Pub Date : 2024-11-28DOI: 10.1016/j.jweia.2024.105938
Yuhui Qin, Luca Caracoglia
This “Short Communication” investigates the dynamics of a torsional-flutter energy harvester in atmospheric winds with stationary turbulence. This apparatus is an example of a flutter mill, which operates by exploiting aeroelastic instability as a competitive alternative and as a renewable energy supply for one or few housing units. The apparatus has a rigid blade-airfoil that rotates about a pivot to generate flapping motion. Contrary to recent studies by the second author, the effect of random stationary turbulence on flutter onset is examined by an analytical approach, employed by Scanlan (1997) for bridge flutter analysis. Turbulence effect is simulated by suitably modifying the span-wise coherence equation of the aeroelastic load. The incipient flutter threshold is found as a function of turbulence properties. Various configurations are studied, i.e., pivot position, aspect ratio, turbulence coherence decay parameter and structural damping. The objective is to perform a thorough sensitivity analysis as the necessary premise for the planned, future examination of post-critical instability and operational efficiency of the harvester by suitable modeling and wind tunnel tests.
{"title":"Turbulence and flapping pivot axis effects on torsional flutter harvester efficiency by closed-form formula","authors":"Yuhui Qin, Luca Caracoglia","doi":"10.1016/j.jweia.2024.105938","DOIUrl":"10.1016/j.jweia.2024.105938","url":null,"abstract":"<div><div>This “Short Communication” investigates the dynamics of a torsional-flutter energy harvester in atmospheric winds with stationary turbulence. This apparatus is an example of a flutter mill, which operates by exploiting aeroelastic instability as a competitive alternative and as a renewable energy supply for one or few housing units. The apparatus has a rigid blade-airfoil that rotates about a pivot to generate flapping motion. Contrary to recent studies by the second author, the effect of random stationary turbulence on flutter onset is examined by an analytical approach, employed by Scanlan (1997) for bridge flutter analysis. Turbulence effect is simulated by suitably modifying the span-wise coherence equation of the aeroelastic load. The incipient flutter threshold is found as a function of turbulence properties. Various configurations are studied, i.e., pivot position, aspect ratio, turbulence coherence decay parameter and structural damping. The objective is to perform a thorough sensitivity analysis as the necessary premise for the planned, future examination of post-critical instability and operational efficiency of the harvester by suitable modeling and wind tunnel tests.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105938"},"PeriodicalIF":4.2,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.jweia.2024.105968
D.P.P. Meddage , D. Mohotti , Kasun Wijesooriya , C.K. Lee , K.C.S. Kwok
Machine learning research on estimating wind pressure on tall buildings has primarily focused on mean pressure predictions with limited studies on time history interpolations. In this study, a Deep Neural Network model (DNN) and Extreme Gradient Boost (XGB) were employed to interpolate the wind pressure time histories around the Commonwealth Aeronautical Advisory Research Council (CAARC) standard tall building for four wind directions. The results of a wind tunnel experiment conducted on a CAARC tall building model (1:300) were used to validate the Computational Fluid Dynamics (CFD) models. The pressure data extracted from the CFD model was used to train the DNN and XGB models. The results demonstrated that both XGB (R2 = 93%) and DNN (R2 = 96%) accurately modelled the wind pressure time histories around the CAARC building. Both models implicitly reconstructed flow features (e.g. pressure gradients, flow separation and conical vortex formations) on the building and compared well with the CFD results. Furthermore, the time-averaged pressure quantities obtained from machine learning models, and CFD models presented good agreement with wind tunnel results. The study shows that the DNN approach is a time-efficient and accurate complementary tool for interpolating wind pressure time histories on isolated tall buildings.
