Sound Sources of Screech Tone Radiated from Circular Supersonic Jet Oscillating in the Helical Mode

2002 ◽  
Vol 1 (4) ◽  
pp. 355-384 ◽  
Author(s):  
Yoshikuni Umeda ◽  
Ryuji Ishii
Keyword(s):  
Wave Front ◽  
Vortical Structure ◽  
Supersonic Jet ◽  
Oscillation Mode ◽  
Shock Cell ◽  
Sound Sources ◽  
Screech Tone ◽  
Mach Cones ◽  
Helical Mode ◽  
Jet Axis

The generation mechanism of the screech tone in the helical oscillation mode is investigated using a series of instantaneous schlieren photographs. From the photographs, six evanescent sound sources are observed as prominent points along the jet axis. These sound sources move along circular orbits in the planes perpendicular to the jet axis and just downstream of the rear edges of each shock cell. The speed of moving sound sources is supersonic and the moving Mach cones generated behind the moving sound sources form the helical-shaped wave front of the screech tone. Existence of the moving Mach cones about the jet axis was confirmed by comparing schlieren photographs and drawings of the envelopes of the moving Mach cones. The helical vortical structure appears to overlap on the envelopes of the moving Mach cones.

On the Sound Sources of the Screech Tone Radiated From Circular Underexpanded Jet Oscillating in the Helical Mode

2003 ◽  
Author(s):  
Yoshikuni Umeda ◽  
Ryuji Ishii
Keyword(s):  
Wave Front ◽  
Vortical Structure ◽  
Oscillation Mode ◽  
Shock Cell ◽  
Sound Sources ◽  
Screech Tone ◽  
Underexpanded Jet ◽  
Mach Cones ◽  
Helical Mode ◽  
Jet Axis

The generation mechanism of the screech tone in the helical oscillation mode is investigated using a series of instantaneous photographs. From the photographs, six evanescent sound sources are observed as prominent points along the jet axis. These sound sources move along circular orbits in the planes perpendicular to the jet axis and slightly downstream of the rear edges of each shock cell. The speed of moving sound sources is supersonic and moving Mach cones generated behind the moving sound sources form helical-shaped wave front of the screech tone. Existence of the moving Mach cones about the jet axis was confirmed by comparing schlieren photographs and drawings of the envelopes of the moving Mach cones. The helical vortical structure appears to overlap on the envelopes of the moving Mach cones.

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.

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 study of the ejection properties of a jet flowing into flooded space

2020 ◽  
Author(s):  
A.Yu. Lutsenko ◽  
V.A. Kriushin
Keyword(s):  
Pressure Distribution ◽  
Nozzle Exit ◽  
Software Package ◽  
Numerical Study ◽  
Supersonic Jet ◽  
Underlying Surface ◽  
Ansys Fluent ◽  
Fluent Software ◽  
Underexpanded Supersonic Jet ◽  
Jet Axis

The purpose of the study was to carry out a numerical simulation of the interaction of an underexpanded supersonic jet flowing into a flooded space with a normally located obstacle, and with the underlying surface. We performed the calculations in the ANSYS Fluent software package and presented flow patterns. For the case when the obstacle is located normally to the axis of the jet, we compared the pressure distribution in the radial direction with experimental data and made a conclusion about the changes in the integral load on the wall with a change in the distance to the nozzle exit. For the case when the obstacle is parallel to the jet axis, we presented the pressure distribution along the wall in the plane of symmetry, estimated the relative net force acting on the underlying surface, analyzed the nature of its change at various values of the off-design coefficient, the Mach number on the nozzle exit and the distance to the jet axis.

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