Flow velocity detection system based on a compact phased array

To address the limitations of conventional acoustic Doppler current profilers (ADCPs) in small and confined spaces—namely, their large physical size, high cost, fixed beam orientation, and limited capability for local flow field measurements—this work presents a low-cost, compact, ring-shaped phased-array flow measurement system with electronically steerable beams. The system employs a planar ring array consisting of eight transducer elements uniformly distributed along the circumference. By optimizing the array layout and operating frequency, the array achieves beam focusing at a depth of approximately 30 cm with an electronic steering range of ±20°. The system integrates a custom-designed FPGA platform featuring range-gated sampling, digital I/Q demodulation, and pulse-wave Doppler (PWD) processing to extract local Doppler velocity signals. Experiments conducted with 150-μm tracer particles at a depth of 30 cm demonstrate the formation of a distinct focal spot. Under 0° steering, the mean upstream flow velocity is 0.149 m/s (compared to a reference value of 0.163 m/s), corresponding to a relative error of 8.5%. For downstream measurements, the mean absolute velocity is 0.154 m/s, with the relative error reduced to 5.5%. Even under 20° beam deflection (focusing condition), the measured flow velocity exhibits a relative error of approximately 10.4%. These results demonstrate that, despite its compact array size and relatively simplified hardware configuration, the system enables localized beam focusing and electronic beam steering—providing a feasible solution for local flow field measurement in constrained spaces.