4 research outputs found
Toward the end-to-end optimization of the SWGO array layout
No full textIn this document we consider the problem of finding the optimal layout for the array of water Cherenkov detectors proposed by the SWGO collaboration to study very-high-energy gamma rays in the southern hemisphere. We develop a continuous model of the secondary particles produced by atmospheric showers initiated by high-energy gamma rays and protons, and build an optimization pipeline capable of identifying the most promising configuration of the detector elements. The pipeline employs stochastic gradient descent to maximize a utility function aligned with the scientific goals of the experiment. We demonstrate how the software is capable of finding the global maximum in the high-dimensional parameter space, and discuss its performance and limitations
Path Instabilities of a Rising or Falling Sphere in a Fluid at Rest: An Experimental Study
No full textMulti-phase flows are ubiquitous in nature and in everyday life surrounding us, impacting us in almost all possible ways. The presence of particles in a flow can change the flow behaviour in an unpredictable manner. The simplest example of a particle-laden flow, that one can think of, is the settling of a single sphere under gravity in a quiescent fluid. This seemingly simple problem has very high relevance in various practical applications ranging from sedimentation of particles for water treatment, process industries, transport of a dense suspension(slurry) through a pipe and even in land reclamation. The settling/ascension of a single sphere, even after having been subject to extensive study for more than a century, remains far from being understood completely. The path and the wake of a falling/rising sphere in a quiescent fluid may be subject to various instabilities depending upon two dimensionless quantities which are sufficient to characterize the motion. One being the Galileo number (Ga), which is the ratio of the net gravity force to the viscous force and the second one being the mass density ratio, which is the ratio of the density of the solid to the density of the fluid. Depending upon Ga and mass density ratio, the sphere can take up various regimes of motion such as vertical, oblique, zigzagging, helical to name a few. This is mainly due to wake instabilities that trigger such path instabilities. Based on Ga and mass density ratio, various regime maps have been proposed in literature. There have been several disagreements regarding the characterization of such paths taken by the sphere. This is due to the strong solid-fluid coupling and the inherent complexity due to triggering of the instabilities in such cases, which is far from being trivial to model numerically and also to test experimentally. The disagreements between different numerical works and different experimental works make the problem hard pressing and tempting to study. Moreover, the settling behaviour of a single sphere can also aid in understanding the collective effects displayed in the settling of dilute suspensions. The goal of the present study is to shed light on the confusion/disagreements in literature until now and characterize various path instabilities. A detailed experimental investigation is conducted to cover the parameter space (regime map) by employment of over 250 different combinations of Ga and mass density ratio to cover as many regimes of motions as possible within the given time framework. The motion of a sphere is tracked in time using high-speed cameras and corresponding path/regime of motion, higher-order statistics like velocity and physical characteristics such as the Strouhal number/ drag coefficient has been computed. The results validate well for some simple regimes of motion for which results from the previous studies perfectly agree with each other. With the confidence obtained after the validation, the current work attempts to draw points of consensus and disagreements with these earlier works for other more controversial regimes. Some regimes, which had only been observed using numerical simulations, have been observed experimentally for the first time. Also, intriguing bi-stable regimes (coexistence of two regimes) have been observed. Moreover, attempt is also made to characterize the suppression of the high-frequency oscillations with increase in the sphere inertia. An update of the regime maps is proposed with the results obtained from the experiments conducted. The results obtained will also serve as an excellent tool for validation of new numerical models, using which the Ga-mass density ratio parameter space can be covered in great detail. Recommendations for future work are given.Mechanical Engineering | Energy and Process Technolog
Videos: terminal settling experiments in water: path instabilities
No full text24 path trajectories of grains setting in water in an advanced TU Delft experimental setup.
