Camera-measured velocity distribution in laboratory open-channel flow with intense transport of bimodal combined-load

Abstract

Abstract An extended stereoscopic method, which identifies, and tracks particles based on their colour in solid-liquid flow, is tested for its capability to separately measure velocity distributions of particles of two fractions transported as bimodal sediment mixture in water flow through a laboratory flume. The principle of the tested method extension is a use of colour-based processing of images collected by two high-speed cameras which enables to filter out particles of one fraction from the image and leave particles of the other fraction in the image based on a selected colour hue range. The modified images are then processed by the original stereoscopic method to produce velocity distribution of particles of the individual fraction in the flow. The method extension is first tested in simple vertical flow carrying neutrally buoyant spherical particles of two distinct colours in a recirculation cell. In the next step, lightweight plastic particles of two fractions of different properties (size, shape, density) and colours are introduced to flow through a laboratory flume and velocity distributions of the two fractions are measured separately at flow conditions which mimic intense transport of bimodal combined-load in an open channel. Results exhibit a very good agreement with previous measurements with unimodal sediment in hydraulically similar flow.