As the important parameters in designing the stilling basin,calculation of the length of the free hydraulic jump plays a major role in the safety,stability and economization for the stilling basin. The research on the variation laws of the vortex roll length of the free hydraulic jump and the hydraulic jump length occurred on the uniform rough height bed of the stilling basin was carried out according to establishing the motion equations for water body particle in the hydraulic jump zone,and developing a th...