The code's lineage can be traced back through Ron Henderson's prism code and ultimately to the original spectral element code nekton — in many ways the implementation is similar to prism (see Henderson & Karniadakis (1995) J Comput Phys 122: 191–217) but without mortar element patching or mesh adaptation. One noteworthy difference is that semtex supports cylindrical as well as Cartesian coordinates, and with full spectral convergence in all directions: see Blackburn & Sherwin (2004) J Comput Phys 197: 759–778 for a detailed description of the method. In addition to an incompressible Navier–Stokes solver, source is also provided for an elliptic solver that will deal with Laplace, Poisson and Helmholtz problems.
Please note that semtex is a research code and is provided 'as-is' with the understanding that it will be used mainly by other computer-literate researchers in computational fluid dynamics. It is not guaranteed to work or to provide correct results, and neither I or any employer accept any liability for detriment or loss consequent on your use of the code. Please see the terms of the Gnu General Public License (GPL) under which the code is released for public use. On the other hand, I'd be happy to hear of your experiences with using the code and your types of applications and results.
If through your use of the code you manage to obtain publishable results, I would be pleased if you could cite Blackburn & Sherwin (2004), where the numerical method is described in some depth, particular to the cylindrical-coordinate formulation.
I'm afraid that I do not have much time to answer routine questions about making semtex compile, running examples, etc. Please consult the user guide for information on these matters. I will be happy to hear of bugs, and even better, suggestions about how to fix them, although I cannot promise to remedy problems on a timely basis (and a big thank you to those who have contributed fixes to some niggling bugs). The source code distribution is occasionally updated, however, the code is quite mature now and does not often change.
More recently we supply two utilities that work with 3rd-party mesh generators.
Python script that will produce semtex session files from quad meshes generated by gmsh (open-source: see http://www.geuz.org/gmsh/). This utility is included in the current source code distribution.
Converter from Fluent Inc's gambit mesh generator to semtex session file format. Written by Erik Torres and Jörg Stiller from the ILR group at TU-Dresden. With user guides in German and English. Source code. With the deletion of gambit from the Ansys code suite, note that the Ansys workbench Fluent .msh format is the same as gambit's, albiet in binary. To get an ASCII .msh file (the starting point for gambit2semtex), set environment variable AWP_WRITE_FLUENT_MESH_ASCII=1 before using workbench.
While the user guide shows a number of visualisations made with the commercial Tecplot code, one can also convert output data files to VTK format, allowing the use of VisIt or Paraview.
Semtex release 7_3 (October 2013). This version employs the "alternating skew symmetric" form of the nonlinear terms in the Navier–Stokes equations (for speed and robustness) by default (though other forms are also available), and does not employ any form of dealiasing (in the interests of simplicity for potential users of the API). Also it includes code for a variety of spatially-varying body forces, including localised damping (sponge regions) and Coriolis effects, coded by Thomas Albrecht.
Final Version 6 (2013).
User guide (PDF) including decription of generalised body forces, a simple introduction to using semtex to study DNS of turbulent channel flow, and some information on the API.
Nektar++ spectral element code project (Spencer Sherwin and Mike Kirby).
Nek5000 spectral element code (Paul Fischer).