{"title":"Interpolating wind pressure time-histories around a tall building - A deep learning-based approach","authors":"D.P.P. Meddage , D. Mohotti , Kasun Wijesooriya , C.K. Lee , K.C.S. Kwok","doi":"10.1016/j.jweia.2024.105968","DOIUrl":"10.1016/j.jweia.2024.105968","url":null,"abstract":"<div><div>Machine learning research on estimating wind pressure on tall buildings has primarily focused on mean pressure predictions with limited studies on time history interpolations. In this study, a Deep Neural Network model (DNN) and Extreme Gradient Boost (XGB) were employed to interpolate the wind pressure time histories around the Commonwealth Aeronautical Advisory Research Council (CAARC) standard tall building for four wind directions. The results of a wind tunnel experiment conducted on a CAARC tall building model (1:300) were used to validate the Computational Fluid Dynamics (CFD) models. The pressure data extracted from the CFD model was used to train the DNN and XGB models. The results demonstrated that both XGB (R<sup>2</sup> = 93%) and DNN (R<sup>2</sup> = 96%) accurately modelled the wind pressure time histories around the CAARC building. Both models implicitly reconstructed flow features (e.g. pressure gradients, flow separation and conical vortex formations) on the building and compared well with the CFD results. Furthermore, the time-averaged pressure quantities obtained from machine learning models, and CFD models presented good agreement with wind tunnel results. The study shows that the DNN approach is a time-efficient and accurate complementary tool for interpolating wind pressure time histories on isolated tall buildings.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105968"},"PeriodicalIF":4.2,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Field measurements of wind pressure fluctuations during high-speed train passages were conducted by horizontally installing several flat plates above sleepers on a straight section of ballasted track. Wind pressure sensors were attached to the top and bottom surfaces of these plates to capture vertical wind pressure fluctuations. The primary objectives of this study are to investigate the nature of fluctuating wind pressure on flat plates during high-speed train passages, to estimate the wind loads acting on flat plates and porous screens on the track surface, and to evaluate their susceptibility to being lifted by wind loads. The results reveal that the differential pressure, which is the primary contributor to wind loads on the flat plates, is driven by the turbulent flow beneath the middle section of the train. Additionally, wind pressure data were used to estimate the wind loads (lift forces) acting on the flat plates and porous screens due to the turbulent flow, and to calculate the fixation loads required to prevent lifting.
{"title":"Wind loads on flat plates and porous screens installed on the track surface during the passage of high-speed trains","authors":"Yutaka Sakuma , Takashi Nakano , Tatsuya Inoue , Youta Kakizaki","doi":"10.1016/j.jweia.2024.105951","DOIUrl":"10.1016/j.jweia.2024.105951","url":null,"abstract":"<div><div>Field measurements of wind pressure fluctuations during high-speed train passages were conducted by horizontally installing several flat plates above sleepers on a straight section of ballasted track. Wind pressure sensors were attached to the top and bottom surfaces of these plates to capture vertical wind pressure fluctuations. The primary objectives of this study are to investigate the nature of fluctuating wind pressure on flat plates during high-speed train passages, to estimate the wind loads acting on flat plates and porous screens on the track surface, and to evaluate their susceptibility to being lifted by wind loads. The results reveal that the differential pressure, which is the primary contributor to wind loads on the flat plates, is driven by the turbulent flow beneath the middle section of the train. Additionally, wind pressure data were used to estimate the wind loads (lift forces) acting on the flat plates and porous screens due to the turbulent flow, and to calculate the fixation loads required to prevent lifting.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105951"},"PeriodicalIF":4.2,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.jweia.2024.105965
Wenhan Yang , Jiahao Dai , Wenli Chen
This study investigates the wind-induced vibrations (WIVs) of photovoltaic (PV) modules possessing unique characteristics such as lightweight construction, low frequency, and susceptibility to wind loads, in contrast to stationary PV systems installed on rooftops and ground surfaces. The complex interference effects within rows of flexible PV arrays were investigated under varying angles of wind attack (AOAs) and inter-row distances, specifically focusing on wind directions of 0° and 180°. A comparative analysis of the WIV of a single row was also conducted. The findings indicated that both single- and multi-row PV modules experience flutter instability as wind speeds increase, resulting in significant vibrations at wind directions of 0° and 180°. Vertical vortex-induced vibrations (VIVs) were observed in multi-row arrays at lower wind speeds prior to the onset of flutter instability, whereas no VIVs occurred in the single-row configuration. Within the three-row array, the middle row exhibited the most significant VIVs. An increase in AOA was found to correlate with elevated maximum VIV responses, wind speed, and vortex amplitude. Throughout various flutter instability scenarios, the third row consistently maintained stable. Notably, the critical wind speed for flutter was lower at a wind direction of 180°, and the VIV response was more pronounced compared to that observed at 0°.
