TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles

ACQUISITION PROGRAM: PMA-275, V-22 Joint Program Office

OBJECTIVE: Develop a system to measure three-component airflow velocities in the vicinity of a full-scale helicopter.

DESCRIPTION: The current focus of computational fluid dynamics (CFD) airwake analysis is to predict the coupled effect of a helicopter rotor operating near a vertical face, for example a ship�s hangar, and the subsequent effect on the rotorcraft's handling qualities. Validation data are required to evaluate these predictions. Currently fielded airflow measurement systems using ultrasonic anemometers are limited in their ability to provide the necessary data. Data measured by these systems are indeterminate when the local flow is outside the device�s cone angle, are limited to discrete points, and are frequently corrupted by electromagnetic interference, especially on board a ship. Furthermore, the local flow can be disrupted by the presence of the measurement device or its mount. A system is needed to provide three-component, concurrent, time accurate airflow measurements at multiple locations in the vicinity of a hovering helicopter. The measured data will be used to validate CFD models of the flowfield and should approach as close as possible the spatial/frequency resolution typically used in full scale CFD analysis (approximately 2ft/20Hz over the volume of interest).

PHASE I: Develop an innovative approach to measure three-component airflow velocities. Demonstrate the feasibility of the approach in a laboratory environment.

PHASE II: Develop and build a full-scale prototype measurement system and use it to measure the downwash in the vicinity of a helicopter hovering near a vertical face. Measure the accuracy of the system.

PHASE III: Build a production measurement system and transition to Government and industry.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial applications include analyzing the effect of rotor downwash on personnel and equipment at airports, offshore installations and building helipads, as well as measuring the flowfield in the vicinity of buildings and other structures.

REFERENCES:
1. Silva, M.J., Geyer, W.P., and Nelson, J., "Full-Scale Rotorcraft Downwash Surveys in a Shipboard Environment". Presented at the American Helicopter Society 60th Annual Forum, Baltimore, MD, June 7-10, 2004.

2. Silva, M.J., Yamauchi, G.K., Wadcock, A.J. and Long, K.R., "Wind Tunnel Investigation of the Aerodynamic Interactions Between Helicopters and Tiltrotors in a Shipboard Environment". Presented at the American Helicopter Society 4th Decennial Specialist�s Conference on Aeromechanics, San Francisco, CA, January 21-23, 2004.

KEYWORDS: Downwash; Helicopter; Rotor; Measurement; Flowfield; Shipboard

** TOPIC AUTHOR (TPOC) **

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