Wind Incidence Angle Research Articles

Experimental and numerical study of wind effect on an ultra‐thin concrete triangular plan shell structure

AbstractSelf‐supporting concrete shell structures are highly efficient in distributing loads, which can result in very reduced thicknesses (ultra‐thin), giving them remarkable slenderness. Due to their geometric complexity, it is difficult to predict how they interact with wind action. The main aim of the present study is to assess the mean surface pressure coefficient distribution in a shell with a triangular plan shape and three supports for different angles of wind incidence. To determine the distribution of surface pressure coefficients and lift and drag force coefficients, an experimental study was carried out in a wind tunnel, and a numerical simulation study was performed through computational fluid dynamics. The experimental and numerical results were analyzed and compared, and making it possible to identify the most critical surface zones and wind incidences when the shell is under the wind action.

Comparative Study of Deflector Configurations under Variable Vertical Angle of Incidence and Wind Speed through Transient 3D CFD Modeling of Savonius Turbine

The demand for clean and sustainable energy has led to the exploration of innovative technologies for renewable energy generation. The Savonius turbine has emerged as a promising solution for harnessing wind energy in urban environments due to its unique design, simplicity, structural stability, and ability to capture wind energy from any direction. However, the efficiency of Savonius turbines poses a challenge that affects their overall performance. Extensive research efforts have been dedicated to enhancing their efficiency and optimizing their performance in urban settings. For instance, an axisymmetric omnidirectional deflector (AOD) was introduced to improve performance in all wind directions. Despite these advancements, the effect of wind incident angles on Savonius turbine performance has not been thoroughly investigated. This study aims to fill this knowledge gap by examining the performance of standard Savonius configurations (STD) compared to the basic configuration of the deflector (AOD1) and to the optimized one (AOD2) under different wind incident angles and wind speeds. One key finding was the consistent superior performance of this AOD2 configuration across all incident angles and wind speeds. It consistently outperformed the other configurations, demonstrating its potential as an optimized configuration for wind turbine applications. For instance, at an incident angle of 0°, the power coefficient of the configuration of AOD2 was 61% more than the STD configuration. This ratio rose to 88% at an incident angle of 20° and 125% at an incident angle of 40°.

Numerical investigation of interference effects on tall power station chimney subjecting varying wind incident angles

Numerical investigation of interference effects on tall power station chimney subjecting varying wind incident angles

Natural Ventilation to Manage Ammonia Concentration and Temperature in a Rabbit Barn in Central Mexico

The concentration of ammonia (NH3) and the temperature of the air surrounding the rabbit habitat in the farm condition basic health processes such as breathing and feeding. The indoor climate in a rabbit farm is largely conditioned by the ventilation system (air conditioning). The objective of this study was to build a numerical model based on computational fluid dynamics (CFD) in order to evaluate, by numerical simulations, the air dynamics of a rustic farm. After the validation of the computational model, the thermal gradient and ammonia concentration were analyzed under three wind incidence angles (0°, 45°, and 90° with respect to the horizontal Z axis of the facility). The results of the simulations showed that, in the area occupied by the rabbits (AOR), the concentration of ammonia with respect to the source was reduced by 37.3% in the most favorable case (wind direction at 45°), and 21.2% in the least favorable case (wind direction at 0°), and the indoor temperature presented a maximum difference of 2 °C with respect to the outside temperature. Climate control is a more expensive cost in rabbit farm exploitation; dynamics modulation can serve as an auxiliary tool for reducing health risks in rabbits. The use of models based on fluid dynamics allowed us to understand the efficiency of the ventilation system, which must be increased to reduce the found temperature gradient. Through numerical simulation it will be possible to find alternatives to increase the ventilation rate.

Interference effects on two rectangular tall buildings with coupling bridge in close proximity

The study is on the variation of pressure in different faces of rectangular plan-shaped tall buildings with interference conditions due to the presence of another building with the same shape and dimension connected through a multipurpose bridge. The analysis is done on computational fluid dynamics (namely ANSYS CFX) for 0° to 90° wind incidence angle (WIA). The buildings are spaced 60 m from each other. Different cases have been taken and analyzed based on the different positions of the bridge (i.e., 0.33H, 0.5H, and 0.67H) and compared with the isolated case (i.e., buildings without the bridge). A comparison study has been done in the form of interference factor (IF), so we can clearly understand the effect of the bridge at different heights of the building and isolated conditions on rectangular plan-shaped buildings. The study shows that when the bridge is at 0.5H and 0.33H, the force coefficient along X and Y produces similar results to an isolated condition for WIA of 60° and 30°, respectively.

