Test section flow quality surveys of the Langley Full-Scale Tunnel

Abstract

A detailed flow survey of the test section of the Langley Full-Scale Tunnel is described. Flow angularity, dynamic pressure, and turbulence intensity were measured in the test section volume over a matrix with three foot spacing. Instrumentation consisted of a rake of four five hole probes and two hot-wire anemometers. Details of probe calibration, installation, and use are presented in addition to survey results. Facility Description Old Dominion University (ODU), working under a Memorandum of Agreement with NASA Langley Research Center, has operated the Langley Full-Scale Tunnel (LFST) since 1997. This facility is the second largest in the United States in terms of test section size and is the largest university run wind tunnel in the world. During its seventy years of service, a wide variety of aerospace test programs have been undertaken. Sub-scale model testing has included high angle of attack testing of current U.S. front-line fighters, high-lift systems on supersonic and subsonic transports, parachutes, and even an airship, submarine, and building complex. Recently testing has included fullscale automobiles, trucks, and UAVs. The open jet test section of the LFST (formerly the NASA 30 by 60) is semi-elliptical in cross section with a width of 60 ft and a height of 30 ft as shown in figure I. The elevated ground board is 42.5 ft wide by 52.3 ft long and features a turntable with a diameter of 28.5 ft. * Graduate Research Assistant Student Member AIAA t Associate Professor of Aerospace Engineering, Senior Member AIAA Copyright © 2002 by the American Institute of Aeronautics and Astronautics, Inc. Power is supplied by two 4000 HP electric motors driving two 35.5 ft diameter fourbladed fans. The dual return tunnel circuit design has a nozzle contraction ratio of approximately 5:1, and no flow conditioning devices such as honeycombs or screens anywhere in the circuit. The test section ground board and balance shield represent the only major modifications to the circuit since the commissioning of the facility. Introduction The large test section and open jet design are ideal for testing large models and UAVs with negligible boundary effects. Special vents provide fresh air exchange, useful when testing with power on. There are two model aircraft support systems available depending on size and weight. Both systems allow a 100° angle of attack sweep and a ±90° yaw sweep. A large scale x-y-z traverse (survey carriage) can be used to position a second model or survey probes in the test section. Interest in a modern flow survey originally stemmed from a planned NASA Blended Wing Body (BWB) test using a large scale model. There have been several flow surveys in the history of the tunnel and much folklore surrounding the flow quality on the tunnel centerline.'' The merging streams of the dual return design were thought to have created a measureable shear layer on the centerline with an elevated turbulence intensity. This report describes the flow quality in the Langley Full-Scale Tunnel (LFST) in terms of flow angularity, dynamic pressure and turbulence intensity. Aerodynamic flow field surveys were made over the entire test section volume. The instrumentation consisted of four five hole hemispherical-head probes for dynamic pressure and flow angularity measurements, two constant-temperature hot-wire anemometers for 1 American Institute of Aeronautics and Astronautics (c)2002 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.