Aerodynamic Force Coefficients Research Articles

Analysis of Wind Field Response Characteristics of Tethered Balloon Systems

Tethered balloon systems encounter various complex wind field environments during flight. To investigate the conditions under which the system can operate safely and smoothly, a longitudinal dynamic model for tethered balloon systems is established. The model incorporates a streamlined balloon shape with its aerodynamic center at the body’s center. Steady-state aerodynamic force coefficients are calculated through simulations and fitted to a function based on the angle of attack within a specified range. The complex cable model is simplified using the lumped mass method, considering the influence of branch cables on the main node position. Experimental results from windless oscillation tests on scaled tethered balloon systems are compared with numerical solutions obtained using the dynamic model under the same conditions, validating the feasibility of the model for simulating different wind field scenarios. Finally, the motion characteristics of tethered balloon systems in different wind fields are analyzed. The numerical simulation results show that in a horizontal step wind field, the cable tension and cable inclination angle increase with the wind speed, and the slower the wind field changes, the shorter the time required for system stabilization. Updrafts greatly increase the likelihood of balloon escape, while downdrafts greatly increase the likelihood of the system making contact with the ground. The findings of this study can provide a basis for selecting suitable wind field conditions and issuing risk warnings for tethered balloon systems.

Aerodynamic interaction between galloping instability and vortices in corner-cut rectangular cylinders

Studies on bluff-body aerodynamics have emphasized that galloping instability is strongly associated with the Kármán vortex. This study discusses the aerodynamic interactions between the galloping instability and Kármán and motion-induced vortices, analyzes the effects of these vortices on vortex-induced vibration and galloping, and investigates the stabilizing effects of various corner cuts on a rectangular cylinder. Wind tunnel tests were performed on a rectangular cylinder with a side ratio of 1.5 under a smooth flow for seven different corner shapes. The rectangular cylinder with cut corners significantly reduced both the aerodynamic force coefficients and the Kármán vortex shedding intensity. Furthermore, spring-supported free vibration tests indicated that the onset reduced wind velocities were high in the response amplitudes of all corner-cut sections that were analyzed despite the significantly low onset reduced wind velocities of the Kármán vortex-induced vibration, which were denoted as the reciprocal of the Strouhal number and closely associated with the onset of galloping. This was attributed to the motion-induced vortex dominating the vibration when the Kármán vortex shedding intensity was reduced. Therefore, this study clarified one of the factors that affected the onset-reduced wind velocity of galloping.

Aerodynamic characterization of noncircular cross-section missile configurations

This article summarizes the computational efforts in the aerodynamic characterization of new missile configurations designed at the U.S. Air Force Academy that have either circular, or square, or triangular cross sections. These missiles were tested with and without strakes (low aspect-ratio fins) for different tail fin deflections and at a Mach number of 4.33 and a Reynolds number per length of 8.74 × 105 per inches. The triangular missile has a V-type fin arrangement. Cruciform (“+”) or cross (“×”) fin arrangements were tested for the square missile models. The simulations are performed for angles of attack in the range of [-4∘ – 15∘]. The aerodynamic force and moment coefficients were extracted from simulation data and compared with each other for different missile configurations and measured data. The effects of fin arrangement/deflections and strake geometries on the aerodynamic performance are investigated. The observed flow features are detailed including separated and vortical flows. The results show a very good agreement between predictions and measured data for all test cases and flow conditions. The missiles with triangular and square cross sections showed better aerodynamic performance than the circular model but they are less stable in the pitch direction.

Numerical Study on Aerodynamic Characteristics of Tail-stabilized Projectile with Asymmetrical Diversion Groove

A surface diversion groove with a specific geometry and position can influence the laminar flow characteristics of a projectile, which may affect the flight trajectory of an aircraft. The asymmetric flow field around the projectile can be induced by the diversion groove, which can produce an obvious aerodynamic force and moment at the projectile nose for trajectory correction. This study applied a diversion groove structure to the nose of tail-stabilized projectiles to investigate its impact on the aerodynamic characteristics of the projectile. The mathematical expressions for the aerodynamic force and aerodynamic coefficient were established theoretically. The change in the aerodynamic coefficient as a function of the phase angle of the diversion groove was determined. A parametric simulation was employed to investigate how the diversion groove affects the aerodynamic attributes of the projectile across various Mach numbers and angles of attack. The simulation results are consistent with the variation trends of aerodynamic forces and moments with respect to the phase angle of the diverter groove, as predicted by the static mathematical model. These findings demonstrate that the variation trends of the lift coefficient and pitching moment coefficient with respect to the angle β approximate a cosine function. Meanwhile, the variation trends of the yaw force coefficient and yaw moment coefficient with respect to the angle β approximate a sine function. The tail-stabilized projectile with asymmetrical diversion groove achieved a reduction of 1.2% in drag coefficient compared with that of the canard rudder corrective projectile, while the lift coefficient and pitch moment coefficient were increased by 6.4% and 16%, respectively, in the subsonic regime. The static margin of the projectile ranging from 13% to 16%. This study offers valuable insights for the design of corrective structures with diversion grooves and trajectory control.

