The PHOENICS code is fully self-contained, structured-grid (or body-fitted-coordinates) code with grid generation, solution, and post processing done in a 3-D virtual reality interface - but one can also learn the Phoenics Input Language (PIL), from which the product first evolved , in order to provide input (and more precise control) via a text editor. It is written in Fortran, is relatively inexpensive unless (one buys the source code for recompilation), and has a flexible english-language interface for introducing source and sink terms and arbitrary equations (In-Form). There are many examples in an online library, as well as an existing library of commonly-used shapes (including vehicles and human forms) and a list of materials and gas laws.
The code originated and is maintained by Prof. Spalding and his team at CHAM in the UK, and uses their SIMPLEST algorithm as its primary solver but also has a few others. There is an interface to the public-domain, industry standard CHEMKIN-II fully implicit solver for gas phase chemical reactions, widely used in the combustion research community. There are many different convection discretization schemes available, many turbulence models (single and dual equation, Large Eddy Simulation, etc.), but it only has first-order time discretization for time-dependent problems. It can solve deformation equations in solids simultaneously with flow equations allowing a single, master solution of structural load problems - a capability apparently unique to PHOENICS. Another unique algorithm in PHOENICS is it's Multi-Fluid Model (MFM) which can be used to derive Probability Density Functions for turbulent flow problems (although only fairly basic validations of this approach have been done to date). It has several dedicated program modules for modeling HVAC systems, computer (laptop) cooling systems, combustors and smelters, and others, as well as some unique, fast algorithms for calculating radiative transfer and inter-wall distances. A newer module allows moving coordinates and moving objects. It also has at least three algorithms for multiphase flow and particle tracking.
Of interest for the Aerospace community: flow-shock modeling can be done but there has been some discussion on the WEB that there appears to be a weakness in the SIMPLEST algorithm which limits practical utility of the code to about MACH 4 (this may not actually be true). Shocks can be captured using higher order convection schemes.