Pressure hydrostatic gradient

A knowledge of hold-up is particularly important for vertical flow since the hydrostatic pressure gradient, which is frequently the major component of the total pressure gradient, is directly proportional to liquid hold-up. However, in slug flow, the situation is complicated by the fact that any liquid which is in the form of an annular film surrounding the gas slug does not contribute to the hydrostatic pressure 14. ... 

In the absence of a direct measurement of the in-line concentration of solids ey. it is necessary to make an estimate of its value in order that the hydrostatic pressure gradient in the pipe may be calculated. This can be done for a given mixture velocity u and delivered concentration C, provided that the velocity of the particles relative to the liquid UR is known. 

The following factors affect net diffusion of a substance (1) Its concentration gradient across the membrane. Solutes move from high to low concentration. (2) The electrical potential across the membrane. Solutes move toward the solution that has the opposite charge. The inside of the cell usually has a negative charge. (3) The permeability coefficient of the substance for the membrane. (4) The hydrostatic pressure gradient across the membrane. Increased pressure will increase the rate and force of the collision between the molecules and the membrane. (5) Temperature. Increased temperature will increase particle motion and thus increase the frequency of collisions between external particles and the membrane. In addition, a multitude of channels exist in membranes that route the entry of ions into cells. 

A value of greater than or equal to 1.1 g/dL (greater than or equal to 11 g/L) identifies portal hypertension as the cause of the ascites with 97% accuracy.22,30 In portal hypertension the ascitic fluid is low in albumin this balances the oncotic pressure gradient with the hydrostatic pressure gradient of... 

Diffusion, particularly of macromolecules, plays a minor role in transport across this barrier. Convection due to leaky blood vessels, on the other hand, should enhance delivery yet the movement of drugs and macromolecnles into the interstitinm is often surprisingly limited. This is generally attributed to a diminished hydrostatic pressure gradient between the vascular compartment and the interstitium, which is explained by decreased vascnlar pressure or increased interstitial pressure, or both. 

The profiles of pendant and sessile bubbles and drops are commonly used in determinations of surface and interfacial tensions and of contact angles. Such methods are possible because the interfaces of static fluid particles must be at equilibrium with respect to hydrostatic pressure gradients and increments in normal stress due to surface tension at a curved interface (see Chapter 1). It is simple to show that at any point on the surface... 

In articular cartilage, streaming potentials have been demonstrated by permeation experiments and confined compression experiments [2, 4, 7, 9, 14, 15], In the permeation experiments, a hydrostatic pressure gradient is applied across the sample. The pressure generates a fluid flow and a streaming potential that can be measured [9, 15]. 

The contents of the parenthesis show velocity of the salt relative to water and is called the diffusional flow JD. The dissipation function provides a natural basis for the analysis of systems in which mechanical energy derived from the volume flow and the hydrostatic pressure gradient are utilized to produce a separation of salt from water in the face of an adverse concentration gradient. 

D. If the water in the leaf xylem is in equilibrium with that in the vacuoles of mesophyll cells, what is the average hydrostatic pressure gradient in the xylem for the wet soil (assume that A 7 601 is constant throughout the plant) ... 

Where there is a choice, select relevant (natural) combinations of derived and base units, e.g. you might choose units of Pam to describe a hydrostatic pressure gradient rather than kgm s , even though these units are equivalent and the measurements are numerically the same. 

Further processes responsible for transport across the sediment-water interface are upward flow of (pore) water caused by hydrostatic pressure gradients... 

The formation pressure gradient, expressed usually in pounds per square inch per foot (abbreviated by psi/ft) in the British system of units, is the ratio of the formation pressure, p, in psi to the depth, z, in feet. It is not the true gradient, dp/dz, but is strictly an engineering term. In general, the hydrostatic pressure gradient, Ph (in psi/ft), can be defined by... 

The flow within a canopy is driven by the combination of turbulent stress generated by the overflow and by potential gradients associated with the hydrostatic pressure gradient and bed slope. The relative importance of these drivers depends on the depth of submergence (H/h) and the canopy momentum absorption, aCo The pressure-potential-) driven component is given in equation (6.6). A simple model for the stress-driven, in-canopy flow has been given for terrestrial canopies by Raupach and Thom [522] and applied to aquatic canopies by Abdelrhman [1], see also discussion in Chapter 4. With Uh the velocity at the top of the canopy (at z = h), the profile within the canopy is... 

Figure 2-7. A sketch of the contours of constant hydrostatic pressure within a drop that is initially placed on a flat surface in air. As discussed in the text, the fact that the horizontal component of the pressure gradient is nonzero implies that this fluid configuration is unstable and will undergo a spontaneous spreading motion to decrease the hydrostatic pressure gradients in any horizontal plane. In this case, this process will continue indefinitely but at a decreasing rate as the contours of hydrostatic pressure become increasingly horizontal and flat If the edge of the drop encounters container walls these will stop further spread and the drop will continue to move only until it has filled the container to a constant depth.

However, if the heated surface makes an angle a( s) / 0 for some or all positions on the surface, then the component of the body force normal to the surface can at least locally be balanced by a hydrostatic pressure gradient normal to the wall, but no such balance is... 

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