Presentation Information
[O12-P45]The Relationship Between Two Buildings and Wind Flow Around Them—Using a Homemade Wind Tunnel Apparatus
*Ryo Taniuchi1, *Yuya Amino1 (1. Johoku Junior & Senior High School)
Keywords:
Building Wind,Wind Tunnel Experiment,Karman vortex,Downwash
The present study aimed to reproduce building-induced strong winds and to identify the conditions under which phenomena analogous to actual building winds may occur. Building winds are strong localized airflows generated around buildings, and they may produce windborne debris that can cause harm to people and damage to structures. To investigate these phenomena, a self-constructed wind tunnel apparatus and scale building models were employed. This study constitutes an improved extension of our previous research, “Elucidating the Relationship Between Building Winds and the Distance Between Buildings: Using a Self-Constructed Wind Tunnel Apparatus” (2024), which was presented at the high school student poster session of the Japan Geoscience Union Meeting 2024. In the previous study, observation from above was hindered by the accumulation of smoke in the upper part of the apparatus. Although an alternative configuration enabled lateral observation by laying the models sideways, that arrangement did not preserve the actual direction of gravity. To overcome this limitation, the present study introduced a transparent acrylic plate that allowed observation from below, together with a mirror inclined at 45 degrees beneath the plate, thereby making it possible to observe the lower view laterally through reflection. In addition, one side of the apparatus was constructed of acrylic plate, enabling direct lateral observation. The apparatus consisted of a smoke generator, a flow straightener made from approximately 900 bundled plastic straws, an observation chamber, and an electric fan. Incense smoke was used to visualize airflow. Two building models, each measuring 15 cm in height, 3 cm in width, and 6 cm in depth, were placed in parallel inside the chamber. The spacing between the models was varied from 1 cm to 10 cm in 1 cm increments, and smoke flow was recorded both directly from the side and indirectly through the mirror from below. The results showed that, in the lower-view recordings, airflow entered the wake region behind the models at spacings of 1–7 cm, resembling the Kármán vortex phenomenon observed around actual buildings. Moreover, at all spacings from 1 cm to 10 cm, airflow impinged on the models and underwent rapid acceleration, a behavior similar to separated flow. In the lateral recordings, the wake flow behind the models exhibited a downward-deflecting trajectory at all spacings, resembling downwash around high-rise buildings. However, because neither velocity distributions nor pressure distributions were measured, it cannot be concluded definitively that these observed behaviors are physically identical to actual building-wind phenomena. In conclusion, the present study succeeded in establishing an experimental configuration closer to real building-wind conditions than that used in our previous work and in revealing several phenomena analogous to those observed around actual buildings. Nevertheless, the absence of quantitative measurements and the failure to consider the Reynolds number limit the direct applicability of the results to real-scale environments. Future work should therefore incorporate measurements of velocity and pressure distributions, together with calculation and analysis of the Reynolds number, in order to strengthen the physical validity and interpretive rigor of the experiment.