Abstract
Irregularity in plan shape is very common for any type of building as it enhances better air ventilation for the
inhabitants. Systematic opening at the middle of the facades makes the appearance of the building plan as a butterfly one. The
primary focus of this study is to forecast the force, moment and torsional coefficient of a butterfly plan shaped tall building.
Initially, Computational Fluid Dynamics (CFD) study is done on the building model based on Reynolds averaged Navier Stokes
(RANS) k-epsilon turbulence model. Fifty random cases of irregularity and angle of attack (AOA) are selected, and the results
from these cases are utilised for developing the surrogate models. Parametric equations are predicted for all these aerodynamic
coefficients, and the training of these outcomes are also done for developing Artificial Neural Networks (ANN). After achieving
the target acceptance criteria, the observed results are compared with the primary CFD data. Both parametric equations and
ANN matched very well with the obtained data. The results are further utilised for discussing the effects of irregularity on the
most critical wind condition.
Key Words
artificial neural networks; force and moment coefficients; irregular building; rational parametric equations; windinduced torques
Address
Prasenjit Sanyal:1)Department of Civil Engineering, Meghnad Saha Institute of Technology, Kolkata, India 2)Department of Civil Engineering, IIEST, Shibpur, Howrah, India
Sayantan Banerjee:1)Department of Civil Engineering, Meghnad Saha Institute of Technology, Kolkata, India 2)Department of Civil Engineering, IIEST, Shibpur, Howrah, India
Sujit Kumar Dalui:Department of Civil Engineering, IIEST, Shibpur, Howrah, India
Abstract
The current work numerically investigates the transient force and dynamic response of an overhead transmission
tower–line structure caused by the passage of a high-speed train (HST). Taking the CRH2C HST and an overhead transmission
tower–line structure as the research objects, both an HST–transmission line fluid numerical model and a transmission tower–line
structure finite element model are established and validated through comparison with experimental and theoretical data. The
transient force and typical dynamic response of the overhead transmission tower–line structure due to HST-induced wind are
analyzed. The results show that when the train passes through the overhead transmission tower–line structure, the extreme force
on the transmission line is related to the train speed with a significant quadratic function relationship. Once the relative distance
from the track is more than 15 m, the train-induced force is small enough to be ignored. The extreme value of the mid-span
dynamic response of the transmission line is related to the train speed and span length with a significant linear functional
relationship.
Key Words
dynamic response; High-speed train (HST); numerical simulation; overhead transmission tower–line structure;
train-induced wind force
Address
Meng Zhang:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
Ying Liu:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
Hao Liu:1)School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
2)China Tower Co., Ltd. Luohe Branch, Luohe, 462000, China
Guifeng Zhao:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
Abstract
Section model test, as the most commonly used method to evaluate the aerostatic and aeroelastic performances of long-span
bridges, may be carried out under different conditions of incoming wind speed, geometric scale and wind tunnel facilities, which may lead
to potential Reynolds number (Re) effect, model scaling effect and wind tunnel scale effect, respectively. The Re effect and scale effect on
aerostatic force coefficients and aeroelastic characteristics of streamlined bridge decks were investigated via 1:100 and 1:60 scale section
model tests. The influence of auxiliary facilities was further investigated by comparative tests between a bare deck section and the deck
section with auxiliary facilities. The force measurement results over a Re region from about 1x105
to 4x105
indicate that the drag
coefficients of both deck sections show obvious Re effect, while the pitching moment coefficients have weak Re dependence. The lift
coefficients of the smaller scale models have more significant Re effect. Comparative tests of different scale models under the same Re
number indicate that the static force coefficients have obvious scale effect, which is even more prominent than the Re effect. Additionally,
the scale effect induced by lower model length to wind tunnel height ratio may produce static force coefficients with smaller absolute values,
which may be less conservative for structural design. The results with respect to flutter stability indicate that the aerodynamic-dampingrelated flutter derivatives A2* and A*1H*3 have opposite scale effect, which makes the overall scale effect on critical flutter wind speed
greatly weakened. The most significant scale effect on critical flutter wind speed occurs at +3° wind angle of attack, which makes the smallscale section models give conservative predictions.
Key Words
auxiliary facilities; bridge; flutter; Reynolds number effect; scale effect; static force coefficients; wind-tunnel test
Address
Tingting Ma and Chaotian Feng: College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China
Abstract
Buildings with mono-sloped roofs are used for different purposes like at railway platforms, restaurants, industrial
buildings, etc. Between two types of mono-slope roofs, clad and unclad, unclad canopy types are more vulnerable to wind load
as wind produces pressure on both upper and lower surfaces of the roof, resulting in uplifting of the roof surface. This paper
discusses the provisions of wind loads in different codes and standards for Low-rise buildings. Further, the pressure coefficients
on mono-slope canopy roof available in wind code and standards are compared. Previous experimental studies for mono-slope
canopy roof along with the recent wind tunnel testing carried out at Indian Institute of Technology, Roorkee is briefly discussed
and compared with the available wind codes. From the study it can further be asserted that the information available related to
staging or blocking under the mono-slope canopy roofs is limited. This paper is an attempt to put together the available
information in different wind codes/standards and the research works carried out by different researchers, along with shedding
some light on the future scopes of research on mono-slope canopy roofs.
Address
Ajay Pratap:Dr. B R Ambedkar National Institute of Technology, Jalandhar, India
Neelam Rani:1)Dr. B R Ambedkar National Institute of Technology, Jalandhar, India
2)Faculty of Engineering (Civil), Dr. B R Ambedkar National Institute of Technology, Jalandhar, India
Abstract
Global Warming has been driven majorly by the consumption of fossil fuels. Harnessing energy from wind is
viable solution towards reducing carbon footprint created due to burning such fuels, However, wind turbines have their
problems of flow separation and aerodynamic stall to tackle with. In an attempt to delay the stall angle and improve the
aerodynamic characteristics of the NACA 0015 symmetrical aerofoil, lateral cylindrical ridges were attached to its suction
surface, at chord positions ranging from 0.1c to 0.5c. The characteristics of the original and ridged aerofoils were
obtained using simultaneous pressure readings taken in a wind tunnel, at a free stream Reynolds number of Re=
2.81 x 105
for a wide range of free stream angles of attack ranging from -45°
to 45°
. Depending on the ridge size, a
delay in stall angle varying from 5°
to 20∘ was achieved together with the maximum increase in lift in the post-stall
phases. Additionally, efforts were made to identify the optimum position for each ridge.
Key Words
cylindrical/circular ridges; flow separation; separation bubble
Address
V.S. Raatan, S. Ramaswami, S. Mano and S. Nadaraja Pillai: Turbulence and Flow Control Laboratory, School of Mechanical Engineering, SASTRA Deemed University, Thanjavur 613401, India
