PIV-based transient flow field characterization through suspended particulate tracking in water

Transient velocity field measurement in aquatic systems represents a fundamental technique for comprehending hydrodynamic processes, optimizing water resource management, and preserving aquatic ecosystems. As a principal methodology for flow field quantification, Particle Image Velocimetry (PIV) serves as the foundation for our proposed novel approach that utilizes naturally occurring suspended particles as imaging targets. To address challenges associated with heterogeneous particle size distribution and varying flow-tracking characteristics, our methodology implements the following procedure: First, we perform preprocessing of adjacent image pairs to eliminate interference from particles exhibiting significant size deviation from the dominant population within the target field of view. Subsequently, we employ an FFT-based cross-correlation algorithm to derive pixel-block level coarse velocity fields. The obtained velocity data then undergoes interpolation using Gaussian radial basis functions to populate velocity vectors for each pixel, followed by spatial filtering. For detection of small-scale velocity vectors missed in the initial analysis, we implement optical flow methodology. Finally, we integrate the velocity fields obtained from both computational stages to generate the refined output velocity field. Experimental validation demonstrates that this approach achieves satisfactory performance across flow velocity ranges of 0.1-2 m/s in lacustrine environments.