  Experiments and numerical simulations of inertial particles in underexpanded
jets are performed. The structure of the jet is controlled by varying the
nozzle pressure ratio, while the influence of particles on emerging shocks and
rarefaction patterns is controlled by varying the particle size and mass
loading. Ultra-high-speed schlieren and Lagrangian particle tracking are used
to experimentally determine the two-phase flow quantities. Three-dimensional
simulations are performed using a high-order, low dissipative discretization of
the gas phase while particles are tracked individually in a Lagrangian manner.
A simple two-way coupling strategy is proposed to handle interphase exchange in
the vicinity of shocks. Velocity statistics of each phase are reported for a
wide range of pressure ratios, particle sizes, and volume fractions. The extent
to which particles affect the location of the Mach disk are quantified and
compared to previous work from the literature. Furthermore, a semi-analytic
model is presented based on a one-dimensional Fanno flow that takes into
account volume displacement by particles and interphase exchange due to drag
and heat transfer. The percent shift in Mach disk is found to scale with the
mass loading, nozzle pressure ratio, interphase slip velocity, and inversely
with the particle diameter.
