Papers by Keyword: Numerical Method

Abstract: Cable-stayed bridge is main kind of modern large-span bridges. Wind load and vehicle load are main dynamic force on cable stayed-bridge, which can cause large amplitude vibration of cables. In the paper, the nonlinear vibration differential equations of cable with dynamic displacement at its end point in 3D space was derived. The differential equations were analysed by the method of multiple scales and the vibration characteristic was discussed. The differential equations were solved by numerical method. The Trajectory of the cable middle point was plotted. The result of this paper indicated that the vibration amplitude of cable in 3D space is relate to the frequency and amplitude of the dynamic displacement of the cable end point. The results in the paper could be a reference for the research of cable vibration in cable-stayed bridge.

Abstract: In order to deal with Hertz contact problem of friction drive in continuously variable transmission (CVT), two methods were proposed in this paper. One is a numerical computation method by MATLAB to solve the elliptic integral equations of Hertz contact, while the other is a finite element method (FEM) which uses the ANSYS Workbench to calculate the point contact between two elastic bodies. The computation results of Hertz contact problem of friction drive in a new CVT proposed by our research group show that, compared with a look-up table method, the numerical solution of MATLAB has many advantages such as high precision and less computational cost, while the finite element method has more simplicity and better visibility. The present methods can provide a reference for the solution of Hertz contact problem of common friction drive.

Abstract: Relying on the status of existing thermal protection system and existing flight parameters, appropriate metal thermal protection system being able to reproduced are designed. Then, based on the highest temperature thermal protection materials can bear, flying height of aerospace plane and Mach number, the numerical method was utilized to reveal the heat-flow density of stagnation point on the sharp- nose and the distribution of heat-flow density.

Abstract: Numerical method is done on effect of wall on upwelling flow induced by air bubbler in a tank. It shows that: this reverse flow causes the increasing upwelling flow with height; when the bubbler distance to wall decreases, it is gradually only influenced at one side and then it affects the upwelling flow; the change of velocity is small in the region below bubbler. So the numerical method is helpful to describe the flow field as figures clearly and design bubbler devices in air-lift engineering applications.

Abstract: To predict the sound radiation of structures, both a structural problem and an acoustic problem have to be solved. In case of thin structures and dense fluids, a strong coupling scheme between the two problems is essential, since the feedback of the acoustic pressure onto the structure is not negligible. A popular idea for solving this class of problems is to discretizing the structural domain with the finite element (FE) method and with boundary element (BE) method on the acoustic field. A wide range of researches has been carried on the coupling the FE and BE methods. For fast prediction of sound radiation characteristic of similar structures, a coupled solver in frequency domain is presented in this essay. Numerical experiments showed acceleration on noise optimization problems of underwater structures with different materials.

Abstract: The fracture distribution around circular cavities has been widely observed in experiments and well documented in literature from 1980. Most of the works are based on experiments’ results, which cost considerable time and money. With varied numerical methods developed more and more researcher employ numerical experiments on computers instead of physical experiments. Firstly, the nodal enrichment functions for Extended Finite Element Method in conjunction with additional degrees are presented. Moreover, we describe the cohesive segments method, which is followed by the damage initiation and evolution laws. In the last a borehole numerical model is built up and the simulation results of the primary fracture propagation are presented.

Abstract: This paper presents numerical investigations of the thermal and fluid flow behavior in an L-shaped of cavity filled with nanofluid. For this purpose, five different water based Cu nanoparticles were selected with concentration of 1%, 3% and 5% were used. Effects of the presence of nanoparticles on the thermal and fluid flow in the enclosure were investigated in different Rayleigh number (Ra = 10³, 10⁴ and 10⁵). Results show that the characteristic of flow and heat transfer are mainly dependent on the dimensionless Rayleigh number. We also found that the presence of nanoparticle enhances the heat transfer rate in the enclosure.

Abstract: In order to study the response of tungsten under high heat load, the nonlinear thermodynamic equations considering the phase transition were established to the tungsten target irradiated by intense pulsed ion beam. Also the equations which describe the thermal stress and the total strain produced by the changed temperature in the material element were built. Numerical method was used to solve the evolutions of the thermal stress field formed in the target, and spatial temporal evolutions of stress field in the tungsten target are obtained. While the ion current density reached 100A/cm2, the surface materials of tungsten target at the beam incident center was melted and then re-solidified due to the heat conduction after the end of a pulse. There exists the gradient of temperature in tungsten, therefore the thermal stress formed. Radial tensile stress is produced within the melting region, meanwhile outside the region compressive stress is formed; the boundary appears on the edge of the melting region. The stresses on the incidental surface of target are larger compared with the internal.

Abstract: The present article describes the combination of the correlation based transition model of Menter et al. with the Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) methodology. The interaction between transition model and DES or DDES method was investigated by T3A test case. The grid sensitivity of the combined methodology is discussed and the resolution is given. Then, the simulation of flow over foil of medium thick at stall angle was performed. The combined methodology produce results that have better agreement with experiment comparing to RANS transition model or fully turbulent DES/DDES alone. And the DDES based combined model shows a better agreement with experiment in the simulation of trailing edge separation comparing to DES based combined model.

Abstract: The effect of slender body on the rolling characteristics of a double delta wing is found by comparing the numerical simulation results of the double delta wing and wing-body configuration. The coupled computation system solving the Navier-Stokes equations and the rolling motion equation alternatively to obtain the unsteady vortical flow around the two configurations while rolling. The results conclusively showed the upwash effect of the slender body enhanced the energy of strake vortex and merged vortex.The aerodynamic lag of double delta wing is weak, contrarily, the time lag effect of the wing-body configuration is significant. The asymmetry vortices structure nearby the trailing edge are believed to be the main reason for the unsteady time lag effect.