Numerical investigation of swirl flow inside a supersonic nozzle

This study reports the Computational Fluid Dynamics (CFD) results of a swirling flow induced by introducing a helical insert inside a supersonic nozzle. The CFD simulation shows a very complex unsteady, non-axisymmetric flow pattern for the swirl flow inside the nozzle.The flow is investigated by solving the Reynolds averaged Navier Stokes (RANS) equations with k- and Reynolds Stress Model (RSM) turbulence models to predict the flow patterns and the type of swirling flow. Computations are conducted for a range of nozzle pressure ratios with and without swirl inside the converging–diverging nozzle. The study has revealed a new understanding and data for flow features such as shock location, mass flow rate and anisotropic turbulence

The Wealth Effect Of The Stock Market Revisited

This paper provides evidence that wealth in the form of stock ownership affects consumption and that the stock wealth effect has increased significantly. Using a consumption function expanded to include wealth as well as income, the paper first confirms that the data indicate the presence of a wealth effect. Then, the paper tests for a break in the relationship and finds that for stock wealth only, the consumption coefficient increased in the early 1990s.

Valuation Ratios As Stock Market Predictors

Using bivariate causality tests, this paper examines price-earnings (PE) and dividend yield (DY) ratios and finds that they do not predict future stock returns but that they do predict future earnings and dividends, lending support to the efficient markets hypothesis.  (JEL: G12, G14

Stock Prices, Consumer Sentiment, And Economic Activity: Some Robust Bilateral Causality Tests For The US And The UK

This paper performs robust bilateral Granger causality tests for stock prices, consumer sentiment, and economic activity for the US and the UK. The robust test procedures involve the use of recently developed time series analysis of nonstationary data with possible structural breaks. Applying a battery of such tests, the paper finds the underlying data to be generally nonstationary and noncointegrated, even after allowing for possible breaks in the data, thus implying that the standard bilateral Granger causality tests are robust. The empirical results indicate the presence of unidirectional causality from stock prices to consumer sentiment for both countries. Given that stock prices drive consumer sentiment, we perform additional causality tests to determine the effect of consumer sentiment on the economy. Our finding of a unidirectional causality from consumer sentiment to the economy in both countries is consistent with a chain of causality from stock prices to consumer sentiment to the economy

Optimised textured surfaces with application in piston-ring/cylinder liner contact

The application of textured surfaces in tribology has recently gained a huge momentum. In this chapter, a systematic approach to investigate the maximum outcomes from employing such surfaces is introduced with an insight into their application in internal combustion engines. A combination of various affecting parameters on the tribological performance of such surfaces is studied and the optimum results are introduced. The effect of employing such optimised textures in enhancing the lubrication condition in piston ring/cylinder liner contact is also studied

Optimization of partially textured parallel thrust bearings with square-shaped micro-dimples

In this study we attempt to find the optimum geometrical parameters of square-shape micro-dimples imposed on parallel flat bearing surfaces which give the best tribological performance, including load capacity and friction coefficient. An analytical solution of Reynolds equation for the surfaces involving numerous dimples is presented, then considering the variations of number of dimples as well as dimple length and height ratios for a constant dimpled length, it is tended to get the optimum value of parameters. It is shown that despite the variations of different studied geometrical parameters, it seems the optimum value of these parameters remain nearly constant

Analytical analysis and optimisation of the Rayleigh step slider bearing

In tribology, the Rayleigh step is known as a bearing with the highest load capacity amongst all other possible bearing geometries. In classical resources on tribology, it is also shown that there is an optimum geometry for the Rayleigh step providing the highest load capacity. However, the analyses are confined to a special case where the effect of hydrostatic pressure is neglected. Furthermore, the possible optimum parameters in terms of the friction force and/or friction coefficient as well as the lubricant flow rate have not been discussed. In this study, the Rayleigh step is comprehensively analysed including the effect of variations of pressure at the boundaries on the optimum parameters. In addition, the bearing is also optimised considering lubricant flow rate, friction force and friction coefficient. It is shown that the optimum bearing parameters are strictly dependent on the variations of the pressure at the boundaries. It is also verified that the optimum point(s) in terms of load capacity are not necessarily equal to the optimum point(s) considering friction coefficient and/or lubricant flow rate even though if there is no pressure difference between bearing endings

Spreadsheet tools to estimate the thermal transmittance and thermal conductivities of gas spaces of an Insulated Glazing Unit

An Insulated Glazing unit (IGU) is constructed with two or more layers of glass panes sealed together by gas spaces in-between. IGUs are prevalent in windows, doors and rooflights, primarily due to their improved thermal resistance. Today, most IGUs are either two or three layered. Adding further layers of glass improves thermal insulation but with the penalty of increased cost and weight. Low emissivity (Low-e) film coatings, when deposited on the glass panes, reduce long-wavelength radiative heat losses. Furthermore, filling the gas spaces with the inert gases (e.g. Argon, Krypton, Xenon and SF6), further reduce conduction and natural convection across the gap. In summary, higher thermal insulation performance of an IGU can be achieved with gas fillings and Low-e coatings on glass. This report discusses spreadsheets that have been developed, capable of estimating the thermal transmittance values of IGU, as per BS EN 673. The spreadsheet tools also have the ability to estimate the thermal conductivity of the gas spaces between the panes of IGU

Thermo-Mechanical Analysis of Dissimilar Al/Cu Foil Single Lap Joints Made by Composite Metal Foil Manufacturing

The paper presents an additive manufacturing process for the production of metal and composite parts. It is termed as composite metal foil manufacturing and is a combination of laminated object manufacturing and brazing techniques. The process has been described in detail and is being used to produce dissimilar aluminum to copper foil single lap joints. A three dimensional finite element model has been developed to study the thermo-mechanical characteristics of the dissimilar Al/Cu single lap joint. The effects of thermal stress and strain have been analyzed by carrying out transient thermal analysis on the heated plates used to join the two 0.1mm thin metal foils. Tensile test has been carried out on the foils before joining and after the single Al/Cu lap joints are made, they are subjected to tensile lap-shear test to analyze the effect of heat on the foils. The analyses are designed to assess the mechanical integrity of the foils after the brazing process and understand whether or not the heat treatment has an effect on the fracture modes of the produced specimens