A PIV Study of Supersonic Impinging Jet

Lou, Huadong; Shih, Chiang; Alvi, Farrukh S.

doi:10.2514/6.2003-3263

Cited by 11 publications

(6 citation statements)

References 15 publications

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“…However, further downstream (y=d > 2), the jet without control spreads at a higher rate (higher slope) than the jet with control. These results are similar to those observed in previous studies on cold impinging jets [16][17][18][19], except that the crossover for the cold jet was at y=d 1. As discussed in previous studies, this initial thickening of the shear layer with control will reduce the receptivity of the shear layer and weaken the feedback loop, which in turn stabilizes the flow and reduces unsteady loads, as already noted in Sec.…”

Section: Effect Of Microjet Controlsupporting

confidence: 91%

“…6a), the rms pressure levels on the ground plane are the highest, followed by the lift plate and near-field microphone. As observed in previous studies on impinging jets [7,[15][16][17][18][19], the magnitude of P rms on the lift plate and OASPL at the near-field microphone is strongly dependent on the nozzle-to-plate distance and is in general high at small h=d (h=d 2-6) and decreases at larger h=d. Overall similar trends in unsteady pressure fluctuations with h=d are observed for the hot jet at TR 1:4 (pressure fluctuation levels are the highest on the ground plane followed by the lift plate and microphone).…”

Section: Unsteady Characteristics Of Impinging Jets 1 Unsteady Prsupporting

confidence: 75%

“…A recent approach to suppress the feedback mechanism of supersonic impinging jets using an array of high-momentum microjets appropriately placed near the nozzle exit has shown highly promising results [15][16][17][18][19]. This control-on-demand technique has many advantages over traditional passive and active control methods and has proven to be successful over a range of geometric and flow conditions.…”

Section: Introductionmentioning

confidence: 99%

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Control of High-Temperature Supersonic Impinging Jets Using Microjets

2009

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The flowfield associated with supersonic impinging jets has been of interest to both engineers and researchers for some time due to its wide range of practical applications and its complex nature from a fundamental fluid dynamic point of view. An example of supersonic impinging jets occurs in short takeoff and vertical landing aircraft, for which the highly oscillatory flowfield and the associated acoustic loads are also accompanied by a dramatic loss in lift during hover, severe ground erosion of the landing surface, and hot gas ingestion into the engine inlets. Another characteristic feature of this flowfield is an intensive heat transfer between the jet and the impingement surface. In the past we have examined impinging jets and their control using microjets at cold conditions; the present study is a step toward examining this flowfield and the effectiveness of microjet control at increasingly realistic thermal conditions. An ideally expanded, Mach 1.5 primary jet issuing from an axisymmetric nozzle was heated up to a stagnation temperature of 500 K. Mean and unsteady temperature and pressure measurements were obtained on a lift plate representative of the undersurface of an aircraft and on the ground plane over a range of nozzle-to-plate distances (representing aircraft hover conditions). In addition, near-field noise was also measured using a microphone. The velocity field of the impinging jet for both cold and hot conditions was mapped using particle image velocimetry. Our results show that the temperature recovery factor at the stagnation point on the ground plane is strongly dependent on the temperature ratio and nozzle-to-plate distance, similar to observations in subsonic impinging jets. The hover lift loss for hot jets is much higher than for cold jets, nearly 75% of the primary jet thrust at small nozzle-to-plate distances. The pressure fluctuations generated by hot impinging jets are also substantially higher than their cold counterparts. As in cold jets, pressure and noise spectra for hot jets show discrete, high-amplitude acoustic tones (generally known as impinging tones) at frequencies varying with jet temperature. The activation of microjet control shows a substantial reduction in pressure fluctuations both in terms of overall sound pressure levels (up to 20 dB on the ground plane and 15 dB on the lift plate) and the attenuation of discrete, high-amplitude impinging tones (up to 32 dB). High-temperature peaks were observed in the temperature spectra at frequencies corresponding to impingement tones in the pressure and noise spectra; these were also substantially attenuated with microjet control. As much as 50% of the lift loss was recovered by using control for hot jets at smaller nozzle-to-plate distances. In general, the results provide evidence of the feasibility of using this active control approach under increasingly realistic conditions to achieve desired reductions in noise, unsteady pressures, and thermal loads.

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Section: Effect Of Microjet Controlsupporting

confidence: 91%

Section: Unsteady Characteristics Of Impinging Jets 1 Unsteady Prsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

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Control of High-Temperature Supersonic Impinging Jets Using Microjets

2009

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“…Lempert et al (1997) developed a MHzrate FRS system by combining a pulse-burst laser system with an ultra-fast framing camera. Nevertheless, improvements in hardware have led to a number of interesting applications, including studies of supersonic jets (Lou, 2003) and flow over a sphere at Mach 6 (Scarano and Haertig, 2003). Reprinted with permission of ASME.)…”

Section: Flow Imagingmentioning

confidence: 99%

Turbulent Shear Layers in Supersonic Flow

Smits¹,

Dussauge

2006

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“…Some subsequent works have focused on the unsteady flow oscillations and acoustic properties especially on acoustic tones. For example, some researches involved in studying the impingement of jet with lift plate [7], driven from convergent and convergentedivergent (CeD) nozzles [8], with real-time imaging system [9], using Particle Image Velocimetry (PIV) [10]. Focusing on the unsteady flow behavior of supersonic impinging jets, some experimental observations commented on the small instability waves (vortices) around the jet shear layers [5] and consequent acoustic noise [5], [11], and explained the feedback loop [12]; while Tam and Ahuja [6] put forward another theoretical model for the acoustic feedback loop.…”

Section: Introductionmentioning

confidence: 99%