Free surface flow past topography : a beyond-all-orders approach

The problem of steady subcritical free surface flow past a submerged inclined step is considered. The asymptotic limit of small Froude number is treated, with particular emphasis on the effect that changing the angle of the step face has on the surface waves. As demonstrated by Chapman & Vanden-Broeck (2006), the divergence of a power series expansion in powers of the square of the Froude number is caused by singularities in the analytic continuation of the free surface; for an inclined step, these singularities may correspond to either the corners or stagnation points of the step, or both, depending on the angle of incline. Stokes lines emanate from these singularities, and exponentially small waves are switched on at the point the Stokes lines intersect with the free surface. Our results suggest that for a certain range of step angles, two wavetrains are switched on, but the exponentially subdominant one is switched on first, leading to an intermediate wavetrain not previously noted. We extend these ideas to the problem of flow over a submerged bump or trench, again with inclined sides. This time there may be two, three or four active Stokes lines, depending on the inclination angles. We demonstrate how to construct a base topography such that wave contributions from separate Stokes lines are of equal magnitude but opposite phase, thus cancelling out. Our asymptotic results are complemented by numerical solutions to the fully nonlinear equations.

Free-surface flow past arbitrary topography and an inverse approach for wave-free solutions

An efficient numerical method to compute nonlinear solutions for two-dimensional steady free-surface flow over an arbitrary channel bottom topography is presented. The approach is based on a boundary integral equation technique which is similar to that of Vanden-Broeck's (1996, J. Fluid Mech., 330, 339-347). The typical approach for this problem is to prescribe the shape of the channel bottom topography, with the free-surface being provided as part of the solution. Here we take an inverse approach and prescribe the shape of the free-surface a priori while solving for the corresponding bottom topography. We show how this inverse approach is particularly useful when studying topographies that give rise to wave-free solutions, allowing us to easily classify eleven basic flow types. Finally, the inverse approach is also adapted to calculate a distribution of pressure on the free-surface, given the free-surface shape itself.

Unsteady free convection flow in the stagnation-point region of a rotating sphere

The unsteady free convection boundary-layer flow in the forward stagnation-point region of a sphere, which is rotating with time-dependent angular velocity in an ambient fluid, has been studied. Both constant wall temperature and constant hear flux conditions have been considered. The non-linear coupled parabolic partial differential equations governing the flow have been solved numerically using an implicit finite-difference scheme. The skin friction and the heat transfer are enhanced by the buoyancy force. The effect of the buoyancy force is found to be more pronounced for smaller Prandtl numbers than for larger Prandtl numbers. For a given buoyancy force, the heat transfer increases with an increase in Prandtl number, but the skin friction decreases.

Unsteady Free-Convection Flow on a Rotating flat-Plate Under Nonuniform Gravity

The free convection problem with nonuniform gravity finds applications in several fields. For example, centrifugal gravity fieldsarisein many rotating machinery applications. A gravity field is also created artificially in an orbital space station by rotation. The effect of nonuniform gravity due to the rotation of isothermal or nonisothermal plates has been studied by several authors [l-5] using various mathematical techniques.

Anomalies in free flux-flow hall effect

The low-T-c layered superconductor 2H-NbSe2 shows remarkable results for free flux-flow Hall effect. At low magnetic fields, the Nozieres-Vinen result of a field-independent Hall angle appears to hold. At larger fields, a marked departure occurs leading to an extremely sharp and pronounced minimum slightly below H-c2, unaccounted for in the standard theoretical models. The results suggest the existence of collective dynamics and phase transitions (such as melting) in a clean flux line lattice.

Unsteady free convection flow under the influence of a magnetic field

The unsteady free convection boundary layer at the stagnation point of a two-dimensional body and an axisymmetric body with prescribed surface heat flux or temperature has been studied. The magnetic field is applied parallel to the surface and the effect of induced magnetic field has been considered. It is found that for certain powerlaw distribution of surface heat flux or temperature and magnetic field with time, the governing boundary layer equations admit a self-similar solution locally. The resulting nonlinear ordinary differential equations have been solved using a finite element method and a shooting method with Newton's corrections for missing initial conditions. The results show that the skin friction and heat transfer coefficients, and x-component of the induced magnetic field on the surface increase with the applied magnetic field. In general, the skin friction, heat transfer and x-component of the induced magnetic field for axisymmetric case are more than those of the two-dimensional case. Also they change more when the surface heat flux or temperature decreases with time than when it increases with time. The skin friction, heat transfer and x-component of the induced magnetic field are significantly affected by the magnetic Prandtl number and they increase as the magnetic Prandtl number decreases. The skin friction and x-component of the magnetic field increase with the dissipation parameter, but heat transfer decreases.