{"title":"Experimental study on wind-induced vibration and aerodynamic interference effects of flexible photovoltaics","authors":"Wenhan Yang , Jiahao Dai , Wenli Chen","doi":"10.1016/j.jweia.2024.105965","DOIUrl":"10.1016/j.jweia.2024.105965","url":null,"abstract":"<div><div>This study investigates the wind-induced vibrations (WIVs) of photovoltaic (PV) modules possessing unique characteristics such as lightweight construction, low frequency, and susceptibility to wind loads, in contrast to stationary PV systems installed on rooftops and ground surfaces. The complex interference effects within rows of flexible PV arrays were investigated under varying angles of wind attack (AOAs) and inter-row distances, specifically focusing on wind directions of 0° and 180°. A comparative analysis of the WIV of a single row was also conducted. The findings indicated that both single- and multi-row PV modules experience flutter instability as wind speeds increase, resulting in significant vibrations at wind directions of 0° and 180°. Vertical vortex-induced vibrations (VIVs) were observed in multi-row arrays at lower wind speeds prior to the onset of flutter instability, whereas no VIVs occurred in the single-row configuration. Within the three-row array, the middle row exhibited the most significant VIVs. An increase in AOA was found to correlate with elevated maximum VIV responses, wind speed, and vortex amplitude. Throughout various flutter instability scenarios, the third row consistently maintained stable. Notably, the critical wind speed for flutter was lower at a wind direction of 180°, and the VIV response was more pronounced compared to that observed at 0°.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105965"},"PeriodicalIF":4.2,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 10.1016/j.jweia.2024.105962
DongHun Yeo , Yong Chul Kim
Accurate pressure measurements on structures via tubing systems during wind tunnel tests are crucial for precise estimation of wind loads. While calibration studies have traditionally focused on the contribution of tubing configuration to pressure distortion, they often overlook the effects of environmental parameter changes between the measurement of tubing response and aerodynamic pressure on structures. However, higher atmospheric pressure and lower ambient temperature can substantially increase tubing response distortion. To address this, this study introduces a dynamic calibration approach that accounts for such laboratory environmental changes. This method integrates the experimental transfer function, obtained under specific environmental conditions, with numerical estimates of the impact of environmental changes, to derive transfer functions for the desired environmental conditions. The effectiveness of this approach was validated using experimental and numerical transfer functions under two distinct environmental conditions. A case study for outdoor open-circuit laboratories revealed that neglecting environmental conditions during dynamic pressure calibrations could lead to overall average deviations in peak pressures across the channels on a building face of up to ≈ 5%, with local maximum deviations reaching ≈ 10%, respectively. Therefore, the proposed calibration method can significantly enhance the accuracy of pressure measurements via tubing systems, particularly when the tubing response and the pressures are measured under different environmental conditions.
{"title":"Calibration of pressures measured via tubing systems: Accounting for laboratory environmental variations between tubing response measurement and wind tunnel testing","authors":"DongHun Yeo , Yong Chul Kim","doi":"10.1016/j.jweia.2024.105962","DOIUrl":"10.1016/j.jweia.2024.105962","url":null,"abstract":"<div><div>Accurate pressure measurements on structures via tubing systems during wind tunnel tests are crucial for precise estimation of wind loads. While calibration studies have traditionally focused on the contribution of tubing configuration to pressure distortion, they often overlook the effects of environmental parameter changes between the measurement of tubing response and aerodynamic pressure on structures. However, higher atmospheric pressure and lower ambient temperature can substantially increase tubing response distortion. To address this, this study introduces a dynamic calibration approach that accounts for such laboratory environmental changes. This method integrates the experimental transfer function, obtained under specific environmental conditions, with numerical estimates of the impact of environmental changes, to derive transfer functions for the desired environmental conditions. The effectiveness of this approach was validated using experimental and numerical transfer functions under two distinct environmental conditions. A case study for outdoor open-circuit laboratories revealed that neglecting environmental conditions during dynamic pressure calibrations could lead to overall average deviations in peak pressures across the channels on a building face of up to ≈ 5%, with local maximum deviations reaching ≈ 10%, respectively. Therefore, the proposed calibration method can significantly enhance the accuracy of pressure measurements via tubing systems, particularly when the tubing response and the pressures are measured under different environmental conditions.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105962"},"PeriodicalIF":4.2,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.jweia.2024.105961
Wenhui Li , Yifan Gu , Weifeng Zhao , Yelin Deng , Xueliang Fan
As high-speed railway lines upgrade speeds or develop ultra-high-speed trains, traditional passive measures may struggle to address tunnel aerodynamics and passenger comfort. This study employs numerical calculations to investigate the aerodynamic mitigation of an ultra-high-speed train traveling at U = 600 km/h through a tunnel, utilizing active suction & blowing techniques in its streamlined nose sections. The simulation employs three-dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes (URANS) methods, validated against full-scale experiments. The effects of slot shapes, suction directions, activation periods, and the suction & blowing velocities (SBv) are examined. Results show that the slit design, normal direction, along with continuous activation, outperforms the rectangular design, parallel direction, and partial activation in reducing pressure peaks. Notably, maximum pressure peaks on the train and tunnel surface exhibit an exponential decay pattern as SBv increases. The micro-pressure wave 20 m from the tunnel exit decreases by 28% as SBv increases from 0 to 0.27U. Additionally, maximum slipstream peaks decrease linearly with SBv, with a more pronounced decline on the near side. While drag on the head and middle cars decreases linearly with increasing SBv, the tail car experiences a quadratic increase in drag, leading to an overall reduction in total drag. Furthermore, the reduction in side force and the positive lift of the tail car enhances train safety during tunnel passage. Overall, the hybrid suction & blowing technique offer promising prospects for enhancing the aerodynamic performance of high-speed maglev trains in the future.
