Under building opening conditions, wind-induced internal pressure may significantly alter the structural behavior of the building envelope. This study investigates the dynamic characteristics and response patterns of wind-induced internal pressure through transient CFD simulations, proposing a computational method for quantifying Helmholtz resonance frequency in buildings with openings. The influence of opening size, quantity, and location on dynamic characteristics and wind load responses was systematically examined. Key findings reveal: 1) The proposed method effectively predicts Helmholtz resonance frequencies, demonstrating consistent trends with theoretical models; 2) The Helmholtz frequency exhibits strong linear correlation with opening area-larger openings increase Helmholtz frequencies while reducing damping ratios, with leeward openings substantially diminishing damping ratios; 3) Changes in indoor and outdoor pressures often exhibit an opposite trend to the net pressure, while an increase in the damping ratio typically leads to higher internal pressure. These results provide critical theoretical support for determining wind loads on openable curtain wall panels and roof penetrations in architectural engineering.
The vortex-induced vibration (VIV) is prone to occur in the long-span bridges in operation within the specific wind speed range, which can lead to the issues of structural durability and driving comfort. To quantitatively assess driving comfort and limit values of VIV based on comfort criteria, a method for analyzing the driving comfort of long span bridges under VIV is proposed using Matlab/Simulink modules in this study. Based on the established method, the VIVs of the Humen Bridge in China and the corresponding traffic control measures are analyzed based on human comfort levels. Firstly, a four-wheel stochastic road excitation model, an eight-degree-of-freedom vehicle model, and a nine-degree-of-freedom seated human body model are established, respectively. Secondly, combined with the established models, the VIV response is converted into wheel excitation and the root mean square (RMS) of comprehensive weighted acceleration of the human body is obtained. Furthermore, based on the VIV observed on the Humen Bridge in China, the driving comfort of passengers and limit value of VIV are further studied by the finite element software LS-DYNA and the established models in this study. The results show that the RMS of the human body in the car calculated with the proposed method in this study agree well with the results of commercial software LS-DYNA. Moreover, by reducing vehicle speed, the comfort level of human body during driving can change from 'A Little Uncomfortable' to 'Not Uncomfortable', ensuring the normal operation of the Humen Bridge and preventing disruptions caused by traffic closures.
Awind power generation system consists electrical, mechanical, aerodynamics and structural dynamics in its model. However, the most of the reported system dynamic models include either electrical and mechanical dynamics or structural and aerodynamics. This may sometimes lead to imperfect analysis when someone is observing impact of the electrical disturbance onto the structural dynamics. Therefore, this paper presents the complete model of the wind power system considering aerodynamics and structural dynamics of the blade along with the electrical and mechanical power balance. Also, the detection of the blade vibration using electrical measurements have been performed through a nonlinear estimator, named Unscented Kalman Filter (UKF) which may further helps to design a controller without additional sensors. The estimation of the impact of the electrical disturbance onto the blade vibrations provide insights into the early detection and observation of the blade vibrations. It was observed that a frequency of edgewise vibrations of the blades of 1.159 Hz other than the fundamental frequency corresponding to the speed of the rotation of the wind turbine, is introduced when the system subjected to an electrical disturbance and it should be taken care of during the control design. Further, the UKF estimates these vibrations perfectly, closely matching with the actual frequency with an estimation error of only 0.35%. The structural model is prepared using Euler-Lagrangian method (ELM) while Blade Element Momentum method (BEMM) is used for aerodynamic power and forces. The structural and blade geometry data of NREL's 5-MW wind turbine have been used for the simulation while the structural model of the wind turbine have been validated using NREL's tool FAST.
