Research On Numerical Simulation Of The Flow Field In A Diversion Project Considering The Effect Of Flow Aeration

Construction diversion is a very important engineering measure that is unique throughout the construction of hydropower projects.Reasonable construction diversion schemes are of great significance for speeding up construction progress,ensuring construction safety and reducing engineering investment.The flow field is complex in the construction diversion process.When drawing up the construction diversion plan for almost every large-scale project,it is necessary to adopt model tests to obtain the hydraulic indicators affecting the diversion construction.The model test of construction diversion is more authentic,but there are still some problems such as the model test results will be affected by the accuracy of instrument measurement,it is difficult to obtain accurate detailed data,more manpower and material resources is consumed,and a long period is taken.Compared with physical model test,numerical simulation can make up for the above shortcomings.In the paper,model tests and different mathematical models are used to simulate the whole flow field and local flow field at different flow rates in diversion.The CATIA software is used to establish three-dimensional geometric model with complex terrain,and it is introduced into FLOW-3D.The RNG k-ε turbulence model,air entrainment model,drift-flux model and Tru VOF method tracing free surface are used to simulate the whole flow field of diversion engineering considering partial aeration in discharge flow of spillway.The flow regime,water level,velocity,turbulent kinetic energy,pressure on the bottom,aeration concentration in the spillway are obtained.Compared with the results of physical model test.the results show that the numerical simulation are better.The velocity and water level in front of the cofferdam are obtained by numerical simulation,and it was known that the foot of the cofferdam does not need to be protected and the design elevation of the upstream cofferdam is reasonable.In order to study the aeration with different mathematical models in the local diversion flow field,the three-dimensional geometric model of spillway is obtained by modifying the whole model through ICEM.The hexahedral core grid technology is used to complete the mesh generation and mesh quality optimization.The aerated flow in the spillway is simulated based on VOF model and Eulerian two-fluid model,and the hydraulic parameters of the local flow field are obtained.The results of velocity,pressure and turbulent kinetic energy are basically the same.The possible location of initial aeration point and the distribution law of aeration concentration can be obtained by comparing the simulation results of entrainment model,VOF model and Eulerian two-fluid model,which can provide better guidance for eliminating cavitation damage.