We use input-output analysis to examine subsonic and supersonic turbulent jet noise. For a supersonic jet, the leading input-output mode closely resembles wavepackets resulting from the parabolized stability equations (PSE). For a subsonic jet, however, input-output analysis produces several sub-optimal modes with nearly the same gain as the leading input-output mode. The sub-optimal modes depe...

There are many approaches to determine the sound propagated from turbulent flows.  In hybrid methods, the turbulent noise source field is computed or modeled separately from the far-field calculations.  To have an initial and quick estimation of the sound propagation, less computationally intensive methods can be developed using stochastic models of the turbulent fluctuations.   In this paper, ...

Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow" (2016).

Non-resonant laser-induced thermal acoustics (LITA) is employed with heterodyne detection to measure temperature (285-295 K) and a single component of velocity (20-150 m/s) in an atmospheric pressure, subsonic, unseeded air jet. Good agreement is found with pitot-tube measurements of velocity (0.2% at 150 m/s and 2% at 20 m/s) and the isentropic expansion model for temperature (0.3%). Key words...

This paper presents experimental observations and a theoretical analysis of the operation of drop-on-demand piezoelectric ink jet devices. By studying experimentally the dependence of several operating characteristics on the length of the cavity in the nozzle of an ink jet device, we have gained insight into the physical phenomena underlying the operation of such a device. It is concluded that ...

Thermoacoustic-Stirling hybrid engines and feedback pulse tube refrigerators can utilize jet pumps to suppress streaming that would otherwise cause large heat leaks and reduced efficiency. It is desirable to use jet pumps to suppress streaming because they do not introduce moving parts such as bellows or membranes. In most cases, this form of streaming suppression works reliably. However, in so...

Prevailing high-speed air-breathing propulsion systems invariably banks on coaxial jets which plays a vigorous role in stabilization of flames and combustion emission. Coaxial jets have applications in supersonic ejectors, noise control techniques and enhancement of mixing. Coaxial jet nozzles regulate spreading rates by developing virtuous mean flow and shortening primary flow potential core l...

This paper investigates the performance of U-type pulsejet engine whose overall length is approximately 160 cm. Gas dynamics, acoustics and chemical kinetics were modeled to gain an understanding of various physical phenomena affecting pulsejet operation, scalability, and efficiency. The pulsejet was run in valveless mode on LPG fuel. Pressure, temperature, thrust, specific impulse, and concent...

Localization of aeroacoustic sound sources in open jet wind tunnel experiments requires an accurate prediction the acoustic propagation time. Most conventional predictions use either a ray-tracer, coupled with modelled continuous velocity field, or ray diffraction and discretization field by means vortex sheets. In this work novel method is proposed which discretized into blocks constant separa...

New technologies are providing innovative ways to reduce sound levels in many areas. Aircraft engineers are finding ways to reduce the noise produced by jet engines, while road builders are using rubber-enhanced pavement to quiet highway noise. Indoor acoustics are benefiting from materials that transform sound waves to heat, and so-called active noise control reduces harmful sounds through pro...