Turbulent flow over a channel with fluid-saturated porous bed

The characteristics of fully developed turbulent flow in a hybrid domain channel, which consists of a clear fluid region and a porous bed, are examined numerically using a model based on the macroscopic Reynolds-averaged Navier-Stokes equations. By adopting the classical continuity interface conditions, the present model treats the hybrid domain problem with a single domain approach, and the simulated results are noted to coincide with the existing experimental data and microscopic data. The effects of porosity φ and Darcy number Da on the flow properties over and inside the porous bed are further investigated in the selected ranges of 0.6≥φ>0.8, and 1.6 × 10^-4>Da>1.6 × 10^-2. It has been demonstrated that the presence of the porous bed causes the significant reduction of the flow velocities inside the clear fluid region relative to that of a smooth impermeable bed, and also reduces the magnitude of the integral constant B of the velocity logarithmic distributions from its traditional value 5.25. Moreover, turbulent shear stress within the upper part of the porous bed increases significantly with the porosity φ and Darcy number Da. The thickness of turbulence penetration remains proportional to the values of porosity φ and Darcy number Da.