Automatic Mask Extraction for PIV-Based Dam-Break Analysis

The analysis focus on dam breaks stems from their ability to offer a simplified, yet effective workbench for debris flow waves, which in turn are helpful in gaining a deeper understanding of the highly destructive debris flows. High-speed recordings of granular flows arising from a dam-break-like event can be processed to extract useful information about the flow dynamics. Gradient-based optical-flow techniques cannot compute the correct velocity field as they detect the flow induced by the boundary evolution. Methods that are based on cross-correlation, such as particle imaging velocimetry (PIV), are able to capture the micro-scale flow, but, as they are designed for flows within fixed boundaries, they cannot deal directly with dam-break-caused flows because such flows, by their own nature, exhibit a fast moving boundary. This paper presents a procedure that is able to compute the evolving background and supply it to a PIV program as a masking region that should be excluded from the computation of the flow velocity field. This improvement leads to reliable results, while reusing existing software. All the resulting quantities are being used to tune a mathematical model describing the observed flows.