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This article provides an overview of local pressure coefficients (Cp) on conventional and unconventional tall buildings with the application of CFD. Various modifications in architectural shapes on tall buildings eventually lead to a reduction in the wind load on building surfaces. The surface pressure on conventional (Square and rectangular) buildings is relatively different in comparison to unconventional tall buildings. This study is to assess the surface pressure coefficient over rectangular, taper and setback buildings. The assessed results show that the taper building has 7% Cp rise at ground level (y/H = 0.225) in the windward face, and 34% Cp fall at the middle level (y/H = 0.475) in the side face when compared with the rectangular building. Whereas for the setback building, Cp at ground level near setback (y/H = 0.225) has reduced to about 25% and about 6% at the middle level (y/H = 0.475) in windward than that in the rectangle building. Also, the side faces of the setback showed a 15% drop in Cp than other buildings. In leeward face, Cp is reduced to 56% near setback at the top of the building (y/H = 0.725). This assessment of the Cp on these buildings shows that the effect of setbacks on building reduces the pressure variation on all faces and the downstream wake vortices. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2021.

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Lecture Notes in Mechanical Engineering

Assessment of local pressure coefficient over conventional and unconventional tall buildings

It is essential to investigate the pressure distribution, aerodynamic coefficients and wind flow fields in-order to predict the wind loads and wind behaviour in building environments. Most of the investigations and international wind load standards haven't highlighted the wind load and wind environment on-and-around buildings under different terrains. The main objective of this investigation is to explore a practical numerical approach for the accurate estimation of wind loads and their impact on buildings under different upstream conditions. In this investigation, simulations are done in IDDES turbulence model along with the formulation of kω SST using CFD. Results indicated the influence of ground roughness in pressure distribution on building faces. Furthermore, CFD results over-predicted the experimental values near the edges due to strong shear-flow and expanding wake-vortices. The cross-validation of the mean drag coefficients showed good-agreement. Hence this investigation promotes the practice of IDDES in wind-resistant designs for tall buildings. Copyright © 2020 Inderscience Enterprises Ltd.

Progress in Computational Fluid Dynamics

CFD validation of wind pressure distribution on a tall building under the influence of upstream terrain

The evaluations of wind forces on structures are highly complex due to overall building design and scale. The wind flow on and around buildings is receiving more importance among architects and urban planners to ensure the safety and economical design. Computational fluid dynamics (CFD) simulation is regularly employed for the evaluation of wind forces like accessing the wind flow pattern and aerodynamic coefficients. The present study focuses on building structures with an aspect ratio in the plan of 1:2:3 for the computational simulation. The building is geometrically scaled down to 1:300 and simulated using the Improved Delayed Detached Eddy Simulation turbulence model (IDDES) along with the formulation of k–ω Shear Stress Transport (SST). This simulation investigates and compares the aerodynamic parameters, wind flow patterns, the size of recirculation, and wake separation zones in a three-dimensional plane. The velocity profiles are quantified in terms of width of the building (D) and Cpmean (mean pressure coefficients) at 0° and 90° wind incidences. The Cpmean is validated against the results obtained from the Boundary Layer Wind Tunnel (BLWT) experimental results. © Springer Nature Singapore Pte Ltd. 2019.

VIT Unitversity

Lecture Notes in Mechanical Engineering Innovative Design, Analysis and Development Practices in Aerospace and Automotive Engineering (I-DAD 2018)

Computational Simulation of Wind Flow Behavior Around a Building Structure

In recent days, the behaviour of wind flow around the buildings receives more interest among urban planners, architects, researchers and wind engineers. Hence, these wind flow patterns are assessed extensively using CFD (Computational Fluid Dynamics) simulations, as it re-creates the atmospheric and wind tunnel environment following the turbulence parameters. This paper presents a logical assessment using IDDES (Improved Delayed Detached Eddy Simulation) turbulence model in CFD for predicting wind pressure coefficients and flow features on and around a 300:1 scaled setback tall building model at 0° and 90° AOI (Angle of Incidence) under open terrain condition. The computation is based on gird sensitivity study and validation with Boundary Layer Wind Tunnel (BLWT) experiment measurements. The evaluation shows that the downdraught and downwind effects are suppressed by the increasing wind pressure distribution along the height. The results demonstrate that IDDES can reproduce wind pressure coefficients and aerodynamic coefficients of the setback building accurately. The maximum deviation of the wind pressure coefficients (Cp rms) is found to be 12% in CFD when compared with wind tunnel measurements. Besides, the CFD simulation demonstrates the wind flow distribution patterns, size of re-circulation, wake separation zones and velocity profiles in a three-dimensional plane which are quantified concerning the width of the building. © 2019, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature.

