Application of fast-responding pressure-sensitive paint to a hemispherical dome in unsteady transonic flow

Fang, Shuo; Disotell, Kevin J.; Long, Samuel R.; Gregory, James W.; Semmelmayer, Frank; Guyton, Robert

doi:10.1007/s00348-010-1010-1

Cited by 35 publications

(8 citation statements)

References 47 publications

(64 reference statements)

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“…When the flow is subsonic everywhere around the turret, essential flow features and related aero-optical distortions have being extensively studied in last few years and fairly well-understood [1,[3][4][5][6][7]. But for incoming Mach numbers larger than approximately 0.55, the flow on top of the turret becomes locally supersonic, with a resulting local moving shock [1,5,8], with the shock extent and the angle depending on the incoming Mach number. The shock creates unsteady density gradients in the flow and promotes an earlier separation of the flow off the turret.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Aero-Optical Wavefronts Using Optical and Non-Optical Measurements

Burns

Gordeyev

Jumper

et al. 2014

52nd Aerospace Sciences Meeting

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In this paper we present two algorithms for estimating the aero-optical aberration of a transonic flow around a 2-D turret based on Malley probe signals or pressure signals from few selected points. These two algorithms use Artificial Neural Networks and Linear Stochastic Estimation of varying model orders to estimate Proper Orthogonal Decomposition modal coefficients. These estimated coefficients are then used to reconstruct an estimated wavefront. This estimated wavefront is subtracted from the true wavefront to obtain a simulated reduction in the overall level of optical aberration. Reductions of up to 48% are achieved for both models. A robustness analysis is also performed, in which it is found that the algorithm is not sufficiently robust to changing flow conditions. Solutions are proposed for further investigation.

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Section: Introductionmentioning

confidence: 99%

Estimation of Aero-Optical Wavefronts Using Optical and Non-Optical Measurements

Burns

Gordeyev

Jumper

et al. 2014

52nd Aerospace Sciences Meeting

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“…To further explore the increased tip unsteadiness on the retreating blade at l = 0.15, the single-shot pressure maps were converted to an AC-coupled form which displays differential pressure changes relative to the mean, hpi, at each pixel (see Fang et al 2010 for a discussion of this method). Figure 19 shows this frame-to-frame complementary view of the root-mean-square data for a subset of eight consecutive images.…”

Section: Transient Pressure Variationsmentioning

confidence: 99%

Single-shot temperature- and pressure-sensitive paint measurements on an unsteady helicopter blade

et al. 2014

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Unsteady pressure-sensitive paint (PSP) measurements were acquired on an articulated model helicopter rotor of 0.26 m diameter in edgewise flow to simulate forward flight conditions. The rotor was operated at advance ratios (free stream velocity normalized by hover tip speed) of 0.15 and 0.30 at a cycle-averaged tip chord Reynolds number of 1.1 9 10 5 , with collective and longitudinal cyclic pitch inputs of 10°and 2.5°, respectively. A single-shot data acquisition technique allowed a camera to record the paint luminescence after a single pulse of high-energy laser excitation, yielding sufficient signal-tonoise ratio to avoid image averaging. Platinum tetra(pentafluorophenyl) porphyrin (PtTFPP) in a porous polymer/ ceramic binder served as the PSP. To address errors caused by image blurring and temperature sensitivity, a previously reported motion deblurring algorithm was implemented and the temperature correction was made using temperature-sensitive paint measurements on a second rotor blade. Instantaneous, unsteady surface pressure maps at a rotation rate of 82 Hz captured different aerodynamic responses between the two sides of the rotor disk and were compared to the nominally steady hover case. Cycle-to-cycle variations in tip unsteadiness on the retreating blade were also observed, causing oblique pressure features which may be linked to three-dimensional stall.

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“…With the exception of [14], these investigations all concerned two-dimensional bumps, a noteworthy difference from the three-dimensionality of hemispherical geometries. Recent investigations by Reid et al [16] and Fang et al [17] have noted the unsteadiness of the shock over a hemisphere, but provide little data on the nature of its motion. Other experiments have directly measured the aero-optical distortion resulting from the turbulent wake [18][19][20], despite remaining below Mach numbers at which shocks would be generated.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Shock Motion in a Transonic Flow over a Wall-Mounted Hemisphere

Beresh

Henfling

Spillers

et al. 2013

43rd Fluid Dynamics Conference

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Particle image velocimetry measurements have been conducted for a Mach 0.8 flow over a wall-mounted hemisphere. The flow is strongly separated, with a mean recirculation length exceeding 5 δ and a mean reverse velocity of -0.2 U ∞ . The shock foot was found to typically sit just forward of the apex of the hemisphere and move within a range of about ±10 deg. Conditional averages based upon the shock foot location show that the separation shock is positioned upstream along the hemisphere surface when reverse velocities in the recirculation region are strong and is located downstream when they are weaker. The recirculation region appears smaller when the shock is located farther downstream. No correlation was detected of the incoming boundary layer with the shock position, nor with the wake recirculation velocities. These observations are consistent with recent studies concluding that for large strong separation regions, the dominant mechanism is the instability of the separated flow rather than a direct influence of the incoming boundary layer.

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Application of fast-responding pressure-sensitive paint to a hemispherical dome in unsteady transonic flow

Cited by 35 publications

References 47 publications

Estimation of Aero-Optical Wavefronts Using Optical and Non-Optical Measurements

Estimation of Aero-Optical Wavefronts Using Optical and Non-Optical Measurements

Single-shot temperature- and pressure-sensitive paint measurements on an unsteady helicopter blade

Unsteady Shock Motion in a Transonic Flow over a Wall-Mounted Hemisphere

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