Numerical Tools Dedicated to Wind Engineering in Large Urban Area

This paper presents a global methodology to compute wind flow in complex urban areas in order to assess wind pedestrian comfort, wind energy, wind safety or natural ventilation potential. The numerical tool presented here is composed of a CFD soft-ware suite covering both regional scale (20 km) and urban scale (1km), and able to model the wind in any complex terrains and in large urban environments. Examples are presented in the paper in order to show the advantages of the methodology for urban designers.

Light-Weight Design of CRH Wind Deflector Panels based on Woven Textile Sandwich Composites

The woven textile sandwich composite（WTSC） is a promising lightweight composite.In bending,two competing core shearing failure modes reduce the strength;deflection induced by the core shearing deformation reduces the flexural rigidity.To replace a solid composite laminate,the span of WTSC panel must be greater than a critical value,which was deduced on the condition that the load capacity and flexural rigidity of the WTSC panel are equal to those of the composite laminate.Three WTSC panels were tested in bending,so that the failure modes were observed,and the critical spans were determined.Using the alternative design method,the WTSC based wind deflector with reduced weight has been fabricated and mounted on the CRH（China Railway High-speed）.

Study on the Rotor Design Method for a Small Propeller-Type Wind Turbine

Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A.

Numerical Optimization and Noise Analysis of High-Tip-SpeedWind Turbine

With lower turbulence and less rigorous restrictions on noise levels,offshore wind farms provide favourable conditions for the development of high-tip-speed wind turbines.In this study,the multi-objective optimization is presented for a 5MW wind turbine design and the effects of high tip speed on power output,cost and noise are analysed.In order to improve the convergence and efficiency of optimization,a novel type of gradient-based multi-objective evolutionary algorithm is proposed based on uniform decomposition and differential evolution.Optimization examples of the wind turbines indicate that the new algorithm can obtain uniformly distributed optimal solutions and this algorithm outperforms the conventional evolutionary algorithms in convergence and optimization efficiency.For the 5MW wind turbines designed,increasing the tip speed can greatly reduce the cost of energy(COE).When the tip speed increases from 80m/s to 100m/s,under the same annual energy production,the COE decreases by 3.2%in a class I wind farm and by 5.1%in a class III one,respectively,while the sound pressure level increases by a maximum of 4.4dB with the class III wind farm case.