Mathematical model of acrosswind dynamic loads on rectangular tall buildings

Full-scale measurements and numerical evaluation of wind-induced vibration of a 63-story reinforced concrete tall building

The twisted wind flow (TWF), referring to the phenomenon of wind direction varying with height, is a common feature of atmospheric boundary layer (ABL) winds, noticeably affecting the wind-resistant structural design and the wind environment assessment. The TWF can be effectively simulated by a guide vane system in wind tunnel tests, but the proper design and configuration of the guide vanes pose a major challenge as practical experience in using such devices is still limited in the literature. To address this issue, this study aims to propose an approach to determining the optimal wind tunnel setup for TWF simulations using a numerical wind tunnel, which is a replica of its physical counterpart, using computational fluid dynamics (CFD) techniques. By analyzing the mechanisms behind guide vanes for generating TWF based on CFD results, it was found that the design must take into account three key parameters, namely, (1) the distance from the vane system to the side wall, (2) the distance from the vane system to the model test region, and (3) the separation between the vanes. Following the optimal setup obtained from the numerical wind tunnel, TWF profiles matching both the power-law and Ekman spiral models, which, respectively, reflect the ABL and wind twist characteristics, were successfully generated in the actual wind tunnel. The findings of this study provide useful information for wind tunnel tests as well as for wind-resistant structural designs and wind environment assessment.

This paper presents detailed study of force and pressure coefficients of an unsymmetrical ‘E’ plan shaped tall building under wind excitation. The building is unsymmetrical about both direction (along and across wind direction) in plan. Experimental and numerical study is carried out by wind tunnel test in boundary layer wind tunnel and Computational Fluid Dynamics (CFD) technique using ANSYS CFX software respectively to study the above model under wind excitation. Two different types of models were used for force and pressure measurements in wind tunnel. Rigid model was used at a model scale of 1:300 for both the cases. Force measurement model was tested under three different wind speeds of 6, 8, 10 m/s whether pressure measurement model was tested under wind speed of 10 m/s in wind tunnel. Wind flow pattern around the building model is studied by CFD technique for both wind flow direction which predicts about the nature of pressure distribution on different surfaces. Some dynamic nature of wind flow is observed at the rear side in case of across wind effects. Maximum positive force and pressure coefficients noticed in case of along wind effects as the surface area is maximum and maximum wind energy dissipates on frontal surface. Same mean pressure occurred on similar faces in case of along wind effects. Pressure contours are symmetrical about vertical axis on frontal faces for both directions of flow and pressure fluctuation noticed at the rear side face due to dynamic effects of flow pattern in case of across wind effect. A comparative study is carried out between experimental and numerical study and results found from these two methods have good agreement to each other.

Comparison of Reynolds Averaging Navier-Stokes (RANS) turbulent models in predicting wind pressure on tall buildings

Structural monitoring of an instrumented experimental single-storey wood building provided important information regarding the behaviour and response of low-rise buildings subjected to wind loads. Foundation wind-induced loads were captured by twenty-seven three-dimensional load cells simultaneously with the envelope pressures and weather characteristics. The distribution of the total wind load to each wall is examined and normalized to the wind speed for each direction. The correlation between loads acting on different wall segments is also quantified in the form of participation factors. In parallel with full-scale findings, a scaled model of the experimental building and its surroundings is tested in a boundary layer wind tunnel. The detailed pressure distribution information for thirty-six wind angles of attack obtained through three different upstream terrain simulations is used to generate expected total uplift wind force. The findings are compared to data acquired directly from the foundation load cells located in the test house. The comparison revealed that in most cases wind tunnel values are within the range of the field results. Discrepancies are somewhat higher for wind tunnel tests conducted using the open/suburban terrain compared to the urban terrain simulation. The results are significant for the improvement of the wind tunnel testing and simulation procedures, for the development of code and standard provisions, as well as for the verification of the finite element numerical model of the test house.

Wind loads on structures and the wind environment around buildings are based on tests in boundary layer wind tunnels with corresponding scale parameters. The lower part of the troposphere boundary layer was simulated inside a small wind tunnel located at the Wind Engineering Centre of the Université de Moncton. The correct scale ratios of the boundary layer thickness combined with the roughness height are two of the most important scales to match. For small wind tunnels, roughness parameters related to the model boundary layer can be difficult to measure since scale ratios for wind load studies are expected to be in the range of 400–1000. Oil-film interferometry was used to determine the roughness parameters (shear stress, friction velocity, and roughness height) of the forced turbulent boundary layer inside the wind tunnel. In this work, the International Organization for Standardization (ISO) Guide to Expression of Uncertainty in Measurements was used to evaluate the standard uncertainty of the roughness parameters on the bottom wall of the wind tunnel. The standard uncertainty of the roughness parameters depends strongly on the oil viscosity and on the accurate measurement of the fringe spacing. Results show that the standard uncertainty of the shear stress and friction velocity determined by the interferometry technique can be less than 5% when the oil viscosity and the fringe spacing can be accurately measured with a standard uncertainty lower than 4% and 1%, respectively.

Validation of ADMS against wind tunnel data of dispersion from chemical warehouse fires

The paper describes a wind tunnel scaled wind farm made of two wind turbine models, each featuring active blade pitch and torque control. The models, governed by supervision and control systems similar to those of a real wind turbine, are capable of simulating steady conditions and transient maneuvers in the boundary layer test section of the wind tunnel of the Politecnico di Milano. Expanding the classical scope of wind tunnel models, the present experimental facility enables the testing of wind farm controllers, as well as the study of interaction phenomena within wind farms.