Effect of compressibility on the velocity gradient tensor at free shear flow boundaries

Analyses of the invariants of the velocity gradient ten- sor were performed on flow fields obtained by DNS of compressible plane mixing layers at convective Mach num- bers Mc=0:15 and 1.1. Joint pdfs of the 2nd and 3rd invariants were examined at turbulent/nonturbulent (T/NT) boundaries—defined as surfaces where the local vorticity first exceeds a threshold fraction of the maximum of the mean vorticity. By increasing the threshold from very small lev-els, the boundary points were moved closer into the turbulent region, and the effects on the pdfs of the invariants were ob-served. Generally, T/NT boundaries are in sheet-like regions at both Mach numbers. At the higher Mach number a distinct lobe appears in the joint pdf isolines which has not been ob-served/reported before. A connection to the delayed entrain-ment and reduced growth rate of the higher Mach number flow is proposed.

Simulation of Free-Surface Flow in a Tank Using the Navier-Stokes Model and Unstructured Finite Volume Method

Modelling free-surface flow has very important applications in many engineering areas such as oil transportation and offshore structures. Current research focuses on the modelling of free surface flow in a tank by solving the Navier-Stokes equation. An unstructured finite volume method is used to discretize the governing equations. The free surface is tracked by dynamically adapting the mesh and making it always surface conforming. A mesh-smoothing scheme based on the spring analogy is also implemented to ensure mesh quality throughout the computaiton. Studies are performed on the sloshing response of a liquid in an elastic container subjected to various excitation frequencies. Further investigations are also carried out on the critical frequency that leads to large deformation of the tank walls. Another numerical simulation involves the free-surface flow past as submerged obstacle placed in the tank to show the flow separation and vortices. All these cases demonstrate the capability of this numerical method in modelling complicated practical problems.

A computational model for defect prediction in shape castings based on the interaction of free surface flow, heat transfer, and solidification phenomena

High-integrity castings require sophisticated design and manufacturing procedures to ensure they are essentially macrodefect free. Unfortunately, an important class of such defects—macroporosity, misruns, and pipe shrinkage—are all functions of the interactions of free surface flow, heat transfer, and solidication in complex geometries. Because these defects arise as an interaction of the preceding continuum phenomena, genuinely predictive models of these defects must represent these interactions explicitly. This work describes an attempt to model the formation of macrodefects explicitly as a function of the interacting continuum phenomena in arbitrarily complex three-dimensional geometries. The computational approach exploits a compatible set of finite volume procedures extended to unstructured meshes. The implementation of the model is described together with its testing and a measure of validation. The model demonstrates the potential to predict reliably shrinkage macroporosity, misruns, and pipe shrinkage directly as a result of interactions among free-surface fluid flow, heat transfer, and solidification.

Stochastic analysis of free surface flow through earth dams

This research investigated the unconfined flow through dams. The hydraulic conductivity was modeled as spatially random field following lognormal distribution. Results showed that the seepage flow produced from the stochastic solution was smaller than its deterministic value. In addition, the free surface was observed to exit at a point lower than that obtained from the deterministic solution. When the hydraulic conductivity was strongly correlated in the horizontal direction than the vertical direction, the flow through the dam has markedly increased. It is suggested that it may not be necessary to construct a core in dams made from soils that exhibit high degree of variability.

Almirante: Evaluating the board game: Board game, startup, discounted cash flow, venture capital method, real options

This thesis evaluates a start-up company (Jogos Almirante Lda) whose single asset is a board game named Almirante. It aims to conclude whether it makes sense to create a company or just earn copyrights. The thesis analyzes the board game’s market, as part of the general toy’s market, from which some data exists: European countries as well as the USA. In this work it is analyzed the several ways to finance a start-up company and then present an overview of the valuation of the Jogos Almirante based on three different methods: Discounted Cash Flow, Venture Capital Method and Real Options.

