Fluids, movement

Everything does not happen continuously at any one moment in the universe. Neither does everything happen everywhere in it. 

The Reynolds number is the ratio of inertial forces (related to the mass of the fluid and its momentum) to the viscous forces (related to fluid thickness and the resistance it causes)  

FIGURE 2.9.1 Laminar flow occurs in layers, diagrammed here schematically as flve layers. The center layer is moving the fastest, but the outside layer is not moving at all. 

FIGURE 2.9.2 Turbulent flow is characterized by eddying and mixing. Velocities of the finid in the pipe are in all directions, but the net flow is from a region of high pressnre to a region of lower pressnre downstream. 

The Reynolds number is a predictor of the transition from laminar to turbulent flow. Flow tends to be laminar at low Reynolds numbers and tends to be turbulent at high Reynolds numbers. 

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This process removes the coarser fractions in the hydrocyclones. Hydrocyclones basically operate within the sand region, and if there is material that is finer than sand (material that passes a 200 mesh screen), then approximately 100 percent of that material will pass out the top. The finer fractions and the wastewater that overflow from the hydrocyclone are not treated any further. The contaminants that reside on the finer fhactions adhere fairly well to such particles, therefore, it does not make any processing sense to try and remove them. The coarser fractions then subsequently move down into the next cells. The fluid movement from right to left and the solid... 

Convection is the heat transfer in the fluid from or to a surface (Fig. 11.28) or within the fluid itself. Convective heat transport from a solid is combined with a conductive heat transfer in the solid itself. We distinguish between free and forced convection. If the fluid flow is generated internally by density differences (buoyancy forces), the heat transfer is termed free convection. Typical examples are the cold down-draft along a cold wall or the thermal plume upward along a warm vertical surface. Forced convection takes place when fluid movement is produced by applied pressure differences due to external means such as a pump. A typical example is the flow in a duct or a pipe. 

Tracers have been used to label fluids in order to track fluid movement and monitor chemical changes of the injected fluid. Radioactive materials are one class of commonly used tracers. These tracers have several drawbacks. One drawback is that they require special handling because of the danger posed to personnel and the environment. Another drawback is the alteration by the radioactive materials of the natural isotope ratio indigenous to the reservoir— thereby interfering with scientific analysis of the reservoir fluid characteristics. In addition, the half life of radioactive tracers tends to be either too long or too short for practical use. 

Understanding the effects of colloid administration on circulating blood volume necessitates a review of those physiologic forces that determine fluid movement between capillaries and the interstitial space throughout the circulation (Fig. 10—5).4 Relative hydrostatic pressure between the capillary lumen and the interstitial space is one of the major determinants of net fluid flow into or out of the circulation. The other major determinant is the relative colloid osmotic pressure between the two spaces. Administration of exogenous colloids results in an increase in the intravascular colloid osmotic pressure. In the case of isosomotic colloids (5% albumin, 6% hetastarch, and dextran products), initial expansion of the intravascular space is essentially that of the volume of colloid administered. In the case of hyperoncotic solutions such as 25% albumin, fluid is pulled from the interstitial space into the vasculature... 

Fluid movement conditions are such that the injected fluids will not migrate within 10,000 years vertically upward out of the injection zone or laterally within the injection zone to a point of discharge or interface with an Underground Source of Drinking Water (USDW). 

Active hydrologic conditions exist, although neither the mechanism nor the rate of fluid movement is indicated. 

Other important issues influencing the economics of oil recovery include methods of determining fluid movement and behavior within the reservoir (191) the effect of oil composition on oil... 

Castro, G.A., Hessel, J.J. and Whalen, G. (1979) Altered intestinal fluid movement in response to Trichinella spiralis in immunized rats. Parasite Immunology 1, 259-266. 

For G/S particle systems, enhancement in convective heat transfer is achieved at the expense of increased pressure drop in moving the gas at higher velocities. A measure of the relative benefit of enhanced heat transfer to added expenditure for fluid movement can be approximated by an effectiveness factor, E, defined as the ratio of the heat transfer coefficient to some kind of a pressure drop factor. For G/S systems in which particles are buoyed by the flowing gas stream, this pressure drop factor is expressed by the Archimedes number Ar, and E can be written... 

Martin, J. P and Koener, R. M., 1984b, The Influence of Vadose Zone Conditions on Ground-water Pollution, Part II, Fluid Movement Journal of Hazardous Materials., No. 9, pp. 181-207. 

As well as his experiments on the heart, Starling proposed a physiological explanation for fluid movement across the capillaries. It depends on the understanding of four key terms. 

