In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses si...In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox （2006） k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.展开更多
Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental stu...Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China （Nos.51309040, 51379033, 51209027, 51309025）, Open Research Fund of State Key Laboratory of Ocean Engineering （Shanghai Jiao Tong University） （Grant No.1402）, and Fundamental Research Fund for the Central Universities （DMU3132015089）.
文摘In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox （2006） k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.
文摘Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.