Numerical investigation on the effect of stroke plane inclination on the aerodynamic performance of dragonfly take-off flight

A numerical investigation is carried out to study the role of inclined stroke plane on the aerodynamic performance of a dragonfly during a take-off flight. A two-dimensional numerical simulation of tandem foils oscillating in-phase along an inclined stroke plane at Re = 160 is performed using ANSYS Fluent. The stroke plane angle is varied from 10° ≤ β ≤ 80° to determine its effect on aerodynamic force coefficients of forefoil and hindfoil. The result shows that the presence of forefoil reduces the hindfoil Cv for low stroke plane angle cases. The cycle-average vertical force coefficient Cv of both foils increases with β up to 50° and then decreases. A vortex pair is present in the wake of the foils during each cycle, which induces a downward dipole jet. The dipole jet characteristics such as jet width, location and maximum velocity components are measured for each stroke plane angle. It is observed that the cause of variation in Cv and CH with stroke plane angle can be explained with the help of dipole jet characteristics.

Study on Fluid–Structure Interaction of a Camber Morphing Wing

The influence of trailing edge deformation on the aerodynamic characteristics of camber morphing wings is an important topic in the aviation field. In this paper, a new memory alloy actuator is proposed to realize trailing edge deformation, and computational fluid dynamics (CFD) and wind tunnel experiments are used to study the influence of trailing edge deformation on the aerodynamic characteristics of the camber morphing wings. The experiments was carried out in a transonic wind tunnel with Mach numbers ranging from 0.4 to 0.8 and angles of attack ranging from 0° to 6°. The external flow fields and aerodynamic force coefficients with and without deformation were calculated using the CFD method. A loose coupled method based on data exchange was used to achieve a fluid–structure interaction (FSI) analysis. The research results indicate that when the trailing edge is deflected downwards, the phenomenon of shock wave forward movement reduces the negative pressure area on the upper wing surface, increases the pressure on the lower wing surface, and ultimately increases the total lift. This work provides a new approach for the implementation of trailing edge deformation and a powerful data reference for the design of camber morphing wings.

Numerical investigation on tornado-like flows and immersed bodies using vortex models

A numerical investigation to evaluate tornado flows with immersed bodies is presented in this work, where vortex profile models are adopted to generate the flow field based on time-dependent boundary conditions. In order to reproduce flow conditions obtained from field data and experimental analyses, a parametric study is performed considering the main model parameters influencing the tornado flow characteristics. A Taylor–Galerkin finite element model is used for flow simulation, where eight-node hexahedral elements with one-point integration are adopted. Vortex flow fields are generated numerically using the Modified Rankine Combined Vortex Method (MRCVM) and a fully three-dimensional approach is utilized for tornado-like flows considering the Vastistas vortex model. Turbulence is analyzed using Large Eddy Simulation (LES) with Smagorinsky's sub-grid scale modeling. The vortex formulations are verified considering a circular cylinder submitted to vortex flows, where aerodynamic force coefficients are obtained. A tornado flow field generated experimentally is reproduced utilizing the vortex models proposed here and a cubic building subject to different tornado flow conditions is also analyzed. Results demonstrate that velocity profile models are able to reproduce tornado flow fields and aerodynamic forces on immersed bodies satisfactorily since the boundary conditions and vortex model parameters are calibrated properly.

