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The aerodynamic levitation technique has been used to achieve contactless surface tension and viscosity measurements of oxide liquids at high temperature (T>2000 K). An analytical approach (hydrodynamic equations) and a new recent approach, the energetic approach, are presented. The energetic approach is interesting because it can be applied to all cases, including ceramic oxides, even for droplets far from spherical shape. A device (VITI: VIscosity Temperature Installation) has been developed to perform viscosity measurements on corium using the aerodynamic levitation method. Specific experimental setups for the preparation and for the heating of the sample have been developed. This device has been successfully tested up to 1950 K for viscosity measurements and up to 2900 K without sample. These steps are indispensable to accomplish the final goal of VITI device: the measurement of rheological properties on oxides corium in this field of temperature. Viscosity models at high temperature for molten oxides are presented and compared.

The axial and azimuthal components of the shear rate on the wall of the outer fixed cylinder of a pair of concentric cylinders with the inner cylinder rotating was measured using a three-segment electrodiffusion probe. The axial distribution of the components was found by sweeping vortices past the probe by means of a small axial flow. A nonzero axial shear rate component indicated the onset of Taylor vortices. Azimuthal waves on the vortices caused fluctuations of both components. The instabilities were measured in two geometries characterized by R1/R2 = 0.84 and 0.7. The probe was calibrated in the same apparatus with R1/R2 = 0.94. The Stuart theory for the growth of vortex velocity with angular velocity agrees well with the amplitude of the fundamental mode measured with R1/R2 = 0.84. Qualitative agreement was found with the numerical results of Fasel and Booz, especially between the axial shear rate component measured with R1/R2 = 0.7 and the vorticity calculated for R1/R2 = 0.5.

Abstract: Mass transfer on a circular cylinder with a diameter of 0.52 mm was studied in polymer solutions by measuring the directional characteristics of a three-segment electrodiffusion velocity probe. The free stream velocity was varied in the range 0.01–0.31 m s−1 and the polyacrylamide concentration in the range 0.001–1% (by mass). A small amount of polymer produced large changes in mass transfer distribution on the cylinder in comparison to the distribution in Newtonian liquid. In particular it has been shown that the transfer rate in the aft portion of the cylinder is greater than in the front part if the Weissenberg number exceeds some critical value. The situation was identified where the local mass transfer was constant around the cylinder, i.e. the surface was uniformly accessible to diffusion.

This article concerns "non conventional" uses of the electrochemical method applied to the study of two-phase flows. One deals with the analysis of transport phenomena at liquid-liquid interface in a set-up where the active electrode is made of Gallium, which is a metal changing from solid to liquid state almost at room temperature (29,8 ?C). With the same hydrodynamic conditions an appreciable reduction of transfer is observed when passing through the melting point to the liquid state. The other application uses a three-segmented probe which is convenient for 3-D analysis of flow. The stability of solid-liquid flow (i.e. fiber suspension) is studied in a Taylor-Couette device. The influence of the fibers on the secondary flow is pointed out.

This study deals with the flow of newtonian and non-newtonian fluids, inside a cylindrical flat cavity, provided with a tangential injection device, model of heat exchangers with spiral flow.

On étudie dans une conduite circulaire, coudée selon un demi-cercle, le frottement en paroi d'un écoulement en régime laminaire et turbulent. Les mesures sont effectuées selon la méthode électrochimique utilisant des sondes locales permettant de déterminer la répartition circonférentielle du frottement en plusieurs sections. On met en évidence la forte modification due au mouvement secondaire. Par intégration, on obtient la loi de perte de charge dans le coude. La mesure des taux de fluctuations en régime turbulent montre l'importante réduction du niveau de turbulence par rapport à celui relevé dans la conduite rectiligne amont.