The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,igno...The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.展开更多
An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient....An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient. The cross-correlation algorithm with sub-pixel accuracy is introduced and used to calculate the background-element displacement of a disturbed image and a fourth-order difference scheme is also developed to solve the Poisson equation. An experiment for a disturbed flow field caused by a burning candle is performed to validate the built BOS system and the results indicate that density and temperature distribution of the disturbed flow field can be reconstructed accurately. A notable conclusion is that in order to make the reconstructed results have a satisfactory accuracy, the inquiry step length should be less than the size of the interrogation window.展开更多
The instantaneous variations of the hydraulic characteristics take place in centrifugal pumps during their start-up,shutdown and other variable speed operations.In this paper,the variable speed method was proposed to ...The instantaneous variations of the hydraulic characteristics take place in centrifugal pumps during their start-up,shutdown and other variable speed operations.In this paper,the variable speed method was proposed to simulate the transient internal flow field and the external performance of the pump during starting and stopping periods.The terms of accelerations due to variable speeds in the flow governing equations were analyzed in a multiple reference of frame(MRF).A transient CFD simulation was performed for a typical centrifugal pump by using ANSYS-CFX with the standard k-εturbulence model.The entire simulation process was composed of four stages:start-up,normal run,shutdown and post-shutdown.The function of rotating speed with regard to time was set by CEL language directly into the impeller domain in the pre-processor of the software to conduct variable speed simulation.The variations of the flow field in the centrifugal pump were obtained from the transient simulation.The changing laws of flow rate,head and other performance parameters over time were also analyzed and summarized.展开更多
The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solution...The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solutions.It is known that in order to eliminate the standing wave field formed by ultrasonic radiation in the water tank,the liquid in the water tank needs to be stirred and the corresponding distribution of acoustic field is simulated by using the finite element method(FEM).The standing wave leads to an uneven distribution of the acoustic field when it is not stirred,and disappears after being stirred,which increases the cavitation area in the ultrasonic cleaning tank.Then,the degradation experiment with agitation is carried out.The experimental results show that the degradation rate of the solution is higher than that when there is no agitation,which confirms the importance of the acoustic field distribution to ultrasonic degradation.In addition,it is clear that with the increase of the stirring speed,the degradation rate increases first and reaches a maximum at 600 rpm before decreasing.Finally,the distribution of flow field is simulated and analyzed.展开更多
A phase-field-based lattice Boltzmann model is proposed for the interface capturing of multi-phase flows based on the conservative Allen–Cahn equation(ACE).By adopting the improved form of a relaxation matrix and an ...A phase-field-based lattice Boltzmann model is proposed for the interface capturing of multi-phase flows based on the conservative Allen–Cahn equation(ACE).By adopting the improved form of a relaxation matrix and an equilibrium distribution function,the time derivative?t(φ)induced by recovering the diffusion term in ACE is eliminated.The conducted Chapman–Enskog analysis demonstrates that the correct conservative ACE is recovered.Four benchmark cases including Zalesak’s disk rotation,vortex droplet,droplet impact on thin film,and Rayleigh–Taylor instability are investigated to validate the proposed model.The numerical results indicate that the proposed model can accurately describe the complex interface deformation.展开更多
基金supported by the National Natural Science Foundation of China (No. 52075350)the Special City School Strategic Cooperation Project of Sichuan University and Zigong (No.2021CDZG-3)
文摘The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.NSFC 91441205)
文摘An experimental system based on the background-oriented schlieren（BOS） technique is built to reconstruct the density and temperature distribution of a flame-induced distorted flow field which has a density gradient. The cross-correlation algorithm with sub-pixel accuracy is introduced and used to calculate the background-element displacement of a disturbed image and a fourth-order difference scheme is also developed to solve the Poisson equation. An experiment for a disturbed flow field caused by a burning candle is performed to validate the built BOS system and the results indicate that density and temperature distribution of the disturbed flow field can be reconstructed accurately. A notable conclusion is that in order to make the reconstructed results have a satisfactory accuracy, the inquiry step length should be less than the size of the interrogation window.
文摘The instantaneous variations of the hydraulic characteristics take place in centrifugal pumps during their start-up,shutdown and other variable speed operations.In this paper,the variable speed method was proposed to simulate the transient internal flow field and the external performance of the pump during starting and stopping periods.The terms of accelerations due to variable speeds in the flow governing equations were analyzed in a multiple reference of frame(MRF).A transient CFD simulation was performed for a typical centrifugal pump by using ANSYS-CFX with the standard k-εturbulence model.The entire simulation process was composed of four stages:start-up,normal run,shutdown and post-shutdown.The function of rotating speed with regard to time was set by CEL language directly into the impeller domain in the pre-processor of the software to conduct variable speed simulation.The variations of the flow field in the centrifugal pump were obtained from the transient simulation.The changing laws of flow rate,head and other performance parameters over time were also analyzed and summarized.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674207 and 11674206)。
文摘The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solutions.It is known that in order to eliminate the standing wave field formed by ultrasonic radiation in the water tank,the liquid in the water tank needs to be stirred and the corresponding distribution of acoustic field is simulated by using the finite element method(FEM).The standing wave leads to an uneven distribution of the acoustic field when it is not stirred,and disappears after being stirred,which increases the cavitation area in the ultrasonic cleaning tank.Then,the degradation experiment with agitation is carried out.The experimental results show that the degradation rate of the solution is higher than that when there is no agitation,which confirms the importance of the acoustic field distribution to ultrasonic degradation.In addition,it is clear that with the increase of the stirring speed,the degradation rate increases first and reaches a maximum at 600 rpm before decreasing.Finally,the distribution of flow field is simulated and analyzed.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFB1504301)the Australian Research Council(Grant No.DE160101098)。
文摘A phase-field-based lattice Boltzmann model is proposed for the interface capturing of multi-phase flows based on the conservative Allen–Cahn equation(ACE).By adopting the improved form of a relaxation matrix and an equilibrium distribution function,the time derivative?t(φ)induced by recovering the diffusion term in ACE is eliminated.The conducted Chapman–Enskog analysis demonstrates that the correct conservative ACE is recovered.Four benchmark cases including Zalesak’s disk rotation,vortex droplet,droplet impact on thin film,and Rayleigh–Taylor instability are investigated to validate the proposed model.The numerical results indicate that the proposed model can accurately describe the complex interface deformation.
