TECHNOLOGY AREAS: Air Platform, Information Systems

ACQUISITION PROGRAM: PMA-261; H-53 Heavy Lift Helicopter Program

OBJECTIVE: Develop an innovative method to incorporate the effects of fully coupled interactions between ship airwake and rotor downwash in real-time dynamic interface simulation.

DESCRIPTION: The shipboard dynamic interface is characterized by complex aerodynamic interactions between the flowfield created by the passage of air over the ship (airwake) and the flowfield created by the helicopter (downwash). Early computational modeling of the dynamic interface sought to minimize the complexity of the problem by adopting a superposition approach in which the helicopter was influenced by the airwake, but the airwake was not changed by the presence of the aircraft. This allowed the ship-alone airwake to be computed offline and used as a look-up table in real-time simulation. However, superposition limits the fidelity of the simulation when the rotorcraft is operating close to a solid structure because recirculation effects are ignored. Recirculation can significantly impact handling qualities and performance and its effects need to be included in the next generation of dynamic interface simulators. Computational Fluid Dynamics (CFD) has been used to predict the fully coupled flowfield but it is not currently possible to do so in real-time. An innovative approach is needed that modifies the ship-alone airwake with rotor recirculation effects as an aircraft model flies through an airwake database in a real-time simulation. The model must account for changes due to rotor proximity to both horizontal and vertical surfaces. Methods may be based on experimental or computational data of a rotor near a surface having both a vertical and horizontal element. Ship alone and coupled ship/helicopter CFD airwake data may be made available by NAVAIR upon request.

PHASE I: Demonstrate feasibility of the proposed approach to incorporate recirculation effects in a ship-alone airwake by applying it to a rotor in a stationary hover near a backward-facing step. Demonstrate the modifications to the ship-alone airwake data due to recirculation effects.

PHASE II: Generalize the proposed real-time modeling approach to account for the recirculation effects of a helicopter moving through the ship airwake in real-time. Emphasis should be placed on regions where coupling effects are significant such as hover position over a flight deck. Compare the results against CFD predictions for the fully coupled flowfield to confirm the fidelity of the method. Demonstrate the prototype method in the Manned Flight Simulator (MFS) for a piloted simulation. Access to the MFS will be provided to the selected Small Business Company (SBC) at no cost to the SBC.

PHASE III: Further develop the prototype method for general implementation in training and engineering simulators for multiple ship and aircraft types.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Coupled rotor-airwake aerodynamic effects are relevant to helicopters operating in confined areas in general, whether shipboard, urban or mountain. It is anticipated that the technology developed will provide a valuable increase in modeling fidelity for emergency services and offshore platform operators, as well as naval operators.

REFERENCES:
1. Landsberg, A.M., Boris, J.P., Sandberg, W, & Young, T.R. Jr. (1995). Analysis of the Nonlinear Coupling Effects of a Helicopter Downwash with an Unsteady Ship Airwake (Publication No. AIAA-1995-47). Paper presented at the Aerospace Sciences Meeting and Exhibit, 33rd. Reno, NV; 9-12 January.

2. Tattersall, P., Albone, C.M., Soliman, M.M., & Allen, C.B. (1998). Prediction of Ship Air Wakes Over Flight Decks Using CFD. Paper presented at the RTO/AVT Symposium on Fluid Dynamics Problems of Vehicles Operating near or in the Air-Sea Interface. Amsterdam, The Netherlands; 5-8 October.

3. Xin, H., He, C., & Lee, J. (2001). Combined finite state rotor wake and panel ship deck models for simulation of helicopter shipboard operations. Paper presented at the American Helicopter Society 57th Annual Forum. Washington, DC; 9-11 May.

4. McKillip, Jr., R.M., Boschitsch, A.H., Quackenbush, T.R., Keller, J.D., & Wachspress, D.A. (2002). Dynamic Interface Simulation Using A Coupled Vortex-Based Ship Airwake And Rotor Wake Model, Paper presented at the American Helicopter Society 58th Annual Forum, Montreal, Canada; 11-13 June.

5. Wakefield, N. H., Newman, S. J., & Wilson P. A. (2002). Helicopter flight around a ship�s superstructure. Journal of Aerospace Engineering, 216, 13-28.

6. Alpman, E., Long, L.N., Bridges, D.O., and Horn, J.F. (2007). Fully-Coupled Simulations of the Rotorcraft/Ship Dynamic Interface. Paper presented at the American Helicopter Society 63rd Annual Forum. Virginia Beach, VA; 1-3 May.

7. Polsky, S.A, & Wilkinson, C.H. (2009). A Computational Study of Outwash for a Helicopter Operating Near a Vertical Face with Comparison to Experimental Data (Publication No. AIAA-2009-5684). Paper presented at AIAA Modeling and Simulation Technologies Conference and Exhibit. Chicago, IL; 10-13 August.

KEYWORDS: Ship Airwake; Rotor; Coupled Aerodynamics; Computational Fluid Dynamics; Helicopter Downwash; Rotorcraft

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between July 20 and August 16, 2010, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting August 17, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (10.3 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 10.3 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.