Flow Visualization of Downstream Weir using Timber Dowels as Displacement Markers

A flow visualization in an open-channel experiment was combined with marker displacement methods to quantify velocity distribution and Froude number classification to characterize the downstream flow of a sharp-crested weir. This study introduced an alternative method for a neutrally buoyant tracer marker composed of timber dowels that were deployed in an open channel with optical marker tracking. Timber dowels with several densities were used to investigate and gain insight into the hydrodynamic behaviour of submerged or emergent conditions in a controlled flume experiment. In this experiment, the selected timber dowels have density criterion from 600 to 900 kg/m3, which is less than that of water. The whole experiment was recorded with a high-speed digital camera. The images from the video recording were processed using Tracker software. It was found that the timber dowel is suitable as an alternative for the tracer and visualizes the flow well. Timber dowel density is related to flow path lines for visualizing the flow characterization in the downstream channel.