International Journal of Engineering Systems Modelling and Simulation (5 papers in press)
Simulation of Ship Seismic Wave Field in Shallow Sea Based on Three - dimensional Staggered Grid
by Xufang Zhu, Bing Yan
Abstract: To find the law of ship seismic wave field in shallow sea, Three-dimensional staggered grid method is adopted. Environmental characteristics of shallow sea and the excitation mechanism of ship seismic wave have been fully considered in this algorithm. Firstly, this algorithm is used to compare wave fields in the YOZ and XOZ planes under three-dimensional environment, which shows that the propagation characteristics of them are basically the same. Secondly, it is used to transform focal depth, which shows that the closer the focus is near to the seabed, the more concentrated the seismic wave signal in the submarine interface propagates along the horizontal direction, and the stronger the surface wave in the wave field; the energy ratio near the focus in horizontal direction is the higher, while the vertical energy ratio is higher. When the center frequency of the focus is transformed, it shows that the lower the center frequency is, the stronger the surface wave signal, and when the central frequency is lower than 10HZ, almost only the surface wave can be observed, when the frequency is higher than 50HZ, the seismic wave signal in the seabed is gradually weakened. At last, the far-field law is observed, which shows that P wave and S wave merge into one wave group, the velocity is somewhere between them, and the surface waves still can be clearly observed due to slow attenuation.
Keywords: Shallow sea; Ship seismic wave; Three-dimensional staggered grid; Simulation.
The safety research of road alignment based on virtual simulation technology
by Change Lv, Dengfeng Shi, Shangbing Gao, Shuo Liu
Abstract: The application of virtual simulation technology in the design and construction of road provides a new way for the road design workers. For using virtual simulation technology to identify dangerous sections of roads that have been built and to provide technical support during the initial stages of road design, it is necessary to first research the reliability of virtual simulation experiments in road safety studies. The man-vehicle-road system model based on multi-body dynamics is proposed using the software of ADAMS/Car. Based on the roll and roll-over evaluation criteria, combined with speed consistency theory, the high risk and high driving load road sections are identified. Furthermore, the simulation results are compared with the measured results from six-dimensional sensor in order to verify the reliability of virtual simulation technology while applied for road shape designing. The comparison results can be seen that the simulation analysis based on virtual prototype technology of 12 sections accidents, 10 with six component based sensor anastomosis of real vehicle road test analysis section, the accident sections of results obtained from the two methods of alignment is 83.3%. The results show that the road risk prediction simulation based on virtual prototype technology can provide high reliability.
Keywords: Traffic safety; geometric design; vehicle dynamics; virtual simulation.
Model Test Study on Seismic Performance of New type Column-Plate Hollow High Pier
by Ziqi Li, Lusong Yu, Yanyan Fan
Abstract: There are many disadvantages in the design of high pier in high intensity zone for traditional circular end-shaped hollow pier. The design concept of multi-column grid pier can improve the seismic performance of high-strength pier. The column-plate hollow high piers not only retain the good seismic performance of the lattice pier, but also improve the longitudinal and transverse stiffness of the hollow high piers, which lays a foundation for the application of the column plate bridge piers to the design of railway bridges. To understand the seismic performance of such piers systematically, a local model of plate pier is made on the basis of the column plate pier of the Zongmu Gou bridge in this paper. The destructive mode and hysteresis characteristics of the pier are studied by means of pseudo-static test. It provides reference for the seismic design of the piers. The test results show that the column-plate structure as a whole has strong seismic performance. Under seismic loading, the inter-column plates can be completely sheared and destroyed, and the frame columns remain flexible. The energy consumption of the inter-column plate during the destruction process ensures the normal operation of the frame column.
Keywords: High pier; High intensity zones; Seismic performance; Column plate pier; Destructive mode; Hysteresis characteristics.
Modeling and analysis of small signal for multi - machine parallel system based on droop control
by Chan Xue
Abstract: Microgrid system based on multi-machine parallel connection has complex structure and various connection modes. In the process of grid-connected splitting, because of the frequency and voltage deviation between sub-microgrid, it will produce large electric power at the PCC point, which will impact the multi-machine microgrid system and affect the dynamic stability of the system. In order to solve the problem of control accuracy and dynamic stability in this such kind of process, considering the voltage drop and voltage phase angle offset of long-distance lines, an improved droop control method is proposed based on the parallel structure of multiple microgrid, the droop control accuracy is optimized, at the same time the corresponding small signal model is established for parameter optimization, and the simulation model of improved droop control is established on MATLAB / Simulink. The simulation results verify the rationality and effectiveness of the improved control strategy.
Keywords: Multi-machine parallel structure; dynamic stability; improved droop control; small-signal analysis.
NUMERICAL ANALYSIS OF MHD NATURAL CONVECTION IN A PARTIALLY OPEN CAVITY WITH INTERNAL ENERGY SOURCE
by Nagarajan Nithyadevi, MUTHU RAJARATHINAM
Abstract: In this paper, the problem of MHD natural convection in a partially open square cavity in the presence of internal energy source has been studied numerically. The bottom and vertical walls are isothermally heated and cooled by different constant temperatures. The top wall of the cavity has been opened in three different positions namely, left, middle and right whereas the remaining unopened part is thermally insulated. The governing non-linear partial differential equations are solved by SIMPLE algorithm where the discretitation is followed by finite volume method. The influence of various pertinent parameters such as internal Rayleigh number, external Rayleigh number and Hartmann number are discussed via graphs and tables. It is found that the fluid flow and heat transfer are strongly depends on the internal and external Rayleigh numbers, Hartmann number and three different opening positions of the top wall.
Keywords: Internal heat source; Magnetohydrodynamics; Natural convection; Open cavity.