Numerical Simulation And Its Applications On Flow Field Of Liquid-solid Two-Phase Flow For Pre-Mixed Abrasive Water Jet

In the field of the study on the flow field inside and outside nozzle and nozzle reasonable parameters for pre-mixed abrasive water jet, this thesis based on the liquid-solid two-phase flow theory and computational fluid dynamics method completed the following works:(1) A liquid-solid two-phase turbulence mathematical model of the abrasive water jet was established based on two-phase flow theory.(2)The SIMPLE algorithm was presented for the two-phase flow according to FVM(3)The flow field inside and outside nozzle for pre-mixed abrasive water jet under submerged condition was numerically simulated and the following results were received:(a)In the convergent section of the nozzle, water and abrasive are both accelerated and their accelerations are basically the same. But they both decreased in the straight tube. Outside the nozzle, the water velocity remains basically unchanged in a certain length. Under the difference in velocity abrasive particles are always accelerated and reach maximum in the end of the core zone.(b)Outside the nozzle, the water velocity in the axis keeps unchanged for the longest distance. The fluid outside the core zone affected by turbulent mixing first begins to accelerate, and then decelerates. The abrasive particles in the axis are accelerated for the longest time until in the end of core zone, where the maximum of abrasive velocity appears.(c)The dynamic pressure of abrasive is significantly higher than that of water. In the convergent section the difference between the two is not too big, but abrasive's growth rate is greatly higher than that of water from the straight tube. In the core zone, the dynamic pressure of water keeps unchanged, but that of abrasive sustains growing and reaches its maximum in the end of core zone.(d)Turbulent kinetic energy is relatively higher in the junction between the convergent section and the straight tube. Outside the nozzle, its value is the highest on the two sides near the core zone, but is very small inside the core zone. Turbulent kinetic energy dissipation rate is relatively higher near the wall of the straight tube and nozzle outlet.(e)Choosing the nozzle with taper angle of 13 degrees is relatively better in the process of abrasive water jet.(f)With the length of straight tube increasing, the maximum of the velocity and the dynamic pressure of water and abrasive will increase, but the length of core zone will decrease However, it will reach its limit state and the core zone will disappear when the length of straight tube is after 12D. Choosing the nozzle with the straight tube length of 4D-6D is relatively better in the process of abrasive water jet.(g)With the abrasive volume fraction increasing abrasive axial velocity will decline. Choosing the concentration of 5% is relatively better in the process of abrasive water jet.