Introduction

CFD SinFlow Library is a classes and objects library for the numeric methods development in the area of Computational Fluid Dynamics.

The way as the library was developed it allows to the graduation and masters degree student the access to the numeric methods in a simplified way, reducing the informatic knowledge necessary for the use of the same ones.

The library was developed in C++, what facilitates a larger abstraction and encapsulation of the classes and implemented objects [Perry 1994, Barton 1994]. The object guided programming also facilitates the reused of computational codes, facilitating the addition of new methodologies and numeric techniques [Barton 1994].

The current version of the library bases on the method of the finite volumes [Patankar 1980] for the discretization of the conservation equations, equations these base for the resolution of problems of Fluids Dynamics.

The finite volumes method consists in the domain discretization in countless control volumes on which mass balances, energy and momentum will be accomplished.

The Illustration below illustrates the domain discretization through finite volumes and it shows in detail the elementary volumes on which the mass balances, energy and momentum will be accomplished.

The formulation totally implicit [Maliska 2004] it creates a dependence among whole the domain variables for a same instant of time, doing with that the problem solution is obtained through the resolution of a linear system.

In the finite volumes method the variables are stored in the elemental volumes centers. The mass balances, moment and energy however, they are accomplished on the faces of the same ones, being then necessary the use of interpolation outlines [Maliska 2004] for the determination of the variables value on the faces starting from those stored in the volumes centers.

The interpolation schemes present in the CFD Sinflow Library are: CDS, UDS and WUDS.

Owed the applications of the boundary conditions the elemental volumes adjacent to borders would owe, a priori, to receive a differentiated treatment when in the energy balance, because they present in one of the faces a well-known behavior.

In the intuit of treating the boundary volumes of the similar way to the interns, it opted for the use of fictitious volumes, that are volumes added about of the physical domain and that present properties that will reproduce the boundary conditions of the problem.

For the equations linear systems resolution the library presents countless solvers, direct and iteractives.

The solvers implemented in CFD SinFlow Library is: TDMA, Jacobi, Gauss-Seidel, Band Diagonal, Cholesky, Conjugate Gradient and LU.

To develop general methods for the problems solution defined in complex geometries it is due, intuitively, to opt for the use of general curvilinear coordinates.

The use of the conventional coordinates systems (Cartesian, polar, cylindrical, spherical, etc.) in the domain discretization of complex geometry, as shown in the Figure, it inhibits the generic abordage on the problem, being necessary a manipulation differentiated for the adjacent elemental volumes the internal domain boundary.

When using the generalized coordinates it can realize coincident discretization with the border [Maliska 2004], as illustrated in the Figure (b), it facilitated the implementation of the numeric model.

A typical Fluids Dynamics problems consist of the velocity fields’ determination, pressure and temperature around a solid block, as showed in the pictures Figure (a) and Figure (b).

The coincident discretization with the boundary, Figure (a), in spite of its generic abordage about the problem, it doesn't allow the problem resolution diffusive in the solid blocks. In the intuit of to facilitate the domain discretization and to solve the conduction problem in the bodies immerged in the flow objects of the type were still created SolidBlocks, that represent domain areas where the flux convective is null [Patankar 1980].

It can solving the problem illustrated below in the Illustration through a coincident discretization with the boundary, Figure (a), or through the use of the solid blocks, it leaves shadowed of the Figure (b).