The objective of this article is to document the multicellular flow in a tall cavity with deformed heated side walls. The article describes an experimental study of natural convection in vertical plane and bent cavities with particle image velocimetry (PIV). On application is the double-glazed window submitted to extreme climate. The dynamic fields obtained from the measures are treated in two ways. The first one is a direct analysis of the instantaneous fields. The second one is the stud of the coefficient of spatial auto-correlation. Results point out the presence of secondary cells in the cavities and a vertical displacement of these cells.