高木 亮治

This study presents a fully automated Cartesian-grid-based compressible flow solver, named FrontFlow/Violet Hierarchical Cartesian for Aeronautics based on Compressible-flow Equations (FFVHC-ACE), for large-eddy simulation (LES) and its aeronautical applications. FFVHC-ACE enables high-fidelity LES of high-Reynolds-number flows around complex geometries by adopting three key numerical methods: hierarchical Cartesian grids, wall modeling in LES, and the kinetic-energy and entropy preserving (KEEP) scheme. The hierarchical Cartesian grids allow fully automated grid generation for complex geometries in FFVHC-ACE, and high-fidelity LES of high-Reynolds-number flows around complex geometries is realized by the wall modeling and the KEEP scheme on the non-body-fitted hierarchical Cartesian grids. We apply FFVHC-ACE to wall-modeled LES around high-lift aircraft configurations at wind-tunnel-scale Reynolds number [Formula: see text] and real-flight Reynolds number [Formula: see text], demonstrating the capability of FFVHC-ACE for fully automated grid generation and high-fidelity simulations around complex aircraft configurations. The computed flowfield and aerodynamic forces at the wind-tunnel-scale Reynolds number agree well with the experimental data provided in the past AIAA High Lift Prediction Workshop (Rumsey et al., Journal of Aircraft, Vol. 56, No. 2, 2019, pp. 621–644). Furthermore, the wall-modeled LES at the real-flight Reynolds number shows good agreement of the lift coefficient with flight-test data.

Electrohydrodynamic (EHD) thrusters can silently propel small unmanned aerial vehicles without moving parts using corona discharges. Computational fluid dynamics would be a powerful tool to model the EHD thrusters and then optimize them. The drift-diffusion-Poisson equations govern corona discharges; hence, the equations can predict the current-voltage characteristics curves of EHD thrusters. However, the equations are too stiff to analyze EHD thrusters in the time domain. Here, we propose a perturbation technique to efficiently solve the stiff drift-diffusion-Poisson system in global (i.e., full two-dimensional or three-dimensional) and nonlinear (i.e., applied voltages higher than the corona inception voltage) regimes. Furthermore, we validated the method with the experimental results of a previous study. (C) 2022 Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY)license (http://creativecommons.org/licenses/by/4.0/).