Effects of transducer geometry and beam spreading on acoustic Doppler velocity measurements near boundaries

The effects of acoustic beam directivity on the accuracy of acoustic Doppler current profiling are discussed. Traditionally, a transducer´s main lobe is considered when analyzing Doppler profiler performance. However, excessively large secondary lobes dominate the overall transducer directivity near boundaries and limit profiler performance. Side-lobe suppression design is shown to improve the overall system directivity by almost 50%. Results of transducer directivity numerical modeling are in good agreement with laboratory calibrations. Practical implications of improved directivity for velocity profiling near boundaries are discussed.