Von K\'arm\'an vortex street in a Bose-Einstein condensate

Vortex shedding from an obstacle potential moving in a Bose-Einstein condensate is investigated. Long-lived alternately aligned vortex pairs are found to form in the wake, as for the von K\'arm\'an vortex street in classical viscous fluids. Various patterns of vortex shedding are systematically studied and the drag force on the obstacle is calculated. It is shown that the phenomenon can be observed in a trapped system.Comment: 4 pages, 5 figure

Experimental investigation of unsteadiness in transonic shock boundary layer interaction

Transonic shock wave/boundary layer interaction over a wall-mounted bump was investigated with specific focus on shock wave unsteadiness and identification of its source. A large separation bubble resulted of an interaction driven by a flow characterized by a peak Mach number of 1.365. Overall this particular type of transonic unsteadiness is characterized with low amplitude and relatively high frequency motion. Low frequency shock unsteadiness was optically estimated and matched spectral content of wall fluctuating pressure. A strong correlation between separation onset and reattachment zones suggested a model of bubble expansion/contraction at the reattachment point where upstream-traveling pressure waves are generated and cause the shock wave excursions

Smooth leading edge transition in hypersonic flow

The boundary layer transition along the attachment line of a smooth swept circular cylinder in hypersonic flow is investigated in a blowdown wind tunnel. A wide range of spanwise Mach numbers Me (3.28 to 6.78) is covered with the help of different models at several sweep angles (60 degrees less than or equal to Lambda less than or equal to 80 degrees). The transition is indirectly detected by means of heat flux measurements. The influence of the wall to stagnation temperature ratio is investigated by cooling the model with liquid nitrogen

Silence, tropisme et stéréotype chez Nathalie Sarraute

La première question qui se pose lorsque l’on aborde le théâtre de Nathalie Sarraute est celle de la transition qui s’est opérée de l’oeuvre romanesque à l’oeuvre dramatique. Comment l’écrivaine fait-elle passer le tropisme dans le dialogue, la sous-conversation dans la conversation? Peut-elle alors éviter les schèmes et catégories de l’imaginaire social? Je me propose ici d’examiner ce problème par le biais d’une analyse comparative de deux textes présentant une thématique semblable : la pièce Le silence (1964), dans laquelle le personnage qui se tait est un homme, et un texte de Tropismes (1939), au centre duquel on trouve un personnage de femme silencieux.The first question which arises when approaching the theatre of Nathalie Sarraute concerns the transition which takes place when going from novel to dramatic work. How does the writer place tropism in the dialogue, the "under-conversation" in the conversation? Can she then avoid the schemes and categories of the social imaginaire? I propose here to examine this problem by the means of a comparative analysis of two works presenting a similar set of themes: the play Le silence (1964), in which the character who is silent is a man, and a text from Tropismes (1939), in the center of which we find a silent female character

Passive scalar mixing downstream of a synthetic jet in crossflow

An experimental investigation on passive scalar mixing due to the interaction of a synthetic jet with a thermal boundary layer is presented. From velocity measurements, performed by particle image velocimetry, two jet behaviours were identified. For jet to crossflow velocity ratios less than 1.2, the velocity fluctuations due to the jet/crossflow interaction stayed close to the wall. At higher ratios, the fluctuations moved away from the wall. The thermal mixing was examined using laser induced fluorescence. During expulsion, the thickness of the downstream thermal boundary layer increased whilst the thermal boundary layer was annihilated immediately downstream of the jet during entrainment

Prediction of pressure drop in multiphase horizontal pipe flow

Empirical correlations were tested against reliable two phase pipe flow data for the prediction of pressure drop. Correlations are recommended for the prediction with stratified and annular type flows. When these correlations were adapted to three phase gaswater-oil pipe flow in general they predicted for intermittent slug type flows. Momentum balance models could not be successfully adapted to the prediction of pipe three phase pressure drop