This book is a senior level undergraduate and graduate textbook for a wide audience of engineering students taking a first course in CFD or Computer Aided Engineering. Fully course matched, with the ...most extensive and rigorous pedagogy and features of any book in the field. The first book in the field aimed at CFD users rather than developers.
Recent discoveries of two-dimensional transitional metal based materials have emerged as an excellent candidate for fabricating nanostructured flame-retardants. Herein, we report an eco-friendly ...flame-retardant for flexible polyurethane foam (PUF), which is synthesised by hybridising MXene (TiFormula: see text) with biomass materials including phytic acid (PA), casein, pectin, and chitosan (CH). Results show that coating PUFs with 3 layers of CH/PA/TiFormula: see text via layer-by-layer approach reduces the peak heat release and total smoke release by 51.1% and 84.8%, respectively. These exceptional improvements exceed those achieved by a CH/TiFormula: see text coating. To further understand the fundamental flame and smoke reduction phenomena, a pyrolysis model with surface regression was developed to simulate the flame propagation and char layer. A genetic algorithm was utilised to determine optimum parameters describing the thermal degradation rate. The superior flame-retardancy of CH/PA/TiFormula: see text was originated from the shielding and charring effects of the hybrid MXene with biomass materials containing aromatic rings, phenolic and phosphorous compounds.
Greater demands for underwater sound absorption materials have been growing due to the concern about underwater noise control in water. Among the range of existing materials, polymer-based materials ...are increasingly being utilized as underwater sound absorption materials. In this paper, different kinds of polymer-based materials for underwater sound absorption with regards to key factors associated with sound absorption properties, measurements, applications, and mechanisms are reviewed and summarized. Commonly used polymers for underwater sound comprise, in general, interpenetrating polymer networks (IPN), polymer foams, and gradient polymers. To further improve underwater sound absorption performance, different types of inclusions that are introduced into the polymer matrix to transform the polymers as underwater sound absorption materials via air voids, solid inclusions, nanofillers, and phononic crystals are discussed. Challenges for further development of better polymer-based acoustic materials to meet requirements of current and future underwater applications are also presented.
•Key factors and tests of polymer-based underwater sound absorption materials.•Different polymers with or without inclusions for underwater sound absorption.•Mechanisms behind the underwater sound absorption.•Challenges for further improving polymer-based underwater water sound absorption materials.
Transduction of mechanical forces and chemical signals affect every cell in the human body. Fluid flow in systems such as the lymphatic or circulatory systems modulates not only cell morphology, but ...also gene expression patterns, extracellular matrix protein secretion and cell-cell and cell-matrix adhesions. Similar to the role of mechanical forces in adaptation of tissues, shear fluid flow orchestrates collective behaviours of adherent cells found at the interface between tissues and their fluidic environments. These behaviours range from alignment of endothelial cells in the direction of flow to stem cell lineage commitment. Therefore, it is important to characterize quantitatively fluid interface-dependent cell activity. Common macro-scale techniques, such as the parallel plate flow chamber and vertical-step flow methods that apply fluid-induced stress on adherent cells, offer standardization, repeatability and ease of operation. However, in order to achieve improved control over a cell's microenvironment, additional microscale-based techniques are needed. The use of microfluidics for this has been recognized, but its true potential has emerged only recently with the advent of hybrid systems, offering increased throughput, multicellular interactions, substrate functionalization on 3D geometries, and simultaneous control over chemical and mechanical stimulation. In this review, we discuss recent advances in microfluidic flow systems for adherent cells and elaborate on their suitability to mimic physiologic micromechanical environments subjected to fluid flow. We describe device design considerations in light of ongoing discoveries in mechanobiology and point to future trends of this promising technology.
Crude oil leakage from tankers, offshore platforms, drilling rigs and wells, causing severe pollution to the environment has led to irreversible damage to ocean habitat and inhabitants. It has become ...one of the greatest global environmental concerns which has recently attracted major public awareness. In addition, the contamination of sea and inhabitants. It has significantly harmed the fishing and seafood industry, and even raises health and life issues for millions of human beings. Until now, there is still no viable and practical method to effectively reduce the damage from crude oil spill. This has attracted numerous researchers’ attention. For developing an environmentally friendly and cost-effective polymer absorbent for oil spill cleaning. Recently, among all the efforts, it is proven that biomass aerogel can be used as an outstanding absorbent for oil–water separation, which is a feasible solution for tackling the crude oil issue. In this article, a comprehensive review on the current state-of-art for biomass-based aerogels utilised in the field of oil/water separation is provided. This includes the preparation procedures, fabrication processes, and the categorisation of various types of aerogels. Additionally, the future direction and technological advancement will be discussed in detail.
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•Algorithm to find interfacial area for mass transfer within volume-of-fluid (VOF).•Test cases show algorithm can calculate multiphase interfacial area correctly.•Algorithm proven to simulate mass ...transfer more accurately.•Superior to the standard |∇α| method for mass transfer area approximation.
