Direct numerical simulation of the drag, lift, and torque coefficients of high aspect ratio biomass cylindrical particles

Biomass straw fuel has the advantage of low-carbon sustainability, and therefore, it has been widely used in recent years in coupled blending combustion with coal-fired utility boilers for power generation. At present, the drag force F_D, the lift force F_L, and the torque T evaluation model are very limited. In this study, within a wide range of Reynolds numbers (10 ≤ Re ≤ 2000) and incident angles (0° ≤ θ ≤ 90°), the computational fluid dynamics open source code OpenFOAM-body-fitted mesh method is used to carry out the direct numerical simulation of the flow characteristics of large cylindrical biomass particles with a high aspect ratio of L/D = 9:1. The results show that (1) the projected area of the cylinder begins to decrease after reaching the maximum at θ = 15°, while the change in the incident angle causes the formation of a smaller recirculation zone on the leeward side of the structure, and the effect of the pressure difference on the drag coefficient (C_D) is reduced. (2) The lift coefficient (C_L) displays a parabolic symmetric distribution when θ = 45°, and then the distribution becomes asymmetrical when Re > 100. The torque coefficient (C_T) exhibits a similar trend. (3) Based on the simulation data and the literature data, new models for C_D, C_L, and C_T for cylinders with L/D = 9:1, 10 ≤ Re ≤ 2000 and 0° ≤ θ ≤ 90° are obtained, and the mean square errors are 2.4 × 10⁻², 1.4 × 10⁻², and 6.4 × 10⁻², respectively. This new model can improve the accuracy and adaptability of the universal model of gas-solid dynamics for biomass particles.