Global warming poses significant challenges, with HVAC-equipped buildings contributing substantially to energy consumption and pollutant emissions. Passive cooling solutions, such as wind towers, offer a sustainable alternative. This study investigates the stack ventilation performance of a circular wind tower attached to a traditional house in Iran's hot-arid climate under no-wind conditions on a spring day. It aims to uncover the mechanism of such centuries-old structures that have evolved to excel even under the desert's still air conditions. ANSYS FLUENT and EnergyPlus (Design Builder) were utilized to predict the flow rate and direction inside the wind tower channels. The data generated by both simulation tools were validated against on-site measurement data from previous studies. Results show that despite its low height, clay construction, and reliance solely on the stack effect, the wind tower ensures adequate ventilation (ACH) for 92% of the diurnal cycle. The primary contributing factor is the high-temperature difference, which can be augmented by the courtyard's microclimate with greenery. During the night and morning, the buoyancy force is dominantly effective. In contrast, it subsides during the warmest hours, leading to downstream flow in wind tower quadrants. The wind tower suction mode dominates around 73% of the circadian cycle.