Numerical Calculation of Underexpanded Axisymmetric Supersonic Jet. Effects of Nozzle Divergence Angle and Mach Number on Shock Cell Length.

1995 ◽  
Vol 61 (589) ◽  
pp. 3236-3242 ◽  
Author(s):  
Hiroshi Katanoda ◽  
Yoshiaki Miyazato ◽  
Mitsuharu Masuda ◽  
Kazuyasu Matsuo
Keyword(s):  
Numerical Calculation ◽  
Mach Number ◽  
Supersonic Jet ◽  
Cell Length ◽  
Divergence Angle ◽  
Shock Cell

scholarly journals Numerical Study of Characteristics of Underexpanded Supersonic Jet

2020 ◽  
Author(s):  
Priyadharshini Murugesan ◽  
Arjun Biju Kumar ◽  
Akhil Teja Kambhampati ◽  
Shashank Pillai ◽  
Girish Chandar Chandrasekar ◽  
...  
Keyword(s):  
Mach Number ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Working Fluid ◽  
Shock Cell ◽  
Specific Heats ◽  
Supersonic Core Length ◽  
The Mean ◽  
Jet Characteristics

Correlations for the supersonic jet characteristics, the mean shock cell length and the supersonic core length, have been obtained in terms of the jet parameters. The jet parameters considered in this study are the exit diameter of the nozzle (de), the design Mach number (Me), the nozzle pressure ratio (NPR) and the ratio of specific heats of the medium (γ). The parameters were varied as follows: exit diameters, from 0.5 to 25 mm; Mach number from 1 to 3; the NPR from 2.14 to 35. Initially, working fluid used is cold air and then effect of variation of γ is taken into consideration. The computational model has been validated and then used for all the numerical simulations. A quadratic fit for both characteristics has been obtained which is applicable to any supersonic jet. The correlations developed are valid within the respective ranges of the parameters stated above.

Investigation on the Source Locations of Axisymmetric Screech Tones Utilizing Data from Numerical Simulation

2019 ◽  
Vol 27 (04) ◽  
pp. 1850058
Author(s):  
Incheol Lee ◽  
Duck Joo Lee
Keyword(s):  
Mach Number ◽  
Fourth Order ◽  
Mixing Layer ◽  
Supersonic Jet ◽  
Shock Cell ◽  
Jet Mixing ◽  
Screech Tone ◽  
Runge Kutta Method ◽  
Cell Structures ◽  
Screech Tones

The source locations of axisymmetric modes of screech tones are numerically investigated. Fourth-order optimized compact scheme and fourth-order Runge–Kutta method are used to solve the 2-D axisymmetric Euler equations. The screech tone is successfully reproduced, and the change in wavelength with respect to jet Mach number shows good agreement with the experimental data. At various low supersonic jet Mach numbers, the time-averaged contours of Mach number and root-mean-square pressure are investigated to identify the location of maximum interaction between shock cell structures and vortices. The source locations of two axisymmetric modes, A1 and A2 modes, are distinctly visualized and identified; the screech tones of A1 mode are generated at the apex of fifth shock cell, and the screech tones of A2 mode are generated at the apex of fourth shock cell. Based on the observation, a simple formula for the prediction of axisymmetric modes of screech tones is proposed. The formula is derived based on a form of Rossiter equation, with the assumption of different convection speeds along the jet mixing layer. The proposed formula successfully estimates the frequency of two axisymmetric modes of screech tones, which verifies that the identified source locations of the axisymmetric screech tones are reasonable.

