  This study presents an innovative direct numerical simulation approach for
complex particle systems with irregular shapes and large numbers. Using
partially saturated methods, it accurately models arbitrary shapes, albeit at
considerable computational cost when integrating a compatible contact model.
The introduction of a novel parallelization strategy significantly improves the
performance of the contact model, enabling efficient four-way coupled
simulations. Through hindered settling studies, the criticality of the explicit
contact model for maintaining simulation accuracy is highlighted, especially at
high particle volume fractions and low Archimedes numbers. The feasibility of
simulating thousands of arbitrarily shaped convex particles is demonstrated
with up to 1934 surface-resolved particles. The study also confirms the grid
independence and linear convergence of the method. It shows for the first time
that cube swarms settle 13 to 26% slower than swarms of volume-equivalent
spheres across different Archimedes numbers (500 to 2000) and particle volume
fractions (10 to 30%). These findings emphasize the shape dependence of
particle systems and suggest avenues for exploring their nuanced dynamics.