Wind-driven rain (WDR) research has predominantly targeted building facades and low-rise buildings, leaving gaps in understanding its effects on large-span roof structures. This study addresses this by analyzing WDR impacts on roofs through computational modeling, focusing on rainfall intensity, rise-to-span ratios, and aerodynamic interactions. The study focuses on the immediate mechanical loading effects of WDR events on intact roof structures. Firstly, raindrop catch ratio evaluations to quantify WDR distribution across curved roofs. Secondly, pressure coefficient comparisons between WDR and wind loading under varying geometries and wind angles. Finally, turbulence intensity assessments on low-sloped roofs using point vortex and Stokes theories. Results demonstrate that 95% of WDR impact was concentrated within 50%-60% of the windward roof surface, diminishing with higher rainfall intensities. Compared to wind-only conditions, WDR results in significantly altered pressure distributions and turbulence patterns, with more pronounced effects observed on curved roofs. On the low-sloped roofs, WDR induces stronger turbulence under equivalent wind angles. These findings demonstrate the spatial non-uniformity of WDR and its compounded interaction with wind loads, challenging conventional wind-resistant design assumptions. Roof-covering type exerts only a marginal influence on wind-driven-rain characteristics. The study underscores the necessity of integrating coupled wind-rain simulations into large-span roof engineering to enhance weather resilience. By bridging gaps between architectural aerodynamics and precipitation dynamics, this work provides a foundational framework for optimizing roof geometries and improving predictive models against multi-hazard environmental conditions.
Short-term wind speed forecasting is critical for dynamic line rating (DLR) to maximize grid capacity, yet existing methods face challenges in handling nonlinearity and stochasticity. We propose a novel hybrid model integrating Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN), ARIMA, and LSTM, with three key contributions: (1) An enhanced ICEEMDAN algorithm reducing residual noise energy by 5-8% and mode mixing by 31% compared to CEEMDAN; (2) A frequency-aware modeling strategy that dynamically assigns linear (ARIMA) and nonlinear (LSTM) sub-models based on Hurst exponent analysis; (3) A GPU-accelerated implementation achieving real-time prediction with 28-second latency. Validated on China's transmission corridors, the model reduces RMSE by 65.2% over standalone LSTM and increases line ampacity by 21.2% compared to static ratings. Its robustness (99.2% availability during typhoons) and computational efficiency (150 & times; faster than conventional systems) demonstrate significant potential for smart grid applications.
Explicitly resolving fine-scale turbulent motions is increasingly prioritized within the Weather Research and Forecasting-Large-Eddy Simulation (WRF-LES) framework. While much is known about turbulence models and grid resolution in flat terrain, few studies have evaluated WRF-LES's performance in resolving separated turbulent flow past obstacles. This study focuses on flows past a three-dimensional axisymmetric hill, examining the effects of advection schemes (3rd to 6th order accuracy) and stabilization filters on simulation accuracy and efficiency. These aspects are often overlooked in WRF-LES practices. We also explore the performance of advection schemes under varying wind speeds and Smagorinsky coefficients. Results indicate that fundamental coherent structures are reproduced in the wake of the hill, regardless of the advection scheme. Switching from odd-order to even-order schemes significantly improve predictions of flow instability and small-scale turbulent motions. Energy spectra show that even-order schemes better capture the turbulence inertial subrange, achieving nearly twice the effective resolution. The study finds that numerical dissipation in odd-order schemes diminishes at lower wind speeds. Increasing the off-centering coefficient enhances numerical stability without significantly affecting flow separation or small-scale turbulence generation.
Downburst outflows interacting with uplifted terrain features, such as escarpments, can substantially accelerate local near-ground wind speeds and thereby aggravate wind hazards. However, existing downburst research has predominantly focused on wind-field characteristics over flat and smooth terrains, whereas the effects of elevated terrains remain insufficiently understood. To address this gap, the present study conducts an experimental investigation into how escarpment terrain modifies the mean and fluctuating components of downburst-like wind-velocity profiles. A downburst-like flow was reproduced using a plane wall-jet facility, and the influences of escarpment slope angle and the upstream (pre-escarpment) surface roughness were systematically examined. The results show that the escarpment terrain significantly impacts the mean and fluctuating wind profiles of the downburst at the escarpment top-position, and the wind profile no longer maintains the "nose" shape, compared to that from the flat ground. Moreover, the escarpment has an apparent obstructive effect on the mean speed profile of the downburst-like wind, showing a deceleration effect at the escarpment toe-position, exhibiting wind speed characteristics similar to those of the flat ground in the mid-escarpment area, and presenting a significant speed-up effect at the escarpment top-position. Meanwhile, the influence of the escarpment on the speed-up ratio at the escarpment top is mainly concentrated in the near-wall region, with the maximum value reaching 1.5. The influence of the roughness area is mainly occurring on the outer layer of the downburst-like flow, and the roughness area significantly impacts the wind speed-up ratio along the entire wind profile.
