Strong wind and rainfall induced by extreme meteorological processes such as typhoons have a serious impact on the safety of bridges and offshore engineering structures. A new bivariate compound extreme value distribution is proposed to describe the probability dependency structure of annual extreme wind speed and concomitant process maximum rainfall intensity in typhoon-affected area. This probability model takes full account of the case that there may be no rainfall in a typhoon process. A case study based on the observation data of typhoon maximum wind speed and maximum rainfall intensity in Shanghai is conducted to testify the efficiency of the model. Weibull distributions with two parameters are applied to fit respective probability margins, and the joint probability distribution is constructed by Gumbel–Hougaard copula. The fitting results and K–S tests show that these models describe the original data well. The joint return periods are calculated by Poisson bivariate compound extreme value distribution we have proposed. They indicate that typhoons with no rain have smaller joint return periods, and wind speed is the main factor which impacts the change of the joint return periods.

Joint return probability analysis of wind speed and rainfall intensity in typhoon-affected sea area

Experimental investigation on spatial attitudes, dynamic characteristics and environmental conditions of rain–wind-induced vibration of stay cables with high-precision raining simulator

The irregular shape of buildings always tenders an enormous challenge to the designers. The wind velocity at the pedestrian level has a specific approach from a comfortable point of view. This investigation highlighted the characteristic of the pedestrian level wind velocity for distinct types of asymmetrical setback buildings. The passed study explored the pedestrian level effect for the axisymmetric models, while this study is based on the models that have symmetry about a single axis. This study investigates the pedestrian level flow fluctuation of setback models with single and double side setbacks at multiple levels. The double-side double setback buildings are efficient to reduce 28%–30% velocity in front of the building and 68%–70% velocity behind the building. Finally it suggests that the double side double setback building is efficient to maintain the velocity at the pedestrian level, roof level, and backside of the building. The setback building can easily control the frequency of fluctuating velocity at downstream flow for both along and across wind conditions.

Wind environment around the setback building models

Validation of a CFD model for the evaluation of urban microclimate at high latitudes: A case study in Trondheim, Norway

Wind load and response are the major factors that govern the most critical condition for designing tall buildings. This study discusses the variability of wind load and pressure on a Y plan shaped tall building due to the change in the building side ratio. The length to width ratio is changed keeping the total plan area same. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and shear stress transport (SST), are used for doing the numerical simulation and the results are compared with the previous wind tunnel results in a similar flow condition. Sample points were selected based on Audze–Eglais Uniform Latin Hypercube (AELH) method and the analytical expressions of force, moment and torsional coefficients of Y plan shaped tall building are proposed. These expressions are fitted very well and the AELH method has given a great set of sample points that have significantly decreased the total computational time. The graphical representations of these expressions for various coefficients are presented and discussed. Then pressure distributions on three different models are compared and the pros and cons of higher and lower values of side ratios are discussed.

Effects of side ratio for ‘Y’ plan shaped tall building under wind load

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.

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 threedimensional plane are determined to assess the flow characteristics of the building at 0 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.

https://jafmonline.net/JournalArchive/download?file_ID=47818&issue_ID=253

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

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 k-ω 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.

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

Effect of Wind Speed, Wind Direction, Rainfall Intensity, Damping and Cable Diameter on Vibration Amplitude of the Cable

This numerical study reports the aerodynamic properties of a hybrid airship. The hybrid airships were designed by combining two semi-ellipsoids with a semi-discoid as the base model. From the base model, three different geometrics were identified to study their aerodynamic characteristics. A circular slot was provided between the pressure side and the suction side of the airship. The objective of this study was to realize the flow behavior, aerodynamic characteristics, and stability properties of such slotted hybrid flying vehicles. Interestingly, the results imply that the lift coefficient increases with an increase in the angle of attack for the slotted configurations; this is because the flow separation is delayed due to the slot opening, which in turn is due to the flow of energies from the high-pressure region to the bottom through the slots. The delayed stall angle was 50 degrees, which was 10% more than that of the base model. Aerodynamic characteristics are discussed based on surface pressure, coefficient of lift, and coefficient of drag for various slotted hybrid airships.

https://www.mdpi.com/2226-4310/8/6/166/pdf

G. Vinayagamurthy

Papers

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

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

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

Effect of Wind Speed, Wind Direction, Rainfall Intensity, Damping and Cable Diameter on Vibration Amplitude of the Cable

Effect of a Circular Slot on Hybrid Airship Aerodynamic Characteristics