Physical modelling of pressure flushing of sediment using lightweight materials

While designing physical hydraulic model tests to investigate the efficiency of pressure flushing, it is most likely that very fine sediments of cohesive nature are required to satisfy the relevant scaling criteria. Cohesive sediments have different physical properties than sand, and a possibility to avoid such scale effects is to use lightweight materials with a specific gravity larger than water but lower than sand as model sediment. This paper addresses this issue by presenting results from laboratory experiments mimicking pressure flushing through a bottom outlet by using different lightweight materials and sand as model sediments. The results consolidate conclusions of previous studies carried out solely with sand and show that lightweight models can be used to predict the length and volume of flushingcones. Empirical relations to predict the length and volume of flushing cones are proposed and validated against a small set of experimental data from a previous study

Simulating pressurized reservoir flushing in scale models using lightweight sediments

The dissertation presents the findings from laboratory experiments conducted to study the pressurised flushing phenomena using lightweight materials as model sediment. The study resulted in four research papers, which are summarized in this thesis and the results are discussed in detail. To speed up the recording of bed levels in the experiments and to produce better quality 3D models of the recorded bed levels, Structure from Motion (SfM) technique was applied. Before adopting to the experiments, different SfM tools available were compared and the suitable one was selected. Then, the applicability of SfM technique with the selected SfM tool was tested in three scale model studies of different scales. Five sets of scaled model experiments on pressurised flushing of non‐cohesive sediment deposit through bottom outlet were carried out. Natural sand and lightweight materials satisfying the scaling criteria were selected to be used as model sediments. The experiments were focused on predicting the dimensions and volume of flushing cones, so two empirical equations were proposed from regression analysis of the experimental data to predict the length and volume of flushing cones. The prediction made by new proposed empirical equations were also compared with the empirical equations proposed by previous laboratory experiments conducted with sand as model sediment. Since the experiments in this study were conducted for variations in different parameters governing the flushing process, the proposed equations performed pretty well for both sand and lightweight materials as model sediment when compared to empirical equations from previous studies

Evaluating the structure from motion technique for measurement of bed morphology in physical model studies

The selection of instrumentation for data acquisition in physical model studies depends on type and resolution of data to be recorded, time frame of the model study, available instrumentation alternatives, availability of skilled personnel and overall budget of the model study. The available instrumentation for recording bed levels or three-dimensional information on geometry of a physical model range from simple manual gauges to sophisticated laser or acoustic sensors. In this study, Structure from Motion (SfM) technique was applied, on three physical model studies of different scales and study objectives, as a cheap, quicker, easy to use and satisfactorily precise alternative for recording 3D point data in form of colour coded dense point cloud representing the model geometry especially the river bed levels in the model. The accuracy of 3D point cloud generated with SfM technique were also assessed by comparing with data obtained from manual measurement using conventional surveying technique in the models and the results were found to be very promising

Evaluating the Structure from Motion Technique for Measurement of Bed Morphology in Physical Model Studies

The selection of instrumentation for data acquisition in physical model studies depends on type and resolution of data to be recorded, time frame of the model study, available instrumentation alternatives, availability of skilled personnel and overall budget of the model study. The available instrumentation for recording bed levels or three-dimensional information on geometry of a physical model range from simple manual gauges to sophisticated laser or acoustic sensors. In this study, Structure from Motion (SfM) technique was applied, on three physical model studies of different scales and study objectives, as a cheap, quicker, easy to use and satisfactorily precise alternative for recording 3D point data in form of colour coded dense point cloud representing the model geometry especially the river bed levels in the model. The accuracy of 3D point cloud generated with SfM technique were also assessed by comparing with data obtained from manual measurement using conventional surveying technique in the models and the results were found to be very promising