In the current study, the effect of wind interference on a principal building caused by the presence of a centrally located interfering building is investigated through experiments conducted in a boundary layer wind tunnel. The distance between the interfering building and the principal building is gradually changed for five different interfering building heights. Principal and interfering buildings have the same rectangular cross-section with an aspect ratio of 1:3. Force and pressure measurements are undertaken independently. For validation, the outcomes of the two measurements are compared with one another and with the Indian Standards. Results of force measurement are presented in terms of wind interference factors for different parameters, while results for pressure measurement are expressed in terms of mean and RMS wind pressure coefficients (C-p and C-p '). The highest along-wind force reduction is noted to be 55.15% under wind interference conditions compared to that under the stand-alone condition, according to the force measurement results. The force measurement results are appropriately and clearly explained by the contour plots for the mean coefficients of wind pressure. Also, it is seen that the suctions observed on the leeward and the side faces are higher for lower height interfering buildings. The highest C-p value noted is 38.16% higher than that observed for the stand-alone condition. Probability density functions plotted for critical pressure points at different spacings reveal that C-p values on the side face reach closer to stand-alone condition faster compared to that on the windward and leeward faces.
The three-dimensional Large Eddy Simulation (LES) method is conducted to investigate the flow characteristics around the square cylinder under a Reynolds number of Re = 2000. The considered corner chamfered ratio C/D ranges from 0% to 50% with an interval of 5%, where C is the chamfered corner dimension and D is the cylinder width. The focus is given on how C/D influences the flow structure, wake recirculation region, flow separation bubbles, Strouhal number and aerodynamic forces of the cylinder. The numerical results indicate that with increasing C/D, the mean drag coefficient, fluctuating lift coefficient, mean pressure coefficient and fluctuating pressure coefficient decrease. Concurrently, the Strouhal number exhibits an initial increase followed by a decrease with a rise in C/D. Significant changes in the recirculation length and wake width are observed within 0% <= C/D <= 50%. The introduction of corner chamfers induces wall-attached evolution of the separated shear layers and suppresses three-dimensional instabilities, significantly attenuating the pressure fluctuating on the surfaces, thereby reducing both mean drag and fluctuating lift coefficients. As the chamfered ratio increases, the wake topology undergoes a transition from disordered fragmented structures to spanwise highly coherent periodic vortices, leading to a narrowband spectral transformation of the power spectra density. Finally, the mathematical relationships between the corner chamfered ratio and the aerodynamic force coefficients and Strouhal number are established.
The aerodynamic behavior of vertical-axis wind turbines (VAWTs), particularly the H-type Darrieus configuration, remains central to renewable energy research due to persistent challenges in self-starting and efficiency at low tip speed ratios (TSRs). This study presents a numerical investigation of a modified NACA0018 aerofoil with chordwise surface openings, termed a J-shaped aerofoil, operating under Darrieus motion. Two-dimensional CFD simulations in ANSYS Fluent evaluated opening ratios of 30%, 60%, and 90% of chord length, focusing on lift, drag, and chordwise force coefficients during dynamic stall. A validated oscillating aerofoil model with user-defined pitching replicated Darrieus kinematics, with systematic variation of TSR and pitch angle. Results show that larger openings enhance lift and delay stall onset in the positive angle of attack phase, improving self-starting potential. However, these gains are offset by increased drag and reduced performance during the negative phase, particularly downstream. The J-shaped aerofoil with 90% opening achieved similar to 30% higher peak lift than the conventional profile, with improved flow reattachment and vortex dynamics observed. Despite elevated downstream losses, the enhanced upstream torque indicates a net advantage for turbine start-up capability. These findings provide insight for optimizing blade design in low-Reynolds-number VAWTs, balancing self-starting improvement against efficiency at higher TSRs.
