V-22 aircraft, including the forward looking infrared (FLIR), AAR47 sensor, refueling boom, engine nacelle (including protuberances), rotor spinner, blades, and tail-section. The engine inlets and exhaust are faired over.
Results
Simulation of the V-22 high-speed cruise case is carried out on the near-body and default off-body grid system. The default off-body grid system, in this case, is based on proximity to the near-body grids and user-supplied bounding-box diagonal end-point coordinates that define the extent of the rotor wake system to be resolved with level-1 grids. Solution adaption within the off-body domain was not initiated because all of the rotor wake is contained within the default level-1 off-body grid system. In this case, adaption would have extended the level-1 grid to resolve the wake system downstream of the aircraft.
Picture 1 Boundaries of off-body grid components at y=o plane colored by refinement capacityPicture 2 Close-up of near-body grid (tail-section) overlapping level-1 off-body grid
Picture 3 Surfaces from selected near-body grid components
Picture 4 Filaments of particles released every 25 time-steps of simulation (post-process) to visualize rotor-wake system
Picture 5 Surface pressure coefficient (Cp) and particles released from engine exhaust (blunt-body)
Picture 6 Horizontal plane at an elevation equal to rotor spinner center line is colored by vertical component of vorticity (red=positive, blue= negative). Note blade-tip vortices clearly captured as part of simulation past the tail section of the aircraft.
Significance
This effort has dual objectives that involve evaluation of project
software and the aerodynamic performance of the V-22 tiltrotor aircraft.
The simulation, combined with existing flight data and scheduled tunnel data, is a basis
to demonstrate design-to-flight analysis capability for tiltrotor aircraft. The
simulation also represents a high-fidelity baseline data-set to which proposed
variable-diameter tiltrotor designs can be evaluated.
References
1. Meakin, R., ``Unsteady
Aerodynamic Simulation of Static and Moving Bodies Using Scalable Computers,'' AIAA-99-3302-CP, pp. 469-483, 14th AIAA Computational Fluid Dynamics Conference, Norfolk,
VA, June 1999.
2. Meakin, R., ``On Adaptive Refinement and Overset Structured Grids,'' AIAA-97-1858-CP,
pp. 236-249, 13th AIAA Computational Fluid Dynamics Conference, Snowmass, CO, June 1997.
Boundaries of off-body grid components at y=o plane colored by refinement capacity
Close-up of near-body grid (tail-section) overlapping level-1 off-body grid
Surfaces from selected near-body grid components
Filaments of particles released every 25 time-steps of simulation (post-process) to visualize rotor-wake system
Surface pressure coefficient (Cp) and particles released from engine exhaust (blunt-body)
Horizontal plane at an elevation equal to rotor spinner center line is colored by vertical component of vorticity (red=positive, blue= negative). Note blade-tip vortices clearly captured as part of simulation past the tail section of the aircraft.
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