Conception of normal modes of vibrations is generalized to finite-amplitude sound fields in enclosures, by taking into account of the nonlinear effects. This includes the solution of the wave equation in the form of n...Conception of normal modes of vibrations is generalized to finite-amplitude sound fields in enclosures, by taking into account of the nonlinear effects. This includes the solution of the wave equation in the form of nonlinear partial differential equations for the sound fields.This is made possible with a deep insight of the standing wav character of the normal modes.The nonlinarity does not change in any way the standing wav character, and ouly modifies the motions at different points of the standing wave. Thus only the time-derivatives of the modifications should be preserved in the wav equations, which become, then, soluble. In this way, the trite-amplitude normal functions are derived for the first thoe, containing basic terms, the same normal functions as in linear acoustics, and their modilications. Besides, timeindepent terms echt in the normal functions of noalinear acoustics, representing the radiation pressure in the finilte-amplitude sound fields.展开更多
The Triassic reservoir in the Jinan area of Tarim Oilfield consists largely of interbedded sand and shale. Because of the large overlap between sandstone and shale impedance, it is difficult to distinguish sandstone f...The Triassic reservoir in the Jinan area of Tarim Oilfield consists largely of interbedded sand and shale. Because of the large overlap between sandstone and shale impedance, it is difficult to distinguish sandstone from shale by acoustic impedance alone. Compared to acoustic impedance, elastic impedance contains more lithologic and physical information of the reservoir. Based on meticulous well-tie calibration, elastic impedance data volumes for 10°, 20°, and 30° emergence angles are obtained using pre-stack elastic impedance inversion. A non-linear statistical relationship between elastic impedance and shale content is set up by a PNN neural network. The non-linear mapping relationship is used to predict the reservoir shale content from elastic impedance, which will depict and predict the reservoir oil-bearing sands.展开更多
This paper deals with the non-linear propagation of sound waves radiated by a thin spherical shell vibrating in ideal lluid. Non-linear sound field is obtained by the method of renormalization proposed by Kelly and Na...This paper deals with the non-linear propagation of sound waves radiated by a thin spherical shell vibrating in ideal lluid. Non-linear sound field is obtained by the method of renormalization proposed by Kelly and Nayfeh. Considering the acoustic load, we use Junger and his cooperators' spherical function expan8ion to obtain the structural response of the spherical shell. By combining both of the above methods, the structural response, the waveshape before the formation of shock wave and the first two order waves (including the 1st and 2nd harmonics, sum and difference frequency waves) are calculated respectively. They vary with frequency, distance and directions. Through the comparison of the above results with linear theoretical olles1 we analyse the rules of generation and propagation of non-linear waves.展开更多
The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various a...The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various approximations are next numerically validated in the case of high-frequency.展开更多
文摘Conception of normal modes of vibrations is generalized to finite-amplitude sound fields in enclosures, by taking into account of the nonlinear effects. This includes the solution of the wave equation in the form of nonlinear partial differential equations for the sound fields.This is made possible with a deep insight of the standing wav character of the normal modes.The nonlinarity does not change in any way the standing wav character, and ouly modifies the motions at different points of the standing wave. Thus only the time-derivatives of the modifications should be preserved in the wav equations, which become, then, soluble. In this way, the trite-amplitude normal functions are derived for the first thoe, containing basic terms, the same normal functions as in linear acoustics, and their modilications. Besides, timeindepent terms echt in the normal functions of noalinear acoustics, representing the radiation pressure in the finilte-amplitude sound fields.
文摘The Triassic reservoir in the Jinan area of Tarim Oilfield consists largely of interbedded sand and shale. Because of the large overlap between sandstone and shale impedance, it is difficult to distinguish sandstone from shale by acoustic impedance alone. Compared to acoustic impedance, elastic impedance contains more lithologic and physical information of the reservoir. Based on meticulous well-tie calibration, elastic impedance data volumes for 10°, 20°, and 30° emergence angles are obtained using pre-stack elastic impedance inversion. A non-linear statistical relationship between elastic impedance and shale content is set up by a PNN neural network. The non-linear mapping relationship is used to predict the reservoir shale content from elastic impedance, which will depict and predict the reservoir oil-bearing sands.
文摘This paper deals with the non-linear propagation of sound waves radiated by a thin spherical shell vibrating in ideal lluid. Non-linear sound field is obtained by the method of renormalization proposed by Kelly and Nayfeh. Considering the acoustic load, we use Junger and his cooperators' spherical function expan8ion to obtain the structural response of the spherical shell. By combining both of the above methods, the structural response, the waveshape before the formation of shock wave and the first two order waves (including the 1st and 2nd harmonics, sum and difference frequency waves) are calculated respectively. They vary with frequency, distance and directions. Through the comparison of the above results with linear theoretical olles1 we analyse the rules of generation and propagation of non-linear waves.
文摘The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various approximations are next numerically validated in the case of high-frequency.
