Abstract: Experimental study was performed for the formation and development of the horseshoe vortex in turbulent boundary layer through using a new method of visualization (moving sheet of laser light) and several experimental skills. The test results show that a main process of formation of the horseshoe vortex in turbulent boundary layer is a secondary instability, which is not different from the horseshoe vortex caused by artificial method in laminar boundary layer and the horseshoe vortexregarded as consummate horseshoe shape usually. In addition, it has rules and characteristics as follows: (1) The transverse size of it increases at uniform velocity up to its stable size; (2) It keeps a uniform motion in longitudinal direction after it forms; (3) Longitudinal vortices have stretch and deformation.

Key words: flow visualization, turbulent boundary layer, vortices