The tuned liquid damper (TLD) is a proven and an increasingly popular auxiliary device for mitigating the dynamic effects induced by wind loading on tall buildings. As buildings become taller, lighter, and more flexible, there is a greater contribution from the dynamic component. The most reliable tool for assessing the dynamic component is wind tunnel testing. A boundary layer wind tunnel is capable of accurately calculating an equivalent static wind load (ESWL) acting on a building. The current study investigates the reduction in the ESWL of a lateral-torsional coupled building with a TLD system installed. The building is sensitive to torsion in the first two vibration modes. The current investigation uses three unique multi-modal TLD systems designed specifically for a lateral-torsional coupled building. The building ESWL is evaluated with the TLD systems using measurements from tests conducted at the Boundary Layer Wind Tunnel Laboratory at Western University.

<p>A wind tunnel test was conducted on a rectangular high-rise building. Firstly, based on the third and the fourth order statistical moments of wind pressure time histories, the non-Gaussian regions were identified. Results show that on the windward face, the non-Gaussian region was near the edge and the corner areas. For the narrower side face, the non-Gaussian region was near the leading edge. However, the non-Gaussian region was discovered close to the trailing edge where the flow reattachment occurred for the wider side face. Then, by parametric analysis and fluctuating wind pressure spectrum fitting, a simplified method for peak factor estimating was derived on the basis of the moment-based Hermite method and the Revised Hermite Model, named Three-parameter Hermite Model. Lastly, the accuracy and efficiency of moment-based Hermite method, Revised Hermite Model and Three-parameter Hermite Model were tested by the instantaneous extreme value and the histogram of wind pressure histories. Results show that compared with the peak factors of the instantaneous extreme values, peak factors calculated by the moment-based Hermite method were overestimated. While the peak factors of Revised Hermite Model and Three-parameter Hermite Model show a smaller error. The PDFs of Three- parameter Hermite Model are in good agreement with the ones of Revised Hermite Model, which show a better fit to the histogram of wind pressure histories.</p>

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

Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) have been instrumental in Fluid Mechanics to help solve scientific and engineering problems. This research attempts to use both techniques to perform a parametric study of turbulence flow around airfoil ClarkY-14 at various velocity and angle of attack (AoA). Clark Y-14 airfoil was designed in the 1920’s. It demonstrated good overall performance at low and moderate Reynolds numbers. With the progress in the aviation field, its performance was sub-optimal for newer aircraft designs. However, with the advent of RC airplanes and model aircrafts, there is a renewed interest in this airfoil. Various research projects have been conducted using this airfoil, but there hasn’t been a combined EFD and CFD study of the performance characteristics of the airfoil itself, which still finds real world applications today. One important aspect of this research included the investigation of the effects of a Force Measurement Device/Sensor, which is typically used in scaled/full-size wind tunnels to mount the test model as well as measure the forces/moments acting on it during the testing. The presence of such a device could affect the quality of the data obtained from the wind tunnel testing when compared to a real world application scenario where the aforementioned device may not be present. To the best of the author’s knowledge, no detailed study has been published on the effects of such devices. In this study, the results with and without the measuring device were generated by using CFD simulations. The results were then compared to see to what extent the inclusion of these devices will affect the results. The methodology used for this research was experimental as well as computational. In the present research, a commercially available CFD software STAR-CCM+ was employed to simulate the flows around airfoil Clark Y-14. The experimental data was obtained from wind tunnel tests using AEROLAB Educational Wind Tunnel (EWT) and compared with the simulation data from the CFD. The two data sets were in good agreement. Both experimental and simulation results were used to understand the effects of the measurement device/sensor used in the scaled wind tunnel on the lift and drag coefficients of the airfoil. Two separate CFD simulation setups were designed to model the presence and absence of the measurement device/sensor. These setups replicated the wind tunnel setup. The airfoil was tested and simulated at different speeds as well as different AoA. The comparative study gave a useful insight on the accuracy of the CFD simulations in relation to the actual testing. The analysis of results concluded that the force measurement device/sensor had insignificant effects on the accuracy and quality of data collected through wind tunnel testing.

It is often imperative to test and validate the development of active flutter suppression technology in wind tunnels or flight near and beyond the flutter speed. This is done not only to fine-tune mathematical models but also to examine the active control laws that were synthesized from such models. However, in-flight flutter tests are often dangerous, costly, and sometimes infeasible. Wind tunnel tests are usually more affordable and less risky leading to higher productivity in evaluating alternative configurations and control law strategies. The University of Washington’s MARGE-I aeroservoelastic wind tunnel model is a flexible half-wing-body-tail model with active ailerons and elevator. The work here studies SISO mixed-sensitivity H∞ control for active flutter suppression, which is designed subject to requirements and hardware constraints. Such controller is validated by wind tunnel tests, where the closed-loop margins in both simulation and experiments are quantified and compared. A previously published safe wind tunnel and flight test technique is used to generate flutter mechanisms. The set of control surfaces is partitioned into destabilizing and stabilizing ones, where a destabilizing controller reshapes the aeroservoelastic system to yield the desired unstable dynamic characteristics, and the stabilizing controller is used to study active flutter control strategies.

Comparison of wind tunnel and full-scale pressure measurement tests on the Texas Texh Building

Comparison of wind tunnel and full-scale pressure measurement tests on the Texas Texh Building