{"title":"Alleviating tunnel aerodynamics through hybrid suction & blowing techniques applied to train nose sections","authors":"Wenhui Li , Yifan Gu , Weifeng Zhao , Yelin Deng , Xueliang Fan","doi":"10.1016/j.jweia.2024.105961","DOIUrl":"10.1016/j.jweia.2024.105961","url":null,"abstract":"<div><div>As high-speed railway lines upgrade speeds or develop ultra-high-speed trains, traditional passive measures may struggle to address tunnel aerodynamics and passenger comfort. This study employs numerical calculations to investigate the aerodynamic mitigation of an ultra-high-speed train traveling at <em>U</em> = 600 km/h through a tunnel, utilizing active suction & blowing techniques in its streamlined nose sections. The simulation employs three-dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes (URANS) methods, validated against full-scale experiments. The effects of slot shapes, suction directions, activation periods, and the suction & blowing velocities (SB<sub><em>v</em></sub>) are examined. Results show that the slit design, normal direction, along with continuous activation, outperforms the rectangular design, parallel direction, and partial activation in reducing pressure peaks. Notably, maximum pressure peaks on the train and tunnel surface exhibit an exponential decay pattern as SB<sub><em>v</em></sub> increases. The micro-pressure wave 20 m from the tunnel exit decreases by 28% as SB<sub><em>v</em></sub> increases from 0 to 0.27<em>U</em>. Additionally, maximum slipstream peaks decrease linearly with SB<sub><em>v</em></sub>, with a more pronounced decline on the near side. While drag on the head and middle cars decreases linearly with increasing SB<sub><em>v</em></sub>, the tail car experiences a quadratic increase in drag, leading to an overall reduction in total drag. Furthermore, the reduction in side force and the positive lift of the tail car enhances train safety during tunnel passage. Overall, the hybrid suction & blowing technique offer promising prospects for enhancing the aerodynamic performance of high-speed maglev trains in the future.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105961"},"PeriodicalIF":4.2,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.jweia.2024.105963
Houssam Al Sayegh , Arindam Gan Chowdhury , Ioannis Zisis , Amal Elawady , Johnny Estephan , Ameyu Tolera
Ballasted photovoltaic (PV) systems, in comparison to roof-anchored systems, are gaining notable popularity on commercial flat roofs due to the benefits they provide in evading roof penetration and the associated insulation issues. However, the accurate estimation of the aerodynamic uplift forces and their consequent effects on system responses presents a new design challenge. Moreover, possible dynamic effects, characterized by wind induced vibrations, are not accounted for in the design of PV systems in ASCE 7–22, potentially rendering the code design coefficients unconservative. Additionally, the available literature is based on roof anchored PV systems, while experiments in the literature utilizing ballasted PV systems which have distinct behavior and dynamic properties are very limited. The current study aims for a better evaluation of the behavior of ballasted PV systems and the mitigation efficiency of wind deflectors under simulated extreme wind events. To fill this knowledge gap, a 2 x 2 full-scale ballasted PV array model, equipped with wind deflectors and located on a model flat roofed structure was tested at the Wall of Wind (WOW) Experimental Facility (EF). The experimental campaign consisted of aerodynamic and dynamic tests, which permits pressure measurements on the panels under high Reynolds number flow, realistically influenced by the vibrations of the deflectors, as well as capturing of array's dynamic characteristics. The results show that wind deflectors effectively reduce both net area-averaged and point pressure coefficients, particularly under cornering wind directions. While the top surface pressures remained unchanged with the addition of deflectors, the bottom surface pressures experienced a substantial decrease, and the power spectral densities of pressure fluctuations were significantly reduced. Wind deflectors also proved to be efficient in reducing the correlation of instantaneous aerodynamic pressures occurring at different points, reducing the area-averaged peak pressures on the panels and, consequently, reducing net uplift on the entire array. Moreover, the aerodynamic loads were amplified by up to 30% due to dynamic effects caused by the wind induced vibration of the panels. Finally, from the failure assessment tests, a cascading failure mode was observed where the supports are consequently lifted before the entire system is flipped.
