Alejandro Clausse

Bio: Alejandro Clausse is an academic researcher from National Scientific and Technical Research Council. The author has contributed to research in topics: Dense plasma focus & Pinch. The author has an hindex of 25, co-authored 194 publications receiving 2202 citations. Previous affiliations of Alejandro Clausse include National Atomic Energy Commission & National University of Central Buenos Aires.

Two-phase flow instabilities: A review

Abstract: An updated review of two-phase flow instabilities including experimental and analytical results regarding density-wave and pressure-drop oscillations, as well as Ledinegg excursions, is presented. The latest findings about the main mechanisms involved in the occurrence of these phenomena are introduced. This work complements previous reviews, putting all two-phase flow instabilities in the same context and updating the information including coherently the data accumulated in recent years. The review is concluded with a discussion of the current research state and recommendations for future works.

A Lattice-Boltzmann solver for 3D fluid simulation on GPU

Abstract: A three-dimensional Lattice-Boltzmann fluid model with nineteen discrete velocities was implemented using NVIDIA Graphic Processing Unit (GPU) programing language “Compute Unified Device Architecture” (CUDA). Previous LBM GPU implementations required two steps to maximize memory bandwidth due to memory access restrictions of earlier versions of CUDA toolkit and hardware capabilities. In this work, a new approach based on single-step algorithm with a reversed collision–propagation scheme is developed to maximize GPU memory bandwidth, taking advantage of the newer versions of CUDA programming model and newer NVIDIA Graphic Cards. The code was tested on the numerical calculation of lid driven cubic cavity flow at Reynolds number 100 and 1000 showing great precision and stability. Simulations running on low cost GPU cards can calculate 400 cell updates per second with more than 65% hardware bandwidth.

Demonstration of neutron production in a table-top pinch plasma focus device operating at only tens of joules

Abstract: Neutron emission from a deuterium plasma pinch generated in a very small plasma focus (6 mm anode diameter) operating at only tens of joules is presented. A maximum current of 50 kA is achieved 140 ns after the beginning of the discharge, when the device is charged at 50 J (160 nF capacitor bank, 38 nH, 20–30 kV, 32–72 J). Although the stored energy is very low, the estimated energy density in the plasma and the energy per particle in the plasma are of the same order as in higher energy devices. The dependence of the neutron yield on the filling pressure of deuterium was obtained for discharges with 50 and 67 J stored in the capacitor bank. Neutrons were measured by means of a system based on a 3He proportional counter in current mode. The average neutron yield for 50 J discharges at 6 mbar was (1.2 ± 0.5) × 104 neutrons per shot, and (3.6 ± 1.6) × 104 for 67 J discharges at 9 mbar. The maximum energy of the neutrons was (2.7 ± 1.8) MeV. Possible applications related to substance detection and others are discussed.

Conceptual engineering of plasma-focus thermonuclear pulsors

Abstract: The basic engineering criteria for conceptual design of plasma focus devices is derived from a thermonuclear model, and applied successfully to the operation of small neutron pulsors. The theory is able to explain the variation of the neutron yield with the gas pressure in deuterium-filled chambers, the current evolution, and the electrode geometrical parameters. The performance of a prototype designed to optimize the flux/fluence ratio is presented, contrasting the experimental outcomes with the model. A set of effective design parameters is deduced, which ensure a band confidence of 20%.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

Abstract: to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Flood inundation modelling

Abstract: This paper reviews state-of-the-art empirical, hydrodynamic and simple conceptual models for determining flood inundation. It explores their advantages and limitations, highlights the most recent advances and discusses future directions. It addresses how uncertainty is analysed in this field with the various approaches and identifies opportunities for handling it better. The aim is to inform scientists new to the field, and help emergency response agencies, water resources managers, insurance companies and other decision makers keep up-to-date with the latest developments. Guidance is provided for selecting the most suitable method/model for solving practical flood related problems, taking into account the specific outputs required for the modelling purpose, the data available and computational demands. Multi-model, multi-discipline approaches are recommended in order to further advance this research field. This paper reviews state-of-the-art flood inundation models.It explores their advantages and limitations.It highlights the most recent advances and discusses future directions.It addresses how uncertainty is analysed and identifies opportunities for handling it better.

Numerical solution of initial value problems in differential - algebraic equations

Abstract: During the last decade, a big progress has been achieved in the analysis and numerical treatment of Initial Value Problems (IVPs) in Differential Algebraic Equations (DAEs) and Ordinary Differential Equations (ODEs). In spite of the rich variety of results available in the literature, there are still many specific problems that require special attention. Two of such, which are considered in this work, are the optimization of order of accuracy and reduction of cost of functional evaluations of Explicit Runge - Kutta (ERK) methods. Traditionally, the maximum attainable order p of an s-stage ERK method for advancing the solution of an IVP is such that p(s) 4 In 1999, Goeken presented an s-stage ERK Method of order p(s)=s +1,s>2. However, this work focuses on the design of a new approximation algorithm that reduces the cost of functional evaluations and yet increases the attainable order higher U n and Jonhson [94]; and the classical ERK methods. The order p of the new scheme called Multiderivative Explicit Runge-Kutta (MERK) Methods is such that p(s) 2. The stability, convergence and implementation for the optimization of IVPs in DAEs and ODEs systems are also considered.