Distributed rough surface boundary layer flow simulation using NNW-PHengLEI software
Based on the NNW-PHengLEI software,for surfaces with uniformly distributed rough ele-ments,rough surface boundary condition corrections and transition momentum thickness Reynolds numbers were introduced into the k-ω SST turbulence model and the γ-Reθt transition model respective-ly.At the same time,some rough surface settings were added to achieve local/global rough surface boundary layer flow simulation capability.Test results show that when an airfoil is in a fully turbulent state,rough surfaces can reduce the stall angle of attack by 4°,and an equivalent roughness height of 1 x 10-3 of chord length can cause a decrease in maximum lift coefficient by approximately 36％.Additional-ly,rough surfaces can advance the boundary layer transition,leading to an increase in skin friction drag.The computational analysis proves that the rough surface boundary condition proposed by Hellsten et al.can reflect the roughness effect more accurately than the dissipation rate boundary condition.The computational aerodynamic forces are consistent with the experimental data,and the flow field simula-tion results conform to the flow characteristics of rough surfaces.In addition,Hellsten's model makes it possible to ensure stable coupling simulation with the transition model and its rough surface correlation function.The simulation results for the transition onset location and its trend with roughness level and freestream turbulent intensity are consistent with the experimental data.Still,the transition length needs further verification and correction through more rigorous experiments.
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