Effect of gable roof with various roof pitches and obstacle heights on natural ventilation performance for an isolated building

AKKIK  ZOBAIED; Vin Cent Tai; Tze Fong Go; Perk Lin Chong; Lip Kean Moey

doi:10.15282/jmes.16.3.2022.06.0715

Authors

A.A. Zobaied Faculty of Engineering, Built Environment & Information Technology, SEGi University, 47810, Selangor, Malaysia.
V.C. Tai Centre for Modelling and Simulation, Faculty of Engineering, Built Environment & Information Technology, SEGi University, 47810, Selangor, Malaysia. Phone: 03-6145 1777; Fax.: 03-6145 1666.
T.F Go Centre for Advance Materials and Intelligent Manufacturing, Faculty of Engineering, Built Environment & Information Technology, SEGi University, 47810, Selangor, Malaysia.
P.L Chong School of Computing, Engineering & Digital Technologies, Teesside University, Middlesbrough, TS1 3BX, United Kingdom.
L.K. Moey Centre for Modelling and Simulation, Faculty of Engineering, Built Environment & Information Technology, SEGi University, 47810, Selangor, Malaysia. Phone: 03-6145 1777; Fax.: 03-6145 1666.

DOI:

https://doi.org/10.15282/jmes.16.3.2022.06.0715

Keywords:

Gable roof, Roof pitch, Obstacle height, CFD, Ventilation rate

Abstract

Numerical analysis based on CFD steady RANS equations was used to study the airflow characteristics around and within an isolated gable roof building. Parameters that are the main study focus of this research include: streamlines of normalized velocity, pressure coefficient and ventilation rate. The effect of gable roof with four different roof pitches namely 15º, 25º, 35º & 45 were investigated against varying obstacle heights of 40, 50, 60 & 70 mm. From the simulation results, the streamlines show that larger roof pitch leads to increased velocity at the window and roof openings due to the external and internal pressure difference in the building. The corresponding increment in internal obstacle height on the other hand leads to gradual alteration of airflow direction in front of the obstacle, and also an increase of the pressure coefficient inside the building because of wind blocking effect. This pressure coefficient also sees a reduction in value at the windward and inside of the building with an increase in steepness of the roof pitch due to increasing internal velocity. Hence, airflow behavior and characteristics are clearly dependent on roof pitch and internal obstacle height which indicates a good agreement with the findings from the previous studies. Gable roof with a steeper roof pitch building coupled with lower internal obstacle height will therefore yield better ventilation rates.

References

Department of Malaysian Standard, “MS 1525:2014 Energy Efficiency and Use of Renewable Energy for Non Residential Buildings Code of Practice,” Stand. Malaysia 2014, pp. 1–74, 2014.

C. H. Lim, Omidreza Saadatian, K. Sopian, M. Yusof Sulaiman, S. Mat, E. Salleh, and K.C. Ng, “Design configurations analysis of wind-induced natural ventilation tower in hot humid climate using computational fluid dynamics,” Int. J. Low-Carbon Technol., vol. 10, no. 4, pp. 332–346, 2015.

M. N. Khan and I. Janajreh, “Transevaporative cooling performance of a three-sided wind catcher,” Jordan J. Mech. Ind. Eng., vol. 11, no. 4, pp. 225–233, 2017.

L. K. Moey, M. F. Kong, V. C. Tai, T. F. Go, and N. M. Adam, “Effects of roof configuration on natural ventilation for an isolated building,” J. Mech. Eng. Sci., vol. 15, no. 3, pp. 8379–8389, 2021.

R. Ramponi and B. Blocken, “CFD simulation of cross-ventilation for a generic isolated building: Impact of computational parameters,” Build. Environ., vol. 53, pp. 34–48, 2012.

J. Kindangen, G. Krauss, and P. Depecker, “Effects of roof shapes on wind-induced air motion inside buildings,” Build. Environ., vol. 32, no. 1, pp. 1–11, 1997.

L. K. Moey, N. M. Adam, and K. A. Ahmad, “Effect of venturi-shaped roof angle on air change rate of a stairwell in tropical climate,” J. Mech. Eng., vol. SI 4, no. 4, pp. 135–150, 2017.

