Acoustic wave propagation in ultrasonic flow measurements is typically assumed to be linear and reciprocal. However, if the transmitting transducer generates a sufficiently high pressure, nonlinear wave propagation effects become significant. In flow measurements, this would translate into more information to estimate the flow and therefore a higher precision relative to the linear case. In this work, we investigate how the generated harmonics can be used to measure flow. Measurements in a custom-made flow loop and simulations using the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation will show that the second harmonic component provides similar transit time differences to those obtained from the fundamental component, their linear combination results in more precise flow measurements compared to the estimations with the fundamental component alone.

超声波流量测量中的声波传播通常被假定为线性且互易的。然而，如果发射换能器产生足够高的压力，非线性波传播效应就会变得显着。在流量测量中，这将转化为更多信息来估计流量，因此相对于线性情况具有更高的精度。在这项工作中，我们研究了如何使用生成的谐波来测量流量。定制流量回路中的测量以及使用 Khokhlov-Zabolotskaya-Kuznetsov (KZK) 方程的模拟将表明，二次谐波分量提供了与基波分量相似的传输时间差，它们的线性组合可实现更精确的流量测量与仅使用基本成分的估计进行比较。