To characterize turbulence over porous media with porosities \(\varphi <0.5\) , three types of packed-beds were manufactured: cubically packed spheres (case S), randomly packed rice-grain-shaped pellets (case E), and crushed stones (case C), with measured porosities of \(\varphi =0.45\) , 0.37, and 0.30, respectively. After measuring their permeabilities, particle image velocimetry (PIV) measurements were conducted for flows under conditions characterized by the permeability Reynolds number ( \(Re_K\) ) ranging from 2.1 to 18.3. The results were then compared with previous data on turbulent flows over foamed ceramics with a porosity of \(\varphi \simeq 0.8\) , reported by Suga et al. (Int J Heat Fluid Flow 31(6), 974–984, 2010). The measured turbulence characteristics were analyzed to examine their correlation with \(Re_K\) and to evaluate the applicability of a unified scaling approach across a wide range of porous beds. The findings suggest that while some distribution profiles generally follow \(Re_K\) , this parameter alone is insufficient as a universal scaling factor for turbulence over packed-beds, as the roughness scale also exhibits significant dependence on surface shape rather than the porosity.