Experimental study on aerodynamic countermeasure for galloping vibration of stay cables attached with lamps: Perforated shrouds

The aerodynamic countermeasure of the perforated shrouds is proposed to reduce the galloping vibration of stay cables installed with rectangular lamps. Ten test models with different parameters were designed and manufactured and a series of wind tunnel tests were carried out to measure the aerodynamic forces on the test models. Then, the mean aerodynamic force coefficients were obtained to further calculate the galloping force coefficients of these test models. Based on the quasi-steady theory, the effectiveness of the perforated shrouds on mitigating galloping vibration was verified by considering the effects of porosities, hole types, shroud diameter, the turbulence of approaching flow, and cable orientation (vertical and inclined). The cable inclination of 35° and a turbulence intensity of 9% was used for the force measurement wind tunnel tests, as well as shrouds with porosities of 0, 8.7%, 19.6%, 28.3%, 34.9%, 36%, 44.2%, and 49.0%. Two types of holes, including circular staggered and square array holes, were adopted, and two outer diameters of the perforated shrouds (125 mm and 88 mm) were used. The results show that the perforated shroud with a diameter of 125 mm plays an important role in mitigating the galloping vibration of both vertical and inclined stay cables with rectangular lamps. For the vertical test model, it seems that the optimal porosity of the perforated shroud is 19.6%, and the optimal porosity of the perforated shrouds for the inclined test model is within the range of 19.6%–34.9%. The minimum galloping force coefficients Cg of them is all greater than 0. The galloping critical wind velocity of the inclined cable-lamp structure without perforated shrouds is significantly lower than that of the vertical cable. However, the inclination of the stay cable induces a higher galloping critical wind velocity if the perforated shrouds are installed. The type of holes, a circular staggered and rectangular array, seems to not affect the galloping vibration. The turbulence intensity of 9% has a significant effect on the galloping critical wind velocity for the vertical and inclined cable attached with rectangular lamps without perforated shrouds but has little effect on the galloping critical wind velocity of the vertical and inclined cable-lamp system with perforated shrouds. The maximum value of combined aerodynamic mean force coefficients CC for the vertical test model with the perforated shroud is the same (1.1), the maximum wind load of the inclined test model with the perforated shroud is increased by 21∼58% due to the larger diameter.

Large eddy simulation on wind-induced interference effects of staggered chamfered square cylinders

Chamfered corners in buildings are the main means to reduce the control effect of wind load on the structure, and the interference effect of chamfered buildings cannot be ignored. At present, only the mutual interference coefficients of square and rectangular section buildings are given in the Chinese code, without the interference effect of chamfered buildings being specified. Therefore, in this paper, aerodynamic force and wind pressure coefficients of chamfered square cylinders of different spacing are obtained by the large eddy simulation method. Wind load characteristics, non-Gaussian characteristics and interference effects of chamfered square cylinders with different arrangements are studied based on aerodynamic coefficients, wind pressure coefficients and interference coefficients. The results show that when the wall y plus value is 1, the large eddy simulation is the most accurate to simulate the wind load and wind field parameters. Besides, the aerodynamic effects, non-Gaussian characteristics and interference effects between the chamfered square cylinders are mainly controlled by the cross-wind interval and the spacing (4.0, 4.0) is the characteristic coordinate. That means, when the spacing is smaller than this coordinate, the interference effect of the square cylinder is more obvious. When the spacing coordinate is greater than (4.0, 4.0), the aerodynamic coefficients and non-Gaussian regional distributions of the principal square cylinder and the isolated cylinder are the same, and the interference factor approaches 1.

Investigation of the Influence of Wake Field Characteristic Structures on Downstream Targets Using the POD Method

This research investigated the impact of complex low-speed wake flow structures on the aerodynamic characteristics of objects downstream. It employed the proper orthogonal decomposition (POD) method and the domain precursor simulation method to compare traditional methods and validate this approach. The study generated several flow structures of parallel dual-cylinder wakes with different scales and spacing. The variations in the aerodynamic coefficient of three downstream objects at various times passing through wakes of varying scales were appropriately compared and analyzed. The study established that the wake with a cylinder spacing of G = 1.5 has a more compact and concentrated modal structure than that with a cylinder spacing of G = 0.35. Smaller objects were more responsive to the wake flow structure with a spacing of G = 1.5, whereas larger objects responded more to the flow structure with a spacing of G = 0.35. The achieved results also revealed that the aerodynamic force coefficients of objects passing through the wakefield at different times were closely related to the temporal characteristics of the wake flow structure with different scales.

