Recent visualisations have shown the instabilities that develop at low Reyn
olds numbers in a closed cavity formed by a rotating disc, a fixed disc and
a fixed outer cylinder. The origin of the spiral structures located near t
he fixed corner of the cavity is still not well understood. A numerical sch
eme associating a finite volume method and a pseudo-spectral method is used
. The velocity and pressure fields are analysed. A description of this comp
lex structure is proposed. (C) 2000 Academie des sciences/Editions scientif
iques et medicales Elsevier SAS.