与固定在屋顶上的系统相比，压载光伏（PV）系统在商业平屋顶上越来越受欢迎，这是因为压载光伏系统具有避免屋顶穿透和相关隔热问题的优点。然而，如何准确估算空气动力上浮力及其对系统响应的影响是一项新的设计挑战。此外，ASCE 7-22 中的光伏系统设计并未考虑可能的动态效应（以风引起的振动为特征），这可能会使规范设计系数变得不严谨。此外，现有文献基于屋顶锚定光伏系统，而利用具有独特行为和动态特性的压载光伏系统进行的实验非常有限。目前的研究旨在更好地评估压载光伏系统的行为以及导风板在模拟极端风力事件下的减缓效率。为了填补这一知识空白，我们在风墙（WOW）实验设施（EF）测试了一个 2 x 2 全尺寸压载光伏阵列模型，该模型配备了导风板，位于一个平屋顶结构模型上。实验活动包括空气动力和动态测试，允许在高雷诺数流下对面板进行压力测量，真实地受到导流板振动的影响，并捕捉阵列的动态特性。结果表明，导风板能有效降低净面积平均压力系数和点压力系数，尤其是在转弯风向下。虽然增加导流板后顶面压力保持不变，但底面压力大幅下降，压力波动的功率谱密度也显著降低。事实证明，导风板还能有效降低不同点的瞬时空气动力压力的相关性，减少面板上的区域平均峰值压力，从而降低整个阵列的净上浮。此外，由于风引起的面板振动所产生的动态效应，空气动力载荷被放大了 30%。最后，从失效评估测试中观察到一种级联失效模式，即在整个系统翻转之前，支撑物会随之抬起。
{"title":"Full-scale experimental investigation of wind loading on ballasted photovoltaic arrays mounted on flat roofs","authors":"Houssam Al Sayegh , Arindam Gan Chowdhury , Ioannis Zisis , Amal Elawady , Johnny Estephan , Ameyu Tolera","doi":"10.1016/j.jweia.2024.105963","DOIUrl":"10.1016/j.jweia.2024.105963","url":null,"abstract":"<div><div>Ballasted photovoltaic (PV) systems, in comparison to roof-anchored systems, are gaining notable popularity on commercial flat roofs due to the benefits they provide in evading roof penetration and the associated insulation issues. However, the accurate estimation of the aerodynamic uplift forces and their consequent effects on system responses presents a new design challenge. Moreover, possible dynamic effects, characterized by wind induced vibrations, are not accounted for in the design of PV systems in ASCE 7–22, potentially rendering the code design coefficients unconservative. Additionally, the available literature is based on roof anchored PV systems, while experiments in the literature utilizing ballasted PV systems which have distinct behavior and dynamic properties are very limited. The current study aims for a better evaluation of the behavior of ballasted PV systems and the mitigation efficiency of wind deflectors under simulated extreme wind events. To fill this knowledge gap, a 2 x 2 full-scale ballasted PV array model, equipped with wind deflectors and located on a model flat roofed structure was tested at the Wall of Wind (WOW) Experimental Facility (EF). The experimental campaign consisted of aerodynamic and dynamic tests, which permits pressure measurements on the panels under high Reynolds number flow, realistically influenced by the vibrations of the deflectors, as well as capturing of array's dynamic characteristics. The results show that wind deflectors effectively reduce both net area-averaged and point pressure coefficients, particularly under cornering wind directions. While the top surface pressures remained unchanged with the addition of deflectors, the bottom surface pressures experienced a substantial decrease, and the power spectral densities of pressure fluctuations were significantly reduced. Wind deflectors also proved to be efficient in reducing the correlation of instantaneous aerodynamic pressures occurring at different points, reducing the area-averaged peak pressures on the panels and, consequently, reducing net uplift on the entire array. Moreover, the aerodynamic loads were amplified by up to 30% due to dynamic effects caused by the wind induced vibration of the panels. Finally, from the failure assessment tests, a cascading failure mode was observed where the supports are consequently lifted before the entire system is flipped.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105963"},"PeriodicalIF":4.2,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.jweia.2024.105960
Ning Zhao , Yu Wu , Fengbo Wu , Xu Wang , Shaomin Jia
Accurate simulation of non-Gaussian nonstationary wind speeds is a prerequisite for the wind resistant design of some nonlinear structures. Due to its efficiency, the time-varying autoregressive (TVAR) model has been extensively employed for simulating non-Gaussian nonstationary processes. Nevertheless, these simulation techniques based on TVAR exhibit suboptimal performance when confronted with nonstationary and highly non-Gaussian processes. Furthermore, they are unable to replicate the bimodal characteristics of specific wind speeds. This paper presents a new method for simulating univariate non-Gaussian nonstationary wind speeds using the TVAR model and the maximum entropy method. Herein, the connection between the statistical moments of input and output processes in TVAR is firstly