Study On Additional Jet Flow Hydraulic Jump Dissipation

In this paper, the joint energy dissipation mechanism of stilling basin and dentoid baffle is analyzed based on additional jet flow hydraulic jump. The water current flows over the top of the dentoid baffle to the hydraulic jump as additional momentum. While it is cooperated with a stilling basin, the flowing condition emerged in the basin may be improved greatly and the length and downstream water depth required by the basin can be decreased to a great extent. Such an appliance may be also used to solve the problems of insufficiently dissipating water flow energy and aerating flow, which are often faced with those hydraulic engineering constraction as acted by high waterhead, great specific discharge and low Froude Number. It has been demonstrated by model tests that the device of dentoid baffle is a safety and effective dissipation tool.The additional flow is formed by the device of dentoid baffle, and the application of the device of dentoid baffle cooperated with a stilling basin has been investigated by systematic model tests. Based on the research results, the hydraulic problems such as the characteristics of hydrodynamic pressure and cavitation on the head of the denotid baffle, the properties of flow under the condition that the device of denotid baffle is used with a stilling basin, the hydraulic computation about a stilling basin, the estimation of energy dissipation and its various affection factors, the mechanism and effect of energy dissipation, and distributions of velocity and pressure and aerating concentration, etc, have been analyzed ;the method and step of hydraulic design of device of denotid baffle by which the additional flow is produced has also been proposed.The economic benefits of new additional energy dissipation facilities are estimated in terms of the decreased percentage of the sequent depth of hydraulic jump and length of jump, or the capacity of hydraulic jump under the unit width.The additional flow hydraulic jump theory has been demonstrated by model tests. The experiment results of the model stilling basin and dentoid baffle attest the theoretic analysis. Using the model experiment data, the authors calculate the decreased percentage of water jump length, unit width hydraulic jump volume and the water depth downstream of the jump; and also calculate the energy dissipation rate of dentoid baffle, It is concluded that the device of dentoid baffle can increase the energy dissipation rate of hydraulic jump theory and decrease the engineering cost. The obvious economic benefits and the predicted effect of additional jet flow hydraulic jump are obtained.Experimental researches of characteristics of hydrodynamics pressure and cavitation on the front of aeration-baffle have been done so as to obtain the distributions of the fluctuating pressure and time-averaged pressure. The distributions of the values of fluctuating pressure conform to the law of normal distribution; and the dominant frequency is low frequency. The cavitation doesn' t appear on the front of aeration-baffle under the conditions that the aeration-baffle surface smoothness is controlled and that a lot of air is supplied from the back of the aeration-baffle. The aeration-baffle configure is one that is opposite to cavitation.The dentoid baffle can be used in the practice of hydraulic engineering as a new type of energy dissipation tool. The principle of the choice of the parameters about the device of dentoid baffle and some research data have been given in the paper, and can be referenced in the early design of hydraulic engineering.