Numerical Methods for a Nonlinear BVP Arising in Physical Oceanography

In this paper we report and compare the numerical results for an ocean circulation model obtained by the classical truncated boundary formulation, the free boundary approach and a quasi-uniform grid treatment of the problem. We apply a shooting method to the truncated boundary formulation and finite difference methods to both the free boundary approach and the quasi-uniform grid treatment. Using the shooting method, supplemented by the Newton's iterations, we show that the ocean circulation model cannot be considered as a simple test case. In fact, for this method we are forced to use as initial iterate a value close to the correct missing initial condition in order to be able to get a convergent numerical solution. The reported numerical results allow us to point out how the finite difference method with a quasi-uniform grid is the less demanding approach and that the free boundary approach provides a more reliable formulation than the classical truncated boundary formulation.Comment: 25 pages, 12 figures, 5 table

Implicit Pseudo-Spectral Methods for Dispersive and Wave Propagation Problems

We consider some implicit pseudo-spectral methods for the numerical solution of nonlinear dispersive wave equations. These methods have been implemented via MATLAB script files. Moreover, application of the considered methods to different wave models is highlighted. [DOI: 10.1685 / CSC06078] About DO

Electrostatic Micro-Electro-Mechanical-Systems (MEMS) Devices: A Comparison Among Numerical Techniques for Recovering the Membrane Profile

In this work, numerical techniques based on Shooting procedure, Relaxation scheme and Collocation technique have been used for recovering the profile of the membrane of a 1D electrostatic Micro-Electro-Mechanical-Systems (MEMS) device whose analytic model considers |E| proportional to the membrane curvature. The comparison among these numerical techniques has put in evidence the pros and cons of each numerical procedure. Furthermore, useful convergence conditions which ensure the absence of ghost solutions, and a new condition of existence and uniqueness for the solution of the considered differential MEMS model, are obtained and discussed

performance of two different types of cathodes in microbial fuel cells for power generation from renewable sources

Abstract Microbial fuel cells (MFCs) technology represents a new approach to the sustainable electric power production, thanks to the advantages of its green features. The performance and the cost efficiency of a MFC are affected by several factors, such as the reactor architecture, the microbial microflora and the "costs per power" ratio of the electrodes. For example, cathodes powered by platinum as catalyzer are really efficient, but also expensive. In this study, two materials for cathode were examined: i) an economical biochar-based material (BC), ii) an activated carbon (AC) cathode with a nickel mesh current collector and a polytetrafluoroethylene (PTFE) binder to limit oxygen diffusion to the anodic compartment. The performances were evaluated in terms of power density and current density

Liquid Dynamics in a Horizontal Capillary: Extended Similarity Analysis

Abstract The topic of this study is an extended similarity analysis for a one-dimensional model of liquid dynamics in a horizontal capillary. The bulk liquid is assumed to be initially at rest and is put into motion by capillarity, that is the only driving force acting on it. Besides the smaller is the capillary radius the steeper becomes the initial transitory of the meniscus location derivative, and as a consequence the numerical solution to a prescribed accuracy becomes harder to achieve. Here, we show how an extended scaling invariance can be used to define a family of solutions from a computed one. The similarity transformation involves both geometric and physical feature of the model. As a result, density, surface tension, viscosity, and capillary radius are modified within the required invariance. Within our approach a target problem of practical interest can be solved numerically by solving a simpler transformed test case. The reference solution should be as accurate as possible, and therefore we suggest to use for it an adaptive numerical method. This study may be seen as a complement to the adaptive numerical solution of the considered initial value problems

Coupling of Biomass Gasification and SOFC – Gas Turbine Hybrid System for Small Scale Cogeneration Applications☆

Abstract In this study the performances of small cogeneration power plants fed by biomass and based on conventional and advanced technologies are presented. Three system configurations have been considered and analyzed. They are characterized by: a) a biomass gasification (G) unit, based on down-draft technology; b) a power unit, based on the SOFC technology or on the micro gas turbine (MGT) technology or on a hybrid configuration SOFC-MGT; c) a thermal recovery unit. The energy analysis of the proposed power plants has been conducted by using thermochemical/thermodynamic models able to study the integrated systems and each unit in terms of operating and performance parameters