Analysis of spherical thermo-acoustic radiation in gas

Abstract

A general solution of the spherical thermo-acoustic (TA) radiation from any solid in gas is derived by using a fully thermally-mechanically coupled TA model. Therefore, the characteristics and regularities of spherical TA emission can be studied more completely. It is shown that flat amplitude-frequency response, the most important feature for planar TA emission from technical standpoint, still exists for spherical TA emission, and changes with the radius of a sphere, thickness of TA sample, and the distance from surface. This expression agrees well with experimental and theoretical results of planer TA emission for much larger sphere and lays the foundation to calculate complex TA emission problems

Characteristics of thermally induced acoustic emission from nanoporous silicon device under full digital operation

“…In the experimental frequency region, the digital acoustic output amplitude exhibits a linear behaviour. This frequency dependence is consistent with the experimental 1 and theoretical results [19][20][21][22][23] reported previously under the analog operation. As the thermo-acoustic output is proportional to q(x)/ ffiffiffiffiffiffi aC p , where q(x) and ffiffiffiffiffiffi aC p are the input power density and the thermal effusivity of the PS layer, 1 respectively, principal factors for the acoustic output are the device size and the porosity.…”

“…Besides the PS device, the thermo-acoustic effect has been demonstrated in various structures using suspended metal wire array, 8 silver nanowires, 9 indium-tin-oxide films, 10 printed semiconductor nanoparticles, 11 polymers, 12,13 carbon nanotubes, 14,15 and graphene films. [16][17][18] The results of theoretical analyses [19][20][21][22][23] support that the resonance-free frequency response is an intrinsic feature of the thermo-acoustic conversion. The broad-band emissivity in the ultrasound region makes it possible to use the PS emitter for reproducing complicated acoustic communication calls between mice.…”

Thermo acoustic study of carbon nanotubes in near and far field: Theory, simulation, and experiment

“…Theories developed in the field of thermo acoustic mostly tried to solve coupled temperature and pressure equations for one dimensional planar or spherical on substrate sources [14][15][16] and arbitrary source taking advantages of point sources. 17 Some have used temperature variations of either sound source or medium in one dimensional domain and then have ascribed the pressure to the temperature variations, 1,3 which requires some assumptions and simplifications.…”

Solution for acoustic field of thermo-acoustic emission from arbitrary source

“…16 Therefore, in our TA radiation model, the influence of solid thermal expansion is neglected, and only the effect of thermal-mechanical coupling in gas, which is assumed ideal and inviscid, is taken into consideration. The fully coupled thermoelastic equation set for determining spherical TA radiation can then be expressed as 17,18 …”

“…[2][3][4][5][6][7][8][9][10][11][12][13] However, theoretical investigation of TA emission seriously lags behind the experimental one due to comparatively fewer efforts. Currently, alomast all the formulas for calculating TA emission so far are one-dimensional, 1,[14][15][16][17]19,22 taking advantage of the plane-wave solution based on the pressure-temperature coupled equations in a fluid given by F. A. McDonald and G. C. Wetsel, Jr., 18 and the problems of near-and far-field TA emission need to be dealt with seperately. The multi-dimensional TA emission problems, e.g.…”