Experimental and numerical research on the solar updraft at a tall building façade

Abstract

This work presents experimental and numerical research on the solar updraft at a tall building façade, which is 55 m high. The measurements are carried out in windless and cloudless weather, so the warmed by the solar irradiation façade is almost the only factor causing the buoyancy-driven airflow. A set of anemometers are used to record the vertical component of the air velocity. The mean value of the airflow velocity reached up to 2 m/s. However, the instantaneous value varied up to 4 m/s. A numerical model for the solar updraft is built using an ANSYS Fluent, and the temperature boundary condition at the façade is set based on a real IR image taken during the measurements. The numerical results are consistent with the experimental data and the theoretical considerations – at the upper façade edge, the total thickness of the buoyant plume is determined to be about 5 m, and the average airflow velocity is around 0.7 m/s. The strongly turbulent nature of the solar updraft is also confirmed.