This study investigates the aerodynamic force characteristics and flow field mechanisms of wide-width double-box composite girders through integrated wind tunnel testing and numerical simulation. Initially, aerodynamic analysis was conducted across eleven wind attack angles (-10 degrees to +10 degrees at 2 degrees intervals) while maintaining the prototype bridge aspect ratio of 12.8. Subsequently, parametric analysis was performed for horizontal flow conditions (0 degrees), examining six aspect ratios (9, 11, 12.8, 15, 17, and 19). The results demonstrate that, under the aspect ratio of 12.8, as the wind attack angle varies from -10 degrees to 10 degrees, the drag coefficient and the absolute value of the lift coefficient initially decreases and then increases, the direction of moment changes from counterclockwise to clockwise. At 0 degrees wind attack angle, as the aspect ratio increases, the drag coefficient remains constant initially and then increases, the absolute value of the lift coefficient initially decreasing and then increasing, and the moment coefficient gradually decreases. The lift and moment coefficients are smaller during the construction and service stages. Calculation formulas for aerodynamic force coefficient with different aspect ratios under 0 degrees wind attack angle are presented, which can provide a reference for the wind load design of wide-width double-box composite girders in practical engineering.
Turbulence integral lengthscale and lateral and vertical turbulence intensities are sometimes not measured in wind tunnel experiments. The resulting uncertainty in inflow conditions cascades into uncertainties in the surface pressure, drag and lift coefficients, and the wind response of tall buildings. This paper utilizes Large Eddy Simulation (LES) with a divergence-free turbulence generator to investigate a set of five inflow conditions generated using different assumptions related to building height and turbulence integral lengthscale, and the ratio between three components of turbulence intensities. The effects of the inflow assumptions on the downstream incident flow, on the surface pressure coefficient of a tall rectangular building of 1:4 width to height ratio, on drag and lift moment coefficients are all evaluated. Furthermore, an example steel-frame-tube structure is considered to investigate the effects of the inflow turbulence on its background, resonant and peak displacement response using modal analysis with gust peak factors. It is observed that distinct turbulence inflow conditions tend to converge towards similar statistical profiles downstream. However, within this envelope of convergence, a range of potential values persists, indicating significant remaining uncertainty. The inflow turbulence integral lengthscale is found to have an effect up to 13% on the peak along-wind response and 4% on the across-wind response. The lateral and vertical turbulence intensity is found to have effects of up to 13% and 24% on the two peak responses, respectively. These results highlight the importance of considering a range of inflow assumptions when conducting LES to reproduce and interpret WT results.
This study compares pressure distributions on non-structural components (doors, windows, soffits, and fascia), due to hurricane winds from Wall of Wind (WoW) facility tests, field measurements on a residential house in Satellite Beach, Florida, during Hurricane Nicole (2022), and computational fluid dynamics (CFD) simulations. WoW testing was on a full-scale single-story building, equipped with wireless pressure sensors and Scanivalve patches. Wind loads were measured in the field using the same sensor system. The CFD simulations reproduced wind tunnel flow conditions. Measured pressure coefficients (Cr) on the doors and windows (with and without shutters), soffits, and fascia are compared against Cp values under ASCE 7-22 provisions. Results indicate that the Cp from field measurements is localized and strongly dependent on wind direction in urban surroundings. Aluminium storm shutters reduce positive Cp values on doors and windows at some angles but do not affect negative values. Soffits exhibit the highest Cp values at their edges, while fascia experience lower Cp values in comparison. The strongest suction forces occur under the roof's corner soffit. Discrepancies are found in the comparisons due to fluctuations in the ambient pressure readings, resulting in uncertainties in the dynamic pressure measurements and Cp estimations.
