Three-dimensional instability in a rotor-stator cavity

This Note considers the direct numerical simulation of transitional flows i nside a rotor-stator cavity using a three-dimensional spectral method. The investigation shows the occurrence of a steady axisymmetric instability whi ch was not previously revealed numerically although demonstrated experiment ally by Sirivat. At the same Reynolds number two axisymmetric and three-dim ensional structures can be found. The instabilities are analysed with respe ct to relevant characteristic flow parameters such as the frequency: the ph ase velocity, the wavelength and the angle of the spiral with respect to th e azimuthal direction. The relevance of type I and type II instabilities is discussed. (C) 1999 Academie des sciences/Editions scientifiques et medica les Elsevier SAS.