Wind Dynamic Pressure Research Articles

Large eddy simulation of aerodynamic wind pressure on a tall rectangular building by modified synthetic volume forcing method

To accurately predict wind pressures on a tall building by numerical Computational Fluid Dynamics (CFD) using the Large-Eddy Simulation (LES) turbulent model, it is essential to generate inflow with realistic turbulence characteristics. The Discretizing and Synthesizing Random Flow Generation (DSRFG) method, as one of the synthetic Fourier methods, has received significant attention in the Computational Wind Engineering (CWE) community because of its ability to strictly satisfy the continuity condition and generate turbulent wind with the desired power spectra. In traditional LES, the desired turbulent wind is normally generated and specified at the inlet. However, this treatment often leads to significant attenuation in turbulence energy in the high-frequency band of the fluctuating wind speed spectrum along the flow direction and unrealistic large-amplitude wind pressure fluctuations, resulting in unsatisfactory prediction performance. The Synthetic Volume Forcing (SVF) method effectively overcomes these limitations by introducing turbulence as volume force into the moment Navier-Stokes (N-S) equations. In this study, the DSRFG method is applied to generate a fluctuating wind field in combination with the SVF method to simulate dynamic wind pressures on a tall rectangular building through open-source software OpenFOAM. The turbulence intensity amplification factor (TIAF) is introduced in the SVF method to further improve its simulation accuracy. Comparison of results with wind tunnel test results verifies that the proposed TIAF-SVF numerical method developed in this study achieved sufficient accuracy in predicting wind pressures on tall buildings.

Investigation of seeding performance of a novel high-speed precision seed metering device based on numerical simulation and high-speed camera

Numerical simulation and high-speed photography technology are used in this work to obtain the key factors affecting the seeding performance of a novel high-speed centrifugal filling-cleaning precision seeding metering device under different conditions. The effects of key parameters, including seed-metering diversion turbine structure, dynamic wind pressure, seed quantity, and ground speed, on the seeding performance of the high-speed seed metering device are investigated. The results show that a diversion turbine structure with diversion and controlled disturbance flow increases seed pressure and enhances the filling process. Meanwhile, a correlation between dynamic wind pressure and seed movement velocity is established using a high-speed camera-based experimental approach. Maintaining 24 internal seeds is crucial to guaranteeing the quality of feed index. Specifically, under the simulation conditions, when the ground speed is 14 km/h (corresponding to a rotation speed of 194.5 rpm), the corresponding dynamic wind pressure is identified as 1.5 kPa, the corresponding seed plate speed is 2 m/s, the corresponding optimal feeding rate should be maintained at about 14 seeds/s, and the seed inlet velocity is 3 m/s. Additionally, the results of comprehensive bench and field seeding performance experiments demonstrate that, as the seeding speed increases, there is no apparent seeding performance decline, and even under high-speed operational conditions, the quality of feed index under different ground speeds exceeds 90%.

Comparison of wind-resistant capacities of standing seam roof systems under static uniform pressures and dynamic non-uniform wind pressures

Static uniform pressure tests are widely recommended to determine the ultimate capacities of standing seam roof systems in many building standards and guidelines, but such ultimate wind-resistant capacities are usually much different from those under dynamic non-uniform wind pressures. Through the comparison of the ultimate capacities of standing seam roof systems under static uniform pressures and dynamic non-uniform wind pressures by finite element simulations, the definition and calculation steps of influence coefficients of dynamic non-uniform wind pressure distribution (ICDNWPD) are proposed to reflect the effects of actual wind pressure distributions on wind-resistant capacities of the roof cladding systems. The effects of roof zones, support spacings, and terrain categories on the ICDNWPDs of flat roofs are investigated. The results show that the ICDNWPDs of the edge and interior regions are approximately 1.27–1.42 times those of the corner zones, and the ICDNWPDs are more sensitive to the roof zone than the support spacings and terrain categories. The factors of safety of roof systems with larger spans or under smoother terrain or located in the roof corner zone should be greater, which cannot remain constant.

