01. Experimental/Computational Fluid Dynamics

Porous materials are placed on the surface of an object to suppress vibration and noise associated with flow separation. This is one of the techniques for controlling the boundary layer on the surface. However, it is not clear whether this change in the behavior of the boundary layer is due to the roughness of the surface or the flow resistance inside the porous material. This study focuses on the effect of flow resistance within the porous material on the surrounding shear layer, and numerical analysis is performed to evaluate this independently of surface roughness. The hydrodynamic resistance of the flow through a porous material due to its micro-structure is known as Darcy's law. However, this model is valid in the low Reynolds number flow and is not appropriate for the high Reynolds number flow with boundary layer or shear layer transition. In this study, the Forchheimer model, which is valid for high Reynolds number flows, was used as the porous resistance model. In addition, large eddy simulations were performed introducing anisotropy and non-uniformity in the model parameters. Numerical results show that in porous cylinders, the drag crisis observed in rigid cylinders does not occur in the same Reynolds number condition. Furthermore, it is shown that lift force was observed for the porous cylinder with anisotropic parameters depending on the anisotropy angle. These results occur because changes in shear layer thickness due to momentum penetration into the porous region prevented local flow instability.