DNS: a tool for numerical experiments

In this paper are described the results obtained by DNS of channel flows where one of the walls is flat and on the other different boundary conditions are imposed or the shape of the boundary is modified. The numerical tool is a second-order accurate finite­ difference scheme in space and time. This method allows the imposition of several kinds of velocity boundary conditions and in combination with the immersed boundary method to change the shape of the boundary. The paper shortly describes the numerical tool; the aim is preferentially oriented to see how the DNS is used to study the wall structure modifications which imply the attainment a deeper knowledge of the wall physics. The modifications of the wall structures have been connected to changes in the velocity and vorticity statistics. The study is mainly oriented to the wall friction control.