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Wind load is the designed control load for super-large cooling tower (SLCT) structures. Studies on wind resistance of those structures have focused mainly on normal winds, not on the influence of strong typhoons, or in particular the values of suction. To study the suction distribution and action mechanism of flow fields in an SLCT in typhoon conditions, in this study a high temporal–spatial resolution simulation of Typhoon Megi was done using a mesoscale weather research and forecasting (WRF) model with a multiple nesting structure. The wind velocity profile in the simulated region was gained through least squares fit. The research object was the world's highest cooling tower (220 m) at the Lu'an power plant in Shanxi Province, China. Three-dimensional (3D) computational fluid dynamics (CFD) wind field simulations of this tower in normal-wind and typhoon conditions were done based on a mesoscale–microscale nesting technology. A comparative analysis on the 3D effect of wind loads on the internal surface of an SLCT in a typhoon was also done, as was a summary of the meridian and circumferential distribution laws of the internal pressure coefficients. Differences on flow field characteristics, pressure coefficients, drag coefficients, and wind resistance in the tower structure in normal-wind and typhoon conditions and relative causes were investigated. Finally, the recommended values of suction in an SLCT in typhoon conditions are proposed. Results demonstrate that a WRF–CFD coupling model can effectively simulate the near-surface 3D wind field of an SLCT in typhoon conditions. Compared with a normal wind, the high wind velocity and strong turbulence of a typhoon causes larger-scale vortices inside the cooling tower, a more turbulent airflow on the leeward side, and a longer development area of vortices. In typhoon conditions, the internal pressure coefficient of the tower increased when the ventilation rate of the louver was 15%, 30%, and 100%. The overall internal pressure coefficient was found to be −0.61 , −0.36 , −0.34 , and −0.42 when the ventilation rates of the louver are 0%, 15%, 30%, and 100%, respectively. [ABSTRACT FROM AUTHOR]

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Summary: A cylindrical–conical steel cooling tower (SCT) is a new type of very large thin‐walled, flexible structure. This study focused on the wind loads on the internal and outer surfaces of this structure and its wind‐induced responses. First, using the computational fluid dynamics method, the numerical wind tunnel was conducted to simulate a 189‐m‐high cylindrical–conical SCT, Asia's highest cooling tower that is still under construction. This numerical method was validated by comparing the wind pressures across typical cross sections of the tower model's cylindrical and conical segments with known standard curves. Based on this, the features of the airflow around the typical cross sections and its wake were extracted, and the distribution of mean wind loads along the internal and outer surfaces of the cylindrical and conical sections was obtained. Then functions for estimating the internal and outer surfaces shape factors of the cylindrical and conical segments were obtained by fitting to the simulated data. Furthermore, finite element method was used to analyze the static wind‐induced response of the cylindrical–conical SCT under internal pressure, external pressure, or both internal and external pressure. The effect patterns of internal pressures on the wind‐induced responses of the main tube, stiffening trusses, and auxiliary trusses of the tower were derived from the analysis results. Main findings of the research can provide a reference for design of very large cylindrical–conical SCTs for wind resistance in the future. [ABSTRACT FROM AUTHOR]

Featured Application: The main research conclusions of this paper could provide references for load prediction of similar wind turbine systems during the occurrence of typhoon, and deepen the understanding on meso/microscale wind field nesting mechanism. Compared with normal wind, typhoons may change the flow field surrounding wind turbines, thus influencing their wind-induced responses and stability. The existing typhoon theoretical model in the civil engineering field is too simplified. To address this problem, the WRF (Weather Research Forecasting) model was introduced for high-resolution simulation of the Typhoon "Nuri" firstly. Secondly, the typhoon field was analyzed, and the wind speed profile of the boundary layer was fitted. Meanwhile, the normal wind speed profile with the same wind speed of the typhoon speed profile at the gradient height of class B landform in the code was set. These two wind speed profiles were integrated into the UDF (User Defined Function). On this basis, a five-MW wind turbine in Shenzhen was chosen as the research object. The action mechanism of speed was streamlined and turbulence energy surrounding the wind turbine was disclosed by microscale CFD (Computational Fluid Dynamics) simulation. The influencing laws of a typhoon and normal wind on wind pressure distribution were compared. Finally, key attention was paid to analyzing the structural response, buckling stability, and ultimate bearing capacity of the wind turbine system. The research results demonstrated that typhoons increased the aerodynamic force and structural responses, and decreased the overall buckling stability and ultimate bearing capacity of the wind turbine. [ABSTRACT FROM AUTHOR]

