Turbulence Effect of Urban-Canopy Flow on Indoor Velocity Fields under Sheltered and Cross-Ventilation Conditions

Ahmad Faiz Mohammad,Naoki Ikegaya,Ryo Hikizu,Sheikh Ahmad Zaki

doi:10.3390/su13020586

Ahmad Faiz Mohammad, Naoki Ikegaya + Show 2 more

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https://doi.org/10.3390/su13020586

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Abstract

Understanding the characteristics of natural, wind-induced ventilation of buildings is essential for accurate predictions of ventilation flow rates; however, indoor ventilation is significantly influenced by surrounding buildings. Therefore, a series of wind-tunnel experiments were performed to clarify the relationship between outdoor and indoor air flows around and within a target cube model with several openings. Two surrounding building arrangements, namely square (SQ) and staggered (ST), were placed under the condition of a building coverage ratio of 25%. The results indicated that the wind speed near the windward openings on the streamwise faces showed 0.3 to the reference wind speed, whereas those on the lateral faces were less than 0.1; these numbers indicate that the opening positions significantly affect the mean indoor wind speed. Furthermore, the temporal fluctuations of velocities near the opening demonstrated that the introduction of the flow is significantly affected by turbulent flow due to the surrounding buildings. In addition, correlation between the outdoor and indoor air flows was observed. The highest correlations were obtained for both opening conditions with a certain temporal delay. This result indicates that indoor air flows become turbulent because of the turbulent flows generated by the surrounding outdoor buildings; however, slight temporal delays could occur between indoor and outdoor air flows. Although the present study focuses on the fundamental turbulent characteristics of indoor and outdoor air flows, such findings are essential for accurately predicting the ventilation flow rate due to turbulent air flows for sheltered buildings.

Highlights

Utilizing wind-induced, natural ventilation is a passive method to reduce the energy consumption associated with mechanical ventilation and air-conditioning load
A series of wind-tunnel experiments were conducted using hot-wire anemometry for the turbulent urban-canopy flow fields generated by ST and SQ arrays
The results indicated that the wind speed near the windward openings on the streamwise faces showed 0.3 to the reference wind speed, whereas those on the lateral faces were less than 0.1

Summary

Introduction

Utilizing wind-induced, natural ventilation is a passive method to reduce the energy consumption associated with mechanical ventilation and air-conditioning load. Dependence on mechanical ventilation can be reduced when indoor spaces are naturally ventilated. Natural ventilation rates depend on various factors such as the shape of the target building, opening condition, and wind direction [1,2]. Studies on indoor air-flow fields for natural ventilation include numerical simulations [3,4,5,6] and experiments [7,8,9,10]. Asfour and Gadi [2] adopted the computational fluid-dynamics (CFD) approach and applied a mathematical model to predict the air-flow rate for the cross-ventilation of an isolated model exposed to perpendicular and oblique wind directions. Bangalee et al [11]

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