Analysis of 3D burn surfaces for solid propellant rockets using tetrahedra based Time Marching Method as an alternative of the Level Set Method. Key features:

• Combustion time computation with tetrahedra meshes for solid propellant rockets
• Supports per node configuration of the recession speed
• Supports isotropic and anisotropic propellants
• Graphical interface to evaluate the results
• Import and export data of any mesh formats with a python script

If you only need a 2D analysis, see burnback-qt.

Built binaries for Windows and MacOS can be found at releases. For Linux is advisable to compile from source as Qt has no compatibility across different distributions (binaries built with Ubuntu CI didn't work on my Arch Linux). It is also possible to run the Windows binary through Wine, with minor flickers.

Supports both light and dark theme. Should use accordingly to your system theme. If you want dark theme, and it isn't, add QT_QUICK_CONTROLS_MATERIAL_THEME=Dark to your environment variables.

The contour visualization is only for preview purposes. For a much more detailed visualization, try ParaView:

First, you will need a mesh in order to use the program for analysis. For instance, Gmsh is an open source meshing software that can generate 2D and 3D finite element mesh.

Once you have the mesh, you will have to convert it into a Json file with tetrahedra based information. A python script that converts Gmsh mesh file to this format using meshio can be found at tools directory: mesh_convert.py. The script is optimized for speed and can convert a mesh with 200K nodes in seconds. If you are using another meshing tool, feel free to edit it (probable you will only need to change the cell names).

When using Gmsh and the script, you can define boundary conditions with physical groups with the following naming conventions in surfaces:

• inlet: The boundary is an inlet, where the propellant starts to burn. You can later give it a value as the boundary in boundary panels, if you want a boundary starts to be already burnt for the given time.
• outlet: Used for boundaries where the combustion ends, like the shell of the container.
• symmetry: Used to indicate that a boundary defines a symmetry. The condition will automatically find the normal vector pointing outwards of the mesh if the boundary triangles are provided in a standard way (such as the output given by Gmsh). In other case, the vector is reversed and you should manually change its sign in the boundary conditions panel.
• condition: Placeholder for conditions that should be changed later in Burnback GUI (will be treated as outlet by default).

In volumes, you can define recession velocities:

• recession 1 [0.5 0.2 45 30 25] (optional): Used to indicate the recession velocity of a node, defaults to 1. When more than 1 number is specified, the velocity is considered to be anisotropic: First 3 numbers are the recession speed to the x, y, and z axis respectively, and the last 3 numbers are the rotation angles in degree with respect to axis x, y, and z respectively.

Everything after the names above will be added to a description field.

Example files of Gmsh can be found at examples/gmsh. The commands to be executed to obtain the Json file are:

gmsh -3 mesh.geo
python mesh_convert.py mesh.msh

If you want to use the exported results to another format other than Json (for instance .CGNS, or .dat for TecPlot/ParaView, etc.) you can use the result_convert.py script. Usage is:

python result_convert.py result.json output.extension

You can provide only the extension name for the output file. In this case the name is inferred from the input file.

Can be compiled by either using command line or using the QtCreator. Binaries should be found at <Project Dir>/target/debug|release. When building with QtCreator, <Project Dir> equals to where the build location is set.

Qt modules dependencies:

• qt-3d
• qt-charts
• qt-declaratives
• qt-quickcontrols2

WARNING: Do not compile with Qt 5.15.2. The 3D model importer is broken for that version.

The project can be easily built with the Makefile. The Makefile is written with multiplatform compilation in mind, it should work with Linux, macOS, or Microsoft Windows:

• make run: Build the debug binary and run
  • make run-sanitizer: Build the debug binary with sanitizer and run
• make debug: Build the debug binary
• make release: Build the release binary

Open burnback-3d.pro with QtCreator, set your compiling options if needed, and runs directly by clicking the play button at bottom-left.