IEEE Trans Ultrason Ferroelectr Freq Control. 2018 Jan;65(1):112-119. doi: 10.1109/TUFFC.2017.2771525.
Ultrasonic guided waves enable flow measurements under harsh conditions, which are important, for instance, to monitor and optimize industrial solidification processes. The usage of single mode waveguides overcomes the problem of overheating the transducers, but requires a mechanical scanning for imaging. A multimode waveguide can carry the information of an image, but a scrambling of the signals occurs due to multiple reflections at the waveguide's boundaries. We propose a new approach to overcome the scrambling and enable flow imaging through a short waveguide: the time-reversal virtual array (TRVA) method. The time invariance of the wave equation in a linear medium allows the refocusing on a limited set of calibrated points, which form the virtual array. This virtual array can conceptually be treated as a phased array. In this paper, the TRVA has been characterized theoretically, numerically, and experimentally. For the first time, a planar velocity measurement of a rotating flow in liquid gallium-indium-tin is demonstrated through a borosilicate waveguide at room temperature. A comparison with reference measurements showed good agreement.
超声导波可在恶劣条件下进行流量测量，这对于监测和优化工业凝固过程等非常重要。使用单模波导可避免传感器过热的问题，但需要进行机械扫描以进行成像。多模波导可以携带图像信息，但由于波导边界的多次反射，信号会发生混叠。我们提出了一种新的方法来克服混叠并通过短波导进行流量成像：时间反转虚拟阵列 (TRVA) 方法。线性介质中波动方程的时间不变性允许在一组有限的校准点上进行重新聚焦，这些点形成虚拟阵列。这个虚拟阵列在概念上可以被视为相控阵。本文从理论、数值和实验上对 TRVA 进行了描述。本文首次通过室温下的硼硅酸盐波导实现了对液态镓铟锡旋转流的平面速度测量，与参考测量结果的比较表明两者吻合良好。