The current work describes a novel technique for wind turbine rotor optimization. The aerodynamic design and optimization of wind turbine rotor can be achieved with different methods, such as the semi-empirical engineering methods and more accurate computational fluid dynamic (CFD) method. The CFD method often provides more detailed aerodynamics features during the design process. However, high computational cost limits the application, especially for rotor optimization purpose. In this paper, a CFD-based actuator disc (AD) model is used to represent turbulent flow over a wind turbine rotor. The rotor is modeled as a permeable disc of equivalent area where the forces from the blades are distributed on the circular disc. The AD model is coupled with a Reynolds Averaged Navier-Stokes (RANS) solver such that the thrust and power are simulated. The design variables are the shape parameters comprising the chord, the twist and the relative thickness of the wind turbine rotor blade. The comparative aerodynamic performance is analyzed between the original and optimized reference wind turbine rotor. The results showed that the optimization framework can be effectively and accurately utilized in enhancing the aerodynamic performance of the wind turbine rotor. [ABSTRACT FROM AUTHOR]

The complicated extreme marine environment is a great challenge against development of the offshore new floating photovoltaic (FPV) system. Such structural system is extremely easy to develop large displacement under the wind-wave coupling effect. In particular, it often develops large deformation failures at connectors between floating modules. It is urgent to explore the motion response laws of platform structure and reveal the energy dissipation mechanism between floating modules under wind-wave coupling effect. Based on an offshore floating photovoltaic demonstration base in Dongshan, Fujian Province, China, a new floating tube flexible photovoltaic (FTPV) four-module array model considering flexible connection was proposed. Firstly, the Computational Fluid Dynamics (CFD)/Computational Structural Dynamics (CSD) real-time two-way coupling simulation method based on overlapping grid technology was established. Subsequently, the dynamic response law of FTPV array under three environmental conditions of operation, design and extreme was compared and analyzed, as well as the characteristics of flexible connector load and mooring tension. Finally, the wind-wave induced energy dissipation mechanism between such new floating platform modules was discussed. Research results show that the FTPV array model based on flexible connectors established in this paper can reflect wind-wave induced dynamic response characteristics of such structures accurately. The displacement and rotating angle of the floating tube platform are mainly dominated by longitudinal and vertical displacements as well as pitch angle. The response of the wave-facing platform outside the array is greater than that of the internal region. Under extreme conditions, the pitch angle of the wave-facing side platform is 2.89 times that of the internal region. The load of the flexible connector and the mooring line are characteristic of positive skewing and multi-peak distribution, respectively. The vibration energy of the structure begins to transfer and diffuse with the increase of the environmental load. 70 % of vibration energy resonates in the low-frequency region and the rest 30 % dissipates in the high-frequency region. • A new floating tube flexible photovoltaic (FTPV) array model considering flexible connection is proposed. • The CFD/CSD real-time two-way coupling simulation method is established. • The dynamic response of the platform on the wave-facing side of the array is significantly greater. • The energy dissipation mechanism between new floating platform modules is revealed. [ABSTRACT FROM AUTHOR]

• • Compressibility effects of the IEA-15 MW wind turbine are examined. • • Compressibility effects have a significant effect on aerodynamic of the large wind turbine. • • A detailed analysis the compressible results for the tip airfoil and the rotor is presented. • • The compressibility effects on the wake of the IEA-15 MW turbine are discussed. • • Validations of the numerical method against experimental data are performed. With the gradual upscaling of offshore wind turbines, the blade size becomes large and the blade tip velocity reaches almost a Mach number of 0.3, the limit of the incompressible flow assumption. To simulate wind turbine flows, an incompressible solver was often a good choice as it gave good predictions and the Mach number of the wind turbine flows were small. When the Mach number is increased to be close to 0.3, the validity of incompressible flow may be questionable and thus needs to be checked. In this paper, an accurate wind turbine flow solution method is proposed to study the compressibility effects. First, the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is used as an example to verify the method at a small Mach number. Through a comparative analysis between the compressible, the incompressible numerical results, and experimental data, the proposed method is found with a good simulation accuracy. Next, the flow fields of the large wind turbine IEA-15 MW, under different wind conditions are simulated. The local Mach number, density and pressure coefficient at different blade cross-sections of the compressible results are analyzed and compared to its incompressible ones, and the influences of compressibility on the thrust, torque and power of the wind turbine are quantified. The results show that at the rated wind speed, the thrust of the compressible flow simulation is 1.40 % higher than that of the incompressible one, and the torque of the compressible flow simulation is nearly 11.07 % higher than that of the incompressible one. As a result, the compressibility effects are recommended to be added in future studies of large wind turbines. [ABSTRACT FROM AUTHOR]