This research study measures the support for learners through the use of a Virtual Learning Environment project website. The website prepares, assists and supports the learners through their Mechanical Engineering Pro...This research study measures the support for learners through the use of a Virtual Learning Environment project website. The website prepares, assists and supports the learners through their Mechanical Engineering Projects in an accredited academic programme. The research question answered was "Is the VLE website helpful to learners in the final years of mechanical engineering projects?" The research focuses on the learners' experiences of using the project website and explores their views regarding the website. The literature relating to the study indicates that similar programmes have had positive results in relation to the adoption of VLEs to support learners.The data collection process involved an initial questionnaire about the website for the quantitative analysis. Thirty-nine project learners from the third and fourth years of the Mechanical Engineering programme participated in the questionnaires. The analysis of the questionnaire results indicated that the project website VLE was very helpful to learners completing their Mechanical Engineering projects. They all used the website for different aspects of the project but they still wanted a lecturer or lecturers to consult with for problems during the course of the project. The kinesthetic learning achieved in the project modules cannot be replicated or replaced by any virtual learning environment. The website afforded the learner to be better prepared for the project start in September. It gives the learner another resource to refer to when they were working at home, during the holidays or when they come to a particular part of the project. The website also teaches the learner to use the internet, videos, screencasts, tutorials, etc. to help them to complete the project.The website has enhanced student learning, motivation, earlier starts to project, peer learning and has improved the quality of projects.展开更多
本文将一种VLES(Very Large Eddy Simulation)模型引入到动网格数值计算中,并验证了VLES模型用于模拟类似振动圆柱绕流的动边界问题的有效性。数值求解了不同振幅和频率下非稳态振动圆柱绕流问题。研究表明:随着振幅和激励频率的增加,...本文将一种VLES(Very Large Eddy Simulation)模型引入到动网格数值计算中,并验证了VLES模型用于模拟类似振动圆柱绕流的动边界问题的有效性。数值求解了不同振幅和频率下非稳态振动圆柱绕流问题。研究表明:随着振幅和激励频率的增加,绕圆柱流动涡脱离形式从2S模式转换到2P0模式,再到P+S模式。在高振幅和激励频率比fe/fs=0.95时,涡脱离形式却表现为2P0模式到P+S模式的过渡状态,振动圆柱在上升或下降过程中涡的脱离造成在每个周期升力曲线的左右侧发生不规则的"跳动"现象,尽管脱落涡可能为涡对或者单涡.展开更多
Following the idea of Speziale＇s Very Large Eddy Simulation （VLES） method, a new unified hybrid simulation approach was proposed which can change seamlessly from RANS （Reynolds-Averaged Navier-Stokes） to LES （La...Following the idea of Speziale＇s Very Large Eddy Simulation （VLES） method, a new unified hybrid simulation approach was proposed which can change seamlessly from RANS （Reynolds-Averaged Navier-Stokes） to LES （Large Eddy Simulation） method depending on the numerical resolution. The model constants were calibrated in accordance with other hybrid methods. Besides being able to approach the two limits of RANS and LES, the new model also provides a proper VLES mode between the two limits, and thus can be used for a wide range of mesh resolutions. Also RANS simulation can be recovered near the wall which is similar to the Detached Eddy Simulation （DES） concept. This new methodology was implemented into Wilcox＇s κ- ω model and applications were conducted for fully developed turbulent channel flow at ReT = 395 and turbulent flow past a square cylinder at Re = 22000. Results were compared with LES predictions and other studies. The new method is found to be quite efficient in resolving large flow structures, and can predict satisfactory results on relative coarse mesh.展开更多
The internal flow in an axial flow rotating machinery is affected by the rotating characteristics, often accompanied by a strong rotating separation under small flow conditions. At present, the very large eddy simulat...The internal flow in an axial flow rotating machinery is affected by the rotating characteristics, often accompanied by a strong rotating separation under small flow conditions. At present, the very large eddy simulation (VLES) model commonly used for the separation flow simulation still has certain limitations in simulating such rotating separation flow: (1) The Reynolds stress level is overestimated in the near-wall region. (2) The influence of the rotating effect cannot be effectively considered. The above two limitations affect the simulation accuracy of the VLES model for the rotating separation flow under small flow conditions in the axial flow rotating machinery. The objective of this paper is to provide a new hybrid unsteady Reynolds average Navier-Stokes/large eddy simulation (URANS/LES) model suitable for the simulation of the rotating separation flow in an axial flow rotating machinery. Compared with the original VLES method, the modifications are as follows: (1) A Reynolds stress damping function in the near-wall region is introduced to reduce the overestimation of the Reynolds stress caused by the near-wall Reynolds average Navier-Stokes (RANS) behavior of the VLES model. (2) A control function driven by the vortex is introduced to reflect the influence of the rotating effect. Three typical cases are used to verify the calculation accuracy of the modified model. It is shown that the modified model can capture more turbulent vortices based on the URANS grids, and the prediction accuracy of the rotating separation flow is effectively improved. Compared with the original VLES model, the modified model can accurately predict the head change in the hump region of the axial flow pump.展开更多
