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Velocity laminar

Viscous Transport. Low velocity viscous laminar dow ia gas pipes is commonplace. Practical gas dow can be based on pressure drops of <50% for low velocity laminar dow ia pipes whose length-to-diameter ratio may be as high as several thousand. Under laminar dow, bends and fittings add to the frictional loss, as do abmpt transitions. [Pg.372]

In a steady-state situation when gas flows through a porous material at a low velocity (laminar flow), the following empirical formula, Darcy s model, is valid ... [Pg.138]

This expression for terminal velocity is called Newton s law. Stokes law for the terminal velocity (laminar flow) in a particular medium can be expressed in simplified form as... [Pg.154]

With higher discharge velocities, laminar jets are produced that disintegrate to droplets at a certain distance from the capillary. The transition from dripping to liquid jet disintegration occurs at higher Weber numbers ... [Pg.44]

Eckert, E.R.G., Engineering Relations for Heat Transfer and Friction in High-Velocity Laminar and Turbulent Boundary Layer Flow over Surfaces with Constant Pressure and Temperature , Trans. ASME, Vol. 78, pp. 1273-1284, 1956. [Pg.156]

Eckert, E.R.G. Engineering relations for heat transfer and friction in high-velocity laminar and turbulent boundary-layer flow over surfaces with constant pressure and temperature. Trans. Amer. Soc. Mech. Eng., J. Heat Transfer 78 (1956) 1273-1283... [Pg.662]

Flame type F. Long, luminous, lazy. No swirl, nor circulation. Low foef and air jet velocity. Laminar jet, buoyancy-controlled. Delayed, slow, diflusion mixing. Used for coverage in tong chambers, and to add luminous radiation. [Pg.248]

Owing to the small channel diameters in MSR, laminar flow can be considered in which the fluid flows in parallel layers without lateral mixing. This situation occurs when the ratio between inertial forces to viscous forces is relatively low. The ratio is characterized by the Reynolds number, which is deflned as follows for circular tubes Re = u-d -pg)ft, where u is the mean fluid velocity. Laminar flow is stable for Re < 2000. At higher Reynolds number, inertia forces become dominant, producing flow instabilities such as eddies and vortices, and the flow becomes turbulent. [Pg.344]

D. E. Jensen and S. C. Kurzius, Determination of positive ion concentrations in high-velocity laminar flames. Combust Flame 13, 219-222 (1969). [Pg.350]

In order to obtain a nondimensionalized expression, characteristic laminar flame propagation values of velocity (laminar burning velocity S ) and length scale (laminar flame thickness are introduced. Now Eq. (4) writes... [Pg.57]

Sealing, wliich is simply the isolation of the transmitter from a clean (no solids, nonplugging) process liquid. Low-velocity laminar flow is usually adequate for sealing, but as we shall see later, may contribute to dynamic measurement errors. For these applications gas purges are usually used. [Pg.266]

Despite its title, and although it contains discussion of relevant numerical techniques, this article is not a comprehensive survey of the numerical methods currently employed in detailed combustion modeling. For that, the reader is referred to the reviews by McDonald (1979) and Oran and Boris (1981). Rather, the aim here is to provide an introduction that will stimulate interest and guide the enthusiastic and persistent amateur. The discussion will center mainly about low-velocity, laminar, premixed flames, which form a substantial group of reactive flow systems with transport. Present computational capabilities virtually dictate that such systems be studied as quasi-one-dimensional flows. We also consider two-dimensional boundary layer flows, in which the variation of properties in the direction of flow is small compared with the variation in the cross-stream direction. The extension of the numerical methods to multidimensional flows is straightforward in principle, but implementation at acceptable cost is much more difficult. [Pg.21]

The solution flow is nomially maintained under laminar conditions and the velocity profile across the chaimel is therefore parabolic with a maximum velocity occurring at the chaimel centre. Thanks to the well defined hydrodynamic flow regime and to the accurately detemiinable dimensions of the cell, the system lends itself well to theoretical modelling. The convective-diffiision equation for mass transport within the rectangular duct may be described by... [Pg.1937]

