|Acquisition Program: ||PMA-205 Naval Aviation Training Systems ACAT IV, PMA-275 V-22 Program|| Objective: ||Develop a robust physics-based model of the rotor induced flow for use in a real-time simulation. The final product should be capable of capturing the interactions associated with the rotor-induced velocity in a naval shipboard landing environment (or other complex environments) to allow pilots to conduct accurate real-time simulations.
|| Description: ||In the development of helicopter training systems, modeling of the induced flow of a rotor system is quite complex and computationally extensive, thus pushing the limits of modeling and simulation technology. Typically, the modeling and simulation of the induced flow can be done many different ways with varying degrees of success. Because simplifying assumptions have to be made in the typical rotor inflow model, the interactions of the inflow with its environment (fuselage, empennages, in ground effect, autorotation, vortex ring state etc.) are also done on an ad-hoc basis. Overall, this has resulted in both numerous models being developed from scratch and poor engineering fidelity. Recent advances have pointed to the feasibility of increasing the fidelity of inflow modeling while maintaining the real-time simulation capability. But challenges remain in the phyiscal understanding of the initial turbulent shed vortex roll up and vortex to vortex interacations (or wake evolution), along with the numerical methods to allow their fast computation. By overcoming these challenges an increase in model fidelity should allow for the inclusion of higher fidelity environment effects directly into the inflow model. Because the model will be physic based and not tailored to a specific airframe, the model should be capable of being applied across multiple helicopter simulations. Therefore as processor speeds increase and the physics-based model is upgraded, these upgrades can be applied across the range of simulations as opposed to developing specific upgrades for each helicopter simulation. This will lead to a reduction of duplication of effort and a reduction in implementation risk. Because helicopter simulations are often used in handling qualities evaluations, the improvement in engineering fidelity will result in improved accuracy at a reduced risk.
|| ||PHASE I: Conduct a feasibility study to determine the potential of creating a real-time software module to represent helicopter rotor induced inflow. The study will examine the following areas: 1) maximizing the physics captured in the flow field, 2) integrating advanced features that can take advantage of the physics-based inflow model (ground planes, air wake effects, etc.), 3) providing fast numerical algorithms to allow implementation in a real-time environment and 4) scaling the model to take advantage of increasing computer performance. The study will result in the software approach that best meets the key areas listed above.
|| ||PHASE II: Develop the software module proposed in Phase I. A prototype software module that can run in a ‘stand alone’ mode will be developed to demonstrate the benefits of the algorithm. Define interfaces that the host simulation/trainer will require in order to work with the model. Provide recommendation as to how a typical rotor model should be modified to maximize the benefits of the new algorithm.
|| ||PHASE III: Integrate the software module into two Navy rotary wing flight simulations. Conduct validation testing to determine that the model has been properly integrated and to define the benefits of the new software integration. Demonstrate the scalability of the inflow model. All testing should be demonstrated in a real-time environment.
|| ||PRIVATE SECTOR COMMERCIAL POTENTIAL: The creation of a physics-based model of the inflow of a rotary wing aircraft that runs in a real time environment will be beneficial to the development of commercial rotary wing training devices.
|| References: ||1. Ramasamy, MandLeishman, J.G., “A Generalized Model for Transitional Blade Tip Vortices,” Journal of the American Helicopter Society, Vol. 51 (1), 2006, pp. 92-103
2. Bagai, A.. and Lesihman, J.G., “Rotor Free-Wake Modeling Using a Pseudo-Implicit Technique – Including Comparison with Experiment,” Journal of the American Helicopter Society, Vol. 40, (3), 1995, pp.29-41
3. Sarinivasan G.R., Baeder J.D., Obayashi S., and McCroskey, W.J. "Flowfield of a Lifting Rotor in Hover: A Navier-Stokes Simulation," AIAA Journal, Vol. 30, (10), pp. 2371-2378
4. Arnold, U., Keller, J.D., Curtiss, H.C., and Reichert G., "The Effect of Inflow Models on the Predicted Response of Helicopters," Journal of the American Helicopter Society, Vol. 43,1), 1998, pp.25-36|
|Keywords: ||Rotary Wing Aircraft; Inflow; Trainers; Air Wake; Ground Effect; Shipboard Landing|