Status of NASA Langley quiet flow facility developments

Abstract

Five supersonic and hypersonic, blowdown wind tunnels at NASA Langely are designed for high-Reynolds-number, quiet-flow opcration covering a Mach number range from 2.4 to 18. A brief status report on each of thc facilities is presented along with new nozzle performance data for the Mach 18 Quiet Helium Tunnel and the Mach 6 Quiet Nozzlc in the Nozzle Test Chamber. Additional items discussed in the paper include: cxperimental transition data on a slender cone with a flared afterbody in the Mach 6 facility under complete quiet flow conditions; nozzle inlet flowfield computations for the Mach 18 helium facility; nozzle coordinate and waviness measurement data for the Mach 8 facility; new Mach 2.4 nozzle design proposals; and an assessment of required quiet tunnel technology research. Introduction Development is continuing on a group of low-,v disturbancc or quiet supersoniclhypersonic wind tunncls for instability and transition testing at NASA Langley. This report provides a progress update including discussion of tunnel fabrication, operational characteristics, quiet tunnel technical issncs that are outstanding, and data for a Mach 6 transition model. The quiet tunnels under consideration are specifically designed for high Reynolds number operation with very low freestream-distnrbancc levcls. This capability is required to provide the proper conditions for * Group I.cadcr, Quiet Tunnel and Transition Group, Experimental Mctliods Branch, Member AIAA. ** Aerospace Engineer, Experimental Methods Branch ?Senior Research Scientist, Experimental Mcthods Branch, Senior Member, AIAA, +Research Scientist, AIAA Member. instability and transition testing at high speeds. The group consists of small-to-medium sized, ideal gas (air, helium), blowdown tunnels covering a Mach number range from 2.4 to 18. The quiet length Reynolds number, R e m , based on free-stream unit Reynolds number and the axial extent of usable quiet flow fall in the overall range of 6 x106 to 25x106 Free-stream disturbance fluctuation levels in the nozzle test regions are in the range of 0.05 percent of the corresponding mean quantities. The Reynolds number range includes both measured values for operational tunnels and theoretical values based on lmear stability theory for those under development. Work is underway to extend the quiet length Reynolds number capability range to 80 million in a Mach 2.4 nozzle to support advanced high speed vehicle tcst requircmcnts, particularly supersonic laminar flow controlThe test capability offered by these facilities is nccessaq due to possible scnsitivity of transition on models to facility-dependent noise at Mach numbers greater than one. The dominant facility noise source at speeds grcater than about 2.5 ts eddy-Mach-wave radiation emanating from transitional or turbulent boundary layers on the tunnel's nozzle walls (ref. 1) Lesser amounts of noise propagate from the settling chamber but this noise source becomes morc important at lower Mach numbers. Qnict tunnel technology aims to eliminate nozzle boundary-layer-in...

Hypersonic boundary layer stability over a flared cone in a quiet tunnel

“…7 In these facilities, the free stream noise is maintained at low levels by treating the settling chamber flow and maintaining the nozzle wall boundary layer in a laminar state. Hence, transition on the nozzle wall is delayed providing lower free stream disturbance levels in the quiet tunnel relative to conventional tunnels.…”

Design of a boundary layer suction device for a supersonic quiet wind tunnel by numerical simulation

“…The upstream Mach number was evaluated in a one dimensional approximation by taking into account the area ratio. Following theoretical analysis that are presently at our disposal [14], the non steady problem is not well posed in this case. This ill posedness is nevertheless not demonstrated for the steady problem.…”

“…The mathematically suitable Navier-Stokes Characteristic Boundary Conditions (NSCBC) for the previously described inlet flow situation are given in [14]. They consist in forcing constant velocity and density or temperature values, the complementary variable (i.e.…”

Experiments on Transition Physics in Hypersonic Boundary Layers: Validation Data for Modeling and Computations

“…Here, it is seen that even at the point of highest apparent spike density (at P o = 145 psia, 38 seconds), the intermittency factor indicates that only approximately 6% of 2-ms windows contain these discrete pressure fluctuations. Another interesting way to visualize the present performance of the M6QT as compared with Langley performance is to directly compare the present Pitot-pressure time histories with the selected uncalibrated hotwire time histories presented in Wilkinson (1994). Figure 8 below shows this comparison.…”