Effects of gradient pressure on resistance law in roll waves and effects of tension surface

摘要

Free surface flow in sufficiently steep channels is unstable and progressive waves develop as periodic distribution of bores connected by smooth profiles. The amplitude of the breakers is higher than the normal water depth. Roll waves in the initial phase development (before overtaking) develop, dissipating for friction less energy than the equivalent uniform stream. Including the gradient pressure effects, an extra saving of energy is computed, which can partially balance the dissipation in the breaker. Assuming different values of the momentum and energy coefficients on the two sides of the breaker, physically acceptable value of the water stream depths are obtained with a limited dissipation rate in the jump. Including the tension surface effects, a new family of roll waves is depicted.