Airflow collision characteristics of double square column attachment ventilation

In the square column attachment ventilation (S-CAV) mode, the introduction of multiple airflows attached to the column into the horizontal diffusion zone inevitably leads to various “airflow collision” phenomena. However, after the floor-attached airflow collides, the indoor air distribution may deviate from the design goal. In this paper, the layout of the axisymmetric and non-axisymmetric arrangement of double columns is summarized. The airflow collision mechanism and flow characteristics for different column layouts are analyzed via experiments and computational fluid dynamics (CFD) simulations, and a new partition form is proposed to more effectively control the indoor environment. A 1:2 scale model was employed for the velocity verification experiments and flow field visualization. The results indicated that the airflow collision area can be divided into impact, transition, and collision zones with axisymmetric double-column layouts. In the range of 1–3 m/s, any variation in the supply air velocity, irrespective of the occurrence of airflow collision, may be considered negligible with respect to its impact on the attenuation trend of the axial velocities. At the same absolute value of the air supply temperature difference, the cooling condition experiences a 3.1 times greater kinetic energy loss due to collision than does the heating condition. In a nonsymmetric arrangement of two columns, the curve formed by the stagnation point rotates, and the direction of rotation is biased toward the side of the column that is farther away. The findings provide a solid theoretical basis for the engineering application and optimal design of CAV modes. •Study the collision mechanism under S-CAV mode by CFD and visualization experiment.•The airflow collision area is categorized into impact, transition, and collision zone.•Air supply velocity showed a limited effect on the attenuation trend of the axial velocities.•Kinetic energy loss due to collision is 3.1 times greater in cooling than heating conditions.•The stagnation line will rotation when the column is arranged non-symmetric.