Estimation of aerodynamic parameters using neural artificial bee colony fusion algorithm for moderate angle of attack using real flight data

Aircraft system identification aims to estimate the aerodynamic force and moment coefficients utilizing intelligent modeling and parametric identification methodologies. Classical methods like output, filter, and equation error methods apply extensively as parametric approaches. In contrast, machine learning approaches like Artificial Neural Networks (ANN), Adaptive Neuro-Fuzzy Inference Systems (ANFIS), etc., are alternatives to model-based methods. This work presents a novel aerodynamic parameters estimation technique that fuses two biologically inspired optimization techniques, (i) the Artificial Bee Colony (ABC) optimization and (ii) ANN for an actual aircraft while incorporating system and measurement uncertainty. The fusion of ABC and ANN imparts the ability to address sensor noise challenges associated with system identification and parameter estimation. Comparison of the proposed method’s results with the benchmark techniques like Least Square, Filter Error, and Neural Gauss Methods using recorded flight data of the ATTAS (DLR German Aerospace Centre) and HANSA-3 (IIT Kanpur) aircrafts established its adequacy and efficacy. Furthermore, the capability of the proposed hybrid method to extract stability and control variables from the stable aircraft kinematics is shown even with insufficient information in its data history.

On the surface flow patterns and associated aerodynamics of an asymmetrical flat-box section

In this study, wind tunnel experiments were carried out in smooth flow to examine the nexus between flow patterns around a flat-box section and its aerodynamics with the variation of the wind angle of incidence (α). The model cross section closely represents the overall asymmetric geometry and attendant aerodynamics of a class of flat-box decks frequently employed in long-span bridges. To explore the flow around and associated aerodynamic properties of this model that are distinct from a typical symmetric section (e.g., rectangular), detailed wind tunnel tests involving smoke-wire based flow visualizations and synchronous multipoint pressure measurements were carried out. Experimental results were analyzed to identify flow patterns, pressure distributions and associated Strouhal numbers, power spectral densities, aerodynamic force coefficients, proper orthogonal decomposition (POD) analyses, and span-wise correlation. Three typical flow patterns previously observed around symmetric bluff bodies with varying α were also observed in the asymmetric cross section, i.e., the trailing-edge vortex shedding (TEVS), the impinging leading-edge vortices (ILEV), and the alternate-edge vortex shedding (AEVS). However, due to the chordwise asymmetry of the section, the three flow patterns identified are distinct from the classical ones associated with symmetric sections in terms of flow separation points, the static “stall” angle of the section, and characteristics of leading-edge vortices. The roles played by these flow patterns in the aerodynamics of the flat-box section have been identified. It is observed that, if the ILEV or AEVS governs the flow topology, the aerodynamic force coefficients vary nonlinearly with the increase in α, in contrast with the linear variation in the TEVS-dominant case. For cases in which the TEVS dominates, the POD mode participation factors of the fluctuating pressure field display energy in higher modes. In this case, the reconstruction process requires that higher POD modes are retained. Finally, in the TEVS flow pattern, a weaker spanwise correlation of the fluctuating forces is noted as compared to the ILEV and AEVS-type flows. This study is limited to the fundamental examination of asymmetric section aerodynamics in smooth flows, which should be extended in case the influences of turbulence and aeroelastic effect are of interest.

Nonlinear Aerodynamic Global Model Identification using Gram-schmidt Orthogonalization

This paper discusses a simple technique to identify global models for nonlinear aerodynamic force and moment coefficients of aircraft using multivariate orthogonal functions. Classical Gram-Schmidt procedure and Predicted Squared Error metric are used to generate the orthogonal functions. Global models for the F-16 aircraft are identified from a simplified subsonic (Mach < 0.6) wind tunnel database available in open literature. The identified models are compared with those found in literature for the same wind tunnel database and conclusions are drawn.

Longitudinal Parameter Estimation Using Wind Tunnel and Simulated Flight Data of Missile Configuration

