Browsing by Author "Hao, Yue"
Now showing 1 - 5 of 5
- Results Per Page
- Sort Options
Item Mechanics of gas-vapor bubbles(Physical Review Fluids, 3/23/2017) Hao, Yue; Zhang, Yuhang; Prosperetti, AndreaMost bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and condensation and of gas diffusion in the liquid and in the bubble. This paper presents a model for this situation and illustrates by means of examples several physical processes that can occur: a bubble undergoing a temporary pressure reduction, which makes the liquid temporarily superheated; a bubble subjected to a burst of sound; and a bubble continuously growing by rectified diffusion of heat in the presence of an incondensible gas.Item Rectified heat transfer into translating and pulsating vapor bubbles(The Journal of the Acoustical Society of America, 11/1/2002) Hao, Yue; Prosperetti, AndreaIt is well known that, when a stationary vapor bubble is subject to a sufficiently intense acoustic field, it will grow by rectified heat transfer even in a subcooled liquid. The object of this paper is to study how translation, and the ensuing convective effects, influence this process. It is shown that, depending on the initial temperature distribution and other factors, convection can cause a destabilization of the bubble or its faster growth. Significant effects occur in parameter ranges readily encountered in practice. The phenomena described can therefore be exploited for bubble management, e.g., by increasing the condensation rate or promoting faster bubble growth and coalescence. In a saturated or a superheated liquid, heat rectification and convection reinforce each other and the bubble growth is accelerated by a translatory motion.Item The Action of Pressure-Radiation Forces on Pulsating Vapor Bubbles(The Physics of Fluids, 2001-05) Hao, Yue; Oguz, H.N.; Prosperetti, AndreaThe action of pressure-radiation (or Bjerknes) forces on gas bubbles is well understood. This paper studies the analogous phenomenon for vapor bubbles, about which much less is known. A possible practical application is the removal of boiling bubbles from the neighborhood of a heated surface in the case of a downward facing surface or in the absence of gravity. For this reason, the case of a bubble near a plane rigid surface is considered in detail. It is shown that, when the acoustic wave fronts are parallel to the surface, the bubble remains trapped due to secondary Bjerknes force caused by an “image bubble.” When the wave fronts are perpendicular to the surface, on the other hand, the bubble can be made to slide laterally.Item The dynamics of vapor bubbles in acoustic pressure fields(The Physics of Fluids, 1999-08) Hao, Yue; Prosperetti, AndreaIn spite of a superficial similarity with gas bubbles, the intimate coupling between dynamical and thermal processes confers to oscillating vapor bubbles some unique characteristics. This paper examines numerically the validity of some asymptotic-theory predictions such as the existence of two resonant radii and a limit size for a given sound amplitude and frequency. It is found that a small vapor bubble in a sound field of sufficient amplitude grows quickly through resonance and continues to grow thereafter at a very slow rate, seemingly indefinitely. Resonance phenomena therefore play a role for a few cycles at most, and reaching a limit size—if one exists at all—is found to require far more than several tens of thousands of cycles. It is also found that some small bubbles may grow or collapse depending on the phase of the sound field. The model accounts in detail for the thermo-fluid-mechanic processes in the vapor. In the second part of the paper, an approximate formulation valid for bubbles small with respect to the thermal penetration length in the vapor is derived and its accuracy examined. The present findings have implications for acoustically enhanced boiling heat transfer and other special applications such as boiling in microgravity.Item The effect of viscosity on the spherical stability of oscillating gas bubbles(The Physics of Fluids, 1999-06) Hao, Yue; Prosperetti, AndreaGas bubbles driven in radial oscillations are subject to an instability of the spherical shape that is opposed by surface tension and viscosity. An exact linear formulation for the study of the phenomenon has been available for many years, but its complexity has discouraged a detailed investigation. With the recent theory of sonoluminescence of Lohse and co-workers [Hilgenfeldt et al., Phys. Fluids, 8, 2808 (1996)], there has been a renewed interest in the problem and new data have become available. This paper presents a numerical method for the solution of the pertinent equations and compares the theory with these new data. The coupling of the strong nonlinearity of the bubble radial oscillations with the parametric mechanism of the surface instability results in a very complex structure for the stability boundary. Nevertheless, a good agreement between theory and data is found. A comparison with earlier approximate models is also made.