Computing Measured Spectra from Hypersonic Pitot Probes with Flow-Parallel Freestream Disturbances

Chaudhry, Ross S.; Candler, Graham V.

doi:10.2514/1.j055396

Cited by 22 publications

(17 citation statements)

References 19 publications

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“…Figure 14 shows the DNS predictions for the transfer functions of angled freestream acoustic disturbances (θ 120 deg) with and without area averaging and their comparison with flow-parallel slow acoustic disturbances (θ 180 deg) computed previously [34]. The transfer function exhibits a geometry-dependent resonance; the acoustic disturbance angle has a large effect on the transfer function, resulting in a smaller resonant frequency and a lower amplification factor for angled freestream acoustic disturbances than for flowparallel freestream disturbances.…”

Section: Recovery Of Tunnel Freestream Disturbancesmentioning

confidence: 96%

“…DNSs of flow around pitot probes were first conducted by the Minnesota team to characterize transfer functions for flow-parallel acoustic and entropy disturbances [34]. Flow-parallel acoustic disturbances are those whose wave-number vector is either aligned with (θ 0 deg) or opposite to (θ 180 deg) the bulk flow, commonly referred to as fast or slow acoustic waves.…”

Section: Recovery Of Tunnel Freestream Disturbancesmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of Freestream Disturbances in Conventional Hypersonic Wind Tunnels

Duan

Choudhari²,

Chou³

et al. 2019

Journal of Spacecraft and Rockets

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Although low-disturbance ("quiet") hypersonic wind tunnels are believed to provide more reliable extrapolation of boundary-layer transition behavior from ground to flight, the presently available quiet facilities are limited to Mach 6, moderate Reynolds numbers, low freestream enthalpy, and subscale models. As a result, only conventional ("noisy") wind tunnels can reproduce both Reynolds numbers and enthalpies of hypersonic flight configurations and must therefore be used for flight vehicle test and evaluation involving high Mach number, high enthalpy, and larger models. This paper outlines the recent progress and achievements in the characterization of tunnel noise that have resulted from the coordinated effort within the AVT-240 specialists group on hypersonic boundary-layer transition prediction. The new experimental measurements cover a range of conventional wind tunnels with different sizes and Mach numbers from 6 to 14 and extend the database of freestream fluctuations within the spectral range of boundary-layer instability waves over commonly tested models. New direct numerical simulation datasets elucidate the physics of noise generation inside the turbulent nozzle wall boundary layer, characterize the spatiotemporal structure of the freestream noise, and account for the propagation and transfer of the freestream disturbances to a Pitot-mounted sensor.

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Section: Recovery Of Tunnel Freestream Disturbancesmentioning

confidence: 96%

Section: Recovery Of Tunnel Freestream Disturbancesmentioning

confidence: 99%

Characterization of Freestream Disturbances in Conventional Hypersonic Wind Tunnels

Duan

Choudhari²,

Chou³

et al. 2019

Journal of Spacecraft and Rockets

Self Cite

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“…For comparison, the other probes range from being a wire sensor 5-µm in diameter to a maximum of 6.35 mm in diameter for the PCB probe. Previous computational 34 and experimental 35 studies have shown that the geometry of pitot probes used can affect the measurement of freestream disturbances. It is possible that this peak is a result of an unsteady bow shock ahead of the larger probe body.…”

Section: B Heat Transfer Fluctuationsmentioning

confidence: 99%

Measurements of Freestream Fluctuations in the NASA Langley 20-Inch Mach 6 Tunnel

Chou

Leidy

Bathel

et al. 2018

2018 Fluid Dynamics Conference

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An experimental campaign was conducted to measure and to characterize the freestream disturbance levels in the NASA Langley Research Center 20-Inch Mach 6 Wind Tunnel. A pitot rake was instrumented with fast pressure transducers, hot wires, and an atomic layer thermopile to quantify the fluctuation levels of pressure, mass flux, and heat flux, respectively. In conjunction with these probe-based measurements, focused laser differential interferometry was used to optically measure density fluctuations. Measurements were made at five nominal different unit Reynolds numbers ranging from 3.28-26.5×10 6 /m. The rake was positioned at two different streamwise locations and several different roll angles to measure flow uniformity within the test section. In general, noise levels were spatially consistent within the tested region. Pitot pressure fluctuation levels ranged from 0.84% at the highest Reynolds number tested to 1.89% at the lowest Reynolds number tested. Freestream mass-flux fluctuations remained relatively constant between 1.8-2.5% of the freestream. The pressure transducers were also used to determine the dominant disturbance speed and angle of propagation. The disturbances were estimated to travel at approximately 54-81% of the freestream speed at an angle of approximately 21-44°from the freestream direction, but these measurements had a significant amount of uncertainty. A comparison to previous measurements of pressure made in 2012 and of mass flux made in 1994 show almost no change in the RMS fluctuation of these flow quantities.

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“…And, when pointwise free-stream measurements are taken, for example by flow intrusive PCB enabled Pitot tubes (Bounitch, Lewis & Lafferty 2011; Masutti et al. 2012), complex flow interactions by preceding bow shock and a concomitant stagnation region confound interpretation of the signal, which has further spurred detailed modelling efforts using simulation (Chaudhry & Candler 2017; Duan et al. 2019).…”

Section: Introductionmentioning

confidence: 99%

Observation-infused simulations of high-speed boundary-layer transition

Buchta

Zaki

2021

J. Fluid Mech.

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Computing Measured Spectra from Hypersonic Pitot Probes with Flow-Parallel Freestream Disturbances

Cited by 22 publications

References 19 publications

Characterization of Freestream Disturbances in Conventional Hypersonic Wind Tunnels

Characterization of Freestream Disturbances in Conventional Hypersonic Wind Tunnels

Measurements of Freestream Fluctuations in the NASA Langley 20-Inch Mach 6 Tunnel

Observation-infused simulations of high-speed boundary-layer transition

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