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CONTENTS
Volume 35, Number 3, September 2022
 


Abstract
This research proposes a wind-lens turbine design that can startup and operate at a low wind speed (< 5m/s). The performance of the wind-lens turbine was investigated using CFD and wind tunnel testing. The wind-lens turbine consists of a 3- bladed horizontal axis wind turbine with a diameter of 0.6m and a diffuser-shaped shroud that uses the suction side of the thin airfoil SD2030 as a cross-section profile. The performance of the 3-bladed wind-lens turbine was then compared to the twobladed rotor configuration while keeping the blade geometry the same. The 3-bladed wind-lens turbine successfully startup at 1m/s and produced a torque of 66% higher than the bare turbine, while the two-bladed wind-lens turbine startup at less than 4m/s and produced a torque of 186 % higher than the two-bladed bare turbine at the design point. Findings testify that adding the wind-lens could improve the bare turbine's performance at low wind speed.

Key Words
CFD; shrouded turbines; wind-lens turbine; wind energy; wind tunnel testing; wind turbine aerodynamics

Address
Mohamed M. Takeyeldein:Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru. Malaysia

I.S. Ishak:UTM Aerolab, Institute for Vehicle System & Engineering, Universiti Teknologi Malaysia, 81310, Johor Bahru, Malaysia

Tholudin M. Lazim:Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru. Malaysia

Abstract
This paper highlights the minimization of drag and lift coefficient of different types both side setback tall buildings by the multi-objective optimization technique. The present study employed 48 number both-side setback models for simulation purposes. This study adopted three variables to find the two objective functions. Setback height and setback distances from the top of building models are considered variables. The setback distances are considered between 10-40% and setback heights are within 6-72% from the top of the models. Another variable is wind angles, which are considered from 0° to 90° at 15° intervals according to the symmetry of the building models. Drag and lift coefficients according to the different wind angles are employed as the objective functions. Therefore 336 number population data are used for each objective function. Optimum models are compared with computational simulation and found good agreements of drag and lift coefficient. The design wind angle variation of the optimum models is considered for drag and lift study on the main square model. The drag and lift data of the square model are compared with the optimum models and found the optimized models are minimizing the 45-65% drag and 25-60% lift compared to the initial square model.

Key Words
drag; lift; multiobjective optimization; poareto optimal solution; setback building; wind load

Address
Amlan Kumar Bairagi and Sujit Kumar Dalui:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India

Abstract
Trains emerging on a streamlined bridge-girder may have salient interference effects on the aerodynamic properties of the bridge. The present paper aims at investigating these interferences by wind tunnel measurements, covering surface pressure distributions, near wake profiles, and flow visualizations. Experimental results show that the above interferences can be categorized into two primary effects, i.e., an additional angle of attack (AoA) and an enhancement in flow separation. The additional AoA effect is demonstrated by the upward-moved stagnation point of the oncoming flow, the up-shifted global symmetrical axis of flow around the bridge-girder, and the clockwise-deflected orientation of flow approaching the bridgegirder. Due to this additional AoA effect, the two critical AoAs, where flow around the bridge-girder transits from trailing-edge vortex shedding (TEVS) to impinging leading-edge vortices (ILEV) and from ILEV to leading-edge vortex shedding (LEVS) of the bridge-girder are increased by 4° with respect to the same bridge-girder without trains. On the other hand, the underlying flow physics of the enhancement in flow separation is the large-scale vortices shedding from trains instead of TEVS, ILEV, and LEVS governed the upper half bridge-girder without trains in different ranges of AoA. Because of this enhancement, the mean lift and moment force coefficients, all the three fluctuating force coefficients (drag, lift, and moment), and the aerodynamic spanwise correlation of the bridge-girder are more significant than those without trains.

Key Words
aerodynamics; streamlined bridge-girder; wind engineering; wind tunnel test

Address
Huan Li:1)National Engineering research center for High Speed Railway construction, Central South University, Changsha 410075, China
2)School of civil engineering, Central South University, Changsha 410075, China
3)Hunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structure, Changsha, 410075, China

Xuhui He:1)National Engineering research center for High Speed Railway construction, Central South University, Changsha 410075, China
2)School of civil engineering, Central South University, Changsha 410075, China
3)Hunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structure, Changsha, 410075, China

Liang Hu:NatHaz Modeling Laboratory, University of Notre Dame, Notre Dame, IN46556, USA

Xiaojun Wei:1)National Engineering research center for High Speed Railway construction, Central South University, Changsha 410075, China
2)School of civil engineering, Central South University, Changsha 410075, China
3)Hunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structure, Changsha, 410075, China

Abstract
The present study focuses on aerodynamic parameters behaviors and control on the single and double side setback building models at the buildings mid-height. The study is conducted by computational fluid dynamics (CFD) simulation. This study estimates the face wise pressure coefficient on single side setback buildings with a setback range of 20%-50% and double side setback buildings with setbacks ranging from 10%-25%. The polynomial fitted graphs from CFD data predict the Cp on different setback model faces within permissible limit ±13% error. The efficient model obtained according to the minimum drag, lift, and moment consideration for along and across wind conditions. The study guides the building tributary area doesn't control the drag, lift, and moment on setback type buildings. The setback distance takes a crucial role in that. The 20% double side setback model is highly efficient to regulate the moment for both along and across wind conditions. It reduces 17.5% compared to the 20% single side setback and 14% moment compared to the 10% double side setback models. The double side setback building is more efficient to control 4.2% moment than the single side setback building.

Key Words
computational fluid dynamics (CFD); force coefficient; peak moment; pressure coefficient; setback building

Address
Amlan Kumar Bairagi and Sujit Kumar Dalui:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India

Abstract
The design of a building is a complex process that encompasses different fields: one of the most relevant is nowadays the energetic one, which has led to the introduction of new typologies of building envelopes. Among them, the Permeable Double Skin Façades (PDSF) are capable to reduce the solar impact and so to improve the energetic performances of the building. However, the aerodynamic characterization of a building with a PDSF is still little investigated in the current literature. The present paper proposes an experimental study to highlight the modifications induced by the outer porous façade in the aerodynamics of a building. A dedicated wind tunnel study is conducted on a rigid model of a prismatic high-rise building, where different façade configurations are tested. Specifically, the single-layer façade is compared to two PDSFs, the former realized with perforated metal and the latter with expanded metal. Outcomes of the tests allow estimating the cladding loads for all the configurations, quantifying the shielding effects ascribable to the porous layers that are translated in a significant reduction of the design pressure that could be up to 50%. Moreover, the impact of the PDSFs on the vortex shedding is investigated, suggesting the capability of the façade to suppress the generation of synchronised vortices and so mitigate the structural response of the building.

Key Words
CFD simulation; complex terrain; surface roughness length; typhoon wind field

Address
Giulia Pomaranzi, Giada Pasqualotto and Alberto Zassso:Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156, Milan, Italy


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