Rotorwash Operational Footprint Modeling

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503 Wind or "rotorwash" generated by rotors, ducts, or jets effect the operational suitability and utility of future Vertical Takeoff and Landing (VTOL) aircraft. As the aircraft's physical size, weight, and disk loading increases beyond the range of current systems, the risk increases that rotorwash operational impact(s) may compromise an aircraft's ability to satisfy the Warfighter's needs. Early definition of anticipated rotorwash conditions will permit an assessment of operational suitability and determine whether specific design changes are warranted and/or if acceptable operational tactics, techniques, and procedures can be established. 1.AGENCY USE ONLY REPORT DATE July 2014 REPORT TYPE AND DATES COVERED Final TITLE AND SUBTITLE Rotorwash Operational Footprint Modeling FUNDING NUMBERS AUTHOR(S)JohnThis report documents the assessment process, environmental limits, rotorwash modeling, and output display supporting the rotorwash operational footprint model. These elements graphically combine to display the rotorwash operational impact assessment on the ground environment as contour plots or "footprints." The tools developed are for the single main rotor helicopter, tandem helicopter, and tiltrotor configurations, but they can be extended to encompass additional configurations. The rotorwash operational footprint displays the effect of winds generated by rotor thrust on the surrounding environment. These footprints can be used to evaluate compliance with aircraft performance specifications, verify safe separation distances, or inform design trade studies. Wind or "rotorwash" generated by rotors, ducts, or jets effect the operational suitability and utility of future Vertical Takeoff and Landing (VTOL) aircraft. As the aircraft's physical size, weight, and disk loading increases beyond the range of current systems, the risk increases that rotorwash operational impact(s) may compromise an aircraft's ability to satisfy the Warfighter's needs. Early definition of anticipated rotorwash conditions will permit an assessment of operational suitability and determine whether specific design changes are warranted and/or if acceptable operational tactics, techniques, and procedures can be established. SUBJECT TERMSThis report documents the assessment process, environmental limits, rotorwash modeling, and output display supporting the rotor...

Brownout Simulations of Model-Rotors In Ground Effect

“…For the other two cases, the forces exceed the caution limit, but do not reach the danger zone threshold. This result is in agreement with other works, such as in [15] where the PAXman forces of a V-22 have been computed starting from an experimental outflow survey. This reference involved several configurations of disk loading and it has been shown that higher values of disk loading result in forces that reached a peak of 600 N. In all three cases, after 2R, the force drops quickly.…”

“…It is based on the projection of a crouching 6ft tall person immersed in the outwash. The details of the geometry of the PAXman model are shown in figure 1, as reported in [14] and [15]. To be comparable with the small rotor size, the PAXman height is scaled with the rotor radius for three different full-scale rotors, chosen to represent three different weight categories: light, medium and heavy.…”

“…This way, it is possible to estimate the outflow velocities generated by a full-scale rotor operating at the same high values of thrust coefficient of the scaled rotor. According to [14] and [15] the caution zone starts when the force acting on the PAXman is more than 80 lbf (335 N), and the hazard zone is (2)…”

Vortex Approach for Downwash and Outwash of Tandem Rotors in Ground Effect

“…The rotor was modelled with two untwisted rectangular blades of circular arc, cambered airfoil sections. The radius of the blade, chord, aspect ratio, and solidity were 86 mm, 19.6mm, 4.39, and 0.14, respectively. The blades were set at a collective pitch of 12°, and the results were obtained at a tip Mach number of 0.08.…”

“…Then, a momentum-based mathematical model with experimental corrections, including a wall jet theory, and a ground effect correction factor, was described by Kiseilowski and Douglas [17]. The wake contraction was taken into account to quickly evaluate the performance of overlapping and non-overlapping rotor configurations [18,19]. Nevertheless, the drawback of this approach was the limited availability of experimental data for the corrections necessary in the model.…”