A new method,the stream surface strip element method,for simulating the three-dimensional deformation of plate and strip rolling process was proposed.The rolling deformation zone was divided into a number of stream su...A new method,the stream surface strip element method,for simulating the three-dimensional deformation of plate and strip rolling process was proposed.The rolling deformation zone was divided into a number of stream surface(curved surface)strip elements along metal flow traces,and the stream surface strip elements were mapped into the corresponding plane strip elements for analysis and computation.The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal were respectively constructed to be a quartic curve and a quadratic curve,of which the lateral distributions were expressed as the third-power spline function,and the altitudinal distributions were fitted in the quadratic curve.From the flow theory of plastic mechanics,the mathematical models of the three-dimensional deformations and stresses of the deformation zone were constructed.Compared with the streamline strip element method proposed by the first author of this paper,the stream surface strip element method takes into account the uneven distributions of stresses and deformations along altitudinal direction,and realizes the precise three-dimensional analysis and computation.The simulation example of continuous hot rolled strip indicates that the method and the model accord with facts and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.展开更多
This article Introduces the clinical experience of treating pain syndrome by shu （stream）points of the hand three Yang meridians.The authors used the shu（stream）points for some pain syndromes.It develops the i...This article Introduces the clinical experience of treating pain syndrome by shu （stream）points of the hand three Yang meridians.The authors used the shu（stream）points for some pain syndromes.It develops the indications of shu（stream）points which used to be only applied to heavy sensations of the body and painful joints.It is highly important for the effective result to be the contralateral puncturing combined with doing exercises and a long retaining of needlles,such as one hour.Most of acute pain can be cured by one treatment.As for stubborn pain,It can be alleviated by 5—10 treatments.展开更多
A new physical structure of vortical flow, i.e., tubular limiting stream surface(TLSS), is reported. It is defined as a general mathematical structure for the physical flow field in the neighborhood of a singularity, ...A new physical structure of vortical flow, i.e., tubular limiting stream surface(TLSS), is reported. It is defined as a general mathematical structure for the physical flow field in the neighborhood of a singularity, and has a close relationship with limit cycles.The TLSS is a tornado-like structure, which separates a vortex into two regions, i.e., the inner region near the vortex axis and the outer region further away from the vortex axis.The flow particles in these two regions can approach to(or leave) the TLSS, but never could reach it.展开更多
The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on...The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on external disturbances such as sound waves and vortices in the free stream, whereas those on the leading-edge receptivity to the three-dimensional free-stream turbulence (FST), which is more general in the nature, are rarely reported. In consideration of this, this work is devoted to investigating the receptivity process of three-dimensional Tollmien-Schlichting (T-S) wave packets excited by the three-dimensional FST in a flat-plate boundary layer numerically. The relations between the leading-edge receptivity and the turbulence intensity are established, and the influence of the FST directions on the propagation directions and group velocities of the excited T-S wave packets is studied. Moreover, the leading-edge receptivity to the anisotropic FST is also studied. This parametric investigation can contribute to the prediction of laminar-turbulent transition.展开更多
This paper gives the detailed mathematical expression of the flow in the spherical coordinates system. Applying the law of conservation of mass, movement theorem of steady flow, and applying the mathematical method of...This paper gives the detailed mathematical expression of the flow in the spherical coordinates system. Applying the law of conservation of mass, movement theorem of steady flow, and applying the mathematical method of stream function with consideration of the axis symmetry, the three components of velocity quantum of the flow are deduced in detail. Here the overall analysis of the flow is presented in the view of the concept of whole, and the paper gives the necessary corrections of some results of Ref.[1]展开更多
Boundary-layer receptivity is always a hot issue in laminar-turbulent tran- sition. Most actual laminar-turbulent transitions belong to three-dimensional flows. An infinite back-swept fiat-plate boundary layer is a ty...Boundary-layer receptivity is always a hot issue in laminar-turbulent tran- sition. Most actual laminar-turbulent transitions belong to three-dimensional flows. An infinite back-swept fiat-plate boundary layer is a typical three-dimensionalflow. Study of its receptivity is important both in theory and applications. In this paper, a free- stream turbulence model is established. A modified fourth-order Runge-Kutta scheme is used for time marching, and compact finite difference schemes are used for space dis- cretization/ On these bases, whether unsteady cross-flow vortices can be excited in the three-dimensional boundary layer （the infinite back-swept flat-plate boundary layer） by free-stream turbulence is studied numerically. If so, effects of the level and the direc- tion of free-stream turbulence on the three^dimensional boundary-layer receptivity are further studied. Differences of the three-dimensional boundary-layer receptivity are then discussed by considering the non-parallel effect, influence of the leading-edge stagnation point of the flat plate, and variation of the back-swept angle separately. Intensive studies on the ＇three-dimensional boundary-layer receptivity will benefit the development of the hydrodynamic stability theory, and provide a theoretical basis for prediction and control of laminar-turbulent transition.展开更多
We construct a cubically nonlinear theory of plural interactions between harmonics of the growing space charge wave（SCW） during the development of the two-stream instability. It is shown that the SCW with a wide fre...We construct a cubically nonlinear theory of plural interactions between harmonics of the growing space charge wave（SCW） during the development of the two-stream instability. It is shown that the SCW with a wide frequency spectrum is formed when the frequency of the first SCW harmonic is much lower than the critical frequency of the two-stream instability.Such SCW has part of the spectrum in which higher harmonics have higher amplitudes. We analyze the dynamics of the plural harmonic interactions of the growing SCW and define the saturation harmonic levels. We find the mechanisms of forming the multiharmonic SCW for the waves with frequencies lower than the critical frequency and for the waves with frequencies that exceed the critical frequency.展开更多
基金Sponsored by National Natural Science Foundation of China(50175095)Provincial Natural Science Foundation of Hebei of China(502173)
文摘A new method,the stream surface strip element method,for simulating the three-dimensional deformation of plate and strip rolling process was proposed.The rolling deformation zone was divided into a number of stream surface(curved surface)strip elements along metal flow traces,and the stream surface strip elements were mapped into the corresponding plane strip elements for analysis and computation.The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal were respectively constructed to be a quartic curve and a quadratic curve,of which the lateral distributions were expressed as the third-power spline function,and the altitudinal distributions were fitted in the quadratic curve.From the flow theory of plastic mechanics,the mathematical models of the three-dimensional deformations and stresses of the deformation zone were constructed.Compared with the streamline strip element method proposed by the first author of this paper,the stream surface strip element method takes into account the uneven distributions of stresses and deformations along altitudinal direction,and realizes the precise three-dimensional analysis and computation.The simulation example of continuous hot rolled strip indicates that the method and the model accord with facts and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.
