Experimental Investigation of Nozzle Orientation Effects on Mixing Characteristics of Elliptic Triple Free Jets

2019 ◽  
Author(s):  
Ella M. Morris ◽  
Seyed S. Aleyasin ◽  
Neelakash Biswas ◽  
Mark F. Tachie
Keyword(s):  
Experimental Investigation ◽  
Potential Core ◽  
Linear Contraction ◽  
Free Jets ◽  
Orientation Effects ◽  
Core Length ◽  
Turbulent Characteristics ◽  
Major Plane ◽  
Nozzle Orientation ◽  
Minor Plane

Abstract An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had all three nozzles oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (2_Minor_1_Major) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (1_Minor_2_Major). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle-to-nozzle distance of 4.1, a nozzle equivalent diameter of 9 mm and a Reynolds number of 10,000. The effects of nozzle orientation on the mean velocity, turbulence intensity and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point, combined point and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The results show that the 3_Minor configuration had shorter potential core length and closer merging point location which are indicative of a faster mixing in the converging region. Two-point correlation, skewness and flatness factors were used to provide insight into the effects of nozzle orientation on turbulence structure and higher order turbulence statistics.

Turbulent Properties of Triple Elliptic Free Jets With Various Nozzle Orientation

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Ella Marie Morris ◽  
Seyed Sobhan Aleyasin ◽  
Neelakash Biswas ◽  
Mark Francis Tachie
Keyword(s):  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Turbulent Intensity ◽  
Potential Core ◽  
Free Jets ◽  
Orientation Effects ◽  
Core Length ◽  
Major Plane ◽  
Nozzle Orientation ◽  
Minor Plane

Abstract An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had each nozzle oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (Min_Maj_Min) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (Maj_Min_Maj). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle spacing ratio of 4.1d, a nozzle equivalent diameter of 9 mm, and Reynolds number of 10,000. Nozzle orientation effects on the mean velocity, turbulent intensity, and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point (MP), combined point (CP), and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The 3_Minor configuration had shorter potential core length and closer MP location which are indicative of a faster mixing in the converging region. The early merging of 3_Minor led to higher levels of streamwise turbulent intensity. One-dimensional plots revealed that jets approached self-similarity at a faster rate in the major axis. The orientation of the middle jet was found to be a key factor in determining transverse diffusion of the Reynolds shear stress in the plane of observation. Two-point correlations were used to provide insight into the effects of nozzle orientation on the spatial coherence of the large-scale turbulence structure and integral length scale.

The Effects of Nozzle Orientation on Mixing Characteristics of Elliptic Twin Free Jets

2019 ◽  
Author(s):  
Ella M. Morris ◽  
Neelakash Biswas ◽  
Seyed S. Aleyasin ◽  
Mark F. Tachie
Keyword(s):  
Symmetry Plane ◽  
Velocity Profiles ◽  
Particle Image Velocimetry System ◽  
Equivalent Diameter ◽  
Linear Contraction ◽  
Turbulent Characteristics ◽  
Major Plane ◽  
Single Jet ◽  
Nozzle Orientation ◽  
Minor Plane

Abstract The effects of nozzle orientation on the mixing and turbulent characteristics of elliptical free twin jets were studied experimentally. The experiments were conducted using modified contoured nozzles with a sharp linear contraction. The centers of the nozzle pair had a separation ratio of 5.5. Four nozzle configurations were tested, one twin jet orientated along the minor plane (Twin_Minor), one twin jet orientated along the major plane (Twin_Major), one single jet orientated along the minor plane (Single_Minor) and one single jet orientated along the major plane (Single_Major). In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 10,000. A planar particle image velocimetry system was used to measure the velocity field in the jet symmetry plane. It was observed that the velocity decay rate is not sensitive to nozzle orientation. However, close to the jet exit the spread rate was highest in the minor plane. In addition, contour plots of Reynolds shear stress and turbulence intensities revealed significant differences between the minor and major plane. Velocity profiles showed little variation close to the jet exit, while further downstream the variations between the velocity profiles were more pronounced between the major and minor planes.

