Flow characteristic of highly underexpanded jets from various nozzle geometries

Li, Xiaopeng; Zhou, Rui; Yao, Wei; Fan, Xuejun

doi:10.1016/j.applthermaleng.2017.07.002

Cited by 58 publications

(30 citation statements)

References 59 publications

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“…The results showed that the ribbed jets performed good mixing characteristics and the inner-ribbed nozzle induced high-flow fluctuations behind the rib, which were characterized by a fluid flapping motion due to the periodic reattachment of the flow on the pipe wall [31]. Li et al [32] reported the flow characteristic of highly under-expanded jets from different nozzle geometry, i.e., the circular, elliptic, square, and rectangular, by using LES. Great differences were shown on the formation and development of the intercepting shocks, while the elliptic jet had the slowest penetration rates.…”

Section: Flow Configurationmentioning

confidence: 99%

Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Fang

Zhang

et al. 2019

Energies

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Pulsed waterjet can break rocks effectively by taking advantage of the water hammer effect, and is thus widely used in mining, petroleum, and natural gas fields. With the aim to further clarify the flow field characteristics of pulsed jets induced by a Helmholtz oscillator, large eddy simulation was conducted under different operating pressures. The velocity distribution, mean flow field, and the coherent structure were examined using the oscillators of different cavity lengths and diameters. The results clearly showed that the major frequency of jet pulsation gradually increased with the increase of operating pressure. A stable periodic velocity core was formed at the outlet of the Helmholtz oscillator, while the external flow field was subjected to periodic impact. As a result, the ambient fluid was strongly entrained into the jet beam. With the increase of the cavity length, the length of the core segment decreased while the energy loss caused by the cavity increased, which was also accompanied by a rapid attenuation of the axial velocity at the jet outlet. The coherent structure of the jet in the oscillator with small cavity diameter was more disordered near the nozzle outlet, and the vortex scale was larger. The effect of cavity diameter can be reflected in the feedback modulation of the jet in the cavity. Compared with the conical nozzle, the length of the core section of the jet was shorter, but the jet had better bunching, a smaller diffusion angle, and better mixing performance. These results provide a further understanding of the characteristics of pulsed water jet for better utilizations in the fields of energy exploitation. a self-propelled water-jet drilling nozzle to drill three-type boreholes to improve gas extraction and drilling experiments were conducted to optimize the nozzle configuration. As a generator of SEOPJ, attention has been paid to the Helmholtz oscillator and extensive research has been done by . The unsteady flow phenomenon in SEOPJ is combined with various theories such as fluid dynamics, fluid resonance, and hydroelasticity, which makes it difficult to measure the flow patterns and vortex structures. In particular, an experimental study was conducted to characterize the discrete model by the change of cavity length and to give stable working regions under various parameters [7]. The identification of the complex mechanism responsible for this phenomenon is difficult because it is the result of multiple factors and data acquisition of all the instantaneous fields simultaneously is unavailable under the existing measurement techniques [8].Energies 2019, 12, x FOR PEER REVIEW 3 of 21 be distinguished. The research results can be used as the theoretical basis for selection and design of SEOPJ nozzles in underground mining.

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Section: Flow Configurationmentioning

confidence: 99%

Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Fang

Zhang

et al. 2019

Energies

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“…The flow characteristics of under expanded jet from different nozzle such as square, circular, elliptical and rectangular are studied using eddy simulation at a pressure ratio of 5.60. The results show the jet penetrates fastest in the square nozzle and even though the turbulence transition is similar [6]- [7]. The effects of nozzle, jet temperature and heat transfer, distribution due to the jet on the smooth surface plate are studied.…”

Section: Introductionmentioning

confidence: 98%

Flow Analysis of Hybrid Rocket Nozzle Exhaust and Its Effects on Launch Pad and Guide Stand

Christopher¹,

Kumar²,

K*³

et al. 2019

IJRTE

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The exhaust from the nozzle will be at very high temperature and the high temperature exhausts effect the launch pad and guide stand. In this research, the computational analysis is done on Hybrid Rocket Nozzle Exhaust and Its Effects on Launch Pad and Guide Stand. The flow characteristics such as pressure, temperature, velocity and Mach number at different time period have been studied for various exit geometries using ANSYS Fluent solver. Exhaust speeds vary, depending on the expansion proportion of the nozzle. The rocket nozzle along with guide stand is modelled. The aeroacoustics effects from the nozzle on Launch Pad and Guide Stand have been studied separately using acoustics model.

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“…Bodony and Lele [21] demonstrated the capability of large-eddy simulations (LES) to recreate farfield acoustic properties of turbulent jets across various Mach regimes and temperature ratios. Simulations have also provided insights into complex operating conditions like high density-ratios [22], presence of control mechanisms [23], effects of non-trivial nozzle geometries [24] and associated instabilities [25] of the shear layer. Such high-fidelity simulations greatly expand access to detailed spatio-temporal fluctuations in the turbulent region and shock-cell dynamics, particularly, for imperfectly expanded jets.…”

Section: Introductionmentioning

confidence: 99%

Energy-Dynamics Resulting in Turbulent and Acoustic Phenomena in an Underexpanded Jet

2018

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Underexpanded jets exhibit interactions between turbulent shear layers and shock-cell trains that yield complex phenomena that are absent in the more commonly studied perfectly expanded jets. We quantitatively analyze these mechanisms by considering the interplay between hydrodynamic (turbulence) and acoustic modes, using a validated large-eddy simulation. Using momentum potential theory (MPT) to achieve energy segregation, the following observations are made. The sharp gradients in fluctuations introduced by the shock-cell structure are captured mostly in the hydrodynamic mode, whose amplitude is an order of magnitude larger than the acoustic mode. The acoustic mode has a relatively smoother distribution, exhibiting a compact wavepacket form. Proper orthogonal decomposition (POD) identifies the third-to-sixth cells as the most dynamic structures. The imprint of shock cells is discernible in the nearfield of the acoustic mode, primarily along the sideline direction. Energy interactions that feed the acoustic mode remain compact in nature, facilitating a simple propagation technique for farfield noise prediction. The farfield sound spectra show peak directivity at 30 • to the downstream axis. The POD modes of the acoustic component also identify two main energetic components in the wavepacket: one representative of the periodic internal structure and the other of intermittent downstream lobes. The latter component occurs at exactly the same frequency as, and displays high correlation with, the farfield peak noise spectra, making the acoustic mode a better predictor of the dynamics than velocity fluctuations.

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Flow characteristic of highly underexpanded jets from various nozzle geometries

Cited by 58 publications

References 59 publications

Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Flow Analysis of Hybrid Rocket Nozzle Exhaust and Its Effects on Launch Pad and Guide Stand

Energy-Dynamics Resulting in Turbulent and Acoustic Phenomena in an Underexpanded Jet

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