SootLib

Overview

Sootlib is an open-source C++ library that computes soot source terms using moment-based particle size distribution models for combustion CFD simulations.

Dependencies and installation

The code is intended to be built and used on Linux-like systems, including MacOS and the Linux subsystem for Windows.

Required software:

• CMake 3.15+
• C++11
• LApack

Optional software:

• Doxygen (for building documentation)
• graphviz (for Doxygen)
• Catch2 (for building tests; will be locally installed automatically via CMake if SOOTLIB_BUILD_TESTS is true)

Build and installation instructions

1. Create and navigate into a top-level build directory
2. Configure CMake: cmake ..
3. Build SootLib: make
4. Install SootLib: make install

CMake configuration variables

The default CMake configuration should be adequate for users that do not immediately require the examples, tests, or documentation. CMake configuration options can be set by editing the top-level CMakeLists.txt file, editing the CMakeCache.txt file (generated in the build directory after running CMake at least once), or specifying them on the command line during step 2 as follows:

cmake -DSOOTLIB_BUILD_EXAMPLES=ON ..

The following project-specific CMake configuration variables can be specified by the user; their default values are also indicated.

CMake variable	Default	Description
CMAKE_INSTALL_PREFIX	top-level project directory	Installation location
SOOTLIB_BUILD_EXAMPLES	OFF	Builds SootLib examples
SOOTLIB_BUILD_TESTING	OFF	Builds SootLib tests; uses Catch2
SOOTLIB_BUILD_DOCS	OFF	Builds SootLib documentation via Doxygen

Using SootLib

The SootLib library consists of two main object classes that users can interact with: sootModel and state, both of which are contained within the soot namespace. The state object holds user-specified details about the current thermodynamic state in which the soot chemistry occurs, including variables such as temperature, pressure, and gas species mass fractions. The sootModel object contains information about the selected models and mechanisms and performs the calculations that generate moment source terms. In the context of a traditional CFD simulation, the state object would be updated via the setState function at each individual time step and/or grid point, while the sootModel parameters only need to be specified once when the object is created, and then its calcSourceTerms function invoked at each step following the setState update. The resulting moment source terms and gas species source terms can be accessed via the sootModel object. Refer to examples/simple_example.cc for a basic example of setting up the objects, calculating source terms, and retrieving values.

Example workflow

1. Create sootModel object, specifying the desired soot chemistry and PSD mechanism.
2. Create an empty state object.
3. Populate the state object with the thermodynamic conditions using the setState function.
4. Calculate the soot source terms using the calcSourceTerms function, which takes a reference to a state object as its input.
5. Retrieve the desired source terms from the sootModel object.

In the case of a temporally or spatially evolving simulation, only steps 3–5 need be performed at each individual step. SootLib does not store previously calculated values, so source terms must be retrieved at each step or otherwise lost.

Examples

Sootlib is written in C++ and includes two example codes that illustrate its use. The first example simple_example.cc illustrates the setup and interaction with the soot variable source terms, which are the key output of the model. The second example, burner_flame.cc integrates soot variables along the length of a flat flame burner with fixed gas variable profiles. This is a simple example that can be used to compare soot model specifications, but does not include soot diffusion, or coupling from the soot phase back to the gas phase.