Wind shadowing of a sonic anemometer in low Reynolds number flows

Computational Fluid Dynamics (CFD) simulations have been carried out to better understand the wind shadowing effects on a sonic anemometer system. The anemometer will measure wind speed on the surface of Mars and the stratosphere of Earth.The wind velocity vector is measured through the difference in acoustic time of flight in 3 directions. However, the structure itself disrupts the flow and creates an internal wake. To understand this and generate correction factors, CFD simulations were run under Mars surface conditions while varying incident angle and flow speed. Spalart-Allmaras turbulence models were employed in both steady and unsteady Reynolds Averaged Navier Stokes (RANS) frameworks and compared to a laminar model. Due to the low Reynold’s number (<150) we observe no shedding at speeds below 10 m/s. At speeds below 10 cm/s the flow diverts around the structure and sensitivity drops. At intermediate speeds near 5 m/s the wind shadow ratio (WSR) varies substantially with incident wind angle. Design changes to the structure allowed us to improve the worst WSR from 38% to 47%. We were also able to quantify correction factors. Validating comparisons to water tunnel and wind tunnel measurements will be presented.

Investigation of interference effect on hexagonal plan-shaped high-rise building under wind excitation

ABSTRACT This paper represents a detailed investigation of tall hexagonal buildings in the presence of a similar type of single-interfering buildings and double-interfering buildings. The building models are analysed using CFD in ANSYS CFX module. The k-ε turbulence model is used to carry out the numerical simulations. For two buildings case (single interfering building), the wind incidence angles (WIA) vary from 0° to 90° at an interval of 15° and from 90° to 360° at an interval of 30°. The variable spacing of 200 mm, 300 mm, 500 mm and 800 mm has been kept apart for two building case. For the three building case (double interfering buildings), the orientation of the interfering buildings kept varying from 15° to 90° with a regular interval of 15°. The variable spacing between the principal building and interfering buildings is kept 300 mm and 500 mm apart. The model height for both cases is 500 mm in 1:300 length scale. The variation of interference factors for both pressure and force coefficients are evaluated and graphically represented to investigate the hexagonal building model. The interference Factor is found to be minimum at 90° WIA in each of the faces irrespective of spacing between buildings.

Distribution of common pipistrelle (Pipistrellus pipistrellus) activity is altered by airflow disruption generated by wind turbines.

The mechanisms underlying bat and bird activity peaks (attraction) or losses (avoidance) near wind turbines remain unknown. Yet, understanding them would be a major lever to limit the resulting habitat loss and fatalities. Given that bat activity is strongly related to airflows, we hypothesized that airflow disturbances generated leeward (downwind) of operating wind turbines-via the so-called wake effect-make this area less favorable for bats, due to increased flight costs, decreased maneuverability and possibly lower prey abundance. To test this hypothesis, we quantified Pipistrellus pipistrellus activity acoustically at 361 site-nights in western France in June on a longitudinal distance gradient from the wind turbine and on a circular azimuth gradient of wind incidence angle, calculated from the prevailing wind direction of the night. We show that P. pipistrellus avoid the wake area, as less activity was detected leeward of turbines than windward (upwind) at relatively moderate and high wind speeds. Furthermore, we found that P. pipistrellus response to wind turbine (attraction and avoidance) depended on the angle from the wake area. These findings are consistent with the hypothesis that changes in airflows around operating wind turbines can strongly impact the way bats use habitats up to at least 1500 m from the turbines, and thus should prompt the consideration of prevailing winds in wind energy planning. Based on the evidence we present here, we strongly recommend avoiding configurations involving the installation of a turbine between the origin of prevailing winds and important habitats for bats, such as hedgerows, water or woodlands.

Wind Effects on Re-Entrant Wing Faces of Plus Plan-Shaped Building

The wind flow patterns and pressure distribution around a plus-shaped building are significantly influenced by re-entrant corner dimensions and building height. The present study aims to find the wind effects and study the pressure distribution with different flow patterns. The building has a plan area of approximately 300 square meters and a height of 50 m, maintaining equal lengths for the re-entrant corners. The research study is performed using the ANSYS CFX academic version. The study employs diverse visualizations, featuring the pressure coefficient (CPe), vertical and specific surface streamlines, and pressure contours. Wind incidence angles for the study are varied from 0° to 90° at an interval of 15°. Building dimensions are scaled down as per the ASCE wind tunnel test manual, and the length scale is kept at 1:100 for CFD investigation. This approach yields crucial insights into the circulation of wind patterns and the distribution of pressure across a wide range of wind incidence angles. The influence of streamlines in the bottom portion of the building model is relatively minimal. In contrast to the upper portion, the bottom exhibits robust vortices, particularly for the wind angles varying from 0° to 30°. Positive pressure is observed on the windward face, and the leeward face and side face exhibit negative pressure. This study furnishes valuable insights into flow patterns and pressure distribution across a wide range of wind incidence angles from 0° to 90° at an interval of 15°. These findings contribute significantly to a thorough comprehension of the wind flow patterns and pressure distribution around the plus-shaped building model.