derived. Secondly, the maximum entropy method is utilized to reconstruct the probability density function of input process and the time-varying translation function is determined. Finally, the translation process theory is applied to generate the input process, which is then input into the TVAR model to output the non-Gaussian nonstationary wind speed. The numerical results demonstrate that the proposed method exhibits superior simulation accuracy for nonstationary and strongly non-Gaussian wind speed processes. Furthermore, it is capable of capturing the bimodal characteristics of certain hardening non-Gaussian nonstationary wind speeds and possesses a broader range of applications.
精确模拟非高斯非平稳风速是一些非线性结构抗风设计的先决条件。时变自回归（TVAR）模型因其高效性而被广泛用于模拟非高斯非平稳过程。然而，这些基于 TVAR 的仿真技术在面对非平稳和高度非高斯过程时表现出了次优性能。此外，它们也无法复制特定风速的双峰特性。本文提出了一种利用 TVAR 模型和最大熵法模拟单变量非高斯非平稳风速的新方法。本文首先推导了 TVAR 中输入和输出过程统计矩之间的联系。其次，利用最大熵法重建输入过程的概率密度函数，并确定时变平移函数。最后，应用平移过程理论生成输入过程，然后将输入过程输入 TVAR 模型，输出非高斯非平稳风速。数值结果表明，所提出的方法对非平稳和强非高斯风速过程具有极高的模拟精度。此外，它还能捕捉某些硬化非高斯非静态风速的双峰特征，具有更广泛的应用前景。
{"title":"Non-Gaussian non-stationary wind speed simulation based on time-varying autoregressive model and maximum entropy method","authors":"Ning Zhao , Yu Wu , Fengbo Wu , Xu Wang , Shaomin Jia","doi":"10.1016/j.jweia.2024.105960","DOIUrl":"10.1016/j.jweia.2024.105960","url":null,"abstract":"<div><div>Accurate simulation of non-Gaussian nonstationary wind speeds is a prerequisite for the wind resistant design of some nonlinear structures. Due to its efficiency, the time-varying autoregressive (TVAR) model has been extensively employed for simulating non-Gaussian nonstationary processes. Nevertheless, these simulation techniques based on TVAR exhibit suboptimal performance when confronted with nonstationary and highly non-Gaussian processes. Furthermore, they are unable to replicate the bimodal characteristics of specific wind speeds. This paper presents a new method for simulating univariate non-Gaussian nonstationary wind speeds using the TVAR model and the maximum entropy method. Herein, the connection between the statistical moments of input and output processes in TVAR is firstly derived. Secondly, the maximum entropy method is utilized to reconstruct the probability density function of input process and the time-varying translation function is determined. Finally, the translation process theory is applied to generate the input process, which is then input into the TVAR model to output the non-Gaussian nonstationary wind speed. The numerical results demonstrate that the proposed method exhibits superior simulation accuracy for nonstationary and strongly non-Gaussian wind speed processes. Furthermore, it is capable of capturing the bimodal characteristics of certain hardening non-Gaussian nonstationary wind speeds and possesses a broader range of applications.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105960"},"PeriodicalIF":4.2,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.jweia.2024.105959
Ya'nan Tang , Jian Yang , Zhongdong Duan , Jinping Ou , Feng Xu , Guirong Yan , Ming Nie
Effective preparedness and prompt restoration efforts are crucial to minimize losses in typhoon-prone areas. Achieving this necessitates reliable estimates of structural damage before typhoons make landfall. This paper develops a damage assessment framework for estimating structural damage in power transportation networks. Within this framework, a typhoon wind field model, a reliability-based fragility model, and a procedure to estimate the damaged number of towers or poles are integrated. A key feature of the framework is a proposed scale factor to correct the inherent bias in the wind field model, with its stochastic nature characterized by probabilistic models based on dense typhoon wind observations. The proposed scale factor is then incorporated into the fragility model to address the variability of the fragility model. The developed framework is applied to assess the damage to concrete poles in the 10 kV distribution networks of Zhanjiang, Guangdong Province, China during three typhoon events. For these events, the predicted number of failed poles has a relative mean error of less than 20% compared to actual values, highlighting the effectiveness of the scale factor in improving wind field model accuracy. The variability in the predicted number of failures is also quantified.
