LBM, a useful tool for mesoscale modelling of single phase and multiphase flow – the variety of applications and approaches at Nottingham

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Giving an overview of Nottingham group’s recent progress on numerical modelling and approaches in developing and applying the lattice Boltzmann method (LBM), the paper tries to demonstrate that the LBM is a useful tool for mesoscale modelling of single phase and multiphase flow. The variety of applications of the LBM modelling is reported, which include single phase fluid flow and heat transfer around or across rotational cylinder of curved boundary, two-phase flow in mixing layer, electroosmotically driven flow in thin liquid layer, bubbles/drops flow and coalescence in conventional channels and in microchannels with confined boundary, liquid droplets in gas with relative large density ratio; viscous fingering phenomena of immiscible fluids displacement, and flow in porous media

Numerical Investigation of Bubble Movement in Magnetic Nanofluids

Department of Mechanical EngineeringIn this study, the idea to generate electrical energy by using waste heat is suggested. In this idea, the electrical energy can be generated by a magnetic nanofluid and bubble movement. Thus, bubble movement in a magnetic fluid is numerically investigated using the commercial CFD package COMSOL Multiphysics for effective energy generation. The slug characteristics are also investigated because it can be generated by merging each bubble. The level-set method and phase-field method are used to simulate the bubble and slug movement, respectively. For the investigation, EFH1 and EFH3 are selected as working fluidsthey are commercial magnetic fluids manufactured by Ferrotec, and each fluid contains different amounts of magnetic particles. The solvers are validated by comparing the numerical results with previous research studies and experimental data for reliable results. The properties of a fluid can be changed by solid particles if the particles are dispersed in the fluid. These particles can affect the bubble and slug characteristics, such as shape, velocity and wake. Thus, the effect of solid particles is first studied by observing the bubble and slug movement in each magnetic fluid. In the slug investigation, the effects of some parameters are also studied, such as slug length and liquid backflow. The patterns of bubble and slug movement are investigated to predict the effective condition for the energy generation. The effective bubble and slug movements are predicted by evaluating the disturbance of the surrounding magnetic fluid for each flow pattern. A magnetic force can be created, and it can affect any phenomena when the magnetic field is applied to the system. Thus, the effect of the magnetic force is also investigated because the magnetic field should be applied to the system for the electrical energy generation. Finally, the important factor for energy generation is identified by comparing the results.ope

Quantitative imaging of the complexity in liquid bubbles' evolution reveals the dynamics of film retraction

The dynamics and stability of thin liquid films have fascinated scientists over many decades. Thin film flows are central to numerous areas of engineering, geophysics, and biophysics and occur over a wide range of length, velocity, and liquid properties scales. In spite of many significant developments in this area, we still lack appropriate quantitative experimental tools with the spatial and temporal resolution necessary for a comprehensive study of film evolution. We propose tackling this problem with a holographic technique that combines quantitative phase imaging with a custom setup designed to form and manipulate bubbles. The results, gathered on a model aqueous polymeric solution, provide an unparalleled insight into bubble dynamics through the combination of full-field thickness estimation, three-dimensional imaging, and fast acquisition time. The unprecedented level of detail offered by the proposed methodology will promote a deeper understanding of the underlying physics of thin film dynamics

A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics

This paper presents a survey of ocean simulation and rendering methods in computer graphics. To model and animate the ocean's surface, these methods mainly rely on two main approaches: on the one hand, those which approximate ocean dynamics with parametric, spectral or hybrid models and use empirical laws from oceanographic research. We will see that this type of methods essentially allows the simulation of ocean scenes in the deep water domain, without breaking waves. On the other hand, physically-based methods use Navier-Stokes Equations (NSE) to represent breaking waves and more generally ocean surface near the shore. We also describe ocean rendering methods in computer graphics, with a special interest in the simulation of phenomena such as foam and spray, and light's interaction with the ocean surface

Physics of puffing and microexplosion of emulsion fuel droplets

The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.This article has been made available through the Brunel Open Access Publishing Fund

Experimental techniques and numerical models to detect pollutant emission in the transport sector

25th International Conference on Urban Transport and the Environment, Urban Transport 2019; Aveiro; Portugal; 25 June 2019 through 27 June 2019; Code 155807In recent years, the growth of fossil fuel use and greenhouse gases emissions (GHGs) has been promoted by the population increase and development of the industry sector. Due to the increasing attention towards the effects of climate changes on quality of life, recent researches on pollutant formation processes have been developed in different sectors, especially in transportation. The last emission standards on pollutants impose limits on the dimensions and on the particle number of the particulate matter emissions, because of the highly dangerous effect on human health. To fight high concentrations of particulate matter (PM) emissions, a wide number of studies are addressed towards the definition of the most important parameters in effective production of particulate matter, especially in spark ignition engines. Physical processes such as mixture formation, engine operating parameters and fuel chemical properties strongly affect the soot formation in gasoline engines. The heat transfer process between the piston hot surface and the fuel gasoline during the post-injection phase is a key aspect of soot emissions for an engine. This paper is devoted to analyzing the fundamental parameters that are responsible for pollutant formation in the transport sector and the actual experimental and numerical techniques used to predict the environmental impact of engines

Two-Phase Cooling of Targets and Electronics for Particle Physics Experiments

An overview of the LTCM lab’s decade of experience with two-phase cooling research for computer chips and power electronics will be described with its possible beneficial application to high-energy physics experiments. Flow boiling in multi-microchannel cooling elements in silicon (or aluminium) have the potential to provide high cooling rates (up to as high as 350 W/cm2), stable and uniform temperatures of targets and electronics, and lightweight construction while also minimizing the fluid inventory. An overview of two-phase flow and boiling research in single microchannels and multi-microchannel test elements will be presented together with video images of these flows. The objective is to stimulate discussion on the use of two-phase cooling in these demanding applications, including the possible use of CO2