A Survey of Interface Tracking Methods in Multi-phase Fluid Visualization

A central feature that scientists are interested in is the dynamics of fluid interfaces or the so called material boundaries in multi-fluid simulation . Visualization techniques for capturing fluid interface are based on one of about three basic algorithms. In this paper, we give a survey of the existing interface tracking algorithms, including backgrounds, terms, procedures as well as pointers to details and further reading. We also provide a glance at the mathematical fundamentals of multi-fluid dynamics for scientists who are interested in understanding the underlying math and physics of multi-phase fluid simulation

A Benchmark Evaluation of the isoAdvection Interface Description Method for Thermally–Driven Phase Change Simulation

A benchmark study is conducted using isoAdvection as the interface description method. In different studies for the simulation of the thermal phase change of nanofluids, the Volume of Fluid (VOF) method is a contemporary standard to locate the interface position. One of the main drawbacks of VOF is the smearing of the interface, leading to the generation of spurious flows. To solve this problem, the VOF method can be supplemented with a recently introduced geometric method called isoAdvection. We study four benchmark cases that show how isoAdvection affects the simulation results and expose its relative strengths and weaknesses in different scenarios. Comparisons are made with VOF employing the Multidimensional Universal Limiter for Explicit Solution (MULES) limiter and analytical data and experimental correlations. The impact of nanoparticles on the base fluid are considered using empirical equations from the literature. The benchmark cases are 1D and 2D boiling and condensation problems. Their results show that isoAdvection (with isoAlpha reconstruct scheme) delivers a faster solution than MULES while maintaining nearly the same accuracy and convergence rate in the majority of thermal phase change scenarios

A Data Fusion and Visualisation Platform for Multi-Phase Flow by Electrical Tomography

Electrical tomography, e.g. electrical resistance tomography (ERT) and electrical capacitance tomography (ECT), has been successfully applied to many industries for measuring and visualising multiphase flow. This research aims to investigate the data fusion and visualisation technologies with electrical tomography as the key data processing tools of a platform for multiphase flow characterisation. Gas-oil-water flow is a common flow in the gas and oil industries but still presents challenges in understanding its complex dynamics. This research systematically studied the data fusion and visualisation technologies using dual-modality electrical tomography (ERT-ECT). Based on a general framework, two data fusion methods, namely threshold and fuzzy logic with decision tree, were developed to quantify and qualify the flow. The experimental results illustrated the feasibility of the methods integrated with the framework to visualise and measure flows in six typical common flow regimes, including stratified, wavy stratified, slug, plug, annular, and bubble flow. In addition, the performance of ERT-ECT was also evaluated. A 3D visualisation approach, namely Bubble Mapping, was proposed to transform concentration distribution to individual bubbles. With a bubble-based lookup table and enhanced isosurface algorithms, the approach overcomes the limits of the conventional concentration tomograms in visualisation of bubbles with sharp boundaries between gas and liquid, providing sophisticated flow dynamic information. The experiments proved that Bubble Mapping is able to visualise typical flow regimes in different pipeline orientations. Two sensing methods were proposed, namely asymmetrical sensing and imaging (ASI) and regional imaging with limited measurement (RILM), to improve the precision of the velocity profile derived from the cross-correlation method by enhancing ERT sensing speed, which is particularly helpful for industrial flows that their disperse phase velocity is very high, e.g. 20 m/s of the gas phase. It is expected that the outcome of this study will significantly move electrical tomography for multiphase flow applications beyond its current challenges in both quantification and qualification

Numerical simulation of multiphase jet fragmentation using Smoothed Particle Hydrodynamics

This thesis is devoted to the study of multiphase jet fragmentation using Smoothed Particle Hydrodynamics (SPH). The theoretical aspects of three hydrodynamic instabilities, namely the Kelvin-Helmholtz instability (KHI), Rayleigh-Taylor instability (RTI), and Rayleigh Plateau instability (RPI) are reviewed. The linear growth rate of the combined KHI and RTI are derived by means of linear perturbation in chapter 2. The linear growth rate of the multiphase RPI is presented in chapter 7. An overview of the Smoothed Particle Hydrodynamics is given in chapter 3. A pseudo-consistent SPH scheme is presented for the simulation of multiphase flow problems. Additionally, two interface stabilisation models are presented: quasi-buoyancy model and gas-repulsion model. When used in combination with the pseudo-consistent SPH scheme, these models are found to be superior than those presented in the weakly-compressible SPH literature and allows for the simulations for density ratio up to three-magnitudes. The development of an idealised KHI and a KHI subjected to constant gravitational acceleration (stratified shear instability) is examined in chapter 5. The extracted linear growth rate are compared with the theoretical growth rate presented both in the literature and in chapter 2 for the purpose of validation. The development of a single- and multi-mode RTI are studied by means of SPH in chapter 6. Chapter 7 presents the results for the three-dimensional RPI occurring between two fluids. Based on the knowledge acquired in chapter 5-7, the multiphase jet fragmentation driven by the previously mentioned hydrodynamic instabilities are presented in chapter 8. Finally, the major research findings and recommendations are summarised in chapter 9

Numerical simulation of multiphase jet fragmentation using Smoothed Particle Hydrodynamics

This thesis is devoted to the study of multiphase jet fragmentation using Smoothed Particle Hydrodynamics (SPH). The theoretical aspects of three hydrodynamic instabilities, namely the Kelvin-Helmholtz instability (KHI), Rayleigh-Taylor instability (RTI), and Rayleigh Plateau instability (RPI) are reviewed. The linear growth rate of the combined KHI and RTI are derived by means of linear perturbation in chapter 2. The linear growth rate of the multiphase RPI is presented in chapter 7. An overview of the Smoothed Particle Hydrodynamics is given in chapter 3. A pseudo-consistent SPH scheme is presented for the simulation of multiphase flow problems. Additionally, two interface stabilisation models are presented: quasi-buoyancy model and gas-repulsion model. When used in combination with the pseudo-consistent SPH scheme, these models are found to be superior than those presented in the weakly-compressible SPH literature and allows for the simulations for density ratio up to three-magnitudes. The development of an idealised KHI and a KHI subjected to constant gravitational acceleration (stratified shear instability) is examined in chapter 5. The extracted linear growth rate are compared with the theoretical growth rate presented both in the literature and in chapter 2 for the purpose of validation. The development of a single- and multi-mode RTI are studied by means of SPH in chapter 6. Chapter 7 presents the results for the three-dimensional RPI occurring between two fluids. Based on the knowledge acquired in chapter 5-7, the multiphase jet fragmentation driven by the previously mentioned hydrodynamic instabilities are presented in chapter 8. Finally, the major research findings and recommendations are summarised in chapter 9