Abstract
We performed direct numerical simulations of turbulent channel flows whose inner layer is replaced by an off-wall boundary condition synthesized from a rescaled interior flow plane. The numerical boundary is placed in the logarithmic layer, and the boundary condition mimics the linear dependence of the length-scales of the velocity fluctuations with respect to the distance to the wall. The logarithmic profile of the mean velocity is recovered well in the present channels, except for the position of the logarithmic origin. The intensity and spectra of velocity fluctuations produced in the wall-less channels also agree well with those in real channels. These results suggest that the logarithmic and outer layers are independent of the inner layer.
