QUAGMIRE v1.3: a quasi-geostrophic model for investigating rotating fluids experiments

QUAGMIRE is a quasi-geostrophic numerical model for performing fast, high-resolution simulations of multi-layer rotating annulus laboratory experiments on a desktop personal computer. The model uses a hybrid finite-difference/spectral approach to numerically integrate the coupled nonlinear partial differential equations of motion in cylindrical geometry in each layer. Version 1.3 implements the special case of two fluid layers of equal resting depths. The flow is forced either by a differentially rotating lid, or by relaxation to specified streamfunction or potential vorticity fields, or both. Dissipation is achieved through Ekman layer pumping and suction at the horizontal boundaries, including the internal interface. The effects of weak interfacial tension are included, as well as the linear topographic beta-effect and the quadratic centripetal beta-effect. Stochastic forcing may optionally be activated, to represent approximately the effects of random unresolved features. A leapfrog time stepping scheme is used, with a Robert filter. Flows simulated by the model agree well with those observed in the corresponding laboratory experiments

A numerical code for the solution of the Kompaneets equation in cosmological context

Context: The cosmic microwave background (CMB) spectrum probes physical processes and astrophysical phenomena occurring at various epochs of the Universe evolution. Current and future CMB absolute temperature experiments are aimed to the discovery of the very small distortions such those associated to the cosmological reionization process or that could be generated by different kinds of earlier processes. The interpretation of future data calls for a continuous improvement in the theoretical modeling of CMB spectrum. Aims: In this work we describe the fundamental approach and, in particular, the update to recent NAG versions of a numerical code, KYPRIX, specifically written for the solution of the Kompaneets equation in cosmological context, first implemented in the years 1989-1991, aimed at the very accurate computation of the CMB spectral distortions under quite general assumptions. Methods: We describe the structure and the main subdivisions of the code and discuss the most relevant aspects of its technical implementation. Results: We present some of fundamental tests we carried out to verify the accuracy, reliability, and performance of the code. Conclusions: All the tests done demonstrates the reliability and versatility of the new code version and its very good accuracy and applicability to the scientific analysis of current CMB spectrum data and of much more precise measurements that will be available in the future. The recipes and tests described in this work can be also useful to implement accurate numerical codes for other scientific purposes using the same or similar numerical libraries or to verify the validity of different codes aimed at the same or similar problems.Comment: 14 pages, 6 figures. Accepted for publication on Astronomy and Astrophysics on July 23, 2009. Abstract shorter than in the version in publicatio

Almost Block Diagonal Linear Systems: Sequential and Parallel Solution Techniques, and Applications

Almost block diagonal (ABD) linear systems arise in a variety of contexts, specifically in numerical methods for two-point boundary value problems for ordinary differential equations and in related partial differential equation problems. The stable, efficient sequential solution of ABDs has received much attention over the last fifteen years and the parallel solution more recently. We survey the fields of application with emphasis on how ABDs and bordered ABDs (BABDs) arise. We outline most known direct solution techniques, both sequential and parallel, and discuss the comparative efficiency of the parallel methods. Finally, we examine parallel iterative methods for solving BABD systems. Copyright (C) 2000 John Wiley & Sons, Ltd

Information and advice on the numerical software available for the Fusion Energy program at Oak Ridge

The purpose of this report is to describe some of the numerical routines that have been obtained for the Fusion Energy program at Oak Ridge. The report is organized by problem area. Each area contains a list of relevant numerical routines. These routines are described in detail and, where appropriate, we give advice on their correct use. Furthermore, we have ranked the subroutine libraries NAG, IMSL, and HARWELL according to how satisfactory their routines are for that particular area. In an Appendix we provide information on how to access the routines and the subroutine libraries described in this report. Moreover, we describe a growing online data base which contains a condensed version of the information in this report