Flow regimes classification

Depending on the Knudsen number value, different flow regime classifications for gas flow have been proposed as follows ... 

Rheological Classification of Drilling Fluids 829. Flow Regimes 830. Principle of Additive Pressures 834. Friction Pressure Loss Calculations 836. Pressure Loss Through Bit Nozzles 839. 

The regions over which the different types of flow can occur are conveniently shown on a Flow Pattern Map in which a function of the gas flowrate is plotted against a function of the liquid flowrate and boundary lines are drawn to delineate the various regions. It should be home in mind that the distinction between any two flow patterns is not clear-cut and that these divisions are only approximate as each flow regime tends to merge in with its neighbours in any case, the whole classification is based on highly subjective observations. Several workers have produced their own maps 4 8. ... 

The basic classification of CWs is based on the type of flow regime and macrophytic growth. In general terms, two types can be described (Figure 10.3). The selection of the most appropriate option shall be according to various operational factors and to the plants available in the region of... 

The problem of two-phase-flow classification is complicated by the inevitable differences due to individual interpretations of visual observations, and also by differences in terminology. Fig. 1, taken from the work of Govier et al. (G6), shows the variation in terminology used for vertical gas-liquid flow patterns. It includes a classification of flow regimes proposed by Govier et al. based on pressure-drop behavior rather than visual observations, as illustrated in Fig. 2. In the definitions adopted by the writer, which follow, an attempt has been made to select the most... 

Perhaps the simplest classification of flow regimes is on the basis of the superficial Reynolds number of each phase. Such a Reynolds number is expressed on the basis of the tube diameter (or an apparent hydraulic radius for noncircular channels), the gas or liquid superficial mass-velocity, and the gas or liquid viscosity. At least four types of flow are then possible, namely liquid in apparent viscous or turbulent flow combined with gas in apparent viscous or turbulent flow. The critical Reynolds number would seem to be a rather uncertain quantity with this definition. In usage, a value of 2000 has been suggested (L6) and widely adopted for this purpose. Other workers (N4, S5) have found that superficial liquid Reynolds numbers of 8000 are required to give turbulent behavior in horizontal or vertical bubble, plug, slug or froth flow. Therefore, although this classification based on superficial Reynolds number is widely used... 

The transport behavior of fluidized bed systems can be described in light of the properties of the fluidized particles and the flow regimes. In the following, particle and regime classifications along with general components in a fluidized bed are given. 

Many types of multiphase flow exist (i.e., gas-liquid, gas-solid, liquid-liquid, gas-liquid-solid) where within one type of flow several possible flow regimes exist. In Fig. 10 (Ishii, 1975) a classification is given for two-phase flow. 

Fig. 10. How regime classification for two-phase flow (Adapted from Ishii (1975)).

The general flow regime diagram shown i Fig 10.2 illustrates the progression of changes in behavior of a bed of solids as the gas velocity is progressively increased. The letters A, B, C and D refer to the Geldart classification of solids. 

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