Shipboard Helicopter Modeling and Simulation

Handling Qualities Analysis of Sling Load Operations and Shipboard Operations

Ducted Fan Modeling and Simulation

CFD/CSD Coupling

Advanced Rotocraft Aerodynamics

Wind Turbine Modeling and Analysis

Shipboard Helicopter Modeling and Simulation
Through an ongoing set of Navy Small Business Innovative Research (SBIR) contracts, ART has developed advanced modeling techniques to support the modeling of the “Dynamic Interface” phenomena between rotorcraft and ships that make a shipboard operating environment particularly difficult for rotorcraft. A CFD model of the ship airwake has been adapted to support real time simulation of the ship airwake interference on each segment of each rotor blade. Panel method modeling of the moving ship deck has been used to model the interaction between the deck and both the rotor downwash and the ship airwake. Partial ground effects resulting from a rotor crossing over the ship’s deck and the ground vortex produced by hovering in ground effects over a moving ship deck have also been modeled. The multi-aircraft interference effect of a rotor wake on other aircraft in close proximity for shipboard operations has also been modeled. Under a PEOSTRI contract, ART has tested these helicopter/shipboard operations models on a UH-60 Operational Flight Trainer at Ft. Campbell and the pilots agreed that the Dynamic Interface effects added realism and accuracy to shipboard operations training applications. A modeling and simulation tool developed for the FLIGHTLAB Development System emphasizes ship/rotorcraft dynamic interface testing in support of shipboard rotorcraft flying qualities evaluation. This modeling tool uses a pilot model to provide simulation analysis on each of the shipboard operation mission task elements, including approach, stationkeeping, descent, landing, lift-off, and departure The simulated tests also include rotorcraft on-deck handling analysis.

Handling Qualities Specification Requirements for Maritime Rotorcraft, VTOL UAVs and Heavy Lift Helicopters
In order to provide rotorcraft design guidance for military rotorcraft flying qualities evaluation, a modern Aeronautical Design Standard 33 (ADS-33E-PRF) was developed under the direction of the U.S. Army as a replacement for the handling qualities military specification MIL-H-8501A. ADS-33E-PRF addresses rotorcraft flying qualities specification requirements in a novel and comprehensive way so that many of the complicated rotorcraft flying maneuvers can be quantitatively assessed. However, ADS 33E-PRF was developed primarily for land-based rotorcraft operations. The Naval rotorcraft flying qualities requirements were not adequately addressed there. There is also inadequate specification for cargo and heavy lift rotorcraft in ADS-33E-PRF.

The objective of this research is to develop a technical basis for augmenting existing ADS-33 flying qualities specification to accommodate the unique requirements for Maritime Rotorcraft, Vertical Takeoff/Landing (VTOL), Unmanned Aerial Vehicle (UAVs), and cargo and heavy Lift Helicopters. Sponsored by the USN through a two phase SBIR, ART is jointly working with Hoh Aeronautics, the original ADS-33 developer, for the ADS-33 upgrade. A series of tests being conducted on NASA’s Vertical Motion Simulator at the Ames Research Center use flight dynamics models developed under ART’s FLIGHTLAB Development System to evaluate new handling qualities specifications for these operational requirements.

Ducted Fan Modeling and Simulation
There have been increased applications of the ducted/shrouded fan as a safe and effective anti-torque device for modern rotorcraft. Ducted/shrouded fans have also attracted much interest as the main VTOL lifting devices for recent uninhabited air vehicle (UAV) developments because of their compact structure and high lifting performance. This research is dedicated to the development of an accurate and efficient ducted fan simulation for helicopter anti-torque and UAV lifting applications. The development has been accomplished through (1) the development of an efficient blade element fan model; (2) the development of duct aerodynamic models; (3) the development of a coupled duct-fan model. The development has provided a comprehensive modeling and analysis tool to support the simulation of rotorcraft and VTOL air vehicles configured with ducted fan devices.

CFD/CSD Coupling
Comprehensive rotor codes such as FLIGHTLAB and the Rotorcraft Comprehensive Analysis System (RCAS) allow analysts to evaluate structural loads using finite element Computational Structural Dynamics (CSD) models coupled with empirical two dimensional aerodynamic tables. ART has now successfully coupled CSD codes with Computational Fluid Dynamics (CFD) codes to apply physics-based modeling to both the structural and aerodynamic domains. The result has demonstrated improved modeling accuracy of structural loads in maneuvering flight and provides an effective design tool that allows both aerodynamic and structural design concepts to be fully utilized to optimize designs for aero acoustics and structural loading applications.

*** The rotor wake drawing previously displayed on this web site alongside a description of our CFD/CSD coupling research was originally displayed on the ONERA web site and was generated by an ONERA CFD code. ART regrets the use of this image on our web site and has removed it.

Advanced Rotorcraft Aerodynamics
Modeling edge of the envelope rotorcraft response, including many shipboard operations effects, requires advanced aerodynamic models that properly address extreme aerodynamic conditions. This research focuses on the development of a new generation rotor wake modeling technology that adopts the first principle-based (Navier-Stokes) viscous vortex particle method for analyzing the complicated unsteady rotor wake problem in hover, forward flight, in ground effect and under the influence of the shipboard environment. The vortex particle model developed showed a significant improvement of prediction accuracy for the complicated rotor interference problem without using empirical formulation, while current potential flow methods have to adopt empirical estimation for their modeling parameters. The research also addressed investigating the blade tip aerodynamics, including the effect of numerous blade tip geometry shapes on the rotor performance. Finally, the research also addresses the rotorcraft aerodynamics and its interaction with rotor dynamics. The initial development included coupling CFD with the finite element blade dynamics code developed by ART for rotor loads calculation.

Wind Turbine Modeling and Analysis
ART has applied our expertise in rotor modeling to address the modeling and analysis of wind turbines. Working with the National Renewable Energy Laboratory (NREL) of the Department of Energy, ART has successfully applied advanced rotor modeling technology to the design and analysis of wind turbines. A prototype comprehensive analysis tool for wind turbines, called AEOLIS after the Greek God of wind, is under development and is currently capable of analyzing the coupled rotor-tower under a variety of wind conditions.