Study Of Particle Settling Patterns In Newtonian Fluids In Circular Tube

Particle settling phenomena are prevalent in nature and have a wide range of engineering applications in the context of sediment transport,movement of rock chips in drilling fluids,and sand settling in sand-out oil wells during oil recovery.Whether from the perspective of engineering application value or basic research,it is of great significance to investigate the mechanism of particle-particle and particle-fluid interaction.In this paper,the settling law of particles in Newtonian fluids in circular tubes is studied experimentally to provide reference and basis for the engineering application of the theoretical law of particle settling.In this paper,single and double particle settling experiments are carried out in a Newtonian fluid in a circular tube using a set of well visualised and accurate experimental equipment.The tube is divided into two cases,without and with internal rods,and the experimental conditions are divided into two types,i.e.fluid at rest and fluid flowing,and two types,i.e.rod at rest and rod rotating,in the case of the internal rod.Firstly,the settling velocity of single particles at different settling positions in Newtonian fluids is obtained by varying the particle size of single particles,the fluid flow velocity and the rotational speed of the inner rod,and the variation of the settling velocity of single particles under the influence of different parameters is summarised;secondly,by varying the particle size of the upper tracking particles and the lower guiding particles,the initial release distance of the two particles and other parameters,experiments are carried out on vertically arranged spherical double particles in a circular tube The settling velocity of the upper tracking particle at different settling positions was studied and compared with the settling velocity of the single particle to summarise the influence of the lower guiding particle on the settling velocity of the upper tracking particle.The experimental results show that: for the single particle settling experiment,the fluid flow velocity in the circular tube will increase the resistance of the particles,resulting in the particle settling velocity is less than its settling velocity in the fluid stationary condition;in the inner rod stationary condition,the distance between the particles and the wall is reduced,and the particle settling velocity is reduced compared with the particle settling velocity in the fluid stationary condition without a rod due to the wall effect;in the inner rod rotation Under the rotating conditions,with the increase of the rotational speed,the particles will make a rod-winding motion,the large particles will be offset and slightly oscillate during the settling process,and there will be less rod-winding motion;the small particles will have a violent rod-winding motion due to the increase of the rotational speed,and the oscillation float is larger during the settling process.In the process of double particle settling,the fluid resistance of the tracking particles is reduced by the guiding particles below,and the settling velocity of the tracking particles is greater than that of their single particle settling,when the particle size is increased or the initial distance between the two particles is reduced,the interaction between the particles will be stronger and the settling velocity of the tracking particles will increase more;as the initial distance between the two particles increases,the drag coefficient of the tracking particles above gradually increases and As the initial distance between the two particles increases,the drag coefficient of the upper tracking particle gradually increases,gradually approaching the drag coefficient of its single particle settling;the smaller the initial distance between the two particles,the stronger the effect of the tail flow of the guiding particle on the upper particle,and when the initial distance exceeds a critical value,the lower guiding particle no longer has an effect on the upper tracking particle,and the settling velocity of the tracking particle is close to the velocity of its individual settling.When the guiding particle is a small particle size,the large particle will continue to settle due to gravity,and the interaction between the two particles will gradually weaken;the initial distance between the two particles is fixed,and as the speed increases,the initial distance between the lower guiding particle and the upper tracking particle with influence is gradually shortened.