nLimiterIter: Number of iterations during limiter construction
    3 (default) is sufficient for 3D simulations with a Courant number 0.5 or so
    For larger Courant numbers larger values may be needed but this is
    only relevant for IMULES and CMULES

smoothLimiter: Coefficient to smooth the limiter to avoid "diamond"
    staggering patters seen in regions of low particle phase-fraction in
    fluidised-bed simulations.

    The default is 0 as it is not needed for all simulations.
    A value of 0.1 is appropriate for fluidised-bed simulations.
    The useful range is 0 -> 0.5.
    Values larger than 0.5 may cause excessive smearing of the solution.