Navsetup

The main components of the NaSt3DGP package are the two parts navsetup and navcalc. As mentioned before, navsetup produces from a so-called scene description file (*.nav) the so-called data-file (*.bin). The scene description file must contain all information to describe the flow configuration. This includes the numbers of grid points, the mesh, the geometry of obstacles, place and type of boundary conditions, etc. From this data a compact, internal representation of the flow configuration is computed and written in the data-file. This data-file now contains initial values of the pressure and velocity ( $p,~{\bf u}$), a flag field which describes the geometry and some general information such as boundary conditions or physical parameters of the fluid.

The data-file is read by navcalc to run the simulation. After a prescribed number of time steps and before finishing, navcalc writes the actual pressure, velocity, etc. values in this file and thus overwrites the initial data. This new data-file can be used for a restart or for the analysis of the simulated flow. Since the format of the data-file is rather complicated navsetup provides the possibility to read a data-file and to write the pressure, velocity components, etc. in separate files which are easier to handle. A simple MatLab V tool which reads such files and stores the entries in an 3D array is tools/matlab/ReadNast.m