Detailed laboratory experiments were performed to study the dynamics and mixing properties of vertically discharged sand-water coaxial jets in stagnant water. The effects of velocity ratio on the fluid dynamics of two-phase coaxial jets were studied. The axial and radial distributions of sand concentration and velocity were measured with an advanced optical fiber probe (PV6), and sand concentration and velocity measurements were formulated based on flow characteristics. The experimental results demonstrated that the axial velocity and concentration decay rate along the mixing zone, a length approximately six times greater than the nozzle diameter, were independent of the velocity ratio, Ru. Beyond the initial mixing zone, the axial decay rate of sand concentration increased with increasing velocity ratio and became similar to the concentration decay rate of slurry jets. The axial velocity decay of sand-water coaxial jets indicated an inverse relationship with velocity ratio: velocity decay rates decreased with increasing Ru. Experimental observations of sand-water coaxial jets showed that the spreading rate of coaxial jets decreased with increasing velocity ratio; for the coaxial jet with the highest Ru, the spreading rate reached the spreading rate of slurry jets. The integral quantities of jets such as mass and momentum fluxes were calculated using sand concentration and velocity profiles. Average drag coefficients were calculated using momentum balance and proposed equations for sand velocity and concentration. The variations of drag coefficient and interparticle collision parameter indicated that the particle grouping effect reduced the drag coefficient in sand-water coaxial jets with lower velocity ratios. The axial variations of the interparticle collision parameter indicated a strong correlation with velocity ratio. The strong correlation between velocity ratio and the mixing properties of sand-water coaxial jets suggests the velocity ratio is an effective design parameter to control and optimize particle mixing in stagnant water.

进行了详细的实验室实验，以研究在死水中垂直排放的砂水同轴射流的动力学和混合特性。研究了速度比对两相同轴射流流体动力学的影响。使用先进的光纤探针（PV6）测量了沙浓度和速度的轴向和径向分布，并根据流动特性制定了沙浓度和速度的测量值。实验结果表明，沿混合区的轴向速度和浓度衰减率（长度约为喷嘴直径的六倍）与速度比Ru无关。。在初始混合区之外，沙质浓度的轴向衰减率随速度比的增加而增加，并与泥浆射流的浓度衰减率相似。砂-水同轴射流的轴向速度衰减与速度比呈反比关系：速度衰减率随Ru的增加而减小。砂水同轴射流的实验观察结果表明，同轴射流的扩散速率随速比的增加而减小。用于Ru最高的同轴射流，扩散速率达到了浆液射流的扩散速率。射流的积分量，例如质量和动量通量，是使用砂浓度和速度分布图计算的。使用动量平衡和提出的沙子速度和浓度方程来计算平均阻力系数。阻力系数和颗粒间碰撞参数的变化表明，颗粒群效应降低了低速比的砂水同轴射流的阻力系数。粒子间碰撞参数的轴向变化表明与速度比有很强的相关性。速度比与砂水同轴射流的混合特性之间的强相关性表明，速度比是控制和优化死水中颗粒混合的有效设计参数。