文摘This article Introduces the clinical experience of treating pain syndrome by shu （stream）points of the hand three Yang meridians.The authors used the shu（stream）points for some pain syndromes.It develops the indications of shu（stream）points which used to be only applied to heavy sensations of the body and painful joints.It is highly important for the effective result to be the contralateral puncturing combined with doing exercises and a long retaining of needlles,such as one hour.Most of acute pain can be cured by one treatment.As for stubborn pain,It can be alleviated by 5—10 treatments.
基金Project supported by the National Natural Science Foundation of China(Nos.11372340 and 11732016)
文摘A new physical structure of vortical flow, i.e., tubular limiting stream surface(TLSS), is reported. It is defined as a general mathematical structure for the physical flow field in the neighborhood of a singularity, and has a close relationship with limit cycles.The TLSS is a tornado-like structure, which separates a vortex into two regions, i.e., the inner region near the vortex axis and the outer region further away from the vortex axis.The flow particles in these two regions can approach to(or leave) the TLSS, but never could reach it.
基金supported by the National Natural Science Foundation of China(Nos.11472139 and11802143)the Natural Science Foundation of Jiangsu Province of China(No.BK20180781)
文摘The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on external disturbances such as sound waves and vortices in the free stream, whereas those on the leading-edge receptivity to the three-dimensional free-stream turbulence (FST), which is more general in the nature, are rarely reported. In consideration of this, this work is devoted to investigating the receptivity process of three-dimensional Tollmien-Schlichting (T-S) wave packets excited by the three-dimensional FST in a flat-plate boundary layer numerically. The relations between the leading-edge receptivity and the turbulence intensity are established, and the influence of the FST directions on the propagation directions and group velocities of the excited T-S wave packets is studied. Moreover, the leading-edge receptivity to the anisotropic FST is also studied. This parametric investigation can contribute to the prediction of laminar-turbulent transition.
文摘This paper gives the detailed mathematical expression of the flow in the spherical coordinates system. Applying the law of conservation of mass, movement theorem of steady flow, and applying the mathematical method of stream function with consideration of the axis symmetry, the three components of velocity quantum of the flow are deduced in detail. Here the overall analysis of the flow is presented in the view of the concept of whole, and the paper gives the necessary corrections of some results of Ref.[1]
基金supported by the National Natural Science Foundation of China(No.11472139)the Startup Foundation for Introducing Talent of Nanjing University of Information Science&Technology(No.2016r046)
文摘Boundary-layer receptivity is always a hot issue in laminar-turbulent tran- sition. Most actual laminar-turbulent transitions belong to three-dimensional flows. An infinite back-swept fiat-plate boundary layer is a typical three-dimensionalflow. Study of its receptivity is important both in theory and applications. In this paper, a free- stream turbulence model is established. A modified fourth-order Runge-Kutta scheme is used for time marching, and compact finite difference schemes are used for space dis- cretization/ On these bases, whether unsteady cross-flow vortices can be excited in the three-dimensional boundary layer （the infinite back-swept flat-plate boundary layer） by free-stream turbulence is studied numerically. If so, effects of the level and the direc- tion of free-stream turbulence on the three^dimensional boundary-layer receptivity are further studied. Differences of the three-dimensional boundary-layer receptivity are then discussed by considering the non-parallel effect, influence of the leading-edge stagnation point of the flat plate, and variation of the back-swept angle separately. Intensive studies on the ＇three-dimensional boundary-layer receptivity will benefit the development of the hydrodynamic stability theory, and provide a theoretical basis for prediction and control of laminar-turbulent transition.
文摘We construct a cubically nonlinear theory of plural interactions between harmonics of the growing space charge wave（SCW） during the development of the two-stream instability. It is shown that the SCW with a wide frequency spectrum is formed when the frequency of the first SCW harmonic is much lower than the critical frequency of the two-stream instability.Such SCW has part of the spectrum in which higher harmonics have higher amplitudes. We analyze the dynamics of the plural harmonic interactions of the growing SCW and define the saturation harmonic levels. We find the mechanisms of forming the multiharmonic SCW for the waves with frequencies lower than the critical frequency and for the waves with frequencies that exceed the critical frequency.
