Study On The Flow Characteristics And PIV In Hydrocyclone With Vibrating Wall

Hydrocyclones are often affected by internal and external flow field and vibration of equipment when they are working.Structural vibration will affect the internal flow field of hydrocyclones.The study of channel flow and circular tube axial flow shows that wall periodic vibration can achieve better turbulent drag reduction effect,but periodic vibration is not clear about the drag reduction performance of circular tube helical flow field in hydrocyclones.In this paper,a single cone cyclone is used as a model,the large eddy simulation is used to simulate the flow field.The large eddy is solved directly by the transient N-S equation.The small eddy is treated by the turbulent kinetic energy transport subgrid model(KET),and the near wall area is solved,obtain the velocity distribution law of the flow field.The numerical simulation results are compared with the experimental data to verify the correctness of the simulation method.Then the periodic vibration is applied to the wall surface,the turbulent drag reduction rate of the periodic vibration of the wall under different T+ is calculated.The distribution of the whole and local velocity,the mean square root of the pulsating velocity and the Reynolds stress are analyzed,and the drag reduction characteristics of the vibratory wall in the spiral flow field in the cyclone are analyzed.The internal flow field PIV test device was designed with a flume,and the internal flow field was tested by PIV.According to the vibration T+ range of the large eddy simulation,the influence of the two parameters of Reynolds number and T+ on the flow characteristics of the flow field in the vibratory wall cyclone was studied.The results show that the wall vibration can increase the axial velocity and radial velocity in the cyclone,and the symmetry becomes better,the vorticity decreases and the Reynolds stress decreases,which shows that the wall vibration has a certain drag reduction effect on the spiral turbulence of the variable diameter circular tube.In order to extract the exact temporal and spatial evolution characteristics of the flow field from the experimental data of a large number of PIV tests,the POD(Proper Orthogonal Decomposition)of the PIV test data was carried out to extract the flow characteristics of the flow field under each order mode.The results show that only a few low order modes can be used in POD analysis,the most important feature of flow field can be obtained,and the energy of corresponding characteristic structure can be obtained.Under all T+ values,the 1 order modes are all main modes,and vibration increases the kinetic energy ratio of the main mode.After the 6 order mode,the kinetic energy ratio increase with the T+ increase,it shows that the vibration has a great influence on the higher order mode.The vibration reduces the change gradient of the kinetic energy ratio of the 2-8 order mode,which shows that the vibration to a certain extent inhibits the velocity fluctuation.By means of numerical simulation and PIV experiment,this study can realize the range ofthe T+ of drag reduction of spiral flow in the cyclone,which can provide theoretical basis and basis for the study of the internal flow characteristics and separation mechanism of the cyclone separator under vibration conditions.It also provides reference for the study of the drag reduction performance of the spiral flow in the circular tube and the study of the complex turbulence.