We consider the efficient approximation of low Mach number flows by a high-order
scheme, coupling a discontinuous Galerkin (DG) discretization in space with an
implicit/explicit (IMEX) discretization in time. The splitting into linear implicit and
nonlinear explicit parts relies heavily on the incompressible solution. The method has
been originally developed for a singularly perturbed ODE and applied to the
isentropic Euler equations. Here, we improve, extend, and investigate the so-called
RS-IMEX splitting method. The resulting scheme can cope with a broader range of
Mach numbers without running into roundoff errors, it is extended to realistic
physical boundary conditions, and it is shown to be highly efficient in comparison to
more standard solution techniques.