Wind loads on structural members of rack-supported warehouses

Rack-supported warehouses (RSWs) represent a modern typology of storage racks. In this system, cladding panel weight and corresponding applied loads, such as wind or snow load, are supported by storage racks, in addition to pallet load and seismic action. While this structural system allows for reducing the amount of structural steel, the uprights and beams, composing each rack, are directly exposed to the wind during the earliest erection phases. This load condition may govern the design of the uprights or that of temporary bracings. Wind load estimation requires the knowledge of the aerodynamic coefficients of each structural member section, for any angles of wind incidence. Unlike any common structural steelwork section, no data are available in the literature for RSW member sections. The current work represents a first step to cover this lack in the literature by reporting the results of an extensive wind tunnel campaign carried out on several portions of uprights and beams commonly designed and produced for RSWs. The results highlight the need for wind tunnel tests on RSW member sections when producers can no longer afford an overestimation of the wind load. In addition, conservative values of the aerodynamic coefficients are provided for preliminary wind load estimations or temporary bracings design. Empirical relationships for the aerodynamic coefficients, changing with equivalent side ratio, are also reported. Finally, design recommendations are provided by highlighting a critical structural configuration during the early erection phases of RSWs that govern the design of the uprights or temporary bracings. A worked example is then developed to clarify the application of the present results in the definition of wind loads.

CFD Study of Pressure Distribution on Recessed Faces of a Diamond C-Shaped Building

A building situated in the flow path of the wind is subjected to differential velocity and pressure distribution around the envelope. Wind effects are influenced by and vary for each individual shape of a tall building. Tall building structures are considered as cantilever structures with fixed ends at the ground. Wind velocity acting along the height of the building makes the velocity and pressure distribution more complex; as the height of the building structure increases, wind velocity increases. This study discusses the effect of the wind on an irregular cross-section shape. The present study was conducted numerically with a building model placed in a virtual wind tunnel using the ANSYS (CFX 2020 Academic Version) software tool. Wind effects are investigated on a building model situated in a terrain category-II defined in IS: 875 (Part 3): 2015; wind scale model of 1:100 and turbulence intensity are at 5% and power law index α is considered to be 0.143. The validation and verification of the study were made by comparing pressure coefficients on different faces of a rectangular model of similar floor area and height as that taken for a C-plan dia-mond-shaped model under similar boundary conditions, wind environment, and solver setting of numerical setups. The values of surface pressures generated on the recessed faces of the model and wind flow patterns within the recessed cavity were studied at wind incident angles 0°, 30°, 60°, 105°, 135°, and 180°. The critical suction on all the recessed faces was observed to be at a 105° angle of wind attack.

Structural parameters of Wrench – C shape building using CFD

Wind flow pattern and generation of strong and large eddies is mainly responsible to the wind pressure and suction intensity in and around the tall building. If the shape of the structure is not vary common then the wind generated effects need to evaluate for the high rise structure this is because of the reason that the data for the regular plan cross sectional shape is available in the various international standards. This study investigating the wind effects on irregular cross sectional shape tall building using CFD tool ANSYS CFX. The current study evaluates the wind impacts for a boundary layer atmospheric wind flow from 0° to 180° at a 15° interval. The power law described in IS: 875 (Part 3): 2015 for terrain category II follows the wind profile. For a rectangular model, the values of the pressure coefficients are compared using the numerical simulation and the information supplied in IS 875. Results are given at numerous locations, including pressure coefficients around the building model’s periphery and force and moment coefficients for wind incidence angles ranging from 0° to 180° at 15° intervals.

