  A numerical study of stably stratified flows past spheres at Reynolds numbers
$Re=200$ and $Re=300$ is reported. In these flow regimes, a neutrally
stratified laminar flow induces distinctly different near-wake features.
However, the flow behaviour changes significantly as the stratification
increases and suppresses the scale of vertical displacements of fluid parcels.
Computations for a range of Froude numbers $Fr\in [0.1,\infty]$ show that as
Froude number decreases, the flow patterns for both Reynolds numbers become
similar. The representative simulations of the lee-wave instability at
$Fr=0.625$ and the two-dimensional vortex shedding at $Fr=0.25$ regimes are
illustrated for flows past single and tandem spheres, thereby providing further
insight into the dynamics of stratified flows past bluff bodies. In particular,
the reported study examines the relative influence of viscosity and
stratification on the dividing streamline elevation, wake structure and flow
separation. The solutions of the Navier-Stokes equations in the incompressible
Boussinesq limit are obtained on unstructured meshes suitable for simulations
involving multiple bodies. Computations are accomplished using the finite
volume, non-oscillatory forward-in-time (NFT) Multidimensional Positive
Definite Transport Algorithm (MPDATA) based solver. The impact and validity of
the numerical approximations, especially for the cases exhibiting strong
stratification, are also discussed. Qualitative and quantitative comparisons
with available laboratory experiments and prior numerical studies confirm the
validity of the numerical approach.
