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Effect of Pipe Bends on the Low-Frequency Torsional Guided Wave Propagation

Wu Wenjun, Wang Junhua

Archives of Acoustics

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2020

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Vol. 45, No. 3

385--391

EN

Wave motion in pipe bends is much more complicated than that in straight pipes, thereby changing considerably the propagation characteristics of guided waves in pipes with bends. Therefore, a better understanding of how guided waves propagate in pipe bends is essential for inspecting pipelines with bends. The interaction between a pipe bend and the most used non-dispersive torsional mode at low frequency in a small-bore pipe is studied in this paper. Experiments are conducted on a magnetostrictive system, and it is observed that T(0,1) bend reflections and mode conversions from T(0,1) to F(1,1) and F(2,1) occur in the pipe bend. The magnitude of the T(0,1) bend reflections increases with increasing propagation distance and excitation frequency. The amplitude of the mode-converted signals also increases with increasing propagation distance, but it decreases with increasing excitation frequency. Because of their longer bent path, the test signals for a pipe bend with a bending angle of 180º are much more complicated than those for one with a bending angle of 90º. Therefore, it is even more difficult to scan a bent pipe with a large bending angle. The present findings provide some insights into how guided waves behave in pipe bends, and they generalize the application of guided-wave inspection in pipelines.

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Progress in theoretical models of the ICRF mode conversion

Kazakov Y. O.

Nukleonika

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2012

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Vol. 57, No. 1

31-35

EN

The technique of heating the plasma with the electromagnetic waves in the ion cyclotron range of frequencies (ICRF) has many important applications that may lead to improved performance of tokamaks. Recently the heating efficiency of the ICRF mode conversion scenarios characterized by a narrow power deposition profiles received much attention. This paper highlights progress in the theoretical models of the ICRF mode conversion that allowed to achieve a successful experimental realisation of these scenarios in present-day tokamaks.

3

Localized plasma polarimetry based on the phenomenon of normal mode conversion

Kravtsov , Y. A., Bieg B.

Nukleonika

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2011

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Vol. 56, No. 2

171-174

EN

A new geometry of microwave polarimetric measurements is presented, which realizes a localized plasma polarimetry based on the phenomenon of electromagnetic mode conversion. Such a conversion takes place in the tokamak plasma, in the vicinity of the point where the microwave beam is orthogonal to one of the helical magnetic lines. In distinction to the traditional plasma polarimetry, which deals with the line averaged plasma parameters, the new methodology allows for a measurement of the local values of plasma parameters near the point of orthogonality. This methodology was shown to be very efficient in studies of the solar radio emission and polarization properties of radio waves passing through the Earth ionosphere. In the following the theory of electromagnetic mode conversion is described and conditions of its applicability are analyzed. It is shown that localized polarimetric measurements of plasma parameters in the geometry of the international thermonuclear experimental reactor (ITER) device would require very high electron densities Ne, exceeding 1017 cm–3, i.e. thousand times higher than those envisaged in the ITER project.