Quantifying the Key Factors Affecting the Escape of Planetary Atmospheres

The habitability of Earth-like planets is an increasingly important subject in astrophysics and in planetary sciences. Atmospheric escape plays a vital role in the evolution of the habitability of Earth-like planets. By systematically analyzing the numerical simulation results of the interactions between the planetary atmospheres and the stellar winds, in this work, we evaluate various factors related to the atmospheric nonthermal ion escape rates, including planetary parameters (e.g., mass, density, radius, semimajor axis, etc.) and stellar wind parameters (e.g., density, velocity, and interplanetary magnetic field (IMF) strength). Furthermore, we determine and quantify the key factors affecting the planetary atmospheric nonthermal ion escape rates. Our results show that the correlation coefficients between planetary atmospheric nonthermal ion escape rates and stellar wind density, IMF strength, and the ratio of the planetary radius to the planetary semimajor axis are 0.98 (0.88), 0.95 (0.81), and 0.87 (0.59), respectively, in the scenario of maximum (minimum) dynamic wind pressure. This means that the planetary atmospheric nonthermal ion escape rates increase with the increasing stellar wind density, the increasing IMF strength, and the increasing ratio of the planetary radius to the planetary semimajor axis. Generally, the nonthermal ion escape rates of planetary atmospheres are more sensitive to stellar wind parameters than to others. In addition, we determine the functional relations of the above three significant parameters for evaluating and quantifying the effects of such key physical factors on the nonthermal ion escape rates of the planetary atmospheres. Our findings will be very useful for better understanding the key factors that influence the escapes of planetary atmospheres.

АЛГОРИТМИЗАЦИЯ ОПРЕДЕЛЕНИЯ СООТВЕТСТВИЙ МЕЖДУ ДИНАМИЧЕСКИМИ ПАРАМЕТРАМИ РЕАКТИВНЫХ ДВИЖЕНИЙ КОНСТРУКТИВНЫХ ЭЛЕМЕНТОВ ЗДАНИЙ ОТ ДИНАМИЧЕСКИХ ВОЗДЕЙСТВИЙ

In this paper, two algorithms have been developed that allow us to obtain in more detail, depending on the kinematic characteristics of structural elements and initial conditions, the estimated dynamic characteristics of external influences as the results of the reactive behavior of structural elements of buildings and structures to these influences. Variants of reactive motions in inertial and non-inertial reference systems from static and dynamic wind pressure are considered. Two problems related to finding correspondences between the resultant acting forces (F) and changes in the velocities and accelerations of reactive movements of structural elements over a certain time interval have been solved.

A framework for estimating water ingress due to hurricane rainfall

Hurricanes can have adverse effects on residential communities and pose a significant risk to their economic prosperity. The ingress of water into a building due to wind-driven rain (WDR) and inland flooding can cause significant damage leading to downtime or temporary loss of housing. Existing frameworks focus on estimating the amount of water ingress due to WDR and inland flooding separately. This paper provides a comprehensive framework that considers both WDR and inland flooding when estimating the amount of water ingress into residential buildings due to hurricane rainfall. The framework estimates the water ingress due to WDR by combining the WDR intensity with the perforated area of the building envelopes. The intensity of the WDR is quantified using an Eulerian Multi-phase Model. The buildings’ envelope is considered susceptible to damage from the impact of windborne debris and excessive dynamic wind pressure. The framework to characterize and quantify inland flooding uses a coupled hydrologic-hydrodynamic model to estimate the inundation depth at each building. A case study consisting of a residential community in Houston, TX, which is subject to Hurricane Harvey illustrates the ability of the framework to capture the influence of WDR and inland flooding when quantifying water ingress.

Risk and fragility assessment of residential wooden buildings subject to hurricane winds

Hurricanes are one of the major causes of damage and loss to residential wooden buildings in the United States. The study of hurricane-imposed risks to residential wooden buildings is, therefore, a fundamental step to mitigate these damages and losses. Within this context, a probabilistic methodology is provided for the fragility analysis of residential wooden buildings. Two damage mechanisms are considered in this methodology, excessive dynamic wind pressure and impact from windborne debris. Unlike existing frameworks, the methodology defines the geometric configuration as well as the required extension of the neighboring buildings to estimate the damage from both mechanisms. A case study illustrates the methodology on residential communities composed of archetype gable-roof buildings. Ten construction cases are defined to cover a range of resistances of building components for both considered damage mechanisms. Three floor-area ratios (FAR) are also considered. The resulting fragility curves highlight: (1) the effect of the FAR on enhancing the performance of residential buildings due to the effect of shielding; and (2) the significance of windborne debris in increasing the estimated hurricane risk. The estimated fragility curves can be used to directly model residential buildings in community resilience frameworks.

