Single Jet-Induced Effects on Small-Scale Hover Data in Ground Effect

Levin, Daniel; Wardwell, Douglas A.

doi:10.2514/2.2183

Cited by 15 publications

(9 citation statements)

References 3 publications

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“…Here, L is the downward force on the plate; L f is the downward force on the plate for a free jet; T is the jet thrust, D is the diameter of the lift plate and d is the nozzle throat diameter. This relationship is very similar to that obtained by Levin & Wardwell (1997).…”

Section: Hover Lift Losssupporting

confidence: 90%

“…Measurable variations in lift loss with NPR are only observed for h/d 6 3. As alluded to in § 1 this nonlinear loss in lift was also observed by previous investigators (Levin & Wardwell 1997). It is speculated that the NPR range over which these variations are observed are, in part, related to the appearance of the stand-off shock and associated bubble.…”

Section: Hover Lift Losssupporting

confidence: 79%

“…In contrast to subsonic flows, very few data are at present available for supersonic impinging jets in STOVL configurations. In a recent study, researchers observed a nonmonotonic lift loss as a function of jet NPR for a supersonic impinging jet (Levin & Wardwell 1997). From the flow-visualization data, they speculated that this nonlinear lift loss behaviour may be related to the jet shock cell structure; however, a more rigorous explanation remains elusive.…”

Section: Hover Lift Lossmentioning

confidence: 99%

“…This issue will be further explored later. Also included in the figure is the data for an underexpanded jet (NPR = 2.75) taken from Levin & Wardwell (1997). Their measurements were obtained directly using a thrust balance and a sonic nozzle.…”

Section: Hover Lift Lossmentioning

confidence: 99%

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Flow field and noise characteristics of a supersonic impinging jet

et al. 1999

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This paper describes the results of a study examining the flow and acoustic characteristics of an axisymmetric supersonic jet issuing from a sonic and a Mach 1.5 converging-diverging (C-D) nozzle and impinging on a ground plane. Emphasis is placed on the Mach 1.5 nozzle with the sonic nozzle used mainly for comparison. A large-diameter circular plate was attached at the nozzle exit to measure the forces generated on the plate owing to jet impingement. The experimental results described in this paper include lift loss, particle image velocimetry (PIV) and acoustic measurements. Suckdown forces as high as 60% of the primary jet thrust were measured when the ground plane was very close to the jet exit. The PIV measurements were used to explain the increase in suckdown forces due to high entrainment velocities. The self-sustained oscillatory frequencies of the impinging jet were predicted using a feedback loop that uses the measured convection velocities of the large-scale coherent vortical structures in the jet shear layer. Nearfield acoustic measurements indicate that the presence of the ground plane increases the overall sound pressure levels (OASPL) by approximately 8 dB relative to a corresponding free jet. For moderately underexpanded jets, the influence of the shock cells on the important flow features was found to be negligible except for close proximity of the ground plane.

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Section: Hover Lift Losssupporting

confidence: 90%

Section: Hover Lift Losssupporting

confidence: 79%

Section: Hover Lift Lossmentioning

confidence: 99%

Section: Hover Lift Lossmentioning

confidence: 99%

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Flow field and noise characteristics of a supersonic impinging jet

et al. 1999

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“…17 The "impingement" tones are generated by a complex flow field structure and are particularly relevant for a large number of applications which develop a host of undesirable phenomena, like significant acoustic emissions, lift loss and surface erosion. [20][21][22][23] The effect of a possible impingement surface on the screech tone is still an open question. We observe that in an axisymmetric circular jet the dominant sound sources of the screech tones are located approximately between the rear edge of the third and the fifth shock cells, 9 depending on the different oscillation modes.…”

Section: Introductionmentioning

confidence: 99%