Fiber tip based sensor system for measurements of pressure gradient, air particle velocity and acoustic intensity

2008 ◽  
Vol 123 (1) ◽  
pp. 19
Author(s):  
Balakumar Balachandran
Keyword(s):  
Pressure Gradient ◽  
Particle Velocity ◽  
Sensor System ◽  
Acoustic Intensity

Anechoic measurements of particle‐velocity probes compared to pressure gradient and pressure microphones

2006 ◽  
Vol 120 (5) ◽  
pp. 3233-3233 ◽  
Author(s):  
Wieslaw Woszczyk ◽  
Masakazu Iwaki ◽  
Takehiro Sugimoto ◽  
Kazuho Ono ◽  
Hans‐Elias de Bree
Keyword(s):  
Pressure Gradient ◽  
Particle Velocity

The effects of contaminating noise on the calculation of active acoustic intensity for pressure gradient methods

2019 ◽  
Vol 145 (1) ◽  
pp. 173-184 ◽  
Author(s):  
Mylan R. Cook ◽  
Kent L. Gee ◽  
Tracianne B. Neilsen ◽  
Scott D. Sommerfeldt
Keyword(s):  
Pressure Gradient ◽  
Gradient Methods ◽  
Acoustic Intensity

scholarly journals Scan and Paint: Theory and Practice of a Sound Field Visualization Method

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Daniel Fernández Comesaña ◽  
Steven Steltenpool ◽  
Graciano Carrillo Pousa ◽  
Hans-Elias de Bree ◽  
Keith R. Holland
Keyword(s):  
Particle Velocity ◽  
Sound Pressure ◽  
Sound Field ◽  
Theory And Practice ◽  
Acoustic Intensity ◽  
Practical Applications ◽  
Transfer Path ◽  
Sensor Position ◽  
Time Requirements ◽  
Visualization Techniques

Sound visualization techniques have played a key role in the development of acoustics throughout history. The development of measurement apparatus and techniques for displaying sound and vibration phenomena has provided excellent tools for building understanding about specific problems. Traditional methods, such as step-by-step measurements or simultaneous multichannel systems, have a strong tradeoff between time requirements, flexibility, and cost. However, if the sound field can be assumed time stationary, scanning methods allow us to assess variations across space with a single transducer, as long as the position of the sensor is known. The proposed technique, Scan and Paint, is based on the acquisition of sound pressure and particle velocity by manually moving a P-U probe (pressure-particle velocity sensors) across a sound field whilst filming the event with a camera. The sensor position is extracted by applying automatic color tracking to each frame of the recorded video. It is then possible to visualize sound variations across the space in terms of sound pressure, particle velocity, or acoustic intensity. In this paper, not only the theoretical foundations of the method, but also its practical applications are explored such as scanning transfer path analysis, source radiation characterization, operational deflection shapes, virtual phased arrays, material characterization, and acoustic intensity vector field mapping.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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