Applying Laser Scanning Technology to Studying Alluvial Flume-Bed Topography in Laboratory Conditions

Abstract

The aim of the research was to compare alluvial bed topography description in laboratory conditions using the "traditional", currently applicable method with an original approach, based on LiDAR technology. LiDAR application in local scours shape investigation in based on the grounds of introducing the autonomic measuring module, which, placed above the bed on dedicated controllable arrangement of guideways, describes the landform as a cloud of coordinates. The result of the performed experiment was obtainment of point clouds (x, y, z), reflecting the bed shape before and after local scour formation during twenty measurement series with varying hydraulic conditions. Objects of the study were basic geometry properties of the scour hole and its volume. The measurement with laser scanner technology application allowed for obtaining much more accurate results in shorter time, comparison to disc probe survey, and also relatively fast conversion of numerical data into figures. The device equipped with portable computer, precise stepper motors and dedicated software permitted the introduction of automation into laboratory work. The effect is not only measurements accuracy, but also significant acceleration of data gathering. The adopted grid is characterized by significant density, which-in connection with meaningfully high accuracy-allows very precise surface description. Bed shape can be presented in numerical or graphical form. It must be pointed out that disc probe method application would never give such accuracy as in the case of introducing laser scanning technology in similar studies.

On local scouring downstream small water structures

“…A group of experiments carried out in a hydraulic laboratory, the results of which were published, among others, in Water or IEEE Access journals ( Kiraga & Popek, 2016 ; Kiraga et al., 2018 ; Kiraga & Popek, 2019 ; Kiraga & Miszkowska, 2020 ), concerned the phenomenon of formation of local scouring as a result of not only varied roughness of the materials building the bed, but also the restriction of the flow field by inserting a model of damming structures into the flume. Namely, due to the flow resistance increment along the whole flume resulting from varied roughness of solid and sandy bottom, the hydraulic gradient increases causing the intensification of shear stress at the bottom.…”

Lane’s Relation in Local Scour Investigations

“…In order to investigate the scour shape, a device equipped with a laser scanner and a disc probe were applied as supportive devices. Prototype A1 of the device was engineered in 2016 by Marta Kiraga and Matvey Razumnik within the university grant for young researchers "The influence of small hydraulic structures on sediment transport conditions" [32].…”

Bed Shear Stress Influence on Local Scour Geometry Properties in Various Flume Development Conditions

“…The result is point cloud with coordinates (x, y, z). The applied device contains laser rangefinder, data transferring software, and automatic moving platform [36] (Figures 9 and 10). The LiDAR device is set above the flume and could move in two axes with presumed step (1 mm in present experiment), triggered by stepper motors.…”