We study the formation of new spiral patterns, denoted SRJ2 at the periphery of an enclosed rotor-stator cavity when an axial inward or outward throughflow is superimposed

Chauve, Marie-Pierre

Poncet, Sébastien

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Crossflow instability in rotor-stator flows with throughflow

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Crossflow instability in rotor-stator flows withthroughflowSe´bastien Poncet, Marie-Pierre ChauveTo cite this version:Se´bastien Poncet, Marie-Pierre Chauve. Crossflow instability in rotor-stator flows with through-flow. 6th Euromech Fluid Mechanics Conference, Jun 2006, Stockholm, Sweden. <hal-00170268>HAL Id: hal-00170268https://hal.archives-ouvertes.fr/hal-00170268Submitted on 7 Sep 2007HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.Crossflow instability in rotor-stator flows with throughflowS. Poncet ∗, M.-P. Chauve ∗We study the formation of new spiral patterns, denoted SRJ2 (figure 1(a)), atthe periphery of an enclosed rotor-stator cavity when an axial inward or outwardthroughflow is superimposed.Figure 1(b) shows the transition diagrams, obtained from flow visualizations, forthree different aspect ratios G = h/R2 in the (Re, V ∗z ) plane, where h is the interdiskspace, R2 the rotating disk radius, Re the rotational Reynolds number and V ∗z thedimensionless axial velocity in the radial gap between the rotor and the shroud. Thus,the results of Poncet and Chauve 1 and Re´my et al. 2 have been extended for bothBatchelor (G = 0.0857) and torsional Couette (G = 0.0171) type of flows. The SRJ2spiral rolls appear essentially when an inward throughflow (V ∗z > 0) is superimposedbut also in the case of an outward throughflow (V ∗z < 0) for G = 0.0857. Numericalcalculations have shown that these structures appear as soon as a strong axial upwardflow is created along the shroud, which may be the case when the outward throughflowimpinges on the shroud. As the axial velocity profiles exhibit inflexion points, thisinstability is of crossflow type. From visualizations and velocity measurements, wehave determined that these are positive spirals located at the periphery of the cavityalong the stator side and characterized by small frequency and phase velocity andlarge inclination angle and azimuthal wavenumber. The influence of the flow controlparameters Re, V ∗z and G on these characteristics have been analysed. There is astrong competition between rotation and throughflow. Nevertheless, the effects of thegeometry G and of the throughflow V ∗z seem to be preponderant to be compared tothe one of the rotation Re.∗IRPHE, Technopoˆle Chaˆteau-Gombert, 13384 Marseille, France.1Poncet and Chauve, J. Fluid Mech. 545, 281 (2005).2Re´my et al., Phys. Fluids 17 (1) (2005).Ω 20000 40000 60000 80000-0,20,00,20,40,60,81,0V z *Re G=0.0171 G=0.0429 G=0.0857(a) (b)Figure 1: (a) Visualization of the SRJ2 patterns for Re = 2.05× 104, V ∗z = 0.515 andG = 0.0429. (b) Existence domains of the SRJ2 spirals in the (Re,V ∗z ) plane.

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Crossflow instability in rotor-stator flows with throughflow

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