Near Field Aeroacoustics of a Jet from Elliptical Nozzle at M=0.8

Sharma, S.K.; Murugan, K. N.

doi:10.2514/6.2010-3955

Cited by 4 publications

(1 citation statement)

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“…Figure 3 shows the mean velocity distribution along the centerline of the jet. The potential core length for the base circular nozzle extends up to about five diameters downstream, which shows good agreement with many of the earlier measurements (Lau et al 1979, Kolpin 1964, Alkislar et al 2007, Tide and Babu 2009, Yu et al 2008, Sharma and Murugan 2010. For chevron nozzles CH-1, CH-2 and CH-3 with a systematically increasing penetration of 2%, 4% and 6% of base nozzle exit diameter, respectively, a reduction in the potential core length and an increase in the centerline velocity decay are noticed with an increasing degree of penetration-albeit the effect of CH-1 is only marginal.…”

Section: Aerodynamicssupporting

confidence: 87%

Effect of chevron nozzle penetration on aero-acoustic characteristics of jet at M = 0.8

Nikam

Sharma

2017

Fluid Dyn. Res.

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Aero-acoustic characteristics of a high-speed jet with chevron nozzles are experimentally investigated at a Mach number of 0.8. The main focus is to examine the effects of the extent of chevron penetration and its position in the mixing layer. Chevron nozzles with three different levels of penetration employed at three different longitudinal locations from the nozzle lip are tested, and the results are compared with those of a plain baseline nozzle. The chevrons are found to produce a lobed shear layer through the notched region, thereby increasing the surface area of the jet, particularly in the close vicinity of the nozzle, which increases the mixing and reduces the potential core length. This effect becomes more prominent with increasing penetration closer to the nozzle lip in the thinner mixing layer. Near field and far field noise measurements show distinctly different acoustic features due to chevrons. The chevrons are found to effectively shift the dominant noise source upstream closer to the nozzle. Present investigation proposes a simpler method for locating the dominant noise source from the peak of the centerline velocity decay rate. The overall noise levels registered along the jet edge immediately downstream of the chevrons are higher, but further downstream they are reduced in comparison with the plain baseline nozzle. Also, the chevrons beam the noise towards higher polar angles at higher frequencies. At shallow polar angles with respect to the jet axis in the far field, chevrons suppress the noise at low frequencies with increasing penetration, but for higher polar angles, while they continue to suppress the low frequency noise, at higher frequencies the trend is found to reverse. The noise measured in the near field close to the | The Japan Society of Fluid Mechanics Fluid Dynamics Research Fluid Dyn. Res. 49 (2017) 065506 (33pp)

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