The Effect of Wind Direction on the Cooling Capacity of Short Dry Natural Draft Cooling Towers Operating in Close Proximity

Abstract The layout of multiple natural draft dry cooling towers could have a significant influence on the performance of the cooling system in concentrated solar power (CSP) plants; however, this has never been quantified. Hence, this work used computational fluid dynamics (CFD) modeling to analyze the cooling capacity of two short natural draft dry cooling towers (NDDCTs) on a common site for a range of tower spacings, wind-speeds, and wind incidence angles. The results show that the cooling performance of the towers is a strong function of tower spacing and their orientation with respect to the wind direction. It was found that when the wind came at a 90-deg wind incidence angle (i.e., normal to a line drawn between the two towers), their cooling capacity was improved at tower spacings of less than 1.8 tower diameters (1.8D), though for the other tower spacings, there was no interaction between the towers. However, with the wind at 45 deg to the towers, the flow around the towers resulted in a decrease in their cooling capacity at tower spacings of 1.8D and 2.6D. Most interestingly, it was found that orienting the towers in line with the prevailing wind direction delivered improvements in the cooling capacity of up to 30%. This is due to the windward tower acting as a passive windbreak. Hence, as CSP plant capacity is increased, and additional cooling towers are required, these should be placed close to any existing tower and oriented along the line of the prevailing winds.

Shape optimization of a corner‐recessed square tall building to reduce mean wind pressure using a multi‐objective genetic algorithm

SummaryThe current study aims to determine how the corner recession affects tall buildings with square plans. A series of numerical simulations have been conducted to find the parametric models' wind pressure. Visualization tools, such as contour plots and streamlines, present the wind flow near the buildings. Numerical simulations are conducted using RANS k‐ℇ turbulence models considering a length scale of 1:300. Subsequently, a shape optimization study has been carried out to propose a suitable percentage of corner recession, which should minimize the wind pressure on different faces of the building. As design factors, the amount of corner recession (S) and the wind incidence angle (Ø) are taken, along with the mean pressure coefficients (Cp) on the various building faces. Due to the eight axes symmetry of the building configuration, the random sampling technique is used for the Design of Experiment while accounting for the 0°–45° wind angle of attack. The Response Surface Approximation (RSA) is used to construct surrogate models of the objective functions. The RSA models are validated with wind tunnel test results presented in previously published articles. The optimization study is carried out using the multi‐objective genetic algorithm technique.

Exploring Controls on Coastal Dune Growth Through a Simplified Model

AbstractProcess‐based morphodynamic models can be useful in understanding coastal dune responses to disturbances, as well as possible evolutionary patterns. To this aim, we employ Duna, a simplified 1D morphodynamic model, to assess the influence of dune morphology (height and slope) on sand transfer and deposition across the dune profile for different beach widths and wind incidence angles through idealized experiments. Simulations of real conditions show good model performance, both in wind flow reproduction and in topographic change along the dune profiles tested. The idealized experiments show that wind speed increases and sand accumulation decreases logarithmically with dune height and linearly with stoss slope along the dune profile. Fetch and cosine transport limiting parameters are reflected in the sand accumulated windwards from the toe, while sand transfer to the dune appears controlled by multiple factors; the higher the dune and/or the narrower the beach, the likelier that maximum accumulation occurs under oblique winds. Results point to two different types of evolution for high dunes. Either the vegetation is dense enough to maintain the stoss position, in which case vertical growth near‐ceases and seaward progradation is promoted, or the stoss is eroded and landward retreat dominates, in which case sand transfer to the crest and lee continues as a mixture of low input from the beach and recycled sand from the stoss.

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.

Estimating Maximum Power from Wind Turbines with a Simple Newtonian Approach

Recent findings in action mechanics showing torques result from rates of variation in impulsive action motivated this more fundamental approach to estimate maximum power from wind turbines. Newton’s third law of equality of action and reaction provides a strictly causal mechanism of wind power from the deflection of wind momentum by twice its angle (θ) of incidence on rotor blades. The lateral reaction needed to conserve wind momentum provides the turning moment for the turbine rotors. This direct approach challenges the current continuum mechanism for generating power from flows of kinetic energy in wind passing through the areas swept by rotating blades. Action mechanics integrates the rates of impulsive wind action on turbine blades as torques (∫mrvdθ/dt ≡ mv2) exerted on rotor surfaces at decreasing radii. Windward torque (Tw) is estimated from rotor dimensions, the angle of wind incidence and radial action of wind impulses on the blade surfaces (also ∫mrvdθ/dt ≡ mv2). A leeward torque (Tb) for back reaction of turbine blades on air mimics drag exerted parallel to the plane of rotation of the blade. Net torque is then converted to potential power (Tw - Tb)Ω by the angular velocity (Ω) of the turbine rotors, a function of tip speed ratio to wind speed. New contributions from action mechanics for managing wind power include larger estimates of its possible magnitude by including vortical energy, much larger than the kinetic energy. Better predictions of limits to wind power can be made, by including control of optimal wind angle and blade length. An analysis of the equivalence of deflected air momentum on turbine blades or air foils for aircraft reveals that even the lifting action on air foils can be explained by the normal reaction to the momentum in an air stream, also deflected by an angle twice that (2θ) of incidence, validating application of action mechanics to airflight. A mechanism for release of vortical field energy from laminar flow of air in anticyclones is predicted in turbulent downstream wakes, possibly assisting achievement of maximum power output by wind farms. Significant heat release by downwind turbulence from vortical energy requires care for their location. Diligence demands that use of windfarms as major sources of renewable energy should minimize any environmental impacts, such as drying of landscapes.

