Coupling effect of ventilation duct bend with different shapes and sizes

The coupling effect of local components is common in buildings and results in energy loss and local drag. This effect is significantly influenced by the shape and size of the components. However, only a few studies have focused on this topic. The numerical simulation method of Reynolds stress model (RSM) is adopted in the present study to investigate the typically coupled local components of ventilation and air conditioning ducts, namely, the coupled bend. By focusing on the core speed and segmented drag in the coupled bend, this study explores the effects of aspect ratio and curvature radius on drag and core speed. This study provides a theoretical basis for the design, construction, and operation management of local components of ventilation and air conditioning ducts. Two evident core-speed reduction processes are observed in the coupled bend and its downstream. With increasing curvature radius (R/D), the drop in core speed downstream decreases gradually in the S-shaped and U-shaped bends.