Numerical Simulation of Industrial Flows

Abstract

Computational Fluid Dynamics (CFD) is a numerical methodology for analyzing flow systems that may involve heat transfer, chemical reactions and other related phenomena. This approach employs numerical methods imbedded in algorithms to solve general conservation and constitutive equations together with specific models within a large number of control volumes (cells or elements) into which the associated computational domain of the flow system has been divided to build up a grid. Numerical simulation of industrial flows using commercial CFD codes is now well developed in a number of technical fields. With the advent of powerful and low-cost computer clusters, events including both complex geometry and high Reynolds numbers, i.e. fully turbulent practical industrial applications, may today be accurately modeled. This technique constitutes a rather new tool for analyzing problems related to, for instance, design, performance, safety and trouble-shooting of industrial systems since time can now be treated fully as the primary independent variable. The first commercial general-purpose CFD code, built around a finite volume solver, the Parabolic Hyperbolic Or Elliptic Numerical Integration Code Series (PHOENICS), was released in 1981. Initially, the solver was conformed to work only with structured, monoblock, regular Cartesian grids but it was subsequently broadened to admit even structured body-fitted grids. The multi-block grid option was developed many years later within this code which still preserves this restricting structured grid topology. Another well known commercial CFD code, FLUENT, was brought out onto the market in 1983 as a structured software that bore a resemblance to PHOENICS, but aimed towards modeling of systems with chemical reactions, specifically those related to combustion. Hence, during the 1980s, CFD simulations were limited to rough time-independent models with very simplified geometry due to the grid-structured character of the software and the vast limitations in, at that time, normally available computer resources at the industry (see e.g. Tinoco & Hemstrom, 1990). It might be of some interest to point out that the top performance of a supercomputer at the end of the 1980s was of the order of 10 GFLOPS (10×109 FLoating point Operations Per Second). The computers normally available at the industry had a thousandth to a hundredth of that performance, i.e. 10-100 MFLOPS. Today, a computer cluster containing a couple of hundred CPUs has a capacity of the order of TFLOPS. At the beginning of the 1990s, important steps in software improvement took place through the development of grid-unstructured, parallelized algorithms (e.g. FLUENT UNS) that