{"title":"Typhoon damage assessment of power transportation networks using bias-corrected typhoon wind field with dense wind measurements","authors":"Ya'nan Tang , Jian Yang , Zhongdong Duan , Jinping Ou , Feng Xu , Guirong Yan , Ming Nie","doi":"10.1016/j.jweia.2024.105959","DOIUrl":"10.1016/j.jweia.2024.105959","url":null,"abstract":"<div><div>Effective preparedness and prompt restoration efforts are crucial to minimize losses in typhoon-prone areas. Achieving this necessitates reliable estimates of structural damage before typhoons make landfall. This paper develops a damage assessment framework for estimating structural damage in power transportation networks. Within this framework, a typhoon wind field model, a reliability-based fragility model, and a procedure to estimate the damaged number of towers or poles are integrated. A key feature of the framework is a proposed scale factor to correct the inherent bias in the wind field model, with its stochastic nature characterized by probabilistic models based on dense typhoon wind observations. The proposed scale factor is then incorporated into the fragility model to address the variability of the fragility model. The developed framework is applied to assess the damage to concrete poles in the 10 kV distribution networks of Zhanjiang, Guangdong Province, China during three typhoon events. For these events, the predicted number of failed poles has a relative mean error of less than 20% compared to actual values, highlighting the effectiveness of the scale factor in improving wind field model accuracy. The variability in the predicted number of failures is also quantified.</div></div>","PeriodicalId":54752,"journal":{"name":"Journal of Wind Engineering and Industrial Aerodynamics","volume":"256 ","pages":"Article 105959"},"PeriodicalIF":4.2,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.jweia.2024.105953
Tomáš Hlavatý , Martin Isoz , Marek Belda , Václav Uruba , Pavel Procházka
To evaluate the suitability of the proper orthogonal decomposition (POD) for validating a simulated flow dynamics, we selected the flow in the wake behind a circular cylinder at Reynolds number of as a well studied canonical problem. The flow was simulated via - SST detached-eddy simulation (DES) and, on selected planes of measurement (PoM), investigated experimentally by a time-resolved variant of the particle image velocimetry (PIV) and stereo-PIV methods. A standard model validation comprising, among other, comparison of the drag coefficient, or separation angle, and of the averaged flow properties and turbulence spectra, was carried out. Subsequently, both the PIV and the numerical data on the selected planes in the geometry were analyzed by POD, and a fully 3D POD analysis of the numerical data was used to evaluate the credibility of the planar POD as a tool for dynamic model validation.
为了评估适当正交分解（POD）是否适用于验证模拟流动动力学，我们选择了雷诺数为 ≈5000 的圆柱体后的尾流作为一个经过深入研究的典型问题。通过 k-ω SST 离散涡流模拟（DES）对流动进行了模拟，并在选定的测量平面（PoM）上通过粒子图像测速（PIV）和立体 PIV 方法的时间分辨变体进行了实验研究。标准模型验证包括阻力系数或分离角的比较，以及平均流动特性和湍流频谱的比较。随后，对几何图形中选定平面上的 PIV 和数值数据进行了 POD 分析，并对数值数据进行了全 3D POD 分析，以评估平面 POD 作为动态模型验证工具的可信度。
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