The ratios of these four pressures alter at different areas of the capillary network so that net fluid movement into or out of the capillary can also change as shown below. 

Radioactive-tracer log Tracer fluid movements are measured to produce a radioactive-tracer log. This shows the flow of fluid in the casing, tubing and the annulus, and helps to estimate flow rates, leaks, and other points of exit or entry for fluid into the borehole... 

It has been demonstrated that radial dispersion contributes more significantly to the dilution of the sample in the flow than does axial dispersion. This type of fluid movement, termed secondary flow by Tijssen [43], results in a washout effect accounting for the low mutual contamination of samples successively injected into a carrier stream. TTiis advantageous feature is a result of the use of low flow rates and small tubing bores, and results in decreased peak-width and hence to increased sampling rate. 

The concentrations and distribution of electrolytes are not fixed, because cell membranes are permeant to ions and to water. Movement of ions and water in and out of cells is determined by the balance of thermodynamic forces, which are normally close to equilibrium. Selective changes of ion concentrations cause movement of water in or out of cells to compensate for these alterations. The kidneys are a major site where changes in salt or water are sensed. The loss of fluids due to illness or disease may alter intracellular and extracellular electrolyte concentrations, with attendant changes in fluid movement in or out of cells. Changes of extracellular or intracellular ion concentrations, particularly for potassium, sodium, and calcium, can have profound effects on neuronal excitability and contractility of the heart and other muscles. 

Osmotic laxatives (e.g., lactulose, sorbitol) are poorly absorbed or nonabsorbable compounds that draw additional fluid into the GI tract. Lumen osmolality increases, and fluid movement occurs secondary to osmotic pressure. Lactulose is a synthetic disaccharide that is poorly absorbed from the GI tract, since no mammalian enzyme is capable of hydrolyzing it to its monosaccharide components. It therefore reaches the colon unchanged and is metabolized by colonic bacteria to lactic acid and to small quantities of formic and acetic acids. Since lactulose does contain galactose, it is contraindicated in patients who require a galactose-free diet. Metabolism of lactulose by intestinal bacteria may result in increased formation of intraluminal gas and abdominal distention. Lactulose is also used in the treatment of hepatic encephalopathy. 

The principal determinants of lOP are the rate of aqueous fluid production by the ciliary epithelium and the rate of fluid drainage (outflow) in the canal of Schlemm. Aqueous fluid production involves passive, near-isosmolar fluid secretion driven by active salt transport across the ciliary epithelium. Ion and solute transporters have been identified on pigmented and non-pigmented layers of the ciliary epithelium that probably facilitate active solute secretion. Aqueous fluid drainage is believed to involve pressure-driven bulk fluid flow in the canal of Schlemm, as well as fluid movement through the sclera by seepage across the ciliary muscle and supraciliary space. 

Our bodies are always surrounded by a thin layer or film of stagnant air. This film is like a layer of insulation. It retards heat transfer between our skin and any surrounding fluid. Movement of the fluid causes turbulence. The turbulence disturbs the film and reduces the film s resistance to heat transfer. 

The interstitial fluid content of the skin is higher than in the subcutaneous fat layer and normal fluid movement is intrinsically finked to lymphatic drainage as governed by mechanical stresses of the tissue. A model of temporal profiles of pressure, stress, and convective ISF velocity has been developed based on hydraulic conductivity, overall fluid drainage (lymphatic function and capillary absorption), and elasticity of the tissue.34 Measurements on excised tissue and in vivo measurement on the one-dimensional rat tail have defined bulk average values for key parameters of the model and the hydration dependence of the hydraulic flow conductivity. Numerous in vivo characterization studies with nanoparticles and vaccines are currently underway, so a more detailed understanding of the interstitial/lymphatic system will likely be forthcoming. 

Permeation of mAbs across the cells or tissues is accomplished by transcellular or paracellular transport, involving the processes of diffusion, convection, and cellular uptake. Due to their physico-chemical properties, the extent of passive diffusion of classical mAbs across cell membranes in transcellular transport is minimal. Convection as the transport of molecules within a fluid movement is the major means of paracellular passage. The driving forces of the moving fluid containing mAbs from (1) the blood to the interstitial space of tissue or (2) the interstitial space to the blood via the lymphatic system, are gradients in hydrostatic pressure and/or osmotic pressure. In addition, the size and nature of the paracellular pores determine the rate and extent of paracellular transport. The pores of the lymphatic system are larger than those in the vascular endothelium. Convection is also affected by tortuosity, which is a measure of hindrance posed to the diffusion process, and defined as the additional distance a molecule must travel in a particular human fluid (i. e., in vivo) compared to an aqueous solution (i. e., in vitro). 

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