Finite Particle Approach for High-Fidelity Simulation on Helicopter Brownout

The brownout dust clouds that surround the helicopter operating in dusty conditions consist of an enormous number of particles, leading to lower visibility and piloting difficulties. The computational cost of tracking all particles is intolerable, while the solutions with insufficient numbers of particles often fail to achieve enough fidelity. This research proposes a finite particle approach for high-fidelity simulation on helicopter brownout, providing particle number concentration distributions to quantitatively evaluate the risk of dust clouds. Based on the summarization of criteria for counting particle number concentration, the total number of particles in the calculation is presented to balance fidelity and efficiency. According to the entrainment model results, only a finite number of particles are injected into the flow to improve computational efficiency. The trajectories of injected particles are reconstructed for high-fidelity results. Combining the Richardson extrapolation and the assessment of average particle spacings, the total number of particles in the calculation is recommended to be 108. The finite particle approach is adopted to investigate dust clouds in various flight conditions. Numerical results demonstrate that, compared to hovering, the maximum value of particle number concentration is greater and closer to the rotor center when flying with a low advance ratio.