Computational fluid dynamics Website
Computational fluid dynamics Website
Keywords: Software, World Wide Web, Computational fluid dynamics, Flow Science, Internet
A new Website called CFD101 provides resources on the emerging technology of computational fluid dynamics (CFD). The technical information resides on the Website of Flow Science, Inc., Los Alamos, New Mexico, and can be reached through the CFD101 link on the company's homepage (www.flow3d.com). CFD101 includes a series of detailed technical articles packed with formulas, illustrations and tables that guide the beginner through the maze of CFD technology and also provide the CFD expert with access to the latest research on advanced techniques such as free surface modelling and free gridding.
The topic of CFD is rapidly becoming more important to a broader range of engineers and scientists because of its ability to predict fluid flow in virtually any situation without the expense and time involved in building a physical model. CFD involves the solution of the governing equations for fluid flow at thousands of discrete points on a computational grid, allowing engineers to determine the direction and speed of flow at any point in the flow domain. Unlike a physical model, the geometry of the CFD model can be changed quickly on the computer and reanalysed to explore different options in project design or operating conditions.
One of the important issues addressed in the CFD101 Website is the basic issue of how to grid a flow problem. Gridding is the process of subdividing a region to be modelled into a set of small control volumes, each of which is associated with values of the dependent flow variables. The Website explains the differences between the major gridding approaches available to the user such as unstructured vs structured grids and also shows several methods that can be used to get better geometric representations of curved obstacle surfaces.
The CFD101 Website also provides information that will be very useful in selecting a numerical solution scheme. This article describes the difference between the explicit method, when the dependent variables are directly calculated, and the implicit method, when the dependent variables are defined by coupled sets of equations. The consequences of selecting an implicit or explicit approach are described in detail in terms of their impact upon computational stability and accuracy.
Free surface modeling is also covered in detail on the CFD101 Website. Free surface refers to the interface between a gas and a liquid, one of the most challenging aspects of CFD because of the large difference in densities between the two. Free surfaces require the introduction of special methods to define their location, movement and influence on flow. CFD101 contains several articles that review the types of numerical approaches that can be used to model free surfaces and indicate the advantages and disadvantages of each method.
Finally, the Website addresses a number of other issues of importance to both the beginning user and experienced practitioner. Guidance is provided in representing turbulence in a CFD analysis. CFD101 discusses the conservation of mass, momentum and energy and an explanation is provided of the many situations where strict adherence to conservation principles may not be a good idea. Artificial and numerical viscosities are explained and the often misunderstood difference between them is clearly delineated.
The sponsor of the CFD101 Website, Flow Science, Inc., is also the developer of the FLOW-3D CFD software package that provides several major advantages over other CFD programs. Geometry and grids are independent of each other,eliminating the tedious task of generating body-fitted or finite-element grids. FLOW-3D uses the volume-of-fluid method to model extremely complex fluid behaviours involving any number of independent free surfaces. The VOF method, as used in FLOW-3D, has three parts: locating the surface, tracking the surface as a sharp interface through a grid, and applying boundary conditions at the interface. All three parts have been found necessary for the accurate treatment of free surfaces.
Further details are available from Flow Science Inc. Tel: +1 505 662 2636;Fax: +1 505 662 6564; E-mail: cfd@flow3d.com;Website: www.flow3d.com
