Numerical Simulation Of Energy Dissipation Characteristics In A Large-Scale Lock Chamber With 60m Water Head

Some navigation locks with large scale and high water head need to be built to satisfy the rapid increase in inland shipping industry based on the significant economic development and the strategy of “the one belt one road”.The kinetic energy,however,of water entering or exiting the lock chamber per unit time(also called filling/emptying power)could be doubled when water head and scale increased to certain values.How to dissipate the large energy efficiently in the limited range of water depth and filling/emptying time becomes a key problem,which restricts the development of the design of filling/emptying system.There are currently only a few investigations found in the open literature.Accordingly,CFD simulations of energy dissipation in the chamber of a lock with the water head 60 m,dimensions of 280 m(length)× 40 m(width)and valve opening time 14 min were conducted using commercial software FLUENT code.In the simulations,the RNG k-e turbulence model was employed and the VOF approach was used to predict the free water surface in the chamber.The main work and results in the present study are listed as follows:(1)By establishing a mathematical model that is consistent with the existing single-ditch physical model and double-ditch physical model test size,the calculation results of the digital model are compared with the measured results of the physical model.The results show that the comparison results are good,thereby verifying the reliability and correctness of the mathematical model.(2)The energy dissipation characteristics of single-layer side-branch single open ditch,double-layer side-branch single open ditch and double-open ditch are studied,and the energy dissipation effect is compared.The results show that the double-opening ditch widening type has the best energy dissipation effect and vertical The single open channel type of the double side branch hole with a spacing of 3m is the second,and the single open channel type of the single side branch hole without energy dissipation threshold is the worst.At the same time,according to the single-ditch double-layer branch hole layout type,the effect of vertical branch hole spacing on the energy dissipation effect was analyzed.The results showed that during the process of increasing the vertical spacing from 2m to 5m,the energy dissipation effect became better and then worse,3m To achieve optimal energy dissipation.(3)According to the layout of the cover plate + pressure energy dissipation chamber,the influence of the outflow height of the cover plate on the energy dissipation effect was analyzed.During the increase of the outflow height from 0.3m to0.6m,the flow pattern of the lock chamber water flow was more uniform,and when After the height of the outlet of the cover plate reaches 0.5m,the energy dissipation effect is significantly improved.At the same time,the energy dissipation characteristics and energy dissipation effect of the cover plate + pressure energy dissipation chamber and the common cover plate arrangement at the same outlet height(0.5m)are studied and compared.The results show that the cover plate + pressure energy dissipation chamber type energy dissipation The effect is obviously better than ordinary cover type.(4)Comparing comprehensively the energy dissipation results from the types mentioned above,results reveal that the two types of the double open ditches with extended width(corresponding width 2.375 m)and the pressured energy dissipation room covered by a horizontal plate(corresponding height 0.6 m)work relatively well.(5)The energy dissipation mechanism of the types,single open ditch and one row of side ports,double open ditches and pressured energy dissipation room,were mainly presented in terms of the corresponding comparison results related to the energy dissipation.Among them,there is nothing special about the energy dissipation mechanism of double open trench widening layout.The energy dissipation mechanism of the single open channel in the double side branch hole is:(1)The side branch hole suddenly expands to generate vortex energy dissipation;(2)The jet of branch hole collides with the side wall of the open ditch to form vortex energy dissipation;(3)The energy dissipation of the upper and lower branch holes after squeezing and mixing after diffusion;(4)Energy dissipation by mixing with each other during the rise of water.The energy dissipation mechanism of cover plate+pressure energy dissipation chamber scheme is:(1)vortex energy dissipation due to sudden expansion of side branch holes;(2)mixing and dissipating energy in the pressure energy dissipation chamber after the branch jet impacts the side wall of the pressure energy dissipation chamber;(3)Vortex energy dissipation caused by sudden contraction and expansion of top branch hole;(4)mixing and dissipating energy in the cavity of the cover plate after the high-speed jet of the top branch hole collides with the cover plate;(5)The outlet water body of the cover plate and the water body of the lock chamber flow into the lock chamber after mixing and dissipating energy.