FULL-SCALE EXPERIMENTAL TESTING TO INVESTIGATE WIND-INDUCED VIBRATIONS ON CURTAIN WALL SYSTEMS

Curtain walls are dominant cladding components of mid to high-rise buildings in modern architecture. However, the curtain wall systems have been observed highly susceptible to vibrations leading to component or system-level failure during recent extreme wind events. This paper studies the complex mechanisms of wind induced vibration (WIV) functionality at the system-and component-levels. A wind testing experiments for a full-scale single-skin façade panel was conducted at the Wall of Wind experimental facility (WOW EF) at Florida International University (FIU). Effect on the vibration of the curtain wall due to the addition of sunshade fin is also studied. The experimental protocol included testing the samples (with and without sunshade fins) at various wind speeds from 22.3 m/s to 40.1 m/s with 8.9 m/s intervals in open terrain. Effect of wind direction is also considered varying from 0 to 180 degrees with 45-degrees interval. The tests were performed on two sets of panels: (1) a polycarbonate panel (with the geometric properties maintained) to obtain dynamic wind pressure data; (2) actual glazing units that are instrumented with accelerometers and strain gauges at critical sensing locations. The experimental results indicate that the sunshade fins have a stiffening effect on the joints of the curtain walls while overall increasing the wind pressure on the panel. Dynamic amplifications on the glazing were in the order of 1.1 to 1.8 which underline the importance of studying dynamic effects on the façade systems.

A RESILIENCE-BASED ASSESSMENT OF THE PERFORMANCE OF RESIDENTIAL COMMUNITIES SUBJECT TO HURRICANE HAZARD

Hurricanes are among the most devastating and costliest natural hazards. This devastating impact urged governments and policymakers to implement mitigation plans and strategies that can enhance the community’s resilience against hurricanes. A fundamental step to gauge the performance and effectiveness of these mitigations plans is to develop computational frameworks that can provide a probabilistic assessment of the resilience of the community. Therefore, this paper presents a framework to probabilistically estimate the resilience of residential wooden buildings against hurricane winds. The framework estimates the post-hurricane damage due to dynamic wind pressure and the impact of windborne debris using an engineering-based hurricane vulnerability. The building recovery function is then estimated by integrating the estimated damage with a building-level recovery model. By aggregating building recovery functions, the community recovery function is obtained. The Monte Carlo simulation method is used to account for uncertainties related to the hazard intensity, community vulnerability, and recovery process. The framework is applied to a residential neighborhood in Miami, FL. This framework can help decision-makers to compare current community resilience with target levels, identify the gap, and set strategies to improve community resilience.

Experimental investigation of the wind direction influence on the cooling of photovoltaic panels integrated in double skin façades

The paper presents a wind tunnel experimental investigation of a small-scale building model (1:30). The main objective of the study is to determine the influence of the reference wind direction over the ventilation inside the double skin façade (DSF) channel. The analyzed system consists of a building equipped with photovoltaic panels as the exterior glazing of DSF. The tests were achieved by conceiving and implementation of an experimental program using a wind tunnel with atmospheric boundary layer. The aim is to determine with acceptable probability the velocities that can be reached in the ventilated façade channel during the warm season and to establish a correlation between the external reference velocity magnitude and direction and the velocity field generated inside the channel of the façade. Measurements were carried out for the reference wind speed, total, dynamic and static pressure both in the reference point and inside the façade channel. The results of the investigation highlighted the correlation between the velocity and direction of the reference wind and the dynamics of the air movement inside the double skin façade. The measurements showed that for the analyzed configuration of the double skin façade, there is an optimal wind direction that ensures the best cooling effect to photovoltaic panels. Also, the convective heat transfer coefficients were determined under these conditions. The decrease of the photovoltaic panel’s temperature determines a raise of its efficiency and generated power.

