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A new cavitation model based on bubble/bubble interactions has been recently proposed by the authors Adama Maiga, Coutier-Delgosha, and Buisine ["A new Cavitation model based on bubble-bubble interactions," Phys. Fluids 30, 123301 (2018)]. It includes all nonlinear interaction terms between two bubbles, and the only input is the local velocity divergence, while the classical Rayleigh-Plesset or Gilmore models only take into account the linear interaction terms and require the local pressure evolution. In this previous publication, the model has been validated against cases of single bubbles growths and collapses. In the present paper, the same model is applied to configurations of high-speed cavitating flow on a Venturi profile and a two-dimensional foil section, where experiments based on X-ray imaging have been recently conducted. Based on the flow velocity fields available in the two cases, the local velocity divergence is calculated, and a one-dimensional mean divergence evolution from the leading edge to the wake of the cavity is extracted and used as an input for the model validation. The evolutions of the biggest bubble and the volume of vapor are both found in good agreement with the experiments. A typical velocity divergence evolution is then defined, and our model is compared to the modified Rayleigh-Plesset equation that includes the interactions between multiple bubbles. It confirms that the radius evolution of the biggest bubble is systematically better estimated by the new model due to its capability to continuously take into account the interactions of big bubbles with smaller bubbles. Eventually, the model is used to investigate the scale effect, by applying 6 different time scales of cavitation development covering more than 5 orders of magnitude. It is shown that the bubble size does not vary proportionally to the scale, but according to a law that is empirically determined. [ABSTRACT FROM AUTHOR]

In this paper, a new model based on bubble-bubble interactions is proposed for cavitation. Unlike the well-known existing models (Rayleigh-Plesset, Gilmore), which are derived from the local balance equations in the vicinity of a single cavitation bubble, the present approach is based on the mutual interaction between two spherical bubbles of different sizes. The mass and momentum conservation equations, coupled with the local flow divergence, lead to two equations for the evolution of the bubble radii and one equation for the local pressure. The bubble size variations predicted by the model are found in close agreement with the previous experimental data reported by Ohl ["Cavitation inception following shock wave passage," Phys. Fluids 14(10), 3512–3521 (2002)]. The distinct radii of bubbles located close to each other, as well as the premature collapse of small bubbles during the initial stage of cavitation inception, are correctly reproduced by the model. The results generally show that bubble/bubble interactions play a primary role in the physics of cavitation inception, which is a preponderant phenomenon in cavitation-induced noise and erosion. The influence of the size of the nuclei on these interactions is discussed. During the expansion phases, the variations in the local flow divergence only slightly affect the growth of the big nuclei, which is mainly governed by their interaction with the neighboring bubbles, while it triggers the expansion of the small nuclei. Conversely, in the compression phase, the behavior of the bubbles is not influenced anymore by the initial size of the nuclei. It is also shown that large amplitude pressure variations resulting from the multiple collapses of small bubbles should be taken into account, in addition to the ambient pressure evolution, to calculate the instantaneous local pressure in the liquid and eventually evaluate the flow aggressiveness and the resulting erosion. [ABSTRACT FROM AUTHOR]

The relaxation of two-dimensional Eulerian turbulence to a quasifinal state is studied. We consider the self-organization of localized vortices (in two-dimensional flows) into clusterlike and spiral-like structures and show that quasifinal states do not "forget" conditions of their initial origin. The numerical study confirms a possibility of the "vortex crystals" formation that have been observed in the plasma experiments. We discuss the physical significance of the obtained results. [ABSTRACT FROM AUTHOR]

The paper analyses hydrodynamic characteristics of a high-speed two-phase flow in a mixing tube of a small-diameter. Different parameters including the water jet velocity and the ratio of diameters — the mixing tube to the water jet orifice — are investigated under two conditions of the air flow rates. Two measurements are used: the static pressure distribution along the mixing tube and the visualisation of the high-speed water jet at the tube inlet and its downstream outlet. The visualisation results show that the configuration of air–water jet flow starts annular near the tube inlet and then occupies the whole cross-section of the tube. Moreover, the pressure distribution results indicate the existence of three distinct-flow zones along the tube: an expansion zone with a high negative pressure gradient at the inlet; a practically constant pressure zone where the flow is nearly established in the middle, and an important recompression zone near the tube outlet. The paper demonstrates that the mixture of the air–water jet flow is not homogenous along the tube in the real behaviours. A schematic representation of the flow along the tube was introduced. [Copyright &y& Elsevier]