The present study makes an attempt to estimate aerodynamic parameters from a typical flight data of a short range missile. Exhaustive wind tunnel testing was conducted to generate longitudinal force and moment coefficients at low speed. Identification methods were applied on the selected wind tunnel data to capture the general form of the aerodynamic model. During the application of Maximum likelihood (ML) method, the estimation algorithm assumed this wind tunnel identified aerodynamic model to be exact. To avoid any requirement of postulation of aerodynamic model, the Delta method was applied to estimate the aerodynamic parameters. The Delta method used measured aircraft motion and control variables as the inputs to the Feed Forward Neural Network and the aerodynamic force or moment coefficient was the output for training the Feed Forward Neural Network. The application of the Delta method results in large scatters in the estimated parameters. To overcome this problem of large scatter, the Delta method was modified by changing the training strategy. The Delta method with new training strategy will be referred as the Modified Delta method. It is expected that the proposed Modified Delta method would result in estimates with less uncertainties. Further to check the robustness of the ML, Delta and the Modified delta methods, the estimation was also carried out with flight data having known measurement noise. The effect of control input form in the accuracy of estimates obtained by ML, the Delta and the Modified Delta methods are also studied. It is observed that the Modified Delta method can advantageously be applied on the flight data of a tactical missile to estimate aerodynamic parameters. The paper progresses with the description of the generation of wind tunnel data and aerodynamic model identification using selected wind tunnel data. Finally it concludes by demonstrating applicability of ML, the Delta and the Modified Delta methods on simulated flight data of a typical short range tactical missile configuration.

Flow simulation around square cylinder with inclined corner gap at low Reynolds number

In this paper, an investigation of the effects of inclined corner gaps of varying widths and lengths on the static aerodynamic force coefficients and flow features of a square cylinder at low Reynolds number (Re of 100) by comparing with an unmodified square cylinder is discussed. The width of the corner gap (x/D) was varied between 0.02 and 0.24, with two different lengths of it (l/D), namely, 0.05 and 0.11. The open-source code OpenFOAM was used as a solver. A second-order accuracy level was ensured for both time and space during the numerical set up of the model. Validation and verification studies were conducted to ensure the authenticity of the results. The mean and rms values of the static force coefficients of these cylinders were compared and important flow features were explored. Even at a low Re, the proposed corner modification was found to be effective in improving the static aerodynamic performance. For different gap widths, the static force parameters evidenced some patterns, with an optimum width for which the mean drag value reached the minimum value identified. Furthermore, the mean and fluctuating pressure and velocity contour were analyzed to understand the underlying flow mechanism.

Novel design of a circulation control airfoil with cylinder rotation

The objective of this research is to investigate the efficacy of Magnus effect on a circulation control airfoil (CCA). To achieve this, the Reynolds-averaged Navier–Stokes method is employed to numerically simulate the flow around a three-dimensional CCA configuration. The numerical verification demonstrates that the k–ω shear stress transport turbulence model provides better characterization of flow circulation and separation in the trailing edge area of the airfoil while ensuring the independence of the grid. The rotation speed is set at 15%, 30%, and 45% of the free-stream velocity, respectively, encompassing both clockwise and counterclockwise directions. The analysis focused on the characteristics of lift-drag forces, velocity circulation, and flow separation. The findings reveal that as the rotational speed increases in a clockwise direction, there is a progressive enhancement in aerodynamic performance of the airfoil. Both the flow separation point and stagnation point exhibit a backward shift in their respective positions. However, counterclockwise rotation produces an opposing effect. The amplitudes of fluctuating aerodynamic force coefficients are suppressed completely whether in clockwise or in counterclockwise rotation, resulting in a stable flow pattern consisting of a pair of vortices near the trailing-edge area. While the qualitative application of Bernoulli's principle explains the correlation between velocity circulation and surface pressure, there is a 12% margin of error in the quantitative analysis. Furthermore, evaluating the efficiency of circulation control while taking into account the input energy reveals that rotating the cylinder at 45% of free-stream velocity leads to a 23.6% increase in the lift-to-drag ratio.

Dynamic analyses of long-span cable-stayed and suspension cooperative system bridge under combined actions of wind and regular wave loads

This paper presents the dynamic analyses of long-span cable-stayed and suspension cooperative system bridge under combined actions of wind and regular wave loads. First, the wind loads acting on the bridge deck are calculated based on the aerodynamic force coefficients which were obtained in the wind tunnel and wave flume tests. Then, the wind loads acting on the bridge towers, piers and suspension cables are calculated based on the aerodynamic force coefficients which are simulated in FLUENT software. Besides, the regular wave loads acting on the composite foundations are simulated in FLOW-3D software. Finally, the dynamic responses of the bridge subjected to the combined actions of wind and regular wave loads are calculated in the Mechanical APDL module of ANSYS 17.0 software. The results indicate that the root mean square (RMS) values rather than the mean values of the time histories of the aerodynamic force coefficients obtained in the wind tunnel and wave flume tests should be selected to calculate the wind loads acting on the deck to accurately evaluate the dynamic responses of the sea-crossing bridge. The maximum RMS values of the displacement responses of the deck midspan and 5# tower top increase with the increase of the regular wave heights for the wind-wave cases, which are larger than those for the wind-only case, respectively. In general, the linear superposition of the dynamic responses under the actions of wind-only and wave-only is a conservative choice compared to the consideration of the combined actions of wind and regular wave loads. The displacement spectrums of the deck midspan and 5# tower top, and the lateral base shear and lateral base bending moment spectrums of 5# tower are analyzed to reveal the contribution mechanism of the wind loads, regular wave loads and natural frequencies of the bridge.

