Aerodynamic Transport Characteristics of Irregular Harmonic Particles at Finite Reynolds Numbers

This study presents the characterization of the aerodynamic forces and moments acting on irregular particles of prescribed sphericity, generated through truncated spherical harmonic expansions and immersed in a uniform flow at intermediate Reynolds numbers (1 ≤ Re ≤ 200). Particle-resolved direct numerical simulations are conducted using the commercial solver ANSYS Fluent to quantify the statistical behavior of drag, transverse lift, and transverse torque coefficients, along with the corresponding force and moment components, as a function of Reynolds number. Deviations from spherical geometry are shown to induce persistent flow asymmetries, leading to finite transverse lift and torque components even under uniform inflow conditions, effects that cannot be captured by models based on dynamically equivalent spheres. For a sphericity of 0.93, represented by six particle realizations, irregular particles exhibit mean drag values approximately 10% higher than those of spheres with the same equivalent diameter. In addition, both the magnitude and the statistical characteristics of the aerodynamic coefficients are strongly modulated by the combined effects of particle shape irregularity and flow regime. These results provide new insight into the role of geometric complexity in fluid–particle interactions and represent a step forward toward improved predictive capability beyond conventional spherical and quasi-spherical approximations. Furthermore, the present findings provide a physically grounded basis for the development of fluid–particle interaction models for irregular particles, suitable for implementation within Euler–Lagrange simulations of turbulent dispersed flows.