Measurement System for a Laboratory Granular Chute to Determine the Flow Behaviour of Gravity-Driven Mass Movements

33-41

Artikel aus einem Buch

200210917

Measurements on gravity-driven mass movements in nature is a complex task, moreover, realscale test sites and gathered data are rare. Considering mass movements as granular flows, scaled laboratory experiments are often used to investigate parameters of the dynamics and the flow behaviour. Therefore the goal of the work is to generate automated 2D velocity field and flow depth information in a scaled mass chute. Two optical measurement techniques are investigated and compared with previous done analogue measurement techniques. Optical Flow (OF) is used to infer the velocity field, which is compared to Optical Speed Measurement (OSM) sensors using UV-diode pairs. The flow depth is estimated using Structured Light Illumination (SLI) technique along a laser line and reference is taken from distance measuring point lasers. A high-resolution 4K camera with a framerate of 160 fps is installed perpendicular to the chute surface. Custom codes are developed for controlling, data acquisition and post-processing. Further components like customizable LED lighting, an electronic tilt mechanism to change the chute angle and an automated granulate inlet are installed. The later reduces the oscillations of the chute to a minimum and ensures the synchronisation of the measurement system. The OF algorithm enables to track velocities up to 31ms−1. The evaluation of the SLI shows that flow depths in the order of 5 to 10mm can be resolved. However, a minimum of 100mW laser power is needed to retrieve continuous depth readings of the dark granulate material.