Characteristics of lifted triple flames stabilized in the near field of a partially premixed axisymmetric jet

2002 ◽  
Author(s):  
X. Qin ◽  
I. Puri ◽  
S. Aggarwal
Keyword(s):  
Near Field ◽  
Axisymmetric Jet ◽  
Partially Premixed

Near-Field Characteristics of a Jet With a Coil-Insert Injector

2006 ◽  
Author(s):  
Hamid R. Rahai ◽  
Ayaz Alware ◽  
Daniel Carpio ◽  
Eyass Khansa
Keyword(s):  
Near Field ◽  
Axial Flow ◽  
Volume Flow ◽  
Turbulent Velocity ◽  
Time Resolved ◽  
Axisymmetric Jet ◽  
Inside Diameter ◽  
Shaped Tube ◽  
Coil Diameter ◽  
Radial Injection

Simultaneous time resolved measurements of two components of turbulent velocity and their cross moments are made at the exit and downstream of an axisymmetric jet with a coil-insert injector. The coil-insert injector is a coil shaped tube with ratios of coil diameter, pitch spacing and length to the jet inside diameter of 0.1, 1.0, and 1.5 respectively. The coil had three round holes of 0.2 mm diameter at the middle of each pitch for radial injection. The volume flow ratios of the radial blowing to the axial flow were 0.075, 0.10, 0.125, and 0.15. Results indicate that the radial blowing enhances asymmetry and increased generation of turbulence intensities at the jet outlet. However, increased entrainment and mixing between the injected flow and the axial flow reduces the asymmetry downstream, resulting in relatively constant intensities in the region with high axial momentum.

Velocity and Pressure Measurements of a Mach 0.85 Axisymmetric Jet

2007 ◽  
Author(s):  
Richa Mann ◽  
Lawrence S. Ukeiley ◽  
John M. Seiner
Keyword(s):  
Velocity Field ◽  
Radial Velocity ◽  
Nozzle Exit ◽  
Near Field ◽  
Streamwise Velocity ◽  
Pressure Measurements ◽  
Pressure Transducers ◽  
Axisymmetric Jet ◽  
Two Jets ◽  
Heated Jet

The turbulent properties of a heated and unheated Mach 0.85 axisymmetric jet have been studied. The velocity field of the jet at static temperature ratios of 0.87 and 2.34, was measured in the streamwise radial plane using Particle Image Velocimetry. The velocity measurements were acquired between streamwise locations of 3D and 8D downstream from the nozzle exit. Proper Orthogonal Decomposition (POD) was applied to the velocity field using snapshot POD. The POD analysis showed that the eigenvalues of the heated jet had higher fraction of energy. The POD eigenfunctions or modes of the streamwise velocity of both jets were similar, while the POD modes of the radial velocity of both jets were very different. The POD modes of radial velocity of the unheated jet were symmetrical about the jet centerline, and the modes of the heated jet seemed to merge at the centerline. The near field pressure measurements were acquired just outside the shearlayer. A linear array of five pressure transducers was placed at 7° to the nozzle lipline, so that it would be parallel to the shear layer. The transducers in the array were spaced one diameter apart. Pressure measurements were acquired at streamwise locations between 4.25D and 10.25D from the nozzle exit. Based on the slope of the pressure spectra, the propagating events in the two jets were identified. The POD was also applied to the pressure data, and the POD modes of the two jets were compared. The peak in the amplitude of the POD mode of the heated jet was at a higher frequency. With increasing mode numbers, the peak in the POD mode of both jets shifted to a downstream location.

Experimental investigation of the fluctuating static pressure in a subsonic axisymmetric jet

2021 ◽  
pp. 1475472X2110048
Author(s):  
Songqi Li ◽  
Lawrence S Ukeiley
Keyword(s):  
Static Pressure ◽  
Near Field ◽  
Scaling Law ◽  
Pressure Fluctuations ◽  
Power Spectra ◽  
Hydrodynamic Pressure ◽  
Turbulent Velocity ◽  
Fluctuating Pressure ◽  
Jet Mixing ◽  
Axisymmetric Jet

Measuring the fluctuating static pressure within a jet has the potential to depict in-flow sources of the jet noise. In this work, the fluctuating static pressure of a subsonic axisymmetric jet was experimentally investigated using a 1/8” microphone with an aerodynamically shaped nose cone. The power spectra of the fluctuating pressure are found to follow the -7/3 scaling law at the jet centerline with the decay rate varying as the probe approaches the acoustic near field. Profiles of skewness and kurtosis reveal strong intermittency inside the jet shear layer. By applying a continuous wavelet transform (CWT), time-localized footprints of the acoustic sources were detected from the pressure fluctuations. To decompose the fluctuating pressure into the hydrodynamic component and its acoustic counterpart, two techniques based on the CWT are adopted. In the first method the hydrodynamic pressure is isolated by maximizing the correlation with the synchronously measured turbulent velocity, while the second method originates from the Gaussian nature of the acoustic pressure where the separation threshold is determined empirically. Similar results are obtained from both separation techniques, and each pressure component dominates a certain frequency band compared to the global spectrum. Furthermore, cross-spectra between the fluctuating pressure and the turbulent velocity were calculated, and spectral peaks appearing around Strouhal number of 0.4 are indicative of the footprint of the convecting coherent structures inside the jet mixing layer.

An Experimental Investigation of the Pressure-Velocity Cross-Correlation in an Axisymmetric Jet

2005 ◽  
Author(s):  
Andre´ M. Hall ◽  
Mark N. Glauser ◽  
Charles E. Tinney
Keyword(s):  
Velocity Field ◽  
Shear Layer ◽  
Cross Correlation ◽  
Near Field ◽  
Mixing Layer ◽  
Ambient Conditions ◽  
Potential Core ◽  
Axisymmetric Jet ◽  
Exit Nozzle ◽  
The Cross

This study investigates the strength of the pressure-velocity correlations of a Mach 0.6, axisymmetric jet, with an exit nozzle diameter of 50.8mm. Experiments are conducted at a constant exit temperature of 25°C, and exit pressure and temperature are balanced with ambient conditions. The instantaneous velocity measurements are acquired using a multi-component LDA system who’s measurement volume is traversed along several radial and streamwise locations within the potential core, and mixing layer regions of the flow. The fluctuating lip pressure is simultaneously sampled by an azimuthal array of (15) dynamic transducers, evenly spaced at 24°. These are positioned just outside the shear layer near the jet exit at z/D = 0.875, and 1.75R from the centerline, where the pressure field has been shown to be hydrodynamic. From this multi-point evaluation, the cross-correlations between the near-field pressure array (fixed), and streamwise component of the velocity field (traversed) are examined as a function of radial, streamwise, and also azimuthal separation. The results illustrate a remarkable coherence between the near field pressure and the velocity field, on the order of 25%. Streamwise convection velocities of 0.77Uj and 0.73Uj are calculated within the potential core and shear layer, respectively. Analysis of the coherency spectra illustrates the frequency band of the correlations and suggest that the potential core and mixing layer regions of the flow are, in general, governed by the high and low frequency motions of the flow, respectively. The azimuthal modal distribution of the cross-correlation shows the dominance of the column mode of the jet, with no higher modes exhibited within the potential core region, and only modes 1 & 2 within the shear layer.

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