This paper discusses the development and the application of the boundary element method, the finite element method, the smoothed particle hydrodynamics method, the finite volume method, the engineering method and the mixing analysis in the planned ditching of a transport airplane, including their advantages and disadvantages.
A Eulerian two-fluid model based on the kinetic theory of granular flow is important for the calculation of large-scale multi-phase flows and reactions. The drag model which describes the interphase interactions is critical with respect to the calculation accuracy. This paper reviews various methods to develop drag models for dense heterogeneous gas-solid flows and discusses their merits and demerits. Based on the energy analysis of multi-phase flows, an energy minimization multi-scale (EMMS) drag model is established. The core of the EMMS model is the conservation equations of mechanical energy and the solution of such equations with the stability condition that the energy for the particle suspension and transport reaches the minimum. This paper discusses the development process of the EMMS model and points out its substantial defects in describing cluster characteristics. New descriptions of cluster characteristics are proposed and verified with experimental data. The predicted drag with the new cluster descriptions agrees well with experimental results, indicating the effectiveness of the model revision. Finally, this paper discusses the EMMS model defects in universal applications and suggests the developing directions.
The free vibration of post-buckling beams subjected to non-conservative load is studied. Based on the large deformation theory for the elastic beams, the geometrically nonlinear dynamic equations are established for beams subjected to a distributed tangential follower force along the central axis. By assuming that the amplitude of beam's vibration is small and its response harmonic, a linear version of the vibration problem is deduced. By employing the numerical shooting technique to solve the governing equations for vibration, numerical solutions of the first three natural frequencies against the load parameter are obtained. The results show that the features of the vibration response of the beams subjected to a non-conservative load are evidently different from those subjected to a conservative load.
The applications and the performance test of the slip rings are reviewed. To overcome the diffculties in the measurement of the contact force between the brush wire and the ring in precision satellite slip rings, a measurement scheme based on the cantilever beam theory is proposed and its principle is explained. According to the deformation linearity of the cantilever beam, the unary regression analysis using the least squares method for the measurement data is carried out to obtain the initial loading force. The contact force is finally calculated according to its relationship with the initial loading force.
The seismic performance of steel frames with reduced beam section connections is evaluated by using the finite element analysis, the modal analysis and the time-history analysis. The vibration period, the dynamic internal force, the dynamic stress and the plastic deformation zone in steel frames are studied in detail; and the results are compared with those of steel frames with ordinary connections. It is shown that the seismic performances of the steel frames with reduced beam section connections are not very satisfactory under weak earthquakes, but they are very good under strong earthquakes, the plastic deformation occurs at the reduced beam, the plastic strain increases, the column base shear and the top displacement of the steel frames are all smaller than those of the steel frames with ordinary connections, so it is suggested that reduced beam section connections should be used in areas with strong earthquakes.
The sediment is in a very active movement along the muddy coast. Both the siltation which is directly related to the shoreline changes and the coastal protection become very important in the last few decades. This paper presents a review, which includes the rheological properties of the cohesive sediment, the interaction between wave and cohesive sediment, the wave attenuation as well as the sediment mass transport.
Based on the random vibration theory, the frequency domain calculation method is adopted to analyze the wind-induced response of a monolayer cable net. Some parameters crucial to the response of the wind vibration are highlighted, and different algorithms for the frequency domain calculation and the selected spatial coherence functions are discussed. According to the different algorithms and spatial coherences, three analysis patterns of the monolayer cable net are established to analyze the effect of the parameters. The results show that the coupling effect between different modes is significant; the selected coherence function greatly affects the computation, and the coherence function related to the wind frequency is more reasonable.