Effects of the solar wind and the solar EUV flux on O+ escape rates from Venus

We investigate dependences of O+ escape rates from Venus both on the solar wind and the solar extreme ultraviolet (EUV) flux by using the 8.5-year dataset (May 2006 to December 2014) of the Ion Mass Analyzer and the magnetometer aboard Venus Express. We examine the O+ escape rates for 8 different conditions depending on the solar wind's dynamic pressure, the magnitude of the motional electric field, and the solar F10.7 index which is a good indicator for the solar EUV flux. We find that the O+ escape rates are mainly controlled by the motional electric field and the solar EUV flux in the magnetosheath. We suggest that the ion pickup by the motional electric field is the main ion escape process in the magnetosheath. On the other hand, in the induced magnetosphere, the O+ escape rates are controlled by not only the solar wind and the solar EUV flux but also return flows. We find that the return flows become dominant in the magnetotail in the solar maximum period, which results in reducing the net escape rates in the induced magnetosphere. As a result, net escape rates tend to become larger in the solar minimum period than those in the solar maximum period. Further analysis of the magnetic field shows that the return flows are preferably observed when the magnetic field component along the Venus-Sun line reverses multiple times in the magnetotail. We suggest that ionospheric irregular structures or IMF sector boundary crossings form the fine scale anti-parallel draping pattern of the interplanetary magnetic field (IMF), and this causes ion acceleration towards Venus due to the magnetic tension force or magnetic reconnections. Another possibility is precipitations of O+ pickup ions on the nightside of Venus under the fine structure of IMF. Since the return flows significantly affect the O+ escape rates from Venus, it is important to study not only long-term transition of ion outflow from Venus but also return flows to estimate the net ion loss from Venus over the long history of the solar system.

Characterization of translating tornado-induced pressures and responses of a low-rise building frame based on measurement data

This study presents an analysis and characterization of dynamic wind pressures and internal forces of a low-rise building frame using measurement data obtained from a tornado simulator. The deterministic time-varying mean pressure component is extracted from the time history record using discrete wavelet transformation (DWT) approach. A continuous wavelet transformation (CWT) based approach is employed for determining the evolutionary power spectral density (EPSD) functions and time-varying standard deviation (STD) as well as co-variance of dynamic pressures. The results showed that the characteristics of dynamic pressures are strongly affected by the location of tornado, and are very different from those under straight-line wind. The pressure drop caused by tornado vortex plays a key role in defining the pressure characteristics. The building frame responses are also calculated from the statistics of pressures. The equivalent static wind loads (ESWLs) causing peak responses are defined by using the gust response factor approach. The effect of translation speed of tornado vortex is also investigated. The translating tornado vortex leads to a delay of occurrence of maximum time-varying mean and STD, and reduction in maximum STD thus peak response. It also makes the energy distribution of pressure fluctuations shifted to higher frequencies with a broader power spectrum. Finally, it is shown that the tornado-induced responses are significantly higher than those from ASCE 7-10.

Quasi static study on tall building based on measured dynamic wind pressure

One important issue that arrives the serviceability design of many high-rise buildings is wind-induced discomfort. The assessment of discomfort risk for the buildings occupants due to the wind action is, therefore, of primary importance. The treatment of wind loading, which is universally applied to the design of typical low to medium-rise structures, can be unacceptably conservative for the design of very tall buildings. This study presents the experimental results of evaluating wind pressure distributions on all four faces of a tall rectangular building with 1:1.5:7 ratio. The model is made up of the acrylic sheet with a geometric scale of 1:300 with plan dimension of 10 cm x 15 cm and height of 70 cm. The model is instrumented with 192 numbers of pressure taps at eight different levels were denoted as Level 1 to level 8 corresponding to the heights of z/H ratio (where H is the height of the model) are 0.10, 0.20, 0.30, 0.50, 0.70, 0.80, 0.90 and 0.95 respectively. The model is tested using a Boundary Layer Wind Tunnel (BLWT) for twelve angles (0°, 5°, 10°, 15°, 25°, 33.5°, 45°, 56.5°, 60°, 75°, 87.5° & 90°) of wind incidence under plain terrain condition. The measured pressure data have been integrated to evaluate mean pressure coefficients, drag & lift coefficients along wind direction and perpendicular to wind direction, mean moment coefficients at each of measured levels. The average pressure coefficient values on the windward face are almost comparable at all levels, while on the smooth face and side faces the lower levels have a minimum value compared to higher levels. Mean force coefficients for level 8 are always higher than all the other levels due to edge effect at top levels. The average drag coefficient values are a good agreement with code values (IS: 875 (Part3)-1987).

