Hydraulic gradient example

Low groundwater velocities are most common in highly impermeable, low K rocks, and deep systems with near-zero hydraulic gradients. Example rocks are unfractured metamorphic and ig-... 

Hydraulic conductivity is defined as volume units per square unit of medium face per unit of time under a unit hydraulic gradient (often expressed as units3/units2/time). However, many variations of this definition are used for convenience. For example, in the United States hydraulic conductivity is referred to in terms of gallons per day per square foot or, by the U.S. Geological Survey, as square feet per day. 

An example of induced infiltration brought about by overpumping. The original hydraulic gradient over much of the area has been reversed so that pollutants can travel in the opposite direction, namely, towards the well. Additionally, the aquifer has become influent (i.e. water drains from the river into the aquifer) instead of effluent as it was originally. 

In a typical mobilization experiment, the hydranlic gradient increases until the oil bank reaches the outflow end piece of the colnmn, i.e. until the oil bank breakthrough time. Many examples of this behavior can be found in the EOR literature [42], In typical solubilization experiments, the hydraulic gradient increases until surfactant breakthrongh. This is followed by a slow decline to lower values. This behavior is shown in Figure 8 where the hydraulic gradient during the surfactant flood and... 

The distillation operation is embodied in a vertical column to take advantage of the difference in density between the liquid and vapor phases. Thus, in stagewise distillation, the more-dense liquid phase L moves down vertically via downcomers at the side of the plate and next to the column wall. The liquid phase is thereby introduced at or on each plate and flows across the plate also by gravity for example, by virtue of the hydraulic gradient that builds up in the downcomer. Meanwhile, the less-dense vapor phase V moves upward, passing up and through the liquid on the plate via holes or bubble caps (or nozzles) and overall moves countercurrently to the liquid phase, as represented schematically in Figure 4.1. 

This sentence covers many similarities in different scientific disciplines. For instance, if the two variables are force and acceleration then the Newton s law can be understood from the sentence. In case of groundwater velocity and hydraulic gradient the law is Darcy s suggestion. Another example to analogy can be found between heat transfer and groundwater movement in aquifers [1]. 

This versatile system can be used in different modes. For example, a high speed separations are possible upon unidirectional application of both electroosmotic and hydraulic flow (Fig. 2.12). However, the primary use of this device is gradient elution CEC illustrated on the examples in Fig. 2.13. 

It is not difficult to observe that in all of these expressions we have a multiplication between the property gradient and a constant that characterizes the medium in which the transport occurs. As a consequence, with the introduction of a transformation coefficient we can simulate, for example, the momentum flow, the heat flow or species flow by measuring only the electric current flow. So, when we have the solution of one precise transport property, we can extend it to all the cases that present an analogous physical and mathematical description. Analogous computers [1.27] have been developed on this principle. The analogous computers, able to simulate mechanical, hydraulic and electric micro-laboratory plants, have been experimented with and used successfully to simulate heat [1.28] and mass [1.29] transport. 

We observe here that in a capillary the volume flow rate due to a fixed pressure gradient is proportional to a Tra l8p. dpldx) for a circular capillary). The electroosmotic flow rate is proportional to U multiplied by the cross-sectional area TTa Therefore, the ratio of electroosmotic to hydraulic flow rate will be proportional to a. Thus, for example, if we employ a capillary model for a porous medium, it is evident that as the average pore size decreases electroosmosis will become increasingly effective in driving a flow through the medium, compared with pressure, provided... 

This example clearly shows that the pressure drop is a minimum in the case of circular pipes, followed by the elliptic, rectangular and triangular cross-sections, and the concentric annulus for flow. On the other hand, if one were to maintain the same hydraulic diameter in each case, the corresponding pressure gradients range from 2500 Pa/m to 4000 Pa/m. 

---