Contribution to the study of multicellular flows inside two-dimensional rectangular and pinched insulated glazing cavities

This paper describes the results of an investigation aimed at examining secondary cells in two-dimensional high aspect ratio cavities, such as those encountered in insulated gluing units (IGU). Numerically, the governing transient equations are solved using a co-located equal order control-volume finite element (CVFEM) approach. Velocity fields are obtained experimentally using a particle image velocimetry (PIV) system. Results for a rectangular cavity with an aspect ratio of 40 and Ra = 9524 are presented first. The secondary cell structure present for such conditions is well captured experimentally and compares favorably with corresponding numerical results. Experimentally, the results show that the secondary cells are in movement toward the bottom of the cavity. Flow structure in two different two-dimensional pinched cavities with an aspect ratio of 20 and Ra = 41606 and 28879 is also examined numerically. The main flow in such cavities is impeded by the restriction at the center, which tends to lower the overall Nusselt number by approximately 28% and 35% when the center plate defections are 0.5 and 0.75 cm, respectively. Finally, for a center plate deflection of 0.75 cm, it is shown that the number of secondary cells is time dependent.