Particle Image Velocimetry Measurements of Turbulent Jets Issuing From Twin Elliptic Nozzles With Various Orientations

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Ella Marie Morris ◽  
Neelakash Biswas ◽  
Seyed Sobhan Aleyasin ◽  
Mark Francis Tachie
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Symmetry Plane ◽  
Velocity Profiles ◽  
Equivalent Diameter ◽  
Linear Contraction ◽  
Turbulent Characteristics ◽  
Image Velocimetry ◽  
Nozzle Orientation ◽  
Minor Plane

Abstract The effects of nozzle orientation on the mixing and turbulent characteristics of elliptical free twin jets were studied experimentally. The experiments were conducted using modified contoured nozzles with a sharp linear contraction. The centers of the nozzle pair had a separation ratio of 5.5. Two nozzle configurations were tested, twin nozzles oriented along the minor plane (Twin_Minor) and twin nozzles oriented along the major plane (Twin_Major) and the results were compared with a single jet. In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 10,000. A planar particle image velocimetry (PIV) system was used to measure the velocity field in the jet symmetry plane. It was observed that the velocity decay rate is not sensitive to nozzle orientation. However, close to the jet exit, the spread rate was highest in the minor plane. In addition, contour plots of swirling strength, Reynolds shear stress and turbulent intensities revealed significant differences between the minor and major planes. Velocity profiles showed little variation close to the jet exit, while further downstream the variations between the velocity profiles were more pronounced between the major and minor planes.

scholarly journals Scaling law for supersonic core length in circular and elliptic free jets

2021 ◽  
Vol 33 (5) ◽  
pp. 051707
Author(s):  
Arun Kumar Perumal ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Scaling Law ◽  
Free Jets ◽  
Core Length ◽  
Supersonic Core Length

Effect of Development-Zone Restrictions on the Turbulent Characteristics of Impinging Jet Flow

2011 ◽  
Author(s):  
Takefumi Kawaguchi ◽  
Chandra Shekhar ◽  
Koichi Nishino
Keyword(s):  
Impinging Jet ◽  
Jet Flow ◽  
Stagnation Region ◽  
Development Zone ◽  
Potential Core ◽  
Turbulent Statistics ◽  
Piv Measurement ◽  
Turbulent Characteristics ◽  
Inner Diameter ◽  
Solid Block

This study is to examine the turbulent characteristics of an axisymmetric impinging jet flow in the stagnation region. The flow measurement is carried out using a standard PIV technique. The changes of the turbulent characteristics of the jet with various levels of the development-zone restriction are examined. The restrictions are imposed by putting an annular, concentric, solid block around the jet, and then varying its inner diameter. The PIV measurement of the flow field is carried out for each case. The height of the block is kept constant for all the cases, with the Reynolds number of 5000, which falls well within the turbulent range. The instantaneous velocity data obtained from the PIV measurement is used to calculate the turbulent statistics. The results are compared for all of the cases. In consequence, it is found that the turbulent statistics do not change much for the block’s inner diameter larger than a critical value, which is found to be three times the inlet diameter of the jet. However, if it is smaller, the turbulent statistics vary significantly, as the inner wall of the block damages the development of the potential core of the jet.

Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

2020 ◽  
Vol 92 (7) ◽  
pp. 955-972
Author(s):  
Roy V. Paul ◽  
Kriparaj K.G. ◽  
Tide P.S.
Keyword(s):  
Flow Characteristics ◽  
Experimental Results ◽  
Potential Core ◽  
Content Type ◽  
Numerical Predictions ◽  
Core Length ◽  
Chevron Nozzle ◽  
Centreline Velocity ◽  
Subsonic Jet ◽  
Lobed Nozzle

Purpose The purpose of this study is to investigate the aerodynamic characteristics of subsonic jet emanating from corrugated lobed nozzle. Design/methodology/approach Numerical simulations of subsonic turbulent jets from corrugated lobed nozzles using shear stress transport k-ω turbulence model have been carried out. The analysis was carried out by varying parameters such as lobe length, lobe penetration and lobe count at a Mach number of 0.75. The numerical predictions of axial and radial variation of the mean axial velocity, u′u′ ¯ and v′v′ ¯ have been compared with experimental results of conventional round and chevron nozzles reported in the literature. Findings The centreline velocity at the exit of the corrugated lobed nozzle was found to be lower than the velocity at the outer edges of the nozzle. The predicted potential core length is lesser than the experimental results of the conventional round nozzle and hence the decay in centreline velocity is faster. The centreline velocity increases with the increase in lobe length and becomes more uniform at the exit. The potential core length increases with the increase in lobe count and decreases with the increase in lobe penetration. The turbulent kinetic energy region is narrower with early appearance of a stronger peak for higher lobe penetration. The centreline velocity degrades much faster in the corrugated nozzle than the chevron nozzle and the peak value of Reynolds stress appears in the vicinity of the nozzle exit. Practical implications The corrugated lobed nozzles are used for enhancing mixing without the thrust penalty inducing better acoustic benefits. Originality/value The prominent features of the corrugated lobed nozzle were obtained from the extensive study of variation of flow characteristics for different lobe parameters after making comparison with round and chevron nozzle, which paved the way to the utilization of these nozzles for various applications.

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