As for the wind resistance design for building structures on hilly terrains, the fundamental issue is to establish the wind topographic acceleration effect. Since the hill slope plays an important role in the wind flow around hilly terrains, its influence on the wind topographic acceleration effect needs further investigation. In this study, the large eddy simulation (LES) was carried out to study the influence of slope variation on the wind topographic acceleration effect around a three-dimensional hill. The results indicate that the hill slope significantly affects the distribution of the wind topographic acceleration effect over the hill. The coverage of the wind topographic acceleration effect increases with the slope increase. At the hill windward, the mean wind topographic acceleration effect is suppressed with the increasing slope and reaches its maximum at the hilltop, while it shows the opposite for the fluctuating counterpart. On the hill leeward, the mean wind topographic acceleration effect gradually reduces with the increase of slope. Moreover, a critical slope of 25 degrees for the fluctuating wind topographic acceleration effect can be found near the hill surface on the leeward side. The fluctuating wind topographic reduces with the slope increase when alpha <= 25 degrees, while exhibits an opposite trend when alpha > 25 degrees. A mathematical model, which incorporates the slope, height and topographic influence factors, was then proposed to depict the distribution of the mean and fluctuating wind topographic acceleration effect coefficients. Compared to different national load codes, the proposed model presents a good performance not only in predicting the mean wind topographic acceleration effect, but also in possessing the capability in the prediction of the fluctuating wind topographic acceleration effect.
Windblown sand disrupts and inundates infrastructure, agricultural farmlands and causes severe environmental impacts. The extent of aeolian erosion is highly influenced by the morphology of sand dunes and wind flow patterns in the vicinity. The current study aims to understand the influence of sand dune geometry on the sand migration and dune evolution system. Wind tunnel experimentation was conducted on three dune geometries of varying stoss slope (320, 200 and 10 degrees) and identical lee slope (32 degrees). The wind tunnel testing on sand-based dune models revealed the temporal dune evolution patterns that represent the strategic influence of the stoss slope on wind flow around the dunes. Until the threshold friction velocity limit of sand grains, the aeolian erosion measured in terms of soil mass loss (SML, %) was negligible even with an increase in testing duration. However, 20% increase in wind speed from 7.8 to 9.4 m/s increased the SML from 0.05% to 14.23%, 0.46% to 24.51% and 4.76% to 37.24% for 32 degrees, 20 degrees and 10 degrees models, respectively. Further testing at higher wind speed of 10.5 m/s evidenced the formation of shadow dunes along with an increase in SML. The migration pattern from temporal dune evolution concludes that dune with steeper slope offered relatively more resistance to initiation of erosion and migration. However, in the secondary stage of erosion, dune topography varies drastically, and steeper slope is no longer the highly resistant dune. The distinct behavior of 10 degrees stoss slope dune piques interest in current study and relates to the dune process and cyclic evolution of dune systems.
Many major cities worldwide have recently initiated tree-planting programs to improve the resilience of urban environment based on several environmental and social benefits of trees. However, wind loads are known to have a significant impact on trees, and presently, little is known about tree aerodynamics. A wind tunnel test at BLWTL of Western University was carried out to investigate the aerodynamic loads and response of a tree using an aeroelastic model with a range of crown porosity. These loads reflect the level of alteration imparted to the momentum of the flow by the presence of trees. This study estimates the changes in the aerodynamic behavior of a tree all around the year, due to seasonal change of leaves by considering different crown porosities. The drag force on the tree was found to vary quadratically with the wind speed, consistent with the literature for stiff trees. Moreover, the results show that for an aerodynamic porosity greater than 0.6, the drag coefficient decreases drastically for all the wind speeds considered in the study.
The design of long-span bridges in complex terrains poses significant challenges, particularly in regions with pronounced topographic variations. This study examines the influence of topography on the wind characteristics and its implications for the aerodynamic design of the Julsundet Bridge, a planned long-span structure in Norway. Experimental data from terrain model wind tunnel tests are analyzed to assess how local topography affects wind speed, turbulence intensity, and directional changes along the bridge axis. Special focus is placed on the variations in angle of attack and velocity distribution induced by the surrounding fjords. Results showing terrain-induced effects on the wind directions, turbulence intensities and mean wind velocities are presented. The results highlight substantial spatial heterogeneity in wind characteristics, which must be considered in the prediction of the buffeting response of the bridge. These findings emphasize the importance of incorporating site-specific topographic effects in the design process to ensure optimal performance and safety of the bridge built in complex terrain.
