Near-field vector intensity measurements of a small solid rocket motor

Abstract

Near-field vector intensity measurements have been made of a 12.7-cm diameter nozzle solid rocket motor. The measurements utilized a test rig comprised of four probes each with four low-sensitivity 6.35-mm pressure microphones in a tetrahedral arrangement. Measurements were made with the rig at nine positions (36 probe locations) within six nozzle diameters of the plume shear layer. Overall levels at these locations range from 135 to 157 dB re 20 microPa. Vector intensity maps reveal that, as frequency increases, the dominant source region contracts and moves upstream with peak directivity at greater angles from the plume axis.

Experimental validation of acoustic intensity bandwidth extension by phase unwrapping

“…8,9 This process increases measurement time and cost. Recently, the challenge of characterizing jet noise fields 10,11 motivated formulation of a new intensity calculation method that extends multimicrophone probes' bandwidth. The phase and amplitude gradient estimator (PAGE) method, 12 which calculates a phase gradient via pairwise microphone transfer functions, greatly reduces bias errors 13 up to the probe's spatial Nyquist frequency, f Nyq .…”

Intensity analysis of the dominant frequencies of military jet aircraft noise

“…Recently, three-dimensional intensity probes have been used to measure the sound field of a solid rocket motor plume. 6,7,8 The same probe design was also used to make nearfield acoustic intensity measurements of the F-22A Raptor. The intensity probe was attached to the top of a 90-microphone rectangular array of microphones, which was moved to multiple locations to the sideline and aft of the aircraft.…”

Development of a Near-field Intensity Measurement Capability for Static Rocket Firings

“…The first was a three-dimensional (3D) spherical probe developed previously for other rocket firings. 3,7,8) The idea of a multimicrophone probe within a rigid sphere was based on prior work [12][13][14] and prompted a number of complementary investigations to further quantify its performance. [15][16][17] Seen in Fig.…”

“…With these constraints in mind, measurement and analysis methodologies have been developed to measure the magnitude, peak directivity, and spectral content of the rocket source. 7,8) Determination of these quantities over a sufficiently large spatial aperture near the rocket provides insight into physical noise generation mechanisms that originate in the turbulent exhaust flow field. The analysis for this paper was based on the measurements of a GEM-60 horizontal static firing at Promontory, Utah on September 6, 2012.…”