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CONTENTS
Volume 33, Number 2, August 2021
 


Abstract
In this study, an iteration-based method to simulate two typical examples of unconventional wind flow in a multi-fan wind tunnel is described: skewed non-Gaussian turbulence and sinusoidal type transient gust. The air flows are generated by 120 actively controlled fans arranged in a 10 wide by 12 high matrix. Time-varying voltages signals can be imported into the fans' servomotors, then corresponding wind flow can be produced in this wind tunnel. At first, the target wind speeds time series are converted to voltages signals, which are input into the fans' motor next, and then the initial wind flow generated can be measured. Then the wind speeds time series to be input are adjusted according to the differences between the target winds speeds and measured flow speeds. The above procedure is iteratively repeated until the measured wind flow is gradually close to the targets. At last, both non-Gaussian turbulence and transient gust can be simulated with satisfied precision after several iterations.

Key Words
actively controlled multi-fan wind tunnel; iteration; Non-Gaussian Turbulence; transient gust

Address
Wei Cui: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China

Lin Zhao: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China/ State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing 400074, China

Shuyang Cao: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China

Yaojun Ge: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China

Abstract
Corner modification plays an essential role in the reduction of the wind load and responses on tall buildings. The present study investigates the effectiveness of different corner modifications (chamfered, rounded, and recessed corners) to reduce the wind load on regular cross plan shaped tall buildings using the computation fluid dynamics technique. Here, ANSYS CFX is used to simulate the boundary layer wind environment around the building and compared with experimental results. The numerically simulated data are compared with some previous wind tunnel test data on the '+' plan building. Based on the numerical study, flow pattern near the corner regions, pressure contour, the variation of pressure coefficient along the periphery of the building, force and moment coefficients for three corner modified models are analyzed and compared with sharp edged cross plan shaped model to comprehend the extent of nonconformities due to corner modifications. The rounded corner modification is most effective in suppressing the wind load compared to chamfered and recessed corners. For rounded corners with 50% corner cut, the reduction in force and moment coefficients is substantial, with up to 26.26% and 28.58%, respectively, compared to sharp edged corners. A sudden shoot up in the negative Cp values near edges of the corner modified model, should require special attention in the design of cladding components. This paper led to comprehend the wind-induced responses of cross plan shaped building with various corner configurations.

Key Words
computational fluid dynamics; corner modifications; force coefficient; moment coefficient; pressure coefficient

Address
Debasish Kumar and Sujit Kumar Dalui: Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India

Abstract
Articulated towers are one of the class of compliant offshore structures that freely oscillates with wind and waves, as they are designed to have low natural frequency than ocean waves. The present study deals with the dynamic response of a double-hinged articulated tower under hydrodynamic and aerodynamic loads. The wind field is simulated by two approaches, namely, single-point and multiple-point. Nonlinearities such as instantaneous tower orientation, variable added mass, fluctuating buoyancy, and geometrical nonlinearities are duly considered in the analysis. Hamilton's principle is used to derive the nonlinear equations of motion (EOM). The EOM is solved in the time domain by using the Wilson-θ method. The maximum, minimum, mean, and standard deviation and salient power spectral density functions (PSDF) of deck displacement, bending moment, and central hinge shear are drawn for high and moderate sea states. The analyses' outcome shows that tower response under multiple-point wind-field simulation results in lower responses compared to that of single-point simulation.

Key Words
double-hinged articulated tower; dynamic analysis; multi-point wind field; offshore; wind-induced response

Address
Mohd Moonis Zaheer: Department of Civil Engineering, Zakir Hussain College of Engineering and Technology, AMU Aligarh-202002, India

Nazrul Islam: Department of Civil Engineering, Jamia Millia Islamia, New Delhi, India

Abstract
High-voltage transmission lines are featured by electrical and structural properties. Current studies on aeolian vibration of transmission lines focus primarily on structural responses of unenergized conductors. However, moderate aeolian vibration can also enhance the convection heat transfer capability of a transmission line, which improves the steady current-carrying capacity. In this paper, a fluid-structure interaction (FSI) model is established to study the structural thermal characteristics of overhead electrified aluminum conductor steel-reinforced cable (ACSR) conductors. Moreover, the fatigue damage of the energized conductor is analyzed under operational conditions. Results show that there is considerable influence from aeolian vibration on the current-carrying capacity of energized conductors. Compared with the nonelectrical conductors, aeolian vibration can enhance the convective heat transfer effect of energized conductors. Additionally, fatigue life of electrified transmission lines is larger than that of nonelectrical conductors under aeolian vibration. The developed structure-fluid-thermal model can be used to aid design and operation optimization of transmission lines.

Key Words
aeolian vibration; current-carrying capacity; electrified conductor; fatigue life; mechanical property

Address
Meng Zhang: School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China/ Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, U.S.A.

Jian Zhou: School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

Guifeng Zhao: School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China/ Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, U.S.A.

Jiankun Xu: School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

Chao Sun: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, U.S.A.

Abstract
The enhancement of fatigue life of ultra-large horizontal axis wind turbine blade using longitudinal stiffening is the theme of this work. For this purpose, a tendon made of shape memory alloy is used along the longitudinal axis of blade, which is modelled in aeroelastic spinning finite element framework. The force developed in the tendon acts against the deformation where the material is modelled using Liang and Rogers constitutive relationship along with the principles of thermodynamics. The fatigue design follows the guidelines provided in internationally recognised codal provisions. The blade responses are simulated using aeroelastic loads obtained from blade element momentum theory. These dynamic responses are utilised to evaluate the longitudinal stress in the extreme fibre over the blade profile. Then, short-term and long-term damages are evaluated using rainflow matrix obtained from these stresses. Finally, the reliability of blade against fatigue failure is investigated. The numerical analysis presented in this study clearly demonstrates the performance of the longitudinal stiffening in combination with pitch angle on the fatigue life of the blade.

Key Words
fatigue damage; Palmgren-Miners summation; reliability analysis; semi-active control; shape memory alloy; wind turbine

Address
M. Mohamed Sajeer and Arunasis Chakraborty: Department of Civil Engineering, Indian Institute of Technology Guwahati, Assam 781039, India


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