Based on the traditional hydraulic bulging process,an improved hydraulic bulging process with axial feeding in the bulging process was proposed.The finite element simulation and experiment of bellows formed by the tra...Based on the traditional hydraulic bulging process,an improved hydraulic bulging process with axial feeding in the bulging process was proposed.The finite element simulation and experiment of bellows formed by the traditional and improved hydraulic bulging processes were conducted.The grid strain measurement system analysis results of strain and wall thickness distribution of the metal bellows,obtained from simulation and experiment,show that the maximum thinning rates of the wall thickness under the traditional and improved processes were 15%and 10%,respectively.And the wall thickness distribution of the metal bellows formed with improved process was more uniform.The strain values from the root to crown of the waveform increased gradually.However,the strain values were smaller than those of traditional process due to the axial feeding of the improved process in bulging process.展开更多
Direct numerical simulations are carried out to assess the potential drag reduction of compressible turbulent flow between isothermal walls.For the sake of achieving drag reduction,the flow is actively controlled by d...Direct numerical simulations are carried out to assess the potential drag reduction of compressible turbulent flow between isothermal walls.For the sake of achieving drag reduction,the flow is actively controlled by deformable dimples lying on the bottom wall of the channel.The first stage of the procedure consists in assessing the optimum geometry of the dimples.In this regard,the lower wall is allowed to freely deform itself according to the loop of control.This method is called the smart wall approach in this paper.By an analysis of the typical shape of the wall deformation thus obtained,it is found that dimples should be thinner than or comparable to the width of streaky structures in the spanwise direction and elongated in the streamwise direction.With active dimples as the wall-deformation actuators,a 15% drag reduction is obtained for the flow at Mam = 0.35 while the drag reduction rate is about 12% for the flow at Mam = 1.5.The fundamental mechanism of the drag reduction is then discussed in this paper.The drag reduction is believed to result from two aspects:the reduction of the mean streamwise velocity gradient near the deformable wall and the suppression of the turbulent fluctuations.展开更多
基金Project (51775479) supported by the National Natural Science Foundation of ChinaProject (E2017203046) supported by the Natural Science Foundation of Hebei Province,China
文摘Based on the traditional hydraulic bulging process,an improved hydraulic bulging process with axial feeding in the bulging process was proposed.The finite element simulation and experiment of bellows formed by the traditional and improved hydraulic bulging processes were conducted.The grid strain measurement system analysis results of strain and wall thickness distribution of the metal bellows,obtained from simulation and experiment,show that the maximum thinning rates of the wall thickness under the traditional and improved processes were 15%and 10%,respectively.And the wall thickness distribution of the metal bellows formed with improved process was more uniform.The strain values from the root to crown of the waveform increased gradually.However,the strain values were smaller than those of traditional process due to the axial feeding of the improved process in bulging process.
基金supported by the National Natural Science Foundation of China (Grant Nos.10932005 and 50910222)
文摘Direct numerical simulations are carried out to assess the potential drag reduction of compressible turbulent flow between isothermal walls.For the sake of achieving drag reduction,the flow is actively controlled by deformable dimples lying on the bottom wall of the channel.The first stage of the procedure consists in assessing the optimum geometry of the dimples.In this regard,the lower wall is allowed to freely deform itself according to the loop of control.This method is called the smart wall approach in this paper.By an analysis of the typical shape of the wall deformation thus obtained,it is found that dimples should be thinner than or comparable to the width of streaky structures in the spanwise direction and elongated in the streamwise direction.With active dimples as the wall-deformation actuators,a 15% drag reduction is obtained for the flow at Mam = 0.35 while the drag reduction rate is about 12% for the flow at Mam = 1.5.The fundamental mechanism of the drag reduction is then discussed in this paper.The drag reduction is believed to result from two aspects:the reduction of the mean streamwise velocity gradient near the deformable wall and the suppression of the turbulent fluctuations.
