Vita, GiulioVranesevic, Kristina KostadinovicBordas, Stephane P. A.Glumac, Anina Sarkic...
18页
查看更多>>摘要：To understand the favourable locations for maximum yield of urban wind energy, understanding the flow pattern on the roof region of high-rise buildings is crucial. However, very few studies in the literature report on the wind energy resource using high-fidelity methods, which combined with the lack of wind tunnel investigations, explains the failure of urban wind energy as a viable contributor to the renewable energy mix. This work aims at proposing a strategy for the reliable evaluation of the wind energy resource by building on validated Large Eddy Simulation and performance maps based on the wind power density and the turbulence intensity above the roof of a prismatic 1:3 square building. Analyses include the effect of flat and decked roof shapes in two wind directions. Results around the facade reveal zones of accelerated flow close to separation edges, while above the roof, a higher potential is noticeable at 45 degrees, than at 0 degrees. Decking of the roof shows insensitivity to the change in wind direction. The tested methodology can be extended to other configurations to predict the wind energy potential as well as used to indicate the positioning of wind turbines in the built environment.
Meddage, D. P. P.Ekanayake, I. U.Weerasuriya, A. U.Lewangamage, C. S....
20页
查看更多>>摘要：This study used explainable machine learning (XML), a new branch of Machine Learning (ML), to elucidate how ML models make predictions. Three tree-based regression models, Decision Tree (DT), Random Forest (RF), and Extreme Gradient Boost (XGB), were used to predict the normalized mean (Cp,mean), fluctuating (Cp,rms), minimum (Cp,min), and maximum (Cp,max) external wind pressure coefficients of a low-rise building with fixed dimensions in urban-like settings for several wind incidence angles. Two types of XML were used - first, an intrinsic explainable method, which relies on the DT structure to explain the inner workings of the model, and second, SHAP (SHapley Additive exPlanations), a post-hoc explanation technique used particularly for the structurally complex XGB. The intrinsic explainable method proved incapable of explaining the deep tree structure of the DT, but SHAP provided valuable insights by revealing various degrees of positive and negative contributions of certain geometric parameters, the wind incidence angle, and the density of buildings that surround a low-rise building. SHAP also illustrated the relationships between the above factors and wind pressure, and its explanations were in line with what is generally accepted in wind engineering, thus confirming the causality of the ML model's predictions.
查看更多>>摘要：This study presents an experimental investigation of the aerodynamic force coefficients for a bridge deck sitting above water waves based on wind tunnel and wave flume tests. A deck sectional model with a scale ratio of 1:60 was manufactured and tests were performed in a wind tunnel and wave flume. A test system that conducts the aerodynamic tests was built, and the aerodynamic forces of the deck sectional model in the wind-only field and wind-wave coupled field were then measured. The studied parameters include four regular wave heights (H), four bridge clearances (a), three wind speeds (U), three regular wave periods (T), and nine angles of attack in the range -12 degrees <= alpha <= +12 degrees. The test results indicated that the time histories of the aerodynamic force coefficients of the deck sectional model change periodically in the wind-wave coupled field, and the variation periods are approximately consistent with the regular wave period. The smaller the relative bridge clearance (a/H), the more significant the effect of the regular wave on the aerodynamic forces of the deck sectional model. The differences among the maximum aerodynamic force coefficients of the deck sectional model in the wind-wave cases for different relative bridge clearances (a/H) are significantly larger than those for different relative propagation velocities (U/c) and different parameter groups (T similar to (lambda, c)), so are the differences among the minimum aerodynamic force coefficients.
查看更多>>摘要：An IR thermography-based detection and localization of turbulent flow separation at an operating wind turbine is presented and verified for the first time. Turbulent flow separation limits the efficiency of wind turbines and causes increased structural loads and acoustic emissions. IR thermography is an established measurement method for stall detection in wind tunnel experiments, however a transfer to operating wind turbines is an open research question. With respect to the state of the art for thermographic stall detection, a novel thermographic measurement approach for a feature-based stall detection is presented, verified and applied on wind turbines. The measurement approach evaluates the surface temperature response to unsteady inflow conditions and enables an unambiguous detection of flow separation by means of temperature fluctuation maxima in the regions of flow transition as well as an increasing temperature fluctuation within the separated flow region. Finally, the aim to obtain a non-invasive and in-process detection of flow separation on an operating wind turbine with IR thermography is achieved and verified using tufts flow visualization.
