Sound sources of the screech tone radiated from circular supersonic jet oscillating in the helical mode

2003 ◽  
Vol 114 (4) ◽  
pp. 2357-2357
Author(s):  
Yoshikuni Umeda ◽  
Ryuji Ishii
Keyword(s):  
Supersonic Jet ◽  
Sound Sources ◽  
Screech Tone ◽  
Helical Mode

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.

Experimental Study of Supersonic Jet Noise Reduction With Microjet Injection

2009 ◽  
Author(s):  
Toshinori Watanabe ◽  
Ryuichi Okada ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Tsutomu Oishi
Keyword(s):  
Experimental Study ◽  
Turbulent Mixing ◽  
Sound Pressure ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Pressure Level ◽  
Broadband Noise ◽  
Screech Tone ◽  
Supersonic Jet Noise ◽  
Mixing Noise

Experimental study was conducted concerning active control of supersonic jet noise with a microjet injection technique. The microjets were injected into a rectangular main jet with Mach number up to 1.49. The nozzle lip of the main jet was equipped with 44 injection holes of the microjets, whose angles against the main jet were changed as 60 and 90 degrees. From far-field sound pressure data, a significant reduction of the jet noise by several dB was found in the cases with 60 and 90 degrees of injection angles. The microjet was found to affect all components of supersonic jet noise, namely, turbulent mixing noise, shock-associated broadband noise and screech tone noise. In the results of FFT analysis, the effect of the microjet was observed in the sound pressure level of the shock-associated broadband noise, the pressure level and frequency of the screech tone noise, and average level of the turbulent mixing noise. Schlieren visualization was also made for the jet flow, and the microjet was seen to change the shock structure and shear layer behavior of the supersonic jet.

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