Techno Press
Tp_Editing System.E (TES.E)
Login Search


was
 
CONTENTS
Volume 24, Number 3, March 2017
 

Abstract
The unsteady flow field disturbance between the blades and tower is one of the primary factors affecting the aerodynamic performance of wind turbine. Based on the research object of a 3MW horizontal axis wind turbine which was developed independently by Nanjing University of Aeronautics and Astronautics, numerical simulation on the aerodynamic performance of wind turbine system in halt state with blades in different position was conducted using large eddy simulation (LES) method. Based on the 3D unsteady numerical simulation results in a total of eight conditions (determined by the relative position with the tower during the complete rotation process of the blade), the characteristics of wind pressure distributions of the wind turbine system and action mechanism of surrounding flow field were analysed. The effect of different position of blades on the aerodynamic performance of wind turbine in halt state as well as the disturbance effect was evaluated. Results of the study showed that the halt position of blades had significant effect on the wind pressure distribution of the wind turbine system as well as the characteristics of flow around. Relevant conclusions from this study provided reference for the wind-resistant design of large scale wind turbine system in different halt states.

Key Words
wind turbine system; halt state; blade position; large eddy simulation; aerodynamic performance; parameter analysis

Address
Shitang Ke: Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;
State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Wei Yu and Tongguang Wang: Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Yaojun Ge: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Yukio Tamura: Wind Engineering Research Center, Tokyo Polytechnic University, 1583 Iiyama, Atsugi,
Kanagawa 243-0297, Japan



Abstract
By using numerical simulation, vast and detailed information and observation of the physics of flow over a train model can be obtained. However, the accuracy of the numerical results is questionable as it is affected by grid convergence error. This paper describes a systematic method of computational grid refinement for the Unsteady Reynolds Navier-Stokes (URANS) of flow around a generic model of trains using the OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is investigated in this paper. This involves solutions on three different grid refinements, namely fine, medium, and coarse grids to investigate the effect of grid dependency. The level of grid independence is evaluated using a form of Richardson extrapolation and Grid Convergence Index (GCI). This is done by comparing the GCI results of various parameters between different levels of mesh resolutions. In this study, monotonic convergence criteria were achieved, indicating that the grid convergence error was progressively reduced. The fine grid resolution\'s GCI value was less than 1%. The results from a simulation of the finest grid resolution, which includes pressure coefficient, drag coefficient and flow visualization, are presented and compared to previous available data.

Key Words
Grid Convergence Index; generic train; CFD simulation; OpenFOAM; flow physics

Address
Izuan Amin Ishak, Mohamed Sukri Mat Ali and Sheikh Ahmad Zaki Shaikh Salim: Wind Engineering, Malaysia-Japan International Institute of Technology, UTM Kuala Lumpur, Malaysia

Abstract
An efficient and accurate algorithm is proposed to estimate flutter safety factor of suspension bridges satisfying prescribed reliability levels. Uncertainties which arise from the basic wind speed at the bridge deck location, critical flutter velocity, the wind conversion factor from a scaled model to the prototype structure and the gust speed factor are incorporated. The proposed algorithm integrates the concepts of the inverse reliability method and the calculation method of the critical flutter velocity of suspension bridges. The unique feature of the proposed method is that it offers a tool for flutter safety assessment of suspension bridges, when the reliability level is specified as a target to be satisfied by the designer. Accuracy and efficiency of this method with reference to three example suspension bridges is studied and numerical results validate its superiority over conventional deterministic method. Finally, the effects of various parameters on the flutter safety factor of suspension bridges are also investigated.

Key Words
inverse reliability method; flutter safety factor; suspension bridges; target reliability index; uncertainties

Address
Jin Cheng: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China;
Department of Bridge Engineering, Tongji University, Shanghai, 200092, China
Fenghui Dong: Department of Bridge Engineering, Tongji University, Shanghai, 200092, China


Abstract
This paper addresses vibration and instability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced pipes conveying viscous fluid. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Flugge shell model is applied for mathematical modeling of structure. Based on energy method and Hamilton

Key Words
nonlinear vibration; Flugge shell model; orthotropic Pasternak medium; FG-CNT-reinforced pipe; DQM

Address
Department of Mechanical Engineering, Sari Branch, Islamic Azad University, Sari, Iran

Abstract
In the present study, a new assessment simulation of ride safety based on a new wind-traffic-pavement-bridge coupled vibration system is developed considering stochastic characteristics of traffic flow and bridge surface. Compared to existing simulation models, the new assessment simulation focuses on introducing the more realistic three-dimensional vehicle model, stochastic characteristics of traffic, vehicle accident criteria, and bridge surface conditions. A three-dimensional vehicle model with 24 degrees-of-freedoms (DOFs) is presented. A cellular automaton (CA) model and the surface roughness are introduced. The bridge deck pavement is modeled as a boundless Euler-Bernoulli beam supported on the Kelvin model. The wind-traffic-pavement-bridge coupled equations are established by combining the equations of both the vehicles in traffic, pavement, and bridge using the displacement and interaction force relationship at the patch contact. The numerical simulation shows that the proposed method can simulate rationally useful assessment and prevention information for traffic, and define appropriate safe driving speed limits for vulnerable vehicles under normal traffic and bridge surface conditions.

Key Words
bridge; traffic; vibration; ride safety; bridge surface

Address
Yin Xinfeng, Liu Yang and Chen S.R.: School of Civil Engineering and Architecture, Changsha University of Science & Technology, Changsha 410004, Hunan, China

Chen S.R.: Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80525, USA


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com