Y. Tominaga, S. ichi Akabayashi, T. Kitahara, and Y. Arinami, “Air flow around isolated gable-roof buildings with different roof pitches: Wind tunnel experiments and CFD simulations,” Build. Environ., vol. 84, pp. 204–213, 2015.

X. Zhou, Y. Zhang, L. Kang, and M. Gu, “CFD simulation of snow redistribution on gable roofs: Impact of roof slope,” J. Wind Eng. Ind. Aerodyn., vol. 185, pp. 16–32, 2019, doi: 10.1016/j.jweia.2018.12.008.

M. G. Badas, S. Ferrari, M. Garau, and G. Querzoli, “On the effect of gable roof on natural ventilation in two-dimensional urban canyons,” J. Wind Eng. Ind. Aerodyn., vol. 162, pp. 24–34, 2017.

L. K. Moey, M. F. Kong, V. C. Tai, T. F. Go, and N. M. Adam, “Effect of gable roof angle on natural ventilation for an isolated building,” Jordan J. Mech. Ind. Eng., vol. 15, no. 3, pp. 291–300, 2021.

C. R. Chu and B. F. Chiang, “Wind-driven cross ventilation with internal obstacles,” Energy Build., vol. 67, pp. 201–209, 2013.

P. Karava, T. Stathopoulos, and A. K. Athienitis, “Airflow assessment in cross-ventilated buildings with operable façade elements,” Build. Environ., vol. 46, no. 1, pp. 266–279, 2011.

J. Franke, A. Hellsten, H. Schlünzen, and B. Carissimo, “Best practice guideline for the CFD simulation of flows in the urban environment,” COST action, vol. 44, no. May, pp. 1–52, 2007.

Y. Tominaga, A. Mochida, R. Yoshie, H. Kataoka, T. Nozu, M. Yoshikawa, and T. Shirasawa, “AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings,” J. Wind Eng. Ind. Aerodyn., vol. 96, no. 10–11, pp. 1749–1761, 2008.

Z. Krishna, P. Gandhar, Balasubramanyam, A. Varghese, ANSYS Inc, K. Zore, B. Sasanapuri, G. Parkhi, and A. Varghese, “Ansys mosaic poly-hexcore mesh for high-lift aircraft configuration,” 21 st Annu. CFD Symp., no. September, pp. 1–11, 2019.

Panagiota Karava, “Airflow prediction in buildings for natural ventilation design: Wind tunnel measurements and simulation,” Concordia Univ., no. May, 2008.

R. Ramponi and B. Blocken, “CFD simulation of cross-ventilation flow for different isolated building configurations: Validation with wind tunnel measurements and analysis of physical and numerical diffusion effects,” J. Wind Eng. Ind. Aerodyn., vol. 104–106, pp. 408–418, 2012.

B. E. Launder and D. B. Spalding, “The numerical computation of turbulent flows,” Comput. Methods Appl. Mech. Eng., vol. 3, no. 2, pp. 269–289, 1974.

T. Cebeci and P. Bradshaw, “Momentum transfer in boundary layers,” New York Hemisph. Publ. Corp., pp. 377–386, 1977.

B. Blocken, T. Stathopoulos, and J. Carmeliet, “CFD simulation of the atmospheric boundary layer: wall function problems,” Atmos. Environ., vol. 41, no. 2, pp. 238–252, 2007.

M. Shirzadi, P. A. Mirzaei, and M. Naghashzadegan, “Improvement of k-epsilon turbulence model for CFD simulation of atmospheric boundary layer around a high-rise building using stochastic optimization and Monte Carlo Sampling technique,” J. Wind Eng. Ind. Aerodyn., vol. 171, pp. 366–379, 2017.

Y. Takano and P. Moonen, “On the influence of roof shape on flow and dispersion in an urban street canyon,” J. Wind Eng. Ind. Aerodyn., vol. 123, pp. 107–120, 2013.

M. Swami and S. Chandra, “Procedures for calculating natural ventilation airflow rates in buildings,” ASHRAE Final Rep. FSEC-CR-163-86, p. 130, 1987.

S. Hawendi and S. Gao, “Impact of an external boundary wall on indoor flow field and natural cross-ventilation in an isolated family house using numerical simulations,” J. Build. Eng., vol. 10, pp. 109–123, 2017.