Bubbles coalescence stability condition

These observations can be linked in a remarkable way. Salt in the human body is at the minimum level for which maximum bubble coalescence stability is achieved (about 0.15 M for NaCl). This level of salt might then act to prevent bubble nucleation at the interface between microscopic hydrophobic organelles in the human body. That is, salt prevents the effects of the "bends" that would otherwise occur even under atmospheric conditions. (Spontaneous cavitation between highly hydrophobic surfaces in water at close separations, without decompression is established.) Examination of Table 3.1 shows us that some salts give no protection and would therefore be inhibiting to organised organic structures. Decompression... 

From the multi-scale point of view, the total energy dissipation Nj can be grouped into three portions, namely, Nsurf, Nturb, and Nbreak- The last portion is generated from bubble breakage and finally dissipated in the process of bubble coalescence. While Nsurf and Nln rb are considered to be directly dissipated on micro-scale, Nbreak is counted as a kind of meso-scale energy dissipation. Therefore, the stability condition can be either expressed with the minimization of micro-scale energy dissipation Nsurf + Nturb 7 min or conveyed as the maximization of meso-scale energy dissipation Nbreak max. 

TheoreticaUy stability condition may offer closure laws for CFD simulation, leading to SCMF CFD model. While the direct integration is difficult, we propose various simplified approaches to derive the closure models for drag, bubble-induced turbulence, and the correction factors for the kernel functions of bubble coalescence and breakup for PBEs. The SCMF CFD model shows much advantage over current closure models. 

It is pointed out in [252] that more than 10% of the world oil recovery is accomplished by injecting steam or CO2 for the production of oil by EOR. Here, the foam bubble size is comparable or slightly more than the pore diameter. To increase oil production, highly disperse steam foam is required, which pushes the oil out of the reservoir while moving both as a continuous and discontinuous flow. It has to be emphasized that the choice of surfactant is important to accomplish the process. Typically, the surfactant concentration is much higher than CMC, which predetermines the expensiveness of the process. The foam is destroyed when coming in contact with oil and rock, which requires its increased consumption. Three mechanisms of foam formation under reservoir conditions are proposed in [253], determined by the liquid flow rate and the throat radius between the pores. When the foam flows in a reservoir, its aggregative stability is disturbed due to coalescence. Hence, the choice of... 

The ability to control foam stability or coalescence rate of bubbles is important in many industrial applications. Foams can persist for a few minutes to several days depending on storage conditions. To effectively utilize foams in any of these situations, it is important to have some control over their stability. Therefore it is very important to deepen our understanding of the mechanisms involved in foam persistence and decay. Most works in this area have been rather empirical and many experimental data are rendered useless because important parameters such as bubble size have not been measured. In this chapter we attempt to summarize the quantitative analysis on foam film stability in aqueous systems in terms of surface tension measurements. 

An important factor that controls the final morphology of foams is the crystallization kinetic of the polymer. In the extrusion process, once the melt exits the die, bubbles nucleate first and then they grow in not isothermal conditions. The viscosity increase occurring during the cooling/ crystallization of the polymer is necessary to stabilize the cellular structure and to avoid the collapse and/or the coalescence of the bubbles. For this reason, the investigation of the crystallization behaviour of the polymer should be known in order to optimize die temperature profile in the extruder and at the die. 

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