Wind-induced tree collapse on critical infrastructures, such as railway lines, results from the interaction between wind in the Atmospheric Boundary Layer, tree aerodynamics and mechanics, and specific features of the infrastructure. Wind-induced tree collapse may affect railway capacity and safety. The resulting losses may be related to delays, cancellations, or even damages caused to the infrastructure or the rolling stock. In order to face the potential adverse events above, risk analysis provides a sound methodological framework to infer critical railway segments referring to the main risk determinants: wind hazard, tree and railway exposure, and tree vulnerability to wind. Each risk determinant has and can be modelled at multiple scales in space and or time. The risk assessment should effectively model hazard, exposure, and vulnerability at a selected scale that is consistent across all three determinants and relevant to the context of interest. In this study, a mesoscale approach is proposed to assess and map the relative risk level of different railway segments along a line or within a network. Wind hazard index is grounded on the extreme wind speed mapping obtained by the Authors by means of a reanalysis-based approach. Tree exposure index is defined on the basis of land cover characteristics. Tree vulnerability index is defined with reference to the critical wind speed for tree collapse. Each index and the resulting risk is mapped by Geographic Information System tools. The Calabria region in Southern Italy is selected as a challenging benchmark due to its variable orography and due to the wide presence of railway lines surrounded by tree canopies both in coastal and mountainous zones. The proposed mesoscale approach allows to identify in quantitative relative terms the most endangered railway segments over the region of interest.
This paper focuses on the topic of structural optimization applied to the case of tall steel buildings subjected to wind action. A detailed study is conducted exploring how structural optimization can be applied in an automated manner using programming software (Matlab (R)). The primary objective is to analyze how the configuration of a tall building changes due to the structural optimization process, and in particular by referring to different objective functions. In particular, three different objective functions are taken into account: total structural steel volume, total structural cost and total CO2 emissions produced by steel production. The optimization is carried out taking into account the results of the structural analysis for both the along-wind and across-wind directions, ensuring the fulfilment of predefined performance levels to guarantee safety and comfort for users. The objective functions also consider the detailed contribution of the connections, thus providing a detailed evaluation of both costs and emissions as a function of these components. The procedure is applied to a case study 40-storey case study steel building for which the incidence of the connections on the total volume, cost, or CO2 emission is evaluated.
This work focuses on the full-scale gust buffeting response of an isolated wind turbine tower (without rotor-nacelle assembly) about 116 m tall placed at & Oslash;sterild Test Center (Denmark). It aims to clarify the reliability of analytical models behind design standards through the analysis of combined measurements of wind and structural response. The tower was instrumented with strain gauges mounted close to the base, which indirectly measured the bending moment (net of the mean component), and an accelerometer at about the top. Wind data, mostly velocity and direction at different heights, were recorded by nearby meteorological masts, and they are used to characterize the wind environment in terms of mean velocity profile, turbulence intensity, power spectral density, integral length scale, and coherence of velocity fluctuations. Mild wind conditions, differently from severe conditions, result not well described by the formulations provided by design standards, whereas the coherence function exhibits a disagreement with theoretical models also at high wind velocities. The measured along-wind and across-wind response (in terms of bending moment) is compared with the values got from the direct implementation of gust buffeting theory for line-like structures, by using the actual wind characteristics. While a good agreement is found for the along-wind response, especially for the upper bound of the estimated structural damping, the across-wind response significantly deviates from a pure gust buffeting response even at high wind velocity, well above the expected lock-in range. Clear nonlinear aeroelastic response features are highlighted in those cases. Moreover, a comparison with common design standards is developed for the along-wind response, which is significantly underestimated in mild wind conditions.
