Comparison of flow quality in subsonic pressure tunnels

Wlezien, R. W.; Spencer, Shelly Anne; Grubb, John W.

doi:10.2514/6.1994-2503

Cited by 12 publications

(2 citation statements)

References 2 publications

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“…In an experiment designed to test the effect of boundary-layer suction on cross-flow instability, travelling waves with amplitudes as high as 1 % of the free-stream speed are observed by Eppink & Wlezien (2011). The streamwise component of the turbulence intensity in this facility (NASA Langley transonic pressure tunnel) is u rms /U ∞ = 0.02 % (Wlezien, Spencer & Grubb 1994), where u rms is the temporal r.m.s. of the streamwise fluctuating velocity.…”

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confidence: 99%

Free-stream turbulence and the development of cross-flow disturbances

Downs

White

2013

J. Fluid Mech.

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The cross-flow instability that arises in swept-wing boundary layers has resisted attempts to describe the path from disturbance initiation to transition. Following concerted research efforts, surface roughness and free-stream turbulence have been identified as the leading providers of initial disturbances for cross-flow instability growth. Although a significant body of work examines the role of free-stream turbulence in the cross-flow problem, the data more relevant to the flight environment (turbulence intensities less than 0.07 %) are sparse. A series of recent experiments indicates that variations within this range may affect the initiation or growth of cross-flow instability amplitudes, hindering comparison among results obtained in different disturbance environments. To address this problem, a series of wind tunnel experiments is performed in which the free-stream turbulence intensity is varied between 0.02 % and 0.2 % of free-stream velocity, U ∞ . Measurements of the stationary and travelling mode amplitudes are made in the boundary layer of a 1.83 m chord, 45 • swept-wing model. These results are compared to those of similar experiments at higher turbulence levels to broaden the current knowledge of this portion of the crossflow problem. It is observed that both free-stream turbulence and surface roughness contribute to the initiation of unsteady disturbances, and that free-stream turbulence affects the development of both stationary and unsteady cross-flow disturbances. For the range tested, enhanced free-stream turbulence advances the transition location except when a subcritically spaced roughness array is employed.

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confidence: 99%

Free-stream turbulence and the development of cross-flow disturbances

Downs

White

2013

J. Fluid Mech.

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“…For the configurations tested in the present investigation, the trailing-edge flow was found to be substantially two dimensional, with a maximum spanwise variation in C p (which was near the C l,max ) of 0.05 in the region between the flap brackets. The LTPT was designed with a large contraction ratio (17:1) and nine antiturbulence screens to produce extremely low-turbulence levels 9 (less than 0.5% for most cases). Because of the ability of the LTPT to provide flight Reynolds numbers for representative narrow-body transports, the model was tested transition-free (not fixed).…”

Section: Ltptmentioning

confidence: 99%