More technical information can be found here:
http://resolver.tudelft.nl/uuid:cbaf6de1-dcf9-41ab-a5bc-3a4d364bfd45
Path Instabilities of a Rising or Falling Sphere in a Fluid at Rest - An Experimental Study
Author: Kaveripuram Ramasamy, Shravan Raaghav
And related videos: https://data.4tu.nl/repository/uuid:1b685d9e-4441-4a53-865c-86622ba49b25
File: Set 1 - Calcium Pellets 1.4-1.7 mm.mp4
File: Set 1 - Glass beads - 1.5 mm.mp4
File: Set 1 - Glass beads - 2.0 mm.mp4
File: Set 1 - Glass beads - 2.5 mm.mp4
File: Set 1 - Glass beads - 3.0 mm.mp4
File: Set 1 - Glass beads - 3.5 mm.mp4
File: Set 1 - Glass beads - 4.0 mm.mp4
File: Set 1 - Rapid Filter Sand 1.0-2.0 mm.mp4
File: Set 1 - Steel shots 3.0 mm.mp4
File: Set 1 – Zirconium balls 2.0 mm.mp4
File: Set 2 - Calcite pellets 1-1.12 mm-case-1.mp4
File: Set 2 - Calcite pellets 1-1.12 mm-case-2.mp4
File: Set 2 - Calcite pellets 1-1.12 mm-case-3.mp4
File: Set 2 - Calcite pellets 1.12-1.25 mm-case-1.mp4
File: Set 2 - Calcite pellets 1.12-1.25 mm-case-2.mp4
File: Set 2 - Calcite pellets 1.12-1.25 mm-case-3.mp4
File: Set 2 - Calcite pellets 1.25-1.4 mm-case-1.mp4
File: Set 2 - Calcite pellets 1.25-1.4 mm-case-2.mp4
File: Set 2 - Calcite pellets 1.25-1.4 mm-case-3.mp4
File: Set 2 - Calcite pellets 1.4-1.7 m-case-2.mp4
File: Set 2 - Calcite pellets 1.4-1.7 mm-case-1.mp4
File: Set 2 - Calcite pellets 1.4-1.7 mm-case-3.mp4
File: Set 2 - Calcite pellets 1.7-2 mm-case-1.mp4
File: Set 2 - Calcite pellets 1.7-2 mm-case-2.mp4
File: Set 2 - Calcite pellets 1.7-2 mm-case-3.mp4
File: Set 2 - Calcite pellets 2-2.36 mm-case-1.mp4
File: Set 2 - Calcite pellets 2-2.36 mm-case-2.mp4
File: Set 2 - Calcite pellets 2-2.36 mm-case-3.mp4
File: Set 2 - Calcite pellets 2.36-2.8 mm-case-1.mp4
File: Set 2 - Calcite pellets 2.36-2.8 mm-case-2.mp4
File: Set 2 - Calcite pellets 2.36-2.8 mm-case-3.mp4
File: Set 2 - Calcite pellets 2.8+mm-case-1.mp4
File: Set 2 - Calcite pellets 2.8+mm-case-2.mp4
File: Set 2 - Calcite pellets 2.8+mm-case-3.mp4
File: Set 3 - Terminal settling 10mm glass bead.MP4
Project
This research is part of the project “Hydraulic modelling of liquid-solid fluidisation in drinking water treatment processes” carried out by Waternet, Delft University of Technology, and HU University of Applied Sciences Utrecht. Financial support came from Waternet Drinking Water Production Department. The videos were recorded at TU Delft, Mechanical, Maritime and Materials Engineerin
Toward the end-to-end optimization of the SWGO array layout
No full textn this document we consider the problem of finding the optimal layout for the array of water Cherenkov detectors proposed by the SWGO collaboration to study very-high-energy gamma rays in the southern hemisphere. We develop a continuous model of the secondary particles produced by atmospheric showers initiated by high-energy gamma rays and protons, and build an optimization pipeline capable of identifying the most promising configuration of the detector elements. The pipeline employs stochastic gradient descent to maximize a utility function aligned with the scientific goals of the experiment. We demonstrate how the software is capable of finding the global maximum in the high-dimensional parameter space, and discuss its performance and limitations
