Abstract
An experimental study using two-dimensional channel flow was performed to investigate the possibility of a spanwise discontinuity of wall roughness as a device to generate secondary currents associated with longitudinal vortex. A k-type rough wall, which consists of an array of two-dimensional rectangular roughness elements, is placed on the wall and makes discontinuity of wall roughness. Mean velocity and turbulent intensity were measured with hot-wire anemometers and crossed wire probes. Velocity vector plot in cross streamwise plane clearly shows that the discontinuity of wall roughness is able to produce secondary currents. It is expected that the secondary currents are associated with longitudinal vorticity. There are certainly some evidence that the secondary currents transport fluid particles and make deformations in the mean velocity and turbulent intensity contour maps.
