Study On Flow Field Of Local Water Blocking Section Of Open Channel Based On LBM Method

With the development of society and economy,people have built and renovated a large number of open channels for water diversion,irrigation,navigation,and used to protect the national industrial,agricultural,industrial and domestic water needs,as well as the needs of inland water transportation.During the operation of various open channels,it is often necessary to construct diversion facilities when wading buildings and maintenance are required.For the normal water conveyance operation of the channel,the construction of various diversion facilities will reduce the cross-sectional area of the channel where the channel is located,which will affect the normal flow of the channel,cause upstream water flow,and even cause severe turbulence of the water flow and escape from the side wall.The phenomenon.These unfavorable phenomena will form eddy currents,which will lead to the deterioration of the diversion facilities and the formation of water jumps in the exit section.As a new fluid numerical simulation method,LBM can simulate turbulent and other complex flows with higher accuracy and efficiency from the mesoscopic perspective.Through a series of theoretical analysis and test methods,this paper analyzes and demonstrates the technical feasibility of steel fences(cofferdams)for non-stop maintenance of the South-to-North Water Transfer Project,and proposes a reasonable and feasible improvement scheme for the form of the fence structure based on experimental data.The main work of this article is as follows:(1)Prototype observation of steel fence maintenance project in Xinxiang section of Southto-North Water Transfer Project.By using ADCP(Acoustic Doppler Current Profilers)and total station and other equipment,the hydraulic characteristic parameter measurement was performed under the condition of Q = 220m3 / s flow rate.The basic rules of the water surface line and flow field of the prototype canal section were mastered.The coefficients of nonuniformity of cross-section flow velocity,mainstream deviation,and single-wide flow power were used to quantify the flow characteristics of the canal.(2)Carry out model tests to study the rationality of the design steel enclosures under different inflow conditions from the perspective of hydraulics,and propose a reasonable and feasible form of improvement of the enclosure structure.The hydrodynamic characteristics of the steel enclosure design scheme were analyzed with the help of generalized model test method.The analysis shows that the steel enclosure design scheme is reasonable in layout and has good hydraulic boundary characteristics under each flow.The water flow in the blocking area is relatively smooth,without complicated and unfavorable flow regimes.On the basis of prototype observation and model test,two improvement schemes of steel enclosure are proposed,and the rationality of the improved structural form in the direction of hydraulics is verified through model tests.(3)Based on the lattice Boltzmann method and the large eddy turbulence model,a numerical model of the open channel gradual section with steel enclosures was established,and the numerical simulation of open channel water flow under multiple incoming flow conditions and multiple steel enclosure dimensions was performed.For the high-speed mainstream in the steel enclosure area,the mainstream trajectory coefficient is used to quantify the regularity of the movement of the mainstream.For mainstream velocity,a quantitative study was performed using a single wide flow power.I have a regular understanding of the specific flow patterns of the mainstream in the steel enclosure area,and discussed the relationship and development process between the main flow and the return area in the form of the steel enclosure structure.And the qualitative analysis of the flow velocity and force of the outer side wall of the steel fence was also made.(4)Based on all the data,the turbulence resistance coefficient of the steel fence was deduced.The calculation method of the turbulent resistance of the steel fence is theoretically deduced,and it is considered that the turbulent resistance coefficient of the steel fence is a function of the current Fourier number and the angle of the forward flow of the steel fence under the premise of the actual project studied in this paper The correlations between the incoming flow Ruide number,the angle of the oncoming flow of the steel fence,the coefficient of turbulence resistance,and the local head loss caused by the steel fence are obtained.