Research on Power Calculation Method of High Speed Rotary Device under Wind Loads Crystals

The wind load has a great influence on the power of large rotary devices working outdoors. In the power calculation formula of the rotary devices, the static air pressure is often used as the wind resistance of the whole device. But in fact, the rotating device bears the dynamic wind pressure during the rotation. This method of calculation will lead to large deviation. Based on this, this paper emphatically studied the dynamic wind load of the rotating device under rotation, and gave a more accurate formula for the calculation of the rotating power. This formula solves the problem of power calculation of the rotating device in high speed rotation. It can be widely used in all kinds of rotating devices.

The response of the H geocorona between 3 and 8 <i>R</i><sub>e</sub> to geomagnetic disturbances studied using TWINS stereo Lyman-<i>α</i> data

Abstract. Circumterrestrial Lyman-α column brightness observations from 3–8 Earth radii (Re) have been used to study temporal density variations in the exospheric neutral hydrogen as response to geomagnetic disturbances of different strength, i.e., Dst peak values between −26 and −147 nT. The data used were measured by the two Lyman-α detectors (LAD1/2) onboard both TWINS satellites between the solar minimum of 2008 and near the solar maximum of 2013. The solar Lyman-α flux at 121.6 nm is resonantly scattered near line center by exospheric H atoms and measured by the TWINS LADs. Along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H column density, assuming optically thin conditions above 3 Re. In the case of the eight analyzed geomagnetic storms we found a significant increase in the exospheric Lyman-α flux between 9 and 23 % (equal to the same increase in H column density ΔnH) compared to the undisturbed case short before the storm event. Even weak geomagnetic storms (e.g., Dst peak values ≥ −41 nT) under solar minimum conditions show increases up to 23 % of the exospheric H densities. The strong H density increase in the observed outer exosphere is also a sign of an enhanced H escape flux during storms. For the majority of the storms we found an average time shift of about 11 h between the time when the first significant dynamic solar wind pressure peak (pSW) hits the Earth and the time when the exospheric Lyman-α flux variation reaches its maximum. The results show that the (relative) exospheric density reaction of ΔnH have a tendency to decrease with increasing peak values of Dst index or the Kp index daily sum. Nevertheless, a simple linear correlation between ΔnH and these two geomagnetic indices does not seem to exist. In contrast, when recovering from the peak back to the undisturbed case, the Kp index daily sum and the ΔnH essentially show the same temporal recovery.

Aerodynamic properties of Wind Turbine Towers based on Wind Tunnel Experiments

The presented investigations aim to suggest more realistic models to predict the dynamic behavior of wind turbine structures. Two key issues are addressed: the aerodynamic damping and the cross-wind vibrations.Based on experimental studies in the boundary layer wind tunnel, aerodynamic information for both effects has been obtained. A scaled model of a wind energy tower (1:150) in combination with complementary models have been tested in a test bench designed to carry out HFFB, dynamic wind pressure and forced-oscillation experiments. Reynolds number based scale effects on the tower model have been studied previously.In the predictions of cross-wind vibrations, the length related correlation of vortices shedding from cylindrical structures plays an important role. Therefore, wind dynamic pressures were measured along static tower and cylinder models using pressure taps to determine realistic values of the vortex shedding correlation length.Motion-induced wind vibrations can be significantly influenced by the aerodynamic damping. Using the forced-oscillations method, experiments have been performed under controlled system oscillation with varying wind speed in prism models and tower model. The measured base model forces were correlated with the model motion using spectral methods to obtain the corresponding aerodynamic stiffness and damping coefficients.Both aerodynamic studies will allow more detailed models for the design of new wind tower structures. The acquired information will be applicable in MB-simulations to obtain more realistic and accurate wind turbine performances

