| The Yellow River is the main water resource for 90% of cultivated land and life in Northwest China,and plays a key role in economic development.Due to the large amount of sand in the Yellow River water and rainy season every year,serious soil erosion and uneven distribution of precipitation in the Yellow River Basin,as well as low density and high viscosity of mud and sand,it is extremely difficult to effectively treat water resources in the Yellow River Basin.Therefore,it is urgent to study the flocculation and sedimentation of the Yellow River mud and sand to improve the efficiency of water treatment in irrigation areas along the Yellow River.In this paper,the settling technology of the Yellow River cement sand is studied,and the traditional settling technology is optimized.Based on the micro vortex theory,the corrugated plate reactor is taken as the research object,and the flocculation analysis model is established according to the internal structure of the reactor and the different boundary conditions of the flow field,and the numerical simulation is carried out.With the help of ANSYS/Workbench and DPM,the internal flow field of corrugated plate reactor is simulated and analyzed,which provides a basis for further optimizing its structure and improving the water treatment efficiency in irrigation area along the Yellow River.Firstly,three flocculation theories are elaborated in detail: classical flocculation theory,turbulent flocculation theory and micro vortex flocculation theory.The influencing factors of flocculation of the Yellow River mud and sand are analyzed,including environmental medium conditions,mud and sand characteristics and dynamic causes.The effects of dynamic factors such as velocity gradient,vortex shear force and energy dissipation rate on the flocculation of Yellow River mud and sand are mainly considered.Secondly,according to the dynamic factors affecting the flocculation of the Yellow River mud and sand,the evaluation index of numerical simulation is obtained(in which the velocity gradient is expressed by vortex velocity gradient).Through the analysis of vortex numerical simulation model,it is found that vortex velocity gradient is related to energy dissipation rate,turbulent kinetic energy determines energy dissipation rate,and vortex shear force is determined by vortex scale and particle size.With the help of Proe,ANSYS/Workbench and other software,a corrugated plate reactor model based on micro vortex flocculation theory was established.According to the evaluation index of numerical simulation,the macroscopic motion law of the internal flow field of the model before and after optimization was studied.Thirdly,the operating parameters of the corrugated plate reactor are simulated and analyzed,including numerical simulation of the flow field of the corrugated plate reactor under different flocculation time and pressure.It is found that the flocculation efficiency can be improved by changing the operating time and pressure of corrugated plate reactor.Finally,the CFD-DPM coupling method is used to simulate and analyze the fluid separation process of the optimized model,and the movement and distribution of sand grains in the model are studied microscopically,and their characteristics are analyzed.The research results show that:1.The flocculation effect of corrugated plate reactor optimized based on micro vortex flocculation theory is better,the number of vortices formed is more,and the vortex scale is closer to the particle size of mud and sand;The residence time of sand grains in vortex region is longer,and the collision of colloidal particles in water is intensified.2.Flocculation effect of corrugated plate reactor is also affected by flocculation time,pressure and particle size.Flocculation time is shortened,flocculation pressure is increased,and vortex scale becomes smaller.When vortex scale is larger than and close to mud and sand particle size,vortex shear damage becomes smaller,and the flocculation effect of reactor is best. |
PDF Full Text Request