查看更多>>摘要：With the wide use of noise barriers along high-speed railways, the aerodynamic problems of noise barrier caused by high-speed train operation become increasingly prominent. At present, the commonly used noise barrier types of high-speed railway can be classified as fully enclosed and semi-closed (inverted 'L' type). The model test of high-speed moving train with scale ratio of 1:16.8 was conducted, and the temporal and spatial laws of aerodynamic pressure of fully enclosed and semi-enclosed noise barriers were compared. These processes were performed to study the difference in the aerodynamic pressure characteristics of noise barriers when high-speed trains at speeds of 350 km/h pass through the two types of noise barriers. On the basis of large eddy simulation turbulence model and 'mosaic' grid technology, the corresponding 3D computational fluid dynamics numerical model of train-noise barrier-bridge was established, and the corresponding improvement schemes were proposed to solve the phenomenon of unreasonable pulsation pressure distribution of fully enclosed and semi-enclosed noise barriers. The pressure relief mechanism of the pressure relief hole on the fully enclosed noise barrier and the buffer mechanism of the buffer structure at the end of the semi-enclosed noise barrier are revealed from the perspective of flow field. The main results show that: (1) Compression wave and expansion wave are the key factors affecting the change in the peak pressure inside the fully enclosed noise barrier, while the pressure of the semi-enclosed noise barrier is directly affected by slipstream of the train. (2) The pressure amplitude in the middle of the fully enclosed noise barrier is 2.1-2.7 times of that at the two ends. The amplitude of transverse force at the two ends of semi-enclosed noise barrier is 1.2-1.4 times of that in the middle. (3) In the longitudinal direction of the noise barrier near the train side, the pressure of the measuring point of the semi-enclosed noise barrier decreases with the increase in the measuring point height; The pressure in the middle section of the fully enclosed noise barrier is unaffected by the height of the measuring point. (4) A triangular buffer structure can effectively alleviate the unreasonable vertical pressure distribution phenomenon caused by the train bursting into the semi-closed noise barrier, and the reduction rate of the transverse force amplitude of the end noise barrier is as high as 21.44%. (5) The pressure relief scheme of three holes can effectively alleviate the phenomenon of excessive pressure amplitude in the middle of the fully enclosed noise barrier caused by the passing train, and the reduction rate of pressure amplitude can reach up to 60.5%. The pressure relief holes with an area of 1.7 H x 1.7 H are arranged at 0.25, 0.5, and 0.75 L, where L is the longitudinal length of the noise barrier.
查看更多>>摘要：This paper presents the analysis of full-scale measurement of the Leatop Plaza (303 m) under a super typhoon (i. e., Mangkhut), during which field data such as wind speed, wind direction, and wind-excited structural response were recorded. The modal properties, e.g., natural frequency, damping ratios, of the building at consecutive short time windows are identified using a Bayesian frequency domain approach, which provides information on the most probable value and identification (estimation) uncertainty. Time-varying and amplitude-dependent features of natural frequencies and damping ratios are investigated, taking into account identification uncertainty. The power spectral density of modal wind load identified from field data also provides an opportunity for bench marking with the prediction from wind tunnel tests developed at the design stage. As Leatop Plaza has similar stiffness and mass properties along the two horizontal directions, the frequencies of corresponding vibration modes are very similar, which inevitably poses a challenge to modal identification. Issues associated with closely spaced modes are highlighted and further studied via a recently developed theory of achievable precision of ambient modal identification.