Building Simulation

Experimental and computational investigation of outdoor wind flow around a setback building

In recent days, building aerodynamics has gained more attention to urban planners, architects, and wind engineers in understanding the wind flow behaviors around tall buildings. CFD (Computational Fluid Dynamics) simulations are the major tool regularly carried out to assess the wind flow pattern around the buildings to demonstrate the atmospheric and wind tunnel environment in accordance with the turbulence parameters. One of the most challenging tasks is to evaluate a turbulence model which precisely represents atmospheric turbulence flow using computation resources. This study is intended to analyze the precision and numerical stability of open terrain wind flow around a setback building with sharp edges of aspect ratio of 1:5. Hybrid turbulence models using Delayed Detached Eddy Simulation (DDES) and Improved Delayed Detached Eddy Simulation (IDDES) are employed with (Y+) wall treatment in combination with roughness parameters. From the numerical simulation, the size of re-circulation zones in addition to wake separation zones in a three-dimensional plane are determined to assess the flow characteristics of the building at 00 wind incidence. The mean pressure coefficients (CP mean) are validated against the results obtained from Boundary Layer Wind Tunnel (BLWT) experiments carried out at CSIR-Structural Engineering Research Centre, Chennai. © 2019 Isfahan University of Technology.

Fulltext

Journal of Applied Fluid Mechanics

Experimental and computational simulation of an open terrain wind flow around a setback building using hybrid turbulence models

Tall buildings with complex designs have been the recent trend in the field of architecture and structural engineering. For t his kind of buildings, wind flow analysis is equally important as structural analysis since wind loads are dominant for these types of structures. Computational simulation (URANS) turbulent models of Computational fluid dynamics are widely used to study the external flow behavior of a bluff body and its influence of shape factors. Nowadays a variety of problems are occurring because of tall buildings environment like down drought wind, vortices, downwind effects, etc. Wind comfort and safety on and around tall buildings have become important parameters for architects and town planners who need guidelines and simplified tools to take account of wind in their buildings. The objective of this study provides more insight on wind flow over tall buildings with different geometry. In order to evaluate the wind flow around the building in terms of upstream wind, downstream wind, recirculation zones are quantified in terms of width (D) and surface pressure measurements were employed to all geometries. Numerical analysis has been performed in FLUENT software with k-ω SST model as solver. © 2018 Author(s).

AIP Conference Proceedings

Numerical simulation of tall buildings with various shape factors and investigation of its surrounding effect

The influence of upstream and downstream flow and its effect due to the operating wind turbine at various wind speeds are important in considering the wind turbine spacing in a turbine park. In this research paper study is made towards what extent the wind turbine with a rotor diameter D, influences the flow in upstream and downstream computationally. The reduction in the maximum power coefficient strongly depends on the distance between the turbines and the operating condition of the upstream turbine. Presently, the standard power curve measurements assumes that the turbine wind condition has negligible influence on the flow at two times the rotor diameter upstream. However, the upstream effect due to the operating wind turbine beyond two times the rotor diameter (2D) leads to the consequences of the power estimate for any given turbine and this leads to the wind farm for total power production. Similarly, the downstream of the operating wind turbine is equally important in terms of the power production of the wind turbine park. Numerical simulations are performed on a wind turbine with a rotor diameter of 80 m and the tower height of 100 m with various blade pitch angles. The NACA-63-425 aerofoil is selected for the blade profile in this analysis. The result shows that the influence of the pitch angle will not influence much difference in upstream flow and much difference in the downstream flow. However, at the distance more than two times (> 2D) of the rotor diameter upstream around 3% change in the velocity is observed when compared to the free stream velocity. In the downstream, velocity the influence of operating wind turbine extends up to 6.5D for a velocity of 20m\s. © 2017, Institute of Advanced Scientific Research, Inc. All rights reserved.

