Snas3D: Software for Flow Simulation

This software package allows you to efficiently simulate three-dimensional (3-D) flows on multi-block, structured grids. It consists of a general purpose flow solver for the solution of the Euler or the Navier-Stokes equations on stationary, as well as on moving / deforming grids. Further included are tools for pre-processing of the grids, generation of the initial solution and for post-processing. The resulting plot files can be visualized using either the free tool Paraview or the commercial software Tecplot.

Main features:

Finite-volume, cell-centered formulation with ALE methodology for dynamic grids
Spatial discretization using either central scheme with scalar artificial dissipation or Roe's flux-difference upwind scheme
Temporal discretization employing explicit, hybrid multi-stage scheme for stationary flows, and classical Runge-Kutta or implicit dual-time stepping schemes for unsteady flows
Turbulence modeling using Spalart-Allmaras one-equation model
Capability to simulate incompressible, compressible and mixed-type flows ranging from very low to high Mach numbers
Convergence acceleration by multigrid (FAS scheme)
Parallelization based on MPI and block decomposition
Prepared for the implementation of various fluid models and for additional species equations
Interfaces for receiving and also for sending boundary data (including geometry) from / to an external driver program
Functions for local or global (across multiple blocks) grid motion

Description of the numerical methods used and the capabilities of an earlier version of Snas3D can be found in this conference paper.

Downloads:

Executables of the flow solver and tools, examples of input files and user's manual for Windows 10-11 platforms (64-bit, single processor) and for GNU/Linux platforms (compiled & tested on Ubuntu 20.04). The programs are completely free for non-commercial use and for evaluation purposes. Other uses require the purchase of a license, possible options are described further below. If you happen to find any problem with the software, please let us know. And if you are interested to learn more about the numerical methods built into the flow solver, you might consider buying the widely recognized CFD book.

Example flow cases (grids, input files):

Inviscid transonic flow in a channel with circular bump, various single- and multi-block grids: channel.zip
Subsonic laminar flow past a turbine guide vane: aavane.zip
Turbulent transonic flow past ONERA M6 wing: onera_m6.zip

Free tool for the generation of 3-D, viscous or inviscid, H-type grids in axial compressor or turbine passages thg3d.zip (for Windows 10-11) or thg3d_linux.tgz (for GNU/Linux). This tool was employed to generate the grid for the above turbine guide vane example. For the generation of general multi-block grids, we suggest to resort to the commercial software from Pointwise.

Licensing:

For commercial purposes or for more extended applications of the software, we offer the following purchase options:

Program executables with MPI enabled for parallel processing (GNU/Linux), 1 year of updates and e-mail support
As above but additionally with the flow solver in the form of a software library. This allows you to invoke the solver from a larger driver program, to change the boundary conditions during a run, and to prescribe motion / deformation of the boundaries over time.
Sources of all programs of the package for the ultimate control of the solver, its extension, or for learning purposes.

Please, feel free to ask us for a quote regarding any of the above options. And if the need shall arise, we are also open to special agreements on the use of the flow simulation package.

Example 1: Turbine Guide Vane

The data for this case were taken from: Zeschky, J.: Experimentelle Untersuchung der dreidimensionalen reibungsbehafteten Rotorströmung einer axialen Kaltluftturbine. PhD Thesis, RWTH Aachen, Germany, 1991. The following pictures show the H-type grid (160x48x48 cells), the (unsteady) convergence history, flow inside the passage, and finally a comparison with experimental data at mid-height:

Example 2: ONERA M6 Wing

The following pictures present the results obtained by Snas3D for the ONERA M6 test case. It constitutes transonic, turbulent flow past a 30° swept wing at Mach 0.8395, angle of attack 3.06° and Reynolds number of 11.72 million:

Example 3: Solid Rocket Motor

The video shows simulation of the ignition and the burnout of a small solid rocket motor. The time-accurate 3-D flow was computed using grid composed of 128 blocks and 220'416 cells. The grid is expanding as the solid fuel burns off:

This is one of the simulations described in the above mentioned conference paper.