Effect of Co-Flow on Near Field Shock Structure

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
T. Srinivasarao ◽  
P. Lovaraju ◽  
E. Rathakrishnan
Keyword(s):  
Near Field ◽  
Shock Structure ◽  
Experimental Results ◽  
Underexpanded Jets ◽  
Core Length ◽  
Central Nozzle ◽  
Supersonic Core Length ◽  
Expansion Level

This paper presents the experimental results of underexpanded jets delivered from a central nozzle surrounded by a co-flow. The co-flow is found to be effective in elongating the supersonic core length of the central jet, at all levels of underexpansion. However, the expansion level of the central jet dictates the elongation caused by the co-flow.

Effect of flat wall length on decay and shock structure of a supersonic square wall jet

2021 ◽  
pp. 095441002110580
Author(s):  
Venkata Satya Manikanta Tammabathula ◽  
Venkata Sai Krishna Ghanta ◽  
Tharaka Narendra Sridhar Bandla
Keyword(s):  
Supersonic Jet ◽  
Leading Edge ◽  
Shock Structure ◽  
Wall Jet ◽  
Pressure Measurements ◽  
Maximum Enhancement ◽  
Flat Wall ◽  
Decay Behaviour ◽  
Core Length ◽  
Supersonic Core Length

Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [Formula: see text] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [Formula: see text] up to [Formula: see text] whereas a downward jet deflection was observed for [Formula: see text]. Noticeable changes in the shock structure were observed for the wall lengths up to 2 D h. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [Formula: see text]. However, when the wall length was increased to [Formula: see text], there was a significant reduction in jet decay and a recovery of [Formula: see text]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [Formula: see text] > [Formula: see text].

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

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

Effect of Mach number on the acoustic field of 2:1 elliptic-slot jet

2001 ◽  
Vol 105 (1043) ◽  
pp. 9-16 ◽  
Author(s):  
S. B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Mach Number ◽  
Fundamental Frequency ◽  
Acoustic Field ◽  
Major Axis ◽  
Shock Structure ◽  
Minor Axis ◽  
Noise Levels ◽  
Underexpanded Jets ◽  
Barrel Shock ◽  
Mach Numbers

Abstract The shock-structure and the related acoustic field of underexpanded jets undergoes significant changes as the Mach number Mj is increased. The present investigation is carried out to study the effect of Mach number on an underexpanded 2:1 elliptic-slot jet. Experimental data are presented for fully expanded Mach numbers ranging from 1.3 to 2.0. It is observed that the ‘cross-over’ point at the end of the first cell at low Mach numbers gets replaced by a normal shock at a highly underexpanded condition resulting in the formation of a ‘barrel’ shock along the minor-axis side with a ‘bulb’ shock formed along the major-axis side. The above change in shock structure is accompanied by a related change in the acoustic field. The amplitude of fundamental frequency along the minor-axis side grows with Mj but falls beyond Mj = 1.75. Along the major-axis side, however, the fundamental frequency does not exist at low Mach numbers. It appears at Mj = 1.75 but then falls at Mj = 2.0. The related azimuthal directivity of overall noise levels (OASPL) shows significant changes with Mj.

An experimental study of underexpanded sonic, coaxial, swirl jets

2004 ◽  
Vol 218 (1) ◽  
pp. 93-103 ◽  
Author(s):  
K-H Lee ◽  
T Setoguchi ◽  
S Matsuo ◽  
H-D Kim
Keyword(s):  
Static Pressure ◽  
Near Field ◽  
Flow Structures ◽  
Experimental Investigations ◽  
Pressure Measurements ◽  
Annular Nozzle ◽  
Free Jets ◽  
Underexpanded Jets ◽  
Secondary Stream ◽  
The Impact

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.

Research of Sewage Marine Discharge Diffusion Effect under Deep Water

2013 ◽  
Vol 726-731 ◽  
pp. 1027-1031
Author(s):  
Hang Yu ◽  
Jing Feng Bai ◽  
Xin Hai Wang ◽  
Hong Xin Zhao
Keyword(s):  
Model Test ◽  
Deep Water ◽  
Near Field ◽  
Large Angle ◽  
Hydraulic Model ◽  
Experimental Results ◽  
Premature Convergence ◽  
Design Parameters ◽  
Diffusion Effect ◽  
Horizontal Angle

The sewage diffusion effect under deep water was carried out between different diffuser design parameters based on the hydraulic model test, and Huizhou Dayawan sewage marine disposal project was taken as an example. The experimental results show that the design parameters are significant for sewage diffusion at the near field. For Dayawan project, jet angle was controlled to be 20 degree, and horizontal angle was controlled to be 90 degree. It not only can ensure that sewage fully diluted mixed, also can avoid the premature convergence and sewage lifting. It is feasible for selecting large angle nozzle under deep water and there are some technical bases have been provided for other sewage marine disposal project.

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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