Unique Testing Capabilities of the NASA Langley Transonic Dynamics Tunnel, an Exercise in Aeroelastic Scaling

Abstract

The NASA Langley Research Center Transonic Dynamics Tunnel (TDT) is well known for its aeroelastic testing capabilities. Its large size, transonic speed range, variable pressure capability, and use of either air or R-134a heavy gas as a test medium enable unparalleled manipulation of flow-and-structure-dependent scaling quantities. This paper will present select scaling quantities that are important for the proper characterization of any dynamic phenomenon and many static aeroelastic phenomena. An analytical demonstration is presented comparing the unique ability of TDT to match these scaling quantities by comparison to other leading facilities with other test mediums. Complementary to aeroelastic testing, the TDT is well-suited for high risk testing and for those tests that require unusual model mount or support systems. Examples are presented. In addition to its unique aeroelastic testing capabilities, flow quality and Reynolds number capability are briefly discussed. Finally, the ability of the TDT to support future NASA research thrusts and likely vehicle designs is presented.* Research Aerospace Engineer, Aeroelasticity Branch, Mail Stop 340, AIAA Senior Member. https://ntrs.nasa.gov/search.jsp?R=20140000340 2020-07-16T13:47:06+00:00Z HE NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) has been operational since 1960 investigating a wide range of aeroelastic and non-aeroelastic phenomena. 1-4 A dedicated aeroelastic test facility, the TDT is a large, variable pressure, transonic wind tunnel that can use either air or heavy gas (R-134a) as a test medium. Unlike typical wind tunnel testing which focuses upon modeling the aerodynamics experienced by a flight vehicle, the study of aeroelasticity requires modeling of the structural response of the flight vehicle when exposed to representative aerodynamics. The coupling between fluid and structural interaction can be described by a series of non-dimensional scaling parameters. Fluid and structural-response coupling tends to increase in sensitivity as the sonic condition is approached since the lift-curve-slope steepens as a function of Mach number and slight structural perturbations have an increasing aerodynamic effect. 5 As a result, many vehicles experience a "transonicdip" in the stability boundary with the lowest stability margins existing at high subsonic Mach numbers. 5,6 High subsonic Mach numbers are where most transport aircraft cruise, where high performance aircraft pass through, where launch vehicles experience the highest unsteady buffet loads during ascent, 7 and are also where computational fluid dynamics (CFD) codes have the greatest difficulty in modeling flow physics; especially unsteady flow physics. 8 Therefore, experimental data in the transonic speed range is of particular importance. Typically regarded as the world's premier aeroelastic test facility, [9][10][11][12][13] TDT fulfills a unique niche in the wind tunnel infrastructure as a result of its unparalleled ability to manipulate fluid-structure scaling parameters. T...

Transonic industrial wind tunnel testing in the 2020s

“…Cryogenic or heavy gas operation will not be considered here, since these would require a review article each to address properly (e.g. Refs 10, 11).…”

Computational Analysis of the Transonic Dynamics Tunnel Using FUN3D

“…In this study, experimental data acquired in the empty tunnel using the R-134a test medium was used to calibrate the computational data. TDT's unique capabilities are well described and summarized in the recent publication by Ivanco, 7 where he states the following "Typically regarded as the world's premier aeroelastic test facility, TDT fulfills a unique niche in the wind tunnel infrastructure as a result of its unparalleled ability to manipulate fluid-structure scaling parameters. "…”

A New High Channel-Count, High Scan-Rate, Data Acquisition System for the NASA Langley Transonic Dynamics Tunnel

“…HE NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) has been operational since 1960 investigating a wide range of aeroelastic and non-aeroelastic phenomena. [1][2][3][4][5] A dedicated aeroelastic test facility, the TDT is a large, variable pressure, transonic wind tunnel that can use either air or heavy gas (currently R-134a) as a test medium. Unlike typical wind-tunnel testing, which focuses on measuring the aerodynamics experienced by a flight vehicle, the study of aeroelasticity considers the structural response of the flight vehicle when exposed to representative aerodynamics.…”

“…Models can be mounted with: various sting mounts; various sidewall mounts; a floor-mounted turntable; a two-cable, free-flight support system; a helicopter test apparatus; a tilt-rotor test apparatus; or custom mount systems. [1][2][3][4][5]11 In addition to the mount type, such as sting or sidewall, various forms of model actuation are also available. The sidewall turntable can either be electrically actuated, or hydraulically actuated with a dynamic system known as the oscillating turntable (OTT).…”