The effect of the moving speed of permanent magnet （PM） on levitation force between PM and high temperature superconducting （HTS） bulk is analyzed and described in the PM-HTS levitation system. The PM vibration ch...The effect of the moving speed of permanent magnet （PM） on levitation force between PM and high temperature superconducting （HTS） bulk is analyzed and described in the PM-HTS levitation system. The PM vibration characteristic in the PM-HTS system is investigated. The PM may collide with the HTS in vibration if the amplitude and frequency of driving force satisfy the relationship Pmin=Afn. When the load of the system is below a threshold, the minimal collision amplitude of the driving force increases with the load increasing, however, it sharply drops to zero when the load exceeds the threshold. With the increase of the initial height of the PM, the threshold load increases, but the minimal driving force which causes a collision between PM and HTS decreases.展开更多
为了研究柱体结构的涡激振动特性预测方法,首先基于Van der Pol尾流振子模型建立了弹性支撑单自由度柱体的涡激振动模型。然后基于计算流体力学(CFD)方法、结构动力学理论以及嵌套网格技术,同时考虑弹性支撑柱体来流向和横向振动,建立...为了研究柱体结构的涡激振动特性预测方法,首先基于Van der Pol尾流振子模型建立了弹性支撑单自由度柱体的涡激振动模型。然后基于计算流体力学(CFD)方法、结构动力学理论以及嵌套网格技术,同时考虑弹性支撑柱体来流向和横向振动,建立了柱体结构的涡激振动高保真仿真模型。通过与国外文献实验数据对比,验证了两种模型的准确性。计算结果表明,在低质量比情况下,Van der Pol尾流振子模型在约化速度较小区域计算误差很大,在柱体振幅最大值附近误差较小,基本上可以捕捉到柱体的涡激振动特性,可以用于工程上快速预测柱体结构的涡激振动特性;在低质量比、高质量比以及指定的约化速度范围内,采用CFD方法和嵌套网格技术,可以避免由于柱体振幅较大引起的网格畸变和负网格问题,且可以获得较好的计算精度和详细的流场信息,但计算效率相比Van der Pol尾流振子模型较低。展开更多
The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. ...The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.展开更多
基金This work was supported by the National Science Foundation of China under Grant No. 50372052, 50588201the National Basic Research Program of China under Grant No. 2007CB616906+1 种基金the Program for Changjiang Scholars and Innovative Research Team in UniversityAustralian Research Council under Grant No. DP0559872, DP0881739.
文摘The effect of the moving speed of permanent magnet （PM） on levitation force between PM and high temperature superconducting （HTS） bulk is analyzed and described in the PM-HTS levitation system. The PM vibration characteristic in the PM-HTS system is investigated. The PM may collide with the HTS in vibration if the amplitude and frequency of driving force satisfy the relationship Pmin=Afn. When the load of the system is below a threshold, the minimal collision amplitude of the driving force increases with the load increasing, however, it sharply drops to zero when the load exceeds the threshold. With the increase of the initial height of the PM, the threshold load increases, but the minimal driving force which causes a collision between PM and HTS decreases.
文摘为了研究柱体结构的涡激振动特性预测方法,首先基于Van der Pol尾流振子模型建立了弹性支撑单自由度柱体的涡激振动模型。然后基于计算流体力学(CFD)方法、结构动力学理论以及嵌套网格技术,同时考虑弹性支撑柱体来流向和横向振动,建立了柱体结构的涡激振动高保真仿真模型。通过与国外文献实验数据对比,验证了两种模型的准确性。计算结果表明,在低质量比情况下,Van der Pol尾流振子模型在约化速度较小区域计算误差很大,在柱体振幅最大值附近误差较小,基本上可以捕捉到柱体的涡激振动特性,可以用于工程上快速预测柱体结构的涡激振动特性;在低质量比、高质量比以及指定的约化速度范围内,采用CFD方法和嵌套网格技术,可以避免由于柱体振幅较大引起的网格畸变和负网格问题,且可以获得较好的计算精度和详细的流场信息,但计算效率相比Van der Pol尾流振子模型较低。
基金This work was supported by the Natural Science Foundation of China through Grant No. 21676051, New Century Excellent Talents in University （NCET-12-0703）. One of the authors （Shuyan Wang） thanks the China Scholarship Council （CSC） for providing financial support to the Sundaresan＇s group of Princeton University.
文摘The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.
