Low-flow-rate regime

In the bubble formation from a horizontal surface, the bubble development and the bubble detachment are coupled. When the buoyancy of a developing bubble overcomes the bubble attachment force due to the interfacial tension, the bubble detaches from the surface and completes the process of the bubble formation. A higher flow rate of air in the low flow rate regime (e.g., 0.2-30 seem) simply increases the frequency of the bubble formation but does not change the volume of bubble [1]. 

The first two data sets were in good accordance, whereas a fit to the intrinsic kinetics without correction was only valid for short residence times and large flow rates. This is the consequence of achieving a low degree of liquid/liquid dispersion at low flow rates, i.e. the reaction becomes mass-transfer limited in this regime. 

Increasing the flow rate of water results in its spreading in stratified fashion as the velocity forces dominate the interfacial one. The oil flow in this case forms either a pearlike drop flow when it is at low flow rate or a stratified oil stream at high flow rate. The inlet junction has an influence on the flow pattern regime as well. To prove this, water flow was introduced from the central inlet and the oil from the two external inlets. Under conditions of high flow rates, similar flow patterns were observed as those shown in Figure 4.16 but in a reverse fashion. Well-defined aqueous droplets were attained at high-water flow rate combined with low-oil flow rate and no pear-... 

This is simply improved methods to form droplets from a needle. The goal is to produce small droplets/microcapsules with low size dispersion (less than 10%) with a good level of production. To avoid broad size dispersion, the liquid flow must be in the laminar regime (avoiding turbulence), thus a relatively low flow rate is required compared to spraying (see below). In most cases, energy is required to reduce the droplet size (from a few millimeters with simple needle). This has led to the following systems. 

The characteristic curve of extrudate flow including adherence to the walls, and hence representative of shghtly to moderately entangled polymer flow in sudden two-dimensional or axisymmetrical contractions [7, 32], is represented in Fig 2. It shows a slope discontinuity above a certain pressm-e level, which depends on the pol3uner-die pair considered. With low flow rates, the flow is stable. Indeed, for these regimes, allowing for entrance effects, the flow curve is in fact representative of the shear rheometry of the polymer imder consideration, at low shear rates [34]. The slope discontinuity of the head loss curve indicates a modification in the structure of flow. It will be seen that this corresponds to the triggering of a hydrodynamic instability upstream of the contraction. 

At relatively low flow rates, the convective component is negligible, and the diffusion component is dominant. As shown in Figure 2.3, at high flow rates, the diffusion component is negligible, and the convective component is dominant. Between these exttemes, both components contribute to the overall dispersion process, and this is the regime commonly encountered in reservoir flow processes. Note that the dimensionless Peclet number is defined in Figure 2.3 as... 

The pressure drop in a straight pipe is determined by factors including fluid velocity and viscosity, pipe surface roughness as well as flow regime—whether or not the flow is turbulent or laminar, a concept introduced by Stokes in 1851. In 1888, Osborne Reynolds conducted experiments that clearly delineated the difference between the different flow regimes. He injected a fine filament of colored water in a pipe together with water. At low flow rates, the filament... 

Vortex Growth The formation and growth of the vortex upstream of the contraction is proportional to the De value, which increases with an increase in flow rate (see Eq. 3). This implies that the elastic forces become more dominant as the flow rate increases. When the elastic effects are large enough to suppress the inertial effects, a viscoelastic fluid undergoes transitions from the Newtonian-like behavior (low flow rate structure) to regimes with vortex formation and... 

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