Experimental Analysis of Rolling Dynamic Compaction Using Transparent Soils and Particle Image Velocimetry

2021 ◽  
Author(s):  
Yue Chen ◽  
Mark B. Jaksa ◽  
Yien Lik Kuo ◽  
David Airey
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Ground Improvement ◽  
Dynamic Compaction ◽  
Scale Model ◽  
Operating Speed ◽  
Transparent Soil ◽  
Image Velocimetry ◽  
Scale Models ◽  
Fused Quartz

Rolling Dynamic Compaction (RDC) is a soil compaction technique, which is capable of improving thick layers of soil at a relatively fast operating speed. The paper presents the results of laboratory experiments conducted on 1:13 scale models of the 4-sided, 8- and 12-tonne, Broons BH-1300 and BH-1300 HD impact rollers to study the performance of the scale model at four different operating speeds. A series of laboratory tests are undertaken using transparent soils and the particle image velocimetry (PIV) technique to investigate the effectiveness of the models. The transparent soil employed in this study consists of fused quartz and a pore fluid which matched the refractive index of the fused quartz. A one-particle thick layer of coloured fused quartz is embedded in the centre plane of the transparent soil to visualise soil internal displacements and a digital camera is used to capture the speckled pattern during the scale model testing process. The results show that the heavier module induces greater soil displacements at each operating speed. The optimal operating speed is approximately 299 mm/s for both module weights. The most significant soil displacements occur within the first 20 passes and, no obvious ground improvement is observed after 35 passes. The results of this study demonstrate the unique capability of transparent soil to study soil displacements induced by the ground improvement scale models.

URANS Models for the Simulation of Full Load Pressure Surge in Francis Turbines Validated by Particle Image Velocimetry

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
J. Decaix ◽  
A. Müller ◽  
A. Favrel ◽  
F. Avellan ◽  
C. Münch
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Electrical Power ◽  
Operating Conditions ◽  
Scale Model ◽  
Load Pressure ◽  
Vortex Rope ◽  
Full Load ◽  
Operating Range ◽  
Image Velocimetry

Due to the penetration of alternative renewable energies, the stabilization of the electrical power network relies on the off-design operation of turbines and pump-turbines in hydro-power plants. The occurrence of cavitation is however a common phenomenon at such operating conditions, often leading to critical flow instabilities which undercut the grid stabilizing capacity of the power plant. In order to predict and extend the stable operating range of hydraulic machines, a better understanding of the cavitating flows and mainly of the transition between stable and unstable flow regimes is required. In the case of Francis turbines operating at full load, an axisymmetric cavitation vortex rope develops at the runner outlet. The cavity may enter self-oscillation, with violent periodic pressure pulsations. The flow fluctuations lead to dangerous electrical power swings and mechanical vibrations, dictating an inconvenient and costly restriction of the operating range. The present paper reports an extensive numerical and experimental investigation on a reduced scale model of a Francis turbine at full load. For a given operating point, three pressure levels in the draft tube are considered, two of them featuring a stable flow configuration and one of them displaying a self-excited oscillation of the cavitation vortex rope. The velocity field is measured by two-dimensional (2D) particle image velocimetry (PIV) and systematically compared to the results of a simulation based on a homogeneous unsteady Reynolds-averaged Navier–Stokes (URANS) model. The validation of the numerical approach enables a first comprehensive analysis of the flow transition as well as an attempt to explain the onset mechanism.

Particle image velocimetry experiments on a macro-scale model for bacterial flagellar bundling

2004 ◽  
Vol 37 (6) ◽  
pp. 782-788 ◽  
Author(s):  
Min Jun Kim ◽  
Mun Ju Kim ◽  
James. C. Bird ◽  
Jinil Park ◽  
Thomas. R. Powers ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Scale Model ◽  
Image Velocimetry ◽  
Macro Scale

A multiscale method for producing homogenized drag laws of a permeable medium by conflating experimental data with Lattice-Boltzmann simulations

2019 ◽  
Vol 29 (11) ◽  
pp. 4394-4407 ◽  
Author(s):  
Alejandro Clausse ◽  
Nicolás Silin ◽  
Gustavo Boroni
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Lattice Boltzmann ◽  
Particle Image ◽  
Numerical Calculations ◽  
Scale Model ◽  
Content Type ◽  
Micro Scale ◽  
Drag Forces ◽  
Image Velocimetry

Purpose The purpose of this paper is to obtain a permeability law of a gas flow through a permeable medium using particle image velocimetry experimental data as primal information, which is conflated with numerical calculations by means of a multi-scale method. Design/methodology/approach The D2Q9 single-relaxation-time Lattice Boltzmann model (LBM) implemented in GPU is used for the numerical calculations. In a first homogenized micro-scale, the drag forces are emulated by means of an effective Darcy law acting only in the close neighborhood of the solid structures. A second mesoscopic level of homogenization makes use of the effective drag forces resulting from the first-scale model. Findings The procedure is applied to an experiment consisting of a regular array of wires. For the first level of homogenization, an effective drag law of the individual elemental obstacles is produced by conflating particle image velocimetry measurements of the flow field around the wires and numerical calculations performed with a GPU implementation of the LBM. In the second homogenization, a Darcy–Forchheimer correlation is produced, which is used in a final homogenized LBM model. Research limitations/implications The numerical simulations at the first level of homogenization require a substantial amount of calculations, which in the present case were performed by means of the computational power of a GPU. Originality/value The homogenization procedure can be extended to other permeable structures. The micro-scale-level model retrieves the fluid-structure forces between the flow and the obstacles, which are difficult to obtain experimentally either from direct measurement or by indirect assessment from velocity measurements.

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