Journal of Advanced Research in Dynamical and Control Systems

Study on influence of operating wind turbine on upstream and downstream flow using K-epsilon turbulence model

In general, Special Purpose Machines are made to carry out certain kind of specific operations in a large quantity. It was necessary for us to carry out four counterboring operations on the hub of the blade as shown in figure 1 and the blade profile has interference with one of the four holes for fastening and therefore cannot be machined for large production using conventional machines. And thus it is planned to design a special counterboring machine for this typical operation. A new design was proposed by overcoming the limitations of the conventional counterboring operations. An optimized design was presented to carry out multiple (four) counterboring operations in a shorter time period. This paper also explains the design of the gear drives and shafts of the Special Purpose Machine. © Research India Publications.

International Journal of Applied Engineering Research

Design of special purpose machine for counter boring operation on the hub of a impeller blade

Stay cables of the cable-stayed bridge exhibits a large amplitude vibration under the action of wind and rain and which may have a greater effect on the fatigue life of the stays. These large amplitude vibrations were strongly influenced by variety of factors concerning the positioning of the cable (inclination angle), meteorological parameters (rain, wind speed and wind direction) and the structural parameters like damping and frequency. This paper explains the effects of wind speed, rainfall, damping, cable diameter, cable inclination angles, wind yaw angles on the vibration amplitude of the stay cables with diameters 0.155 m and 0.128 m. The observations show's large amplitude vibrations when the cable is inclined at 25° and 30° and wind yaw angles are from 30° and 35° under 10 mm/hr rainfall condition.

Journal of Structural Engineering (India)

Effect of wind speed, wind direction, rainfall intensity, damping and cable diameter on vibration amplitude of the cable

Couplings are used to connect one shaft to another or to couple driving members and load members. The couplings are classified into rigid and flexible couplings. The types of couplings are Gear, Oldham, Universal and Elastic couplings. The problem of stress concentration effects in a spider type coupling is of concern.In a spider type coupling we have projections in the flanges. Due to these projections, stress concentrations effects are induced that are unknown in this spider type of coupling. So here, we try to find out the stress concentration effects to suggest a proper design procedure In this project, we vary the length of the protrusions and at the same time vary the angles between the rigid protrusions of the spider type couplings. The couplings are designed using modeling software PRO/ENGINEER WILDFIRE 3 and then it is imported to analysis software FEMAP NX NASTRAN for static analysis. The spider type coupling is given a constant torque, is analysed using FEM technique rather than mathematical or experimental method because the mesh is made sufficiently fine around the areas of geometric discontinuity or stress raiser. The analysis is performed using FEMAP with NX NASTRAN by constraining all the degrees of freedom in the driving shaft and then the torque is applied on the driven shaft in order to calculate the resultant stress. The analysis is carried out. The results are tabulated and graphically shown. Finally, the comparison is done with NASTRAN results and manually calculated results. © IDOSI Publications, 2013.

Middle - East Journal of Scientific Research

Stress analysis of spider type flexible couplings by using NX nastran

Stay cables of the cable-stayed bridge exhibits a large amplitude vibration under the action of wind and rain and which may have a greater effect on the fatigue life of the stays. These large amplitude vibrations were strongly influenced by variety of factors concerning the positioning of the cable (inclination angle), meteorological parameters (rain, wind speed and wind direction) and the structural parameters like damping and frequency. This paper explains the effects of wind speed, rainfall, damping, cable diameter, cable inclination angles, wind yaw angles on the vibration amplitude of the stay cables with diameters 0.155 m and 0.128 m. The observations show’s large amplitude vibrations when the cable is inclined at 25° and 30° and wind yaw angles are from 30° and 35° under 10 mm/hr rainfall condition. Copyright © 2013 APCWE-VIII. All rights reserved. Published by Research Publishing, Singapore.

Proceedings of the 8th Asia-Pacific Conference on Wind Engineering, APCWE 2013

Aerospace vehicles are subjected to various types of severe environmental loads. The basic design criterion includes the minimum weight configuration that results in very flexible structures, which leads to various types of structural interaction problems like flutter, divergence etc. Hence every aerospace vehicle should be analysed for its aeroelastic instabilities. In the present work the flutter analysis of a typical space vehicle was carried out in substructure level with the interface fixed condition. The doublet lattice, zona51 and piston theories are used in the unsteady aerodynamic calculations for the subsonic, supersonic and hypersonic speed regimes. As there is no theoretical procedure for transonic speeds, doublet lattice method has been used in the present analysis. Frequency and damping versus velocity are presented to identify the flutter velocities and the flutter behavior. © (2012) Trans Tech Publications, Switzerland.