Real-time Flow Field Aerodynamics Two-way Coupled to Rotorcraft Flight Dynamics for Piloted Simulations
Abstract
Rotorcraft downwash gains importance in flight close to terrain and obstacles where strong aerodynamic forces may act on nearby personnel, objects and other aircraft. Furthermore, in these situations, the downwash may interact with stationary or moving grounds or obstacles, and objects such as a (moving)ship structure. Interferences between rotor wake, ship deck and ship airwake and/or varying wind fields may lead to substantial modifications to the rotor inflow distribution, producing rapidly changing forces and moments that affect the rotorcraft flight dynamics and handling qualities. Thus, maneuvers in vicinityof terrain and complex obstacles, such as landing and take-off on ship decks and offshore platforms, account for the most demanding and hazardous situations in rotorcraft operations. Better taking into account the abovementioned effects in pilot training simulators can be expected to improve pilot training for such critical situations, thereby reducing the risk of mishaps. Because of the extreme computational power requirements, real-time flow field simulations with the necessary spatial resolutions are challenging using state-of-the-art (RANS based) CFD approaches. So far, no other research group has achieved/demonstrated a two-way coupled (flow field aerodynamics/flightdynamics) simulation, where the flow field and rotorcraft flight dynamics are fully, i.e., two-way coupled, yet still running in real-time (which is imperative if the model is to be used in piloted flight simulators).Lattice-Boltzmann methods (LBM) lend themselves to heavy parallelization, thus making them computationally extremely efficient when GPU architectures are used to solve for a flow field and, therefore, they are attractive for real-time simulations. However, these methods have not yet been successfully applied to ship airwakes and never been used for rotorcraft aerodynamics simulations.In a proof of concept we showed that our fully-coupled LBM based approach performed similar or better (depending on the specific investigated pilot input and dynamic vehicle response) when compared to other methods currently being used in flight simulations, such as the Pitt-Peters inflow model. However, such widely-used models do not offer the versatility and the capabilities of the discussed model herein (in regard to the effects of a rapidly changing flow field or arbitrary surroundings), also including the added benefit of being independent of prior knowledge about the flow field (on the ship). The model capturescomplex boundary conditions and calculates aircraft- and flight-state specific flow fields in real-time. In contrast to existing simulation approaches that are encumbered by the need for look-up tables and preexisting measurements (e.g., of the ship airwake), boundary conditions are realized at simulation runtimeusing ray-tracing algorithms. Therefore, the model is able to incorporate arbitrary dynamic obstacles, such as moving ship decks and superstructures, their effect on the flow field including rotor downwash, and any wake interferences (e.g., ship airwake with rotor wake) in real-time and without preexisting knowledge (other than the geometry of, e.g., a ship). Furthermore, the introduced two-way coupling between the flow field aerodynamics and rotorcraft flight dynamics enables the feedback of any interactional flow field modifications to the flight dynamics and vice versa, making the model suitable for more realistic pilot-in-the-loop simulations, whereas current models do not accurately represent theaforementioned effects in real-time. After model development is finished, full-scale and reduced-scale aerodynamic and flight dynamic measurement data are used for validation purposes, as well as pilot evaluations in the flight simulator environment. Besides the objective to provide higher-fidelity aerodynamic modeling for more realistic pilot simulator training, another objective is to investigate significant couplings between flow field aer
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 25, 2019
- Source ID
- N000141912238
Entities
People
- Juergen Rauleder
Organizations
- Office of Naval Research
- Technische Universität Ilmenau
- United States Navy