Bubbles cloud-type

Most bubbles in gas-solid fluidized beds are of spherical cap or ellipsoidal cap shape. Configurations of two basic types of bubbles, fast bubble (clouded bubble) and slow bubble (cloudless bubble), are schematically depicted in Fig. 9.7. The cloud is the region established... 

A number of terms have been used to describe inclusions, some of which are self-explanatory, such as bubbles, Ijords (parallel channels), veils (thin sheets of small bubbles), clouds (random clusters of small bubbles), negative crystals (faceted inclusions) and so on. Most frequently inclusions are distributed randomly throughout the crystal, but sometimes they show a remarkable regularity, e.g. as in hexamine (Denbigh and White, 1966 Bourne and Davey, 1977) and ammonium perchlorate (Williams, 1981). Sometimes hour-glass or Maltese cross patterns may appear, e.g. as in sucrose (Powers, 1969/70 Man-tovani et al., 1985). Several examples of different types of inclusion in crystals are illustrated in Figure 6.46. 

Fig. S3. Ratio of cloud radius to bubble radius ri, on vertical axis above three-dimensional bubbles. Comparison of experimental values with various theoretical predictions. The curve Jackson (modified) refers to results obtained by Jackson s type of analysis, but with the Davies-Taylor type rise velocity where k is chosen to give the best... 

These developments led to a novel type of reactor models, the hydrodynamic models, in which the bed behavior was based on the characteristics of the rising bubbles. Several models of this kind were derived for the industrial relevant fine particle suspensions in which the rising bubbles are surrounded by very thin clouds of circulating gas. Various combinations of assumptions have been used to represent the phase interaction phenomena in this region [81] ... 

Condensation of vapor occurs in a variety of engineering applications. For example, when a vapor is cooled below its saturation temperature, or when a vapor-gas mixture is cooled below its dew point, homogeneous condensation occurs as a fog or cloud of microscopic droplets. Condensation also occurs when vapor comes in direct contact with subcooled liquid such as spraying a fine mist of subcooled liquid droplets into a vapor space or injecting vapor bubbles into a pool of subcooled liquid. The most common type of condensation occurs when a cooled surface, at a temperature less than the local saturation temperature of the vapor, is placed in contact with the vapor. Vapor molecules that strike this cooled surface may stick to it and condense into liquid. 

Experiments on cavitation prove that the noise level is highly dependent on the type of cavitation. Usually it is expected that bubble cavitation is much less severe than cloud cavitation. To verify this expectation, noise measurements on a bubble stream over a hydrofoil were done at Marin (Wageningen, The Netherlands). These experiments show that there is not much difference irrespective of the fact whether the bubbly flow is clustering or not. 

An analysis of the above pnbUcations indicates a wide range of experimental conditions (laser parameters, target, and type of Uqnid) tested to determine the combination favorable for formation of diamond structures by PLA. It is believed that this process evolves formation of the so-called laser plume or a cloud of reaction products consisting of the evaporated substrate material and, partially, the surrounding liquid. These evaporated substances form bubbles inside the liquid. As the amount of the evaporated material increases, the bubbles expand and, as the pressure and temperature reach a certain critical combination, they collapse. At the collapse of the bubbles, the temperature and pressure may reach in the range of thermodynamical stability of diamond. 

Type of data cloud points and bubble points ... 

Several papers on Euler—Euler simulations (both RANS based and of the above EELES type) report about the need to include a separate turbulent dispersion term (or force) for reproducing a correct spatial distribution of suspended particle clouds or bubble swarms. Various models for this turbulent dispersion have been suggested, all of them modeling this effect in terms of the gradient of the particle or bubble volume fraction. Sometimes, this additional term is in the continuity equations (Bakker and Van den Akker, 1994 Sardeshpande and Ranade, 2012 Tamburini et al, 2014) with the justification that is due to fluctuations in the volume fractions however, as the volume fraction which anyhow is an averaged variable does not vary... 

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