Mass transfer occurs in many simple and complex processes. As mass transfer persists across the interface separating immiscible fluids, the proper determination of the interfacial area is critical in accurately capturing the mass transfer process. In this paper, an algorithm is proposed and developed whereby the interfacial area is ascertained within the framework of the volume-of-fluid (VOF) multiphase model. The algorithm is based on a concept similar to the Piecewise-Linear Interface Calculation (PLIC) method where a plane cutting an orthogonal mesh cell is considered. Through this algorithm, the interfacial area can be approximated as the area of the resulting polygon from the plane cut. A series of test cases are conducted to verify the accuracy of the algorithm. The results indicate that the algorithm is able to correctly calculate the interfacial area of multiphase systems including for complex cases such as droplets in microchannels. The algorithm is also shown to simulate mass transfer accurately and is demonstrated to be superior to the standard |∇α| function, which is used widely in literature to approximate the interfacial area in VOF simulations.
Increasing demands in minimization of fire risks and meeting fire safety requirements by polymers require advances in knowledge of flame-retardant materials suitable for use in fire-retardancy ...applications. The present work represents the seminal review of alginate/polymer-based materials as flame retardants. Alginates are suitable for this application as they represent alternatives to petroleum-based polymer feedstocks. The content of the present work is structured into four sections: synthesis and structure, including alginate synthesis and modification by polymeric conjugation; properties, including four-stage mechanism of thermal degradation; applications, including commercial information on alginates and polymers; and flame retardancy, including comprehensive summaries of test methods and published data, discussion of key parameters, eight fire retardancy mechanisms, four char generation mechanisms, and extensive quantitative analysis of polymer char formation. The final section culminates in a first-principles approach to the prediction of quantitative polymer char formation. The goal of the review is to provide guidance for the application of alginates and alginates conjugated with fire-retardant polymers as a new generation flame retardant material.
A paradigm shift towards the utilization of carbon-neutral and low emission fuels is necessary in the internal combustion engine industry to fulfil the carbon emission goals and future legislation ...requirements in many countries. Hydrogen as an energy carrier and main fuel is a promising option due to its carbon-free content, wide flammability limits and fast flame speeds. For spark-ignited internal combustion engines, utilizing hydrogen direct injection has been proven to achieve high engine power output and efficiency with low emissions. This review provides an overview of the current development and understanding of hydrogen use in internal combustion engines that are usually spark ignited, under various engine operation modes and strategies. This paper then proceeds to outline the gaps in current knowledge, along with better potential strategies and technologies that could be adopted for hydrogen direct injection in the context of compression-ignition engine applications—topics that have not yet been extensively explored to date with hydrogen but have shown advantages with compressed natural gas.
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•Waste coffee grounds improve the flame retardancy and reduce toxic gases emissions of epoxy composites.•Reducing the size of coffee grounds further improves the flame.•Reduced size ...coffee grounds can achieve similar peak heat release rate reduction as commonly used inorganic flame retardants.•A micro mechanical finite element model has been developed to predict the tensile strength of particle/epoxy composites.
Waste coffee grounds, a biomaterial with high carbon content, have been suggested as a non-toxic organic flame retardant due to their high char forming and radical scavenging properties. Herein, investigations are conducted on the effects of waste coffee grounds, especially their concentration and particle size, on the mechanical properties, flame retardancy, toxic gas production of epoxy composites. Results reveal that reducing average size of the waste coffee grounds from 46 µm to 16 µm, using freeze-milling or filtering, can reduce peak heat release rate and total heat release of their epoxy composites by 52.0% and 33.7% respectively, exceeding the effectiveness of other bio-based flame retardants such as chitosan, lignin and seashell. More importantly, the fine coffee grounds can achieve the same performance as aluminium trihydrates, the most widely used non-bio flame retardant. Furthermore, the burning rates and emissions of toxic gas have also been greatly reduced, almost entirely suppressing the highly toxic NO2 gas. The findings provide new insights into the effect of particle size of waste coffee grounds on both the mechanical properties and flame retardancy performnance of epoxy composites.
In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery ...systems has always been a global concern for the end-users. The separator is an indispensable part of lithium-ion batteries since it functions as a physical barrier for the electrode as well as an electrolyte reservoir for ionic transport. The properties of separators have direct influences on the performance of lithium-ion batteries, therefore the separators play an important role in the battery safety issue. With the rapid developments of applied materials, there have been extensive efforts to utilize these new materials as battery separators with enhanced electrical, fire, and explosion prevention performances. In this review, we aim to deliver an overview of recent advancements in numerical models on battery separators. Moreover, we summarize the physical properties of separators and benchmark selective key performance indicators. A broad picture of recent simulation studies on separators is given and a brief outlook for the future directions is also proposed.
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