Abstract
The method using the mean velocity profiles was developed for the resistance law of open channel with the v-grooved ribret surface. First, an approximation to the virtual origins were estimated by the closest match between the measured velocity profiles and the velocity profile calculated using several values of van Driest's damping coefficient. Then, the profiles of the mixing length were evaluated from the measured velocity profiles. The present method can be applied to the other kind of roughness. However, although the linear profile of the shear stress in the open channel flow can be employed, other techniques are required to apply the present method for boundary layer flow.
