Application of the Particle Image Velocimetry to the Couette-Taylor Flow

For longtime, the investigation of flow regimes has been achieved using fluorescent particles or anisotropic reflective particles. Fluorescent particles are suitable for open flows (Van Dyke, 1982) such as flows in channels (Peerhossaini et al., 1988) or flows behind a cylinder (to visualize Benard-von Karman street) (Provansal et al., 1986; Mutabazi et al., 2006). For closed flows such as flows in a rectangular cavity or in an annular cylindrical rotating cavity, fluorescent particles rapidly color the entire flow and no flow structure can be caught. Anisotropic reflective particles (aluminium, iriodin or Kalliroscope flakes) are more convenient for detection of the flow structures (Taylor, 1923; Andereck et al., 1986; Coles, 1965; Matisse et al., 1984; Dominguez-Lerma et al. , 1985; Thoroddsen et al. 1999). A laser light is used to illuminate the flow cross-sections and to detect the flow structure in the axial, radial and azimuthal directions. The motion of the seeded particles in a fluid gives a qualitative picture of flows which can be used to develop appropriate theoretical models. The development of chaotic models of fluid flows (Rayleigh-Bénard convection, CouetteTaylor flow or plane Couette flow) has benefited from observations using visualizations techniques (Bergé et al., 1994). Using appropriate signal processing techniques such as spacetime diagrams and complex demodulation, it is possible to obtain spatio-temporal evolution of the flows (Bot et al., 2000). In order to obtain quantitative data on velocity fields, different velocimetry techniques have been developed such as Laser Doppler Velocimetry (LDV, Durst et al., 1976, Jensen 2004), Ultrasound Doppler Velocimetry (UDV, Takeda et al., 1994) and Particle Image Velocimetry (PIV, Jensen, 2004). Nowadays, there is a lot of literature on velocimetry techniques the development of which is beyond the scope of this chapter, some of them and their applications are described in this volume. Each velocimetry technique has its advantages and own limitations depending on the flow system under consideration. For example, in the case of the Couette-Taylor flow, the LDV (Ahlers et al., 1986) gives time averaged velocity in a point, the UDV measures a velocity profile along a chosen line in the flow and the PIV gives a velocity field in a limited flow cross section. The Couette-Taylor system is composed of a flow in the gap between two coaxial differential rotating cylinders. This system represents a good hydrodynamic prototype for the study of the transition to turbulence in closed systems. The experimental results obtained from this system have led