Most current rotorcraft analysis codes adopt potential flow based singularity methods for rotor wake solutions. These codes are limited to capturing the first order effects and therefore rely on empirical estimation such as vortex decay factor, vortex core size, wake roll-up, etc. The first principle based viscous vortex particle method was developed to accurately model rotor/wing wake interference problems including vorticity convection in the flow-field for long durations without artificial dissipation and wake distortion and physical diffusion due to air viscosity. This new method has been fully parallelized and is extremely efficient using modern desktop computers equipped with a GPU card. The new method has been extensively validated for different rotorcraft/compound aircraft configurations and under various flight conditions.
ART has developed an efficient and high fidelity analysis capability for simulating the aerodynamic interactions of compound rotorcraft and other aircraft configured with multiple rotors. The methodology is based on the first-principle viscous Vortex Particle Method (VPM), whose rotor wake modeling accuracy has been validated through extensive simulation. This research extended the VPM modeling methodology to address modern multiple rotor systems by representing the mutual interactions between the rotors, wings, fuselage, and aerodynamic surfaces of a full rotorcraft. The developed methodology aims to provide an effective modeling tool to support the design and analysis of next generation vertical lift vehicles.
ART is developing the capability to couple CFD analysis with RCAS for an elastic fuselage. This capability enables the full air vehicle to be aeroelastically modeled and coupled with CFD to provide an improved prediction of interactional rotorcraft vibration phenomena, such as buffeting.
ART is developing a CREATE A/V Helios/RCAS Graphical User Interface (GUI) to significantly advance coupled modeling and analysis capabilities. CREATE A/V Helios is a leading rotary-wing computational aeromechanics simulation framework. This effort will enable coupled CFD/CSD modeling and analysis of complex rotorcraft configurations in steady or maneuvering flight, while providing seamless model definition, simulation, and post-processing.
Modern advanced rotorcraft configurations often involve multiple rotors, fans, wings, etc. and their aerodynamic interactions can be complex. A unified state-space inflow formulation has been developed that addresses the aerodynamic interactions and is well suited for flight dynamics analysis and control design applications. In implementation, the unified inflow model is derived through system identification using data generated from VPM simulations. Identifying the model from VPM allows complex rotor wake physics to be captured. This includes both the wake distortion and wake diffusion that are essential for accurate interactional wake solutions.
ART is building a next generation web based simulation platform to reduce the cost of aircraft simulation development, deployment, and maintenance. Web technology offers many advantages, such as platform independence, extensive software framework support, and minimal installation and configuration time. An avionics trainer server has been prototyped that uses web technology to allow multiple tablets and smartphones, running their default web browsers, to be utilized together as a single flight training device. With future iterations of this technology, ART seeks to improve the maintainability and reduce the cost of complex flight simulators.
Aerodynamic interactions between the rotor and ship have a significant effect on rotorcraft shipboard operations. However, the complexity and computational cost of simulating this complex phenomena is prohibitive for practical applications. To address this limitation, an efficient high fidelity hybrid VPM/CFD methodology was developed. An additional and dramatic computational efficiency gain was also achieved by developing a Reduced Order Model (ROM) of the CFD and performing coupled VPM/ROM simulation.
A “Virtual Pilot” Laboratory toolset was developed that pilots an aircraft simulation through prescribed flight profiles for various configurations in support of avionics system testing. Without the virtual pilot, flying a simulation through a prescribed flight profile to generate consistent simulated sensor data would normally require a pilot. The use of pilots is costly and cannot provide precise repeatability, which is essential to evaluating the effect of mission parameters. A “virtual pilot” is therefore required to generate a repeatable control that accurately drives the simulation through a user defined flight profile.
This research was in support of upgrade of the Army Design Standard for Rotorcraft (ADS-33E-PRF) to include flying qualities specifications for shipboard rotorcraft, heavy lift helicopters, and unmanned air vehicles. Simulation and evaluation methodologies were developed to support the ADS-33 criteria and specification upgrade. In addition, an ADS-33 analysis toolkit was also developed and integrated with FLIGHTLAB.