Drag coefficient is obtained by using computational fluid dynamics

What is it about?

The wind is the main horizontal force acting on tall buildings. This force is proportional to the drag coefficient. The drag coefficient is an important factor in their structural design of tall buildings. For tall buildings, wind loads represent the predominant horizontal design load. The magnitude of the airflow velocity, aside from the construction material roughness, interferes with the wind pressure. Recent trends involve designing taller and more irregularly shaped buildings. These types of structures are potentially more sensitive to wind excitation. By using fluid dynamics simulations, the drag coefficient is determined for each terrain condition. CFD can effectively simulate the drag force and resultant forces in the direction of the flow, as well as the vortices that result during coating detachment and other types of damage.

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Photo by Katarzyna Kos on Unsplash

Photo by Katarzyna Kos on Unsplash

Why is it important?

Designers have historically relied upon experimental wind tunnel results to estimate the drag coefficient. However, this process is both expensive and time-consuming. In this study, we alternatively computed the drag coefficient (apart from the pressure, force, and bending moment) using computational fluid dynamics for a typical 93-m-high residential building. The simulation considers the actual building geometry. We compared these results with the conventional estimates contained in the Brazilian code NBR-6123/1988 and Eurocode EC1. The results indicated that the pressures obtained herein near the top of the building were lower compared to those obtained using conventional estimation methods given in codes. Comparatively, the obtained bending moment relative to the base of the building was higher, indicating the existence of significant drag forces not considered in codes.

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