EFFECTS OF ROOF SHAPES ON WIND PRESSURE DISTRIBUTION OF MULTI-SPAN LOW-RISE BUILDINGS

The present study demonstrates the numerical investigation to find out the effects of roof shapes on the wind pressure distribution of multi-span low-rise buildings. Most of the wind load standards of various nations are provided with wind load information of isolated low-rise buildings which in turn practically came out to be inapplicable during the designing of low-rise buildings with multi-spans. Also, most of the wind load studies are carried out using boundary layer wind tunnel (BWLT) which is sometimes not available, time taking process, and is expensive. Therefore, in the present research, numerical simulation has been done for the model of a low-rise building. For investigation, the Ansys CFX platform has been used with the k-ε turbulence model for different angles of wind incidence at an interval of 15°. The wind pressure distribution has been investigated for the model low-rise building with a rectangular plan having six spans of different roof forms i.e., cylindrical roof, mono-slope roof, hip roof, and dome roof. The outcomes of the present numerical investigations are presented in the contour plots of wind pressure and coefficients of wind-induced pressure on the different roof forms of low-rise buildings. The outcomes of the study will be so much beneficial to structural design engineers while considering the wind loads calculations on the different roof forms for low-rise buildings.

Impact of MTMD on response control of “V” shaped tall building under dynamic wind excitation

In the present study, the principal objective is to investigate the role of multiple tuned mass damper (MTMD) to reduce aerodynamic effect of wind force on “V” plan-shaped high-rise buildings with the various internal limb angle. Distinct cases have been made by considering the angle between the limbs is 90° which is gradually increased from 90° to 150° with 15° regular interval and decreased from 90° to 40° with 10° regular interval maintaining same plan area and limb width subjected from 0° to 180° wind incidence angle with 30° regular interval. Computational fluid dynamics (CFD) is adopted to determine the aerodynamic coefficients by numerical simulation. A polynomial expression has been proposed to compute force, moment, and torsional coefficient along X, Y, and Z direction from the entire result for avoiding rigorous calculation. Dynamic wind time history in along and crosswind is obtained using maximum force coefficient. The dynamic response analysis such as peak displacement, acceleration is obtained for selected models with MTMD and effectiveness of MTMD is computed. Finally, the influence of MTMD and internal angle variation on the wind-induced response of “V” plan-shaped buildings have been observed to determine suitability of internal angle variation based on the numerical result.

Numerical Simulation of the Lunar Polar Environment: Implications for Rover Exploration Challenge

The lunar polar regions are key areas for future exploration due to the long-term continuous illumination and persistently shadowed regions that can cold trap abundant water and other volatiles. However, the complex terrain, dynamic lighting, and solar wind-induced electric-field environment present multiple challenges for polar investigation and sampling missions. China’s Chang’E-7 (CE-7) will explore the Moon’s south polar region in 2026. One of the scientific goals is to drill samples in a wide area with a rover for in situ analysis. This study analyzes the engineering constraints of the polar illumination condition, slopes, and electric field for landing and sampling-site selection. Then, we create a 3D model of CE-7’s lunar rover in three operating environments by employing the Spacecraft Plasma Interaction Software, with the rover sampling (i) on a flat surface, (ii) in a shadow, and (iii) near a meter-scale crater under different solar altitude angles. The results show that the rover can be charged to different potentials under the combined effects of solar wind incident angles and surrounding terrains. We find that a favorable traversing and/or sampling site of the rover for future polar exploration is in the upwind direction of a bulge (positively elevated terrains, such as the lander or boulders) or crater, which will cause a minimum charging effect on the rover. Our results have important implications for minimizing the risk of charging effects and guiding the lunar polar region exploration.