2026 年 21 巻 2 号 p. JFST0009
Impingement jet cooling is widely used in industrial applications such as gas turbine blades and electronic equipment. Previous studies have shown that thermal performance can be further enhanced when the impingement channel is partially or fully packed with high-porosity metal foams. Although direct numerical simulations (DNS) of impinging jets and channel flows with porous foams have provided valuable insights, the flow characteristics of impinging jets with porous walls remain insufficiently understood. Therefore, this study numerically investigates the flow characteristics of turbulent slot jets with porous walls using DNS based on the lattice Boltzmann method (LBM), as a preliminary step toward evaluating heat transfer performance. Simulations are conducted at a Reynolds number of 5,000 based on the jet inlet velocity and jet slot width. The porous wall is modelled using Kelvin cell arrays with a porosity of 0.95. Three configurations are considered: a solid wall (Case S), a low-permeability porous wall (Case LP), and a high-permeability porous wall (Case HP). The jet slot width and channel height are identical in all cases. The flow structure and turbulence characteristics are first examined, followed by an analysis of the hydraulic characteristics. The results show that the porous wall significantly alters the mean flow structure. In Case LP, only a small portion of the jet penetrates the porous wall near the impingement region, while the main flow forms a wall jet along the porous wall surface. In contrast, in Case HP, most of the jet penetrates the porous wall, forming a wall jet within the porous wall before gradually re-emerging into the clear flow region. Intense vortices smaller than the Kelvin cell size were generated inside the porous wall by wake flows around the cell ligaments. Such fine-scale turbulence can only be captured by geometry-resolved DNS. Turbulence intensity becomes relatively large inside the porous wall, particularly in Case HP. The drag coefficient reaches its maximum near the impingement point regardless of permeability; however, the peak value depends on wall permeability. Overall, the presence of the porous wall increases the hydraulic penalty due to the additional flow resistance of the porous wall.