Measurements of dynamic wind pressures on gable roofs – comparison with ČSN EN 1991-1-4

The contribution is dealing with the wind tunnel measurements of dynamic pressures on the canopy roofs. It compares experimentally determined pressure coefficients C p with the values in CSN EN 1991-1-4 and former code CSN 73 0035 as well. The pressures are expressed by the dynamic values. Thus, the averaged values are presented together with the fluctuating part, which significantly contributes to the overall loading. The measurement is carried out at two roof models, two basic directions, and two turbulence intensities.

Processing of dynamic wind pressure loads for temporal simulations

This paper discusses the processing of the wind loads measured in wind tunnel tests by means of multi-channel pressure scanners, in order to compute the response of 3D structures to atmospheric turbulence in the time domain. Data compression and the resulting computational savings are still a challenge in industrial contexts due to the multiple trial configurations during the construction stages. The advantage and robustness of the bi-orthogonal decomposition (BOD) is demonstrated through an example, a sail glass of the Fondation Louis Vuitton, independently from any tentative physical interpretation of the spatio-temporal decomposition terms. We show however that the energy criterion for the BOD has to be more rigorous than commonly admitted. We find a level of 99.95 % to be necessary in order to recover the extreme values of the loads. Moreover, frequency limitations of wind tunnel experiments are sometimes encountered in passing from the scaled model to the full scale structure. These can be alleviated using a spectral extension of the temporal function terms of the BOD.

Specific features of daytime long-period pulsations observed during the solar wind impulse against a background of the substorm of August 1, 1998

Long-period geomagnetic pulsations in the (1.7–6.7) mHz frequency range at 18.25–18.48 UT on August 1, 1998, caused by several successive sudden changes in the solar wind (SW) dynamic pressure, are studied against a background of substorm intensification. The data of the ground stations, which were near local noon (the CANOPUS Canadian network) and on the nightside (the auroral stations in Yakutia and at the IMAGE network), and the INTERBALL-1, ACE, WIND, and GOES 8, extramagnetospheric satellites are used. The effect of the SW plasma and IMF parameters, SW inhomogeneity front inclination, and geomagnetic activity on the pulsation propagation and polarization direction and amplitude is discussed. The properties of pulsations, recorded before the substorm, correspond to the pulsation excitation by the inhomogeneity front incident on the magnetopause during the magnetically quiet period: pulsations propagate from the contact point onto the nightside when the amplitude increases and the polarization sense of rotation is opposite on the dawn and dusk sides. Substorm intensification results in the propagation direction reversal and in a more complex behavior of the pulsation amplitude and polarization on the dayside.

ON THE IMPACT OF RADIATION PRESSURE ON THE DYNAMICS AND INNER STRUCTURE OF DUSTY WIND-DRIVEN SHELLS

Massive young stellar clusters are strong sources of radiation and mechanical energy. Their powerful winds and radiation pressure sweep-up interstellar gas into thin expanding shells which trap the ionizing radiation produced by the central clusters affecting the dynamics and the distribution of their ionized gas. Here we continue our comparison of the star cluster winds and radiation pressure effects on the dynamics of shells around young massive clusters. We calculate the impact that radiation pressure has on the distribution of matter and thermal pressure within such shells as well as on the density weighted ionization parameter $U_w$ and put our results on the diagnostic diagram which allows one to discriminate between the wind-dominated and radiation-dominated regimes. We found that model predicted values of the ionization parameter agree well with typical values found in local starburst galaxies. Radiation pressure may affect the inner structure and the dynamics of wind-driven shells only at the earliest stages of evolution or if a major fraction of the star cluster mechanical luminosity is dissipated or radiated away within the star cluster volume and thus the star cluster mechanical energy output is significantly smaller than star cluster synthetic models predict. However, even in these cases radiation dominates over the wind dynamical pressure only if the exciting cluster is embedded into a high density ambient medium.