Flow field and acoustics characteristics of elliptical jet

2018 ◽  
Vol 90 (9) ◽  
pp. 1364-1371 ◽  
Author(s):  
S. Manigandan ◽  
Vijayaraja K.
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Rapid Change ◽  
Supersonic Jet ◽  
Major Axis ◽  
Minor Axis ◽  
Shock Cell ◽  
Potential Core ◽  
Content Type ◽  
Elliptical Jet

Purpose The purpose of this paper is to present the results of mixing promotion and screech frequency of controlled elliptical supersonic jet. Design/methodology/approach Flow field characteristics of low-aspect-ratio elliptical jets are examined at over-expanded, under-expanded and correctly expanded conditions. The tabs are placed at elliptical jet exit along the major and minor axes. Findings The results show that the mixing done by the minor axis is superior to the tabs along major axis. At all pressure ratios, the content of jet noise and the frequency are high for the tabs along the major axis because of increase in the amplitude of screech frequency. Further the tabs along minor axis show a dominance of large-scale vertical structures. In under-expanded conditions, the shock cell shows the rapid change because of the presence of tabs. The tabs along minor axis are making the shock weaker, hence no evidence of axis switching. Practical implications To achieve the greater performance of jet, the authors need to reduce the potential core length of the issuing jet. This can be achieved by implementing different types of tabs at the exit of the nozzle. Originality/value The present paper represents the flow of controlled jet using inverted triangular tabs. By achieving the controlled jet flow, the performance of propulsion systems can be improved. This can be used in systems such as combustion chamber, missile’s noise reduction and thrust vector control.

Noisefield of Underexpanded Notched Circular-Slot Jets

2002 ◽  
Vol 33 (6) ◽  
pp. 9-23
Author(s):  
S.B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Acoustic Emission ◽  
Aspect Ratio ◽  
Cell Length ◽  
Emission Characteristics ◽  
Far Field ◽  
Shock Cell ◽  
Acoustic Spectrum ◽  
Compression Waves ◽  
Noise Field ◽  
Notch Geometry

The effect of notches on the flow and noise field of jets from circular-slots is experimentally investigated. Three types of slot geometries, namely, semicircular, triangular and square are studied. The results demonstrate that the presence of the notch introduces a slight aspect-ratio in the initial circular-slot geometry so that the notched jet exhibits characteristics, similar to jets exiting from non-circular geometries. At underexpanded condition, additional expansion and compression waves are observed to emanate from the region of notches that modifies the jet development and results in a reduction in the average shock-cell length, which is accompanied by a reduction in far-field shock associated noise. The acoustic spectrum of the radiated shock noise indicates that notch geometry variation strongly alters the acoustic emission characteristics of these jets both in the screech component and broadband shock associated noise.

Experimental Investigation on Supersonic Jet Screech Tones

2012 ◽  
Vol 232 ◽  
pp. 213-217
Author(s):  
Jia Ming Li ◽  
Chun Bo Hu ◽  
Jun Hua Bai
Keyword(s):  
Mach Number ◽  
Field Distribution ◽  
Experimental Measurement ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Occurrence Frequency ◽  
Supersonic Jet Noise ◽  
Nozzle Size ◽  
Screech Tones ◽  
Peak Value

In order to investigate the characteristic of the supersonic jet screech tones, an experimental bench of the supersonic jet was designed and a free field noise signal acquisition system was established. Effects of the nozzle size and jet Mach number on jet noise sound field distribution was analyzed, through the result comparison of supersonic jet noise experimental measurement. Results indicate that the field distribution of supersonic jet screech tones is characterized with very strong directivity. Peak value of the screech tones decrease and occurrence frequency of the screech tones increase with the decreasing jet exit Mach number; occurrence frequency of the screech tones decrease with the increasing nozzle size, but the peak value change very less. The experimental measurement of supersonic jet noise provides mechanism research of sound production with data supports and references; and also provides the numerical modeling of supersonic jet noise with validation criteria.

