The radiation impedance and energy partition among elastic waves generated by a normal force strip radiator on an isotropic solid surface are investigated in this paper. Two methods are used to obtain the radiation en...The radiation impedance and energy partition among elastic waves generated by a normal force strip radiator on an isotropic solid surface are investigated in this paper. Two methods are used to obtain the radiation energy. One is to get the total radiation energy from the radiation conductance. And the other is to get energy of all elastic waves at far field. The results indicate: (1) the energy ratio of the compressional wave increases with the width of the radiator becoming wider; (2) the energy of each elastic wave is nearly same while the width of the radiator changes in a some small range; (3) for different width of the strip radiator, the total energy gotten from the radiation conductance is equal to the energy sum of all waves gotten at far field. This not only proves the conservation of the energy wnile generating elastic waves,but also mutually reflects that approximate expressions of wave fields obtained from the method of the steepest descent are correct.展开更多
The modal acoustic radiation load on a spherical surface undergoing angularly periodic axisymmetric harmonic vibrations while immersed in an acoustic halfspace with a rigid (infinite impedance) planar boundary is anal...The modal acoustic radiation load on a spherical surface undergoing angularly periodic axisymmetric harmonic vibrations while immersed in an acoustic halfspace with a rigid (infinite impedance) planar boundary is analyzed in an exact fashion using the classical technique of separation of variables. The formulation utilizes the appropriate wave field expansions, the classical method of images and the appropriate translational addition theorem to simulate the relevant boundary conditions for the given configuration. The associated acoustic field quantities such as the modal impedance matrix and the modal acoustic radiation force acting on the spherical surface are determined. The analytical results are illustrated with a numerical example in which the spherical surface, excited in vibrational modes of various orders, is immersed near an impervious rigid wall. The presented solution could eventually be used to validate those obtained by numerical approximation techniques.展开更多
Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular elemen...Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2 mm-thick and a 4 mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the2 mm-thick and 4 mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable.展开更多
文摘The radiation impedance and energy partition among elastic waves generated by a normal force strip radiator on an isotropic solid surface are investigated in this paper. Two methods are used to obtain the radiation energy. One is to get the total radiation energy from the radiation conductance. And the other is to get energy of all elastic waves at far field. The results indicate: (1) the energy ratio of the compressional wave increases with the width of the radiator becoming wider; (2) the energy of each elastic wave is nearly same while the width of the radiator changes in a some small range; (3) for different width of the strip radiator, the total energy gotten from the radiation conductance is equal to the energy sum of all waves gotten at far field. This not only proves the conservation of the energy wnile generating elastic waves,but also mutually reflects that approximate expressions of wave fields obtained from the method of the steepest descent are correct.
文摘The modal acoustic radiation load on a spherical surface undergoing angularly periodic axisymmetric harmonic vibrations while immersed in an acoustic halfspace with a rigid (infinite impedance) planar boundary is analyzed in an exact fashion using the classical technique of separation of variables. The formulation utilizes the appropriate wave field expansions, the classical method of images and the appropriate translational addition theorem to simulate the relevant boundary conditions for the given configuration. The associated acoustic field quantities such as the modal impedance matrix and the modal acoustic radiation force acting on the spherical surface are determined. The analytical results are illustrated with a numerical example in which the spherical surface, excited in vibrational modes of various orders, is immersed near an impervious rigid wall. The presented solution could eventually be used to validate those obtained by numerical approximation techniques.
基金the National Technology Research and Development Program in the 12th Five Year Plan of China(No.2011BAE22B05)the Canada-ChinaUSA Collaborative Research and Development Project(No.2011DFA50900)
文摘Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2 mm-thick and a 4 mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the2 mm-thick and 4 mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable.