NEW PRODUCT DESIGN AS PART OF THE DIGITAL FACTORY CONCEPT

The concept of digital production represents the basis for the development of a digital production system, i.e. a digital factory. The digital factory represents the integration of the virtual and real factory. Inside the virtual factory, products, processes and resources are modeled on the basis of real data, which are then tested, improved and optimized through the application of digital production tools. Finally, when the results of the virtual factory are verified and all possible irregularities are removed, they can be applied in the real factory.
 The primary goal of this paper is to present the process of designing a new product. The design process is an integral part of the modern digital factory concept. The concept requires full integration of product data, as well as systems for design, planning and production, including the design of technological processes.
 The aim of this paper is to solve the problem of the budget coefficient of aerodynamic drag force of axisymmetric aircraft without wings. The problem is interesting because it provides a simple calculation of the axial aerodynamic coefficient of drag force for different airspeed. Ruling allows for easier comparison of the components of aerodynamic force coefficient of drag when changing airspeed and experimental values ​​from wind tunnel. The dependences of aerodynamic coefficients of aerodynamic parameters and shape aerodynamic configuration.The application of the proposed solutions will accelerate the flow of information theoretical researches aerodynamics of the aircraft. The accuracy in determining the values ​​of aerodynamic coefficients is one of the key factors for the assessment of flight "rapidly rotating" axisymmetric bodyes.

Effect of the upper rivulet on the aerodynamic forces and vibration of stay cables in the critical Reynolds number range

During the rain-wind-induced vibration (RWIV) process, a water rivulet forms on the surface of stay cables, and the upper rivulet is considered to be an important factor in RWIV formation. The cables also exhibit galloping in the absence of rain. To reveal the effect of a rivulet on galloping and help explain the mechanism of RWIV, from the viewpoint of the Reynolds number effect, a cylinder with an artificial rivulet at multiple angles was tested in wind tunnel experiments. The results show that the rivulet has a significant effect on the aerodynamic force coefficients, and the increase in the rivulet position decreases the onset Reynolds number of TrBL0-1 transition. A large-angle rivulet limits reattachment on the upper surface of the model, and the vortex appears in TrBL1. Due to reattachment, bistability can be observed in the TrBL0-1 and TrBL1-2 transitions, and the wake vortex is suppressed. During the formation of a separation bubble, the aerodynamic forces change dramatically, which affects the aerodynamic damping of the cables and induces galloping instability in most cases. The condition of reattachment on the upper surface of cables may be an important reason for RWIV occurrences.

Duration of extreme synoptic wind speeds for North America in a changing climate and its engineering implementation

In modern wind engineering practice, wind load effects are often defined as a function of a basic design wind speed, an aerodynamic force coefficient, several multipliers to consider surrounding terrain, topographic effect, and the directionality of the wind climate. Among these variables, the basic design wind speed is associated with an averaging time (also known as gust duration), e.g., 0.02-second, 3-second, 10-minute, or one hour. The design level aerodynamic force coefficients are defined as a specific percentile within a reference period, representing the generic time duration of wind events, i.e., wind duration, which is assumed to be one hour. A recent study showed that the hurricane wind duration could differ from this assumption. There has not been any study that investigated synoptic wind duration and its engineering implementations comprehensively. It is also unclear whether climate change impacts the synoptic wind duration. Historical records, often less than 50 years, are insufficient to calculate the wind duration for threshold wind speeds at a higher return period. Therefore, this study employed 15 long-term hourly wind speed simulations covering most of North America, each of which has 70 years in the past (1050 years in total) and 80 years into a future changing climate (1200 years in total), to investigate the wind durations in the current and future changing climate. It was found that the durations for winds of about 700-year return period are close to the traditionally assumed one hour and have limited effects on the wind loads for the strength design. However, wind durations can be much longer than one hour for the lower return period level wind speeds, which can impact the wind responses for serviceability limit state design and cladding and component (C&C) design.