查看更多>>摘要：Structural vibrations caused by turbulent wind and their contributions to fatigue are still difficult to predict concisely. With regard to fatigue life prognosis, different methods have been discussed in recent years -but general reliable guidance for the determination of stress cycle counts allowing for damage accumulation concepts (besides individual calculations in the time-domain) is still not available. A parameter study in time and frequency domain has been performed to discover the dependencies of wind conditions and structural properties on the resulting cycle count distributions. The findings allowed to formulate of a first simplification approach (level 1), connecting significant parameters to realistic cycle count distributions for arbitrary wind conditions and dynamic properties of the structure. At this stage, the usage of arbitrary Acr-N resistance curves is preserved to determine the expected structural damage, but a detailed calculation in time-or frequency domain can be waived on this level. In a second (level 2) simplification, a unique delta sigma-N resistance curve with a constant slope and no fatigue endurance limit has been assumed. Due to this restriction, the damage prediction derived is functionally dependent on the ratio of present maximum structural stress delta s(max) and the detail category delta sigma(c). Consequently, damage equivalence factors K-F are introduced on this level, which allows for a straightforward and safe-side estimation of the expected fatigue damage. Recommendations have been compared to detailed time domain solutions, and examples have been provided to apply both introduced concepts.
查看更多>>摘要：As one of the most destructive natural disasters, Tropical Cyclone (TC) can cause severe casualties and economic losses almost every year in TC-prone areas. For the prevention and reduction of TC-induced disasters in wind engineering, it is of vital importance to forecast TC's intensity and track both accurately and efficiently. Although great achievements have been made in this field, it remains a challenge to balance accuracy and efficiency during the forecast. In recent years, deep learning techniques have gained fast development and demonstrated huge application potential in various fields. This article presents a study on the short-term prediction of TCs in Northwest Pacific basin via the newly developed Convolutional Long and Short Term Memory (ConvLSTM) network which is able to extract both time-related correlations (involved in the sequence of a single parameter) and parameter-related correlations (among different parameters) from input information of different feature parameters. Results demonstrate that the proposed ConvLSTM model has good performance in terms of prediction accuracy and working stability. Through comparison, it is also suggested the proposed model works better than the standard LSTM model. Meanwhile, unlike most dynamic methods which require expensive computational resources, the proposed model can be operated conveniently and economically. Thus, it can be readily applied for engineering practices.
Kia, SeyedahmadFlesch, Thomas K.Freeman, Brian S.Aliabadi, Amir A....
16页
查看更多>>摘要：Inverse Dispersion Modelling (IDM) establishes a relationship between an air pollutant concentration downstream of a source and the strength of an emission source by reliance on an air dispersion model. Thus, ideally measuring pollutant concentration downstream is sufficient to infer the emission source strength. However, the accuracy of IDM relies on the accuracy of the underlying air dispersion model. Diagnostic dispersion models face difficulty when applied to complex terrains of open-pit mines. To elucidate such difficulties and their causes, the diagnostic CALifornia PUFF (CALPUFF) model is compared to a Computational Fluid Dynamics-Lagrangian Stochastic (CFD-LS) model for quantifying the short-range dispersion of fugitive gases released from a synthetic open-pit mine. Two mine depths (100-500 m) and three thermal stability conditions (stable-neutral-unstable) are investigated. In all cases the surface concentration predicted by the two models are in disagreement, regardless of CALPUFF model setup. Overall, less than 30% of receptor points predict the concentration within a factor of two of CFD-LS simulations (FAC2 < 0.3). Model differences appear to be related to the internal algorithms of the CALPUFF model to predict the wind field appropriately. The results should caution practitioners considering diagnostic models for IDM analysis over complex terrain.
查看更多>>摘要：Power generation using renewable energy, specifically from wind power is reliable, affordable and pollution-free energy. Turbine is the basic component in a wind energy conversion system. This research article, is on Savonius vertical axis wind turbine (VAWT) installed on building rooftops targeting power extraction from low wind speed. The novel idea proposed in this work is attachment of channel confinement with local waviness to increase drag on the advancing blade. The study has been carried out using ANSYS Fluent 2019 R3 software. The systematic study conducted on the effect of location of turbine in the wavy channel has been presented. The new configuration has improved the turbine output significantly. The maximum increase in power coefficient is 44.67% for waviness confinement channel than plain confinement channel.
NSTL
Elsevier