文摘This research study measures the support for learners through the use of a Virtual Learning Environment project website. The website prepares, assists and supports the learners through their Mechanical Engineering Projects in an accredited academic programme. The research question answered was "Is the VLE website helpful to learners in the final years of mechanical engineering projects?" The research focuses on the learners' experiences of using the project website and explores their views regarding the website. The literature relating to the study indicates that similar programmes have had positive results in relation to the adoption of VLEs to support learners.The data collection process involved an initial questionnaire about the website for the quantitative analysis. Thirty-nine project learners from the third and fourth years of the Mechanical Engineering programme participated in the questionnaires. The analysis of the questionnaire results indicated that the project website VLE was very helpful to learners completing their Mechanical Engineering projects. They all used the website for different aspects of the project but they still wanted a lecturer or lecturers to consult with for problems during the course of the project. The kinesthetic learning achieved in the project modules cannot be replicated or replaced by any virtual learning environment. The website afforded the learner to be better prepared for the project start in September. It gives the learner another resource to refer to when they were working at home, during the holidays or when they come to a particular part of the project. The website also teaches the learner to use the internet, videos, screencasts, tutorials, etc. to help them to complete the project.The website has enhanced student learning, motivation, earlier starts to project, peer learning and has improved the quality of projects.
文摘本文将一种VLES(Very Large Eddy Simulation)模型引入到动网格数值计算中,并验证了VLES模型用于模拟类似振动圆柱绕流的动边界问题的有效性。数值求解了不同振幅和频率下非稳态振动圆柱绕流问题。研究表明:随着振幅和激励频率的增加,绕圆柱流动涡脱离形式从2S模式转换到2P0模式,再到P+S模式。在高振幅和激励频率比fe/fs=0.95时,涡脱离形式却表现为2P0模式到P+S模式的过渡状态,振动圆柱在上升或下降过程中涡的脱离造成在每个周期升力曲线的左右侧发生不规则的"跳动"现象,尽管脱落涡可能为涡对或者单涡.
基金supported by the National Natural Science Foundation of China (Grant No. 50936005)the National Basic Research Program of China (Grant No. 2010CB227302)
文摘Following the idea of Speziale＇s Very Large Eddy Simulation （VLES） method, a new unified hybrid simulation approach was proposed which can change seamlessly from RANS （Reynolds-Averaged Navier-Stokes） to LES （Large Eddy Simulation） method depending on the numerical resolution. The model constants were calibrated in accordance with other hybrid methods. Besides being able to approach the two limits of RANS and LES, the new model also provides a proper VLES mode between the two limits, and thus can be used for a wide range of mesh resolutions. Also RANS simulation can be recovered near the wall which is similar to the Detached Eddy Simulation （DES） concept. This new methodology was implemented into Wilcox＇s κ- ω model and applications were conducted for fully developed turbulent channel flow at ReT = 395 and turbulent flow past a square cylinder at Re = 22000. Results were compared with LES predictions and other studies. The new method is found to be quite efficient in resolving large flow structures, and can predict satisfactory results on relative coarse mesh.
基金the National Natural Science Foundation of China(Grant Nos.51836010,51779258).
文摘The internal flow in an axial flow rotating machinery is affected by the rotating characteristics, often accompanied by a strong rotating separation under small flow conditions. At present, the very large eddy simulation (VLES) model commonly used for the separation flow simulation still has certain limitations in simulating such rotating separation flow: (1) The Reynolds stress level is overestimated in the near-wall region. (2) The influence of the rotating effect cannot be effectively considered. The above two limitations affect the simulation accuracy of the VLES model for the rotating separation flow under small flow conditions in the axial flow rotating machinery. The objective of this paper is to provide a new hybrid unsteady Reynolds average Navier-Stokes/large eddy simulation (URANS/LES) model suitable for the simulation of the rotating separation flow in an axial flow rotating machinery. Compared with the original VLES method, the modifications are as follows: (1) A Reynolds stress damping function in the near-wall region is introduced to reduce the overestimation of the Reynolds stress caused by the near-wall Reynolds average Navier-Stokes (RANS) behavior of the VLES model. (2) A control function driven by the vortex is introduced to reflect the influence of the rotating effect. Three typical cases are used to verify the calculation accuracy of the modified model. It is shown that the modified model can capture more turbulent vortices based on the URANS grids, and the prediction accuracy of the rotating separation flow is effectively improved. Compared with the original VLES model, the modified model can accurately predict the head change in the hump region of the axial flow pump.
