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Numerical simulation of an acoustic field generated by a phased arc array in a fluid-filled cased borehole 被引量:8
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作者 Che Xiaohua Qiao Wenxiao +1 位作者 Wang Ruijia Zhao Yuhong 《Petroleum Science》 SCIE CAS CSCD 2014年第3期385-390,共6页
Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources.... Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe. 展开更多
关键词 Phased arc array azimuthal angle first-arrival amplitude acoustic field cased borehole
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Numerical simulation of an acoustic field generated by a phased arc array in a fluid-filled borehole 被引量:5
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作者 Che Xiaohua Qiao Wenxiao 《Petroleum Science》 SCIE CAS CSCD 2009年第3期225-229,共5页
The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used ... The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used to evaluate the azimuthal character of borehole formation. In this paper, a 3D finite difference method was used to simulate the acoustic fields in a fluid-filled borehole generated by a traditional monopole source and a phased arc array. Acoustic waveforms were presented for both cases. The analysis of the simulated waveforms showed that different from the monopole source, the acoustic energy generated by the phased arc array transmitter mainly radiated to the borehole in a narrow azimuthal range, which was the key technique to implement azimuthal acoustic well logging. Similar to the monopole source, the waveforms generated by the phased arc array in the fluid-filled borehole also contain compressional (P) waves and shear (S) waves refracted along the borehole, which is the theoretical foundation of phased arc array acoustic well logging. 展开更多
关键词 Phased arc array acoustic field acoustic well logging AZIMUTH finite difference method
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The characteristics of primary and secondary arcs on a solar array in low earth orbit 被引量:1
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作者 朱立颖 付林春 +3 位作者 乔明 崔波 陈琦 林君毅 《Plasma Science and Technology》 SCIE EI CAS CSCD 2017年第5期29-36,共8页
In this paper, the characteristics of the primary arc and secondary arc on a solar array in low earth orbit(LEO) are investigated. The vacuum plasma environment in LEO has been used to study the primary arc and seco... In this paper, the characteristics of the primary arc and secondary arc on a solar array in low earth orbit(LEO) are investigated. The vacuum plasma environment in LEO has been used to study the primary arc and secondary arc of a high-voltage solar array. Silicon solar cells with rigid substrate specimens are used for the experiment. The series-parallel spacing of the silicon solar cells is 1 mm. The string currents of the solar cells are 0.7 A, 1.5 A and 2 A. The primary arc and secondary arc are photographed by high-speed cameras. The differences between the primary arc and secondary arc are observed. The secondary arc can be observed before the primary arc is extinguished. The primary arc is a single arc when the string current is 0.7 A. Multiple arc columns are accompanied by higher arc current. Two arc columns of the primary arc can be observed at 1.5 A string current and 2 A string current. The multiple primary arc columns are related to higher bias voltage. The threshold for sustained arcing is near 145 V/0.7 A, 105 V/1.5 A and 100 V/2 A at 1 mm string gap. Moreover, the transition time of secondary arc formation is analyzed, and found to be about 10–13 μs. The string currents, string voltages and primary arc have no effect on the transition time of the secondary arc formation. 展开更多
关键词 secondary arc solar array electrostatic discharge LEO
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