Simulation and analysis of the effect of ungrounded rectangular loop distributed parameters on TEM response
| Autor: | Zhi Geng, Lihua Liu, Pan Xiao, Guangyou Fang, Fubo Liu, Zongyang Shi |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Physics
Mathematical analysis 020206 networking & telecommunications 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences Transfer function Numerical integration Loop (topology) Geophysics Position (vector) Transmission line 0202 electrical engineering electronic engineering information engineering Waveform Node (circuits) Transient (oscillation) 0105 earth and related environmental sciences |
| Zdroj: | Journal of Applied Geophysics. 149:105-113 |
| ISSN: | 0926-9851 |
| DOI: | 10.1016/j.jappgeo.2017.12.018 |
| Popis: | An ungrounded loop in the shallow subsurface transient electromagnetic surveys has been studied as the transmission line model for early turn-off stage, which can accurately explicate the early turn-off current waveform inconsistency along the loop. In this paper, the Gauss-Legendre numerical integration method is proposed for the first time to simulate and analyze the transient electromagnetic (TEM) response considering the different early turn-off current waveforms along the loop. During the simulation, these integral node positions along the loop are firstly determined by solving these zero points of Legendre polynomial, then the turn-off current of each node position is simulated by using the transfer function of the transmission line. Finally, the total TEM response is calculated by using the Gauss-Legendre integral formula. In addition, the comparison and analysis between the results affected by the distributed parameters and that generated by lumped parameters are presented. It is found that the TEM responses agree well with each other after current is thoroughly switched off, while the transient responses in turn-off stage are completely different. It means that the position dependence of the early turn-off current should be introduced into the forward model during the early response data interpretation of the shallow TEM detection of the ungrounded loop. Furthermore, the TEM response simulations at four geometric symmetry points are made. It shows that early responses of different geometric symmetry points are also inconsistent. The research on the influence of turn-off current position dependence on the early response of geometric symmetry point is of great significance to guide the layout of the survey lines and the transmitter location. |
| Databáze: | OpenAIRE |
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