Reporting cash flow evidence from campanies listed in the Euronext Lisbon

Based on the 2013 and 2014 consolidated statements of cash flows of companies listed in Euronext Lisbon, this Work Project analyses the cash flow disclosures, namely if they are in accordance with International Accounting Standards 7, specifically the format, the choice of classification interests, dividends paid and received and the composition of cash and cash equivalents. Additionally, quality of income ratio is analyzed due to its importance for users of financial statements. The results show evidence of uniformity and consistency in the use of the direct method for reporting operational activities in both years, but there are some differences regarding the disclosure of interests and dividends, paid and received, respectively.

Ownership Effects on Unrelated Diversification: An Institutions' Perspective

Purpose To show that differences in the extent to which firms engage in unrelated diversification can be attributed to differences in ownership structure. Methodology/approach We draw on longitudinal data and use a panel analysis specification to test our hypotheses. Findings We find that unrelated diversification destroys value; pressure-sensitive Anglo-American owners in a firm’s equity reduce unrelated diversification, whereas pressure-resistant domestic owners increase unrelated diversification; the greater the firm’s free cash flow, the greater the negative effect of pressure-sensitive Anglo-American owners on unrelated diversification. Research limitations/implications We contribute to corporate governance and strategy research by bringing in owners’ institutional origin as a shaper of owner preferences in particular with regards to unrelated diversification. Future research may expand our investigation to more than one home institutional context, and theorize on institutional origin effects beyond the dichotomy between Anglo-American and non-Anglo-American (not oriented toward shareholder value maximization) owners. Practical implications Policy makers, financial analysts, owners, and managers may want to reflect about the implications of ownership structure, as well as promoting or joining corporations with particular ownership configurations. Social implications A shareholder value-destroying strategy, such as unrelated diversification has adverse consequences for society at large, in terms of opportunity costs, that is, resources could be allocated to value-creating activities instead. Promoting an ownership configuration that creates value should contribute to social welfare. Originality/value Owners may not be exclusively driven by shareholder value maximization, but can be influenced by normative beliefs (biases) stemming from the institutional context they originate from.

Modelos de presupuestación de capital en finanzas corporativas y utilidad de los mismos

La siguiente investigación describe una aproximación teórica al tema de los modelos de presupuestación de capital, el objetivo fundamental se basa en comprender su enfoque e importancia al momento de tomar decisiones de inversión por parte de los directores de una empresa, así como de prever los efectos de esta en un futuro. Al respecto, y sobre la base de que los modelos de presupuestación de capital son herramientas para analizar posibles erogaciones de capital por parte de una empresa, es necesario para efectos del presente proyecto de investigación, definir sus diferentes modelos desde lo teórico y metodológico, explicando los diferentes conceptos relacionados con el tema. Así mismo, se explican algunos de los indicadores financieros utilizados en las compañías para medir y estimar la “salud financiera” de la empresa, además de puntualizar su impacto en la perdurabilidad de las entidades, lo cual permite dar una visión más general sobre la importancia que trasciende de los indicadores financieros, generando un impacto positivo en la evolución o crecimiento de la organización. En complemento, la investigación aborda la presupuestación de capital de manera particular aplicado en la gestión empresarial, sean estas privadas o públicas (estatal y gubernamental). En este sentido, se abordan conceptos elaborados por diferentes académicos en los que se exponen algunas aproximaciones respecto al posible mejoramiento de la presupuestación para los sectores a los que pertenecen determinadas entidades. Finalmente, se presenta de manera explícita las conclusiones que surgieron a lo largo de la construcción del documento de investigación, con el fin de dar cumplimiento concreto al objetivo general del trabajo, el cual constituye una respuesta a la pregunta de investigación que se enunciará en el desarrollo del documento.

Cash flow management in construction firms

The level of insolvencies in the construction industry is high, when compared to other industry sectors. Given the management expertise and experience that is available to the construction industry, it seems strange that, according to the literature, the major causes of failure are lack of financial control and poor management. This indicates that with a good cash flow management, companies could be kept operating and financially healthy. It is possible to prevent failure. Although there are financial models that can be used to predict failure, they are based on company accounts, which have been shown to be an unreliable source of data. There are models available for cash flow management and forecasting and these could be used as a starting point for managers in rethinking their cash flow management practices. The research reported here has reached the stage of formulating researchable questions for an in-depth study including issues such as how contractors manage their cash flow, how payment practices can be managed without damaging others in the supply chain and the relationships between companies’ financial structures and the payment regimes to which they are subjected.