Tall buildings are being developed at rapid rates owing to the need for optimization of space for increasing urban crawl. Tall buildings having simple cross – sections are designed using IS 875 (Part 3) – 2015, however there is a lack of set of codal provisions for complex cross – section shapes. This study has been undertaken to interpret the wind flow characteristics of an isolated tall building (Model A) utilizing CFD (Computational Fluid Dynamics) and k - ɛ turbulence model in ANSYS: CFX (Analysis of Computational Fluid Dynamics program). Model A is 192 m in height having two types of cross sections – plus and square; each of height 96 m. Wind of intensity 10 m/s is incident on it at four incidence wind angles 0°, 30°, 60° and 90°. Pressure contours obtained on simulation indicate that for incident wind angles 0° and 90°, all lateral faces of the Model A (proposed design model) show similar pressure impact. Whereas, for incident wind angles 30° and 60°, wind ward faces (A and C) show decreased pressure impact with respect to 0° case. Vertical streamlines depict a recirculation zone at one – third the height of Model A for incident wind angle, 30°. Whereas, horizontal streamlines indicate the occurrence of vortex formation in the wake region of the building for incident wind angles, 0° and 90°.

PurposeIn this study the comparison is presented for the variation in cross-sectional shape along the height of the building model. For this purpose Model B and Model C are having the considerable variation and Model A result can be easily predicted on the basis of the result of Model B and C while Model X is considered for the validation purposes only and it is well established that the results are within the allowable limit. This paper aims to discuss these wind generated effects in the tall building model.Design/methodology/approachComputational Fluid Dynamics (CFD) in ANSYS: CFX is used to investigate the wind effects on varying cross-sectional shape along the height of the building model.FindingsFrom pressure contours, it was observed that shape and size of the face is independent of the pressure distribution. It is also observed that pressure distribution for the windward face (A) was less than the magnitude of the leeward face for both models. The leeward face and lateral faces had similar pressure distribution. Also slight changes in pressure distribution were observed at the periphery of the models.Originality/valueThis study has been performed to analyse and compare the wind effect on tall buildings having varying cross sections with variation of different cross sections along the height. Most of the studies done in the field of tall buildings are concentrated to one particular cross-sectional shape while the present study investigates wind effects for combination of two types of cross sections along the height. This analysis is performed for wind incidence angles ranging from 0° to 90° at an interval of 30°. Analysis of wind flow characteristics of two models, Models B and C will be computed using CFD. These two models are the variation of Model A which is a combination of two types of cross section that is square and plus. Square and plus cross-sectional heights for Model B are 48 m and 144 m, respectively. Similarly, square and plus cross-sectional heights for Model C are 144 m and 48 m, respectively. The results are interpreted using pressure contours and streamlines, and comparative graphs of drag and lift forces are presented.

No abstract

Tall buildings are being developed at rapid rates owing to the need for optimization of space for increasing urban crawl. Tall buildings having simple cross -sections are designed using IS 875 (Part 3) -2015, however there is a lack of set of codal provisions for complex cross -section shapes. This study has been undertaken to interpret the wind flow characteristics of an isolated tall building (Model A) utilizing CFD (Computational Fluid Dynamics) and k -ɛ turbulence model in ANSYS: CFX (Analysis of Computational Fluid Dynamics program). Model A is 192 m in height having two types of cross sections -plus and square; each of height 96 m. Wind of intensity 10 m/s is incident on it at four incidence wind angles 0°, 30°, 60° and 90°. Pressure contours obtained on simulation indicate that for incident wind angles 0° and 90°, all lateral faces of the Model A (proposed design model) show similar pressure impact. Whereas, for incident wind angles 30° and 60°, wind ward faces (A and C) show decreased pressure impact with respect to 0° case. Vertical streamlines depict a recirculation zone at one -third the height of Model A for incident wind angle, 30°. Whereas, horizontal streamlines indicate the occurrence of vortex formation in the wake region of the building for incident wind angles, 0° and 90°.

Study of wind is empirical for the designing of tall structures because it considers the instability due to slender behavior of these structures. In this study, three models namely A, B, and C are analyzed on ANSYS using Computational fluid dynamics approach. These three models have a total height of 192 m built of two types of cross – sections as plus and square (below plus). These models differ by the heights of the cross sections only. Plus and square cross – section heights for Model A are 96 m each, for Model B are 48 m and 144 m respectively and for Model C are 144 m and 48 m respectively. CFD simulations are performed for wind of magnitude 10 m/s when incident on these three modes at wind incidence angle 0° and the results are interpreted in terms of pressure contours and streamlines. It is observed that designing for critical faces is a must. Also from streamlines it may be observed that as the cross – sectional height of irregular shape increase, more stability is noticed. It is also observed that the wind velocity increases at the top most points of the models.