Most of the SimTK numerical methods you will need are wrapped by the OpenSim API, so you will not need to access them directly through SimTK. However, many such numerical methods are available if you need them. Some of the most commonly used are:
- Linear algebra (various object-oriented factorization and eigenvalue classes, as well as direct access to Lapack and Blas if needed)
- Optimization (constrained and unconstrained)
- Numerical integration
- Numerical differentiation
- Random number generation
- Polynomial root finding
For more information, see https://simtk.org/home/simbody, Documents tab. Detailed Doxygen documents that describe individual classes and methods are there.