Numerical Simulation of Supersonic Jet Control by Tabs with Slanted Perforation

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
G. Ezhilmaran ◽  
Suresh Chandra Khandai ◽  
Yogesh Kumar Sinha ◽  
S. Thanigaiarasu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Near Field ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Pressure Gradients ◽  
Nozzle Pressure Ratio ◽  
Nozzle Pressure ◽  
Jet Control ◽  
Different Diameters

Abstract This paper presents the numerical simulation of Mach 1.5 supersonic jet with perforated tabs. The jet with straight perforation tab was compared with jets having slanted perforated tabs of different diameters. The perforation angles were kept as 0° and 10° with respect to the axis of the nozzle. The blockage areas of the tabs were 4.9 %, 4.9 % and 2.4 % for straight perforation, 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.3 mm) and 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.65 mm) respectively. The 3-D numerical simulations were carried out using the software. The mixing enhancements caused by these tabs were studied in the presence of adverse and favourable pressure gradients, corresponding to nozzle pressure ratio (NPR) of 3, 3.7 and 5. For Mach number 1.5 jet, NPR 3 corresponds to 18.92 % adverse pressure gradients and NPR 5 corresponds to 35.13 % favourable pressure gradients. The centerline Mach number of the jet with slanted perforations is found to decay at a faster rate than uncontrolled nozzle and jet with straight perforation tab. Mach number plots were obtained at both near-field and far field downstream locations. There is 25 % and 65 % reduction in jet core length were observed for the 0° and 10° perforated tabs respectively in comparison to uncontrolled jet.

scholarly journals Density measurements for rectangular free jets using background-oriented schlieren

2013 ◽  
Vol 117 (1194) ◽  
pp. 771-785 ◽  
Author(s):  
T. J. Tipnis ◽  
M. V. Finnis ◽  
K. Knowles ◽  
D. Bray
Keyword(s):  
Supersonic Jet ◽  
Digital Camera ◽  
Shock Cell ◽  
Axisymmetric Jets ◽  
Cell Spacing ◽  
Optical Alignment ◽  
Background Oriented Schlieren ◽  
Set Up ◽  
Axis Switching ◽  
Good Agreement

AbstractAn experimental study incorporating the use of the Background-Oriented Schlieren (BOS) technique was performed to measure the density field of a rectangular supersonic jet. This technique is easier to set up than conventional schlieren since the optical alignment involving the various mirrors, lenses and knife-edge is replaced by a background pattern and a single digital camera. The acquired images which contain information of density gradients in the flow are solved as a Poisson equation and further processed using deconvolution and tomographic algorithms to generate a 3D domain which contains information about the actual density. 2D slices can then be extracted to quantitatively visualise the density along any required planes. The results from supersonic axisymmetric jets are used for validation of the code; these show excellent agreement with pre-validated CFD data. The results for a rectangular supersonic jet are then obtained. These show good agreement with the CFD data, in terms of shock-cell spacing and overall structure of the jet. The technique has proved useful for investigating axis-switching, a phenomenon generally associated with non-axisymmetric jets.

Numerical Simulation of Rocket Nozzle

2014 ◽  
Vol 984-985 ◽  
pp. 1210-1213
Author(s):  
G. Srinivas ◽  
Srinivasa Rao Potti
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Divergence Angle ◽  
Performance Parameters ◽  
Ansys Fluent ◽  
Rocket Nozzle ◽  
The Public ◽  
Pressure Distributions ◽  
Fluent Software ◽  
Computational Fluid Dynamics Cfd

The vent or opening is called nozzle. The objectives are to measure the flow rates and pressure distributions within the converging and diverging nozzle under different exit and inlet pressure ratios. Analytic results will be used to contrast the measurements for the pressure and normal shock locations. In this paper computational Fluid Dynamics (CFD) Analysis of various performance parameters like static pressure, the Mach number, intensity of turbulence, the area ratio are studied in detail for a rocket nozzle from Inlet to exit by using Ansys Fluent software. From the public literature survey the geometry co-ordinates are taken. The throat diameter and exit and diameter are same for all nozzles. After the simulation the results revealed that the divergence angle varies the mach number and other performance parameters also varies. For smaller nozzle angle the discharge coefficient increases with increasing pressure ratio until the choked condition is reached for varying the divergence angle.

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