Acoustic heating effects in Hartmann whistle
TL;DR: In this article, the effects of thermal losses on the end-wall heating of a Hartmann whistle were investigated by conducting experiments on bare metal cavities, insulated metal and in wooden cavities.
Abstract: This paper systematically explores the heating effects in a Hartmann whistle Effects of thermal losses on the end-wall heating of the whistle are demonstrated by conducting experiments on bare metal cavities, insulated metal cavities, and in wooden cavities The heating studies are done on wooden cavities of three different configurations, namely, regular cylindrical, stepped and conical ones The cavity with conical geometry is observed to provide the maximum heating effect at the end-wall Further, the effects of various parameters such as nozzle pressure ratio, cavity length, and stand-off distance on the end-wall heating of the cavities are also studied The relationship between acoustic resonance and heating effects are established
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TL;DR: In this article, the authors investigated the heat transfer variations and nature of shock around a blunt body with cylindrical and parabolic cavity geometries and found that the parabolic cavities exhibited a substantial reduction of aero heating effects.
9 citations
TL;DR: In this article, a model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow.
Abstract: In high-pressure gas–jet Hartmann generators, the source of acoustic energy is kinetic energy of a gas jet by the supercritical ratio between the operation and ambient pressure. Under certain conditions, onflow of a supersonic jet to a resonator is accompanied by powerful self-sustained oscillations with irradiation of acoustic waves into the environment and resonator cavity. A model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow. The physical pattern of the flow in the gas–jet generator has been discussed and the study of the dependence of the self-sustained oscillation characteristics on the key gas-dynamic and geometric parameters has been performed.
3 citations
TL;DR: In this article, self-oscillatory flow in the Hartmann resonator is numerically calculated within the framework of ideal (inviscid and non-heat-conducting) gasdynamics.
Abstract: Self-oscillatory flow in the Hartmann resonator is numerically calculated within the framework of ideal (inviscid and non-heat-conducting) gasdynamics. The calculations are performed for the case o...
2 citations
Cites background from "Acoustic heating effects in Hartman..."
...In Brocher et al.20 the heating was studied for tubes of different depths (h=R ¼ 16 to 30) at a fixed spacing and different NPR for tubes of different shapes (cylindrical, conical, and stepped) and made of different materials (metals and mahogany wood)....
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...Thus, Brocher et al.21 constructed a wave diagram of the processes occurring in the Hartmann tube and related the propagation of compression and expansion waves within the tube with the air inflow into and outflow from the cavity....
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...In Brocher et al.(20) the heating was studied for tubes of different depths (h=R 1⁄4 16 to 30) at a fixed spacing and different NPR for tubes of different shapes (cylindrical, conical, and stepped) and made of different materials (metals and mahogany wood)....
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TL;DR: In this paper, the design of a subsonic jet-edge rod generator of the Hartmann-type oscillator and a scheme of measuring its acoustic parameters are presented, where an annular gas jet moving along the thin cylindrical rod positioned at the axis of the generator nozzle is used.
Abstract: The design of a subsonic jet-edge rod generator of the Hartmann-type oscillator and a scheme of measuring its acoustic parameters are presented. In this generator, unlike the Hartmann oscillator, not a cylindrical gas jet but an annular gas jet, moving along the thin cylindrical rod positioned at the axis of the generator nozzle, is used. A parametric investigation of the gasdynamic and acoustic processes arising in the tubular cavity of such a generator as a result of the interaction of a subsonic gas jet with this cavity has been performed with consideration for the nonstationary structure of the gas flow in the generator cavity. Recommendations on the choice of the design of a jet-edge rod generator of acoustic radiation with regard for its practical application are given.
1 citations
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06 Jan 1992
8,784 citations
TL;DR: In this article, an extended acoustic theory is worked out for a gas-filled resonance tube, and the results show cooling in the section of the tube with maximum velocity amplitude and marked heating in the region of the velocity nodes.
Abstract: New experiments with a gas-filled resonance tube have shown that not only heating, but also cooling of the tube wall is possible and that these phenomena are not restricted to oscillation amplitudes that generate shocks. The present paper concentrates on amplitudes outside the shock region. For this case, an extended acoustic theory is worked out. The results show cooling in the section of the tube with maximum velocity amplitude (and thus dissipation) and marked heating in the region of the velocity nodes. A strong dependence of these effects on the Prandtl number is noted. The results are in good agreement with experiments. Although the theory is not valid for proper resonance conditions, it nevertheless sheds some light on what happens when nonlinear effects dominate.Closely related to the limit of validity of the thermoacoustic theory is the question of transition from laminar to turbulent flow in the viscous boundary layer (Stokes layer). This problem has also been investigated; the results are given in a separate paper (Merkli & Thomann 1975). In the present article laminar flow is assumed.
165 citations
"Acoustic heating effects in Hartman..." refers background in this paper
...Merkli and Thomann [12] experimentally illustrated the cooling effect of the resonance tube, apart from heating....
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TL;DR: In this paper, a simplified wave-diagram and the gas-speed/sound-speed diagram are used to show how the oscillations start and grow within a resonance tube, and the amplitude tends to a limiting value which is obtained when the jet is fully swallowed by the tube during the phase of compression of the cycle.
Abstract: Using a simplified wave-diagram and the gas-speed/sound-speed diagram, it is shown how the oscillations start and grow within a resonance tube. It is found that the oscillation amplitude tends to a limiting value which is obtained when the jet is fully swallowed by the tube during the phase of compression of the cycle. Experiments are carried out for jet Mach numbers from 0·1 up to 2. To achieve an adequate evacuation of the tube in the expansion phase, a thin cylindrical body must be used, which is laid along the axis of the jet to produce a wake and a correlative local deficiency of the kinetic energy of the jet. Measured amplitudes of pressure fluctuations are in good agreement with theoretical values.
110 citations
"Acoustic heating effects in Hartman..." refers methods in this paper
...[2] showed how the fluctuations commence and grow within the resonance tube using a simplified wave diagram and gas/sound speed diagram....
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TL;DR: A review of the development of the Hartmann tube from discovery to recent advances in understanding, prediction and application of the resonance tube can be found in this paper, where Hartmann demonstrated the possibility of obtaining high acoustic efficiencies when a jet is aimed at the open end of a tube closed at the other end.
68 citations
"Acoustic heating effects in Hartman..." refers background in this paper
...Recently, Raman and Srinivasan [16] reviewed the research on Hartmann whistles and traced their evolution to the powered resonance tube - an active flow control device....
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TL;DR: In this paper, a tapered resonator was introduced in the thermoacoustic-Stirling heat engine (TASHE) to explore its potential of achieving higher pressure ratio.
30 citations