When a sample is injected into the carrier stream it has the rectangular flow profile (of width w) shown in Figure 13.17a. As the sample is carried through the mixing and reaction zone, the width of the flow profile increases as the sample disperses into the carrier stream. Dispersion results from two processes convection due to the flow of the carrier stream and diffusion due to a concentration gradient between the sample and the carrier stream. Convection of the sample occurs by laminar flow, in which the linear velocity of the sample at the tube s walls is zero, while the sample at the center of the tube moves with a linear velocity twice that of the carrier stream. The result is the parabolic flow profile shown in Figure 13.7b. Convection is the primary means of dispersion in the first 100 ms following the sample s injection. [Pg.650]

A low Reynolds number indicates laminar flow and a paraboHc velocity profile of the type shown in Figure la. In this case, the velocity of flow in the center of the conduit is much greater than that near the wall. If the operating Reynolds number is increased, a transition point is reached (somewhere over Re = 2000) where the flow becomes turbulent and the velocity profile more evenly distributed over the interior of the conduit as shown in Figure lb. This tendency to a uniform fluid velocity profile continues as the pipe Reynolds number is increased further into the turbulent region. [Pg.55]

Fig. 1. Flow profiles, where N is velocity (a) laminar, and (b) turbulent for fluids having Reynolds numbers of A, 2 x 10, and B, 2 x 10 . Fig. 1. Flow profiles, where N is velocity (a) laminar, and (b) turbulent for fluids having Reynolds numbers of A, 2 x 10, and B, 2 x 10 .
Most flow meters are designed and caHbrated for use on turbulent flow, by far the more common fluid condition. Measurements of laminar flow rates may be seriously in error unless the meter selected is insensitive to velocity profile or is specifically caHbrated for the condition of use. [Pg.55]

Enough space must be available to properly service the flow meter and to install any straight lengths of upstream and downstream pipe recommended by the manufacturer for use with the meter. Close-coupled fittings such as elbows or reducers tend to distort the velocity profile and can cause errors in a manner similar to those introduced by laminar flow. The amount of straight pipe required depends on the flow meter type. For the typical case of an orifice plate, piping requirements are normally Hsted in terms of the P or orifice/pipe bore ratio as shown in Table 1 (1) (see Piping systems). [Pg.55]

As velocity continues to rise, the thicknesses of the laminar sublayer and buffer layers decrease, almost in inverse proportion to the velocity. The shear stress becomes almost proportional to the momentum flux (pk ) and is only a modest function of fluid viscosity. Heat and mass transfer (qv) to the wall, which formerly were limited by diffusion throughout the pipe, now are limited mostly by the thin layers at the wall. Both the heat- and mass-transfer rates are increased by the onset of turbulence and continue to rise almost in proportion to the velocity. [Pg.90]

Entrance flow is also accompanied by the growth of a boundary layer (Fig. 5b). As the boundary layer grows to fill the duct, the initially flat velocity profile is altered to yield the profile characteristic of steady-state flow in the downstream duct. For laminar flow in a tube, the distance required for the velocity at the center line to reach 99% of its asymptotic values is given by... [Pg.91]

In configurations more complex than pipes, eg, flow around bodies or through nozzles, additional shearing stresses and velocity gradients must be accounted for. More general equations for some simple fluids in laminar flow are described in Reference 1. [Pg.96]

In general, V For laminar Newtonian flow the radial velocity profile is paraboHc and /5 = 3/4. For fully developed turbulent flow the radial... [Pg.108]

The shear stress is hnear with radius. This result is quite general, applying to any axisymmetric fuUy developed flow, laminar or turbulent. If the relationship between the shear stress and the velocity gradient is known, equation 50 can be used to obtain the relationship between velocity and pressure drop. Thus, for laminar flow of a Newtonian fluid, one obtains ... [Pg.108]

Averaging the velocity using equation 50 yields the weU-known Hagen-Poiseuille equation (see eq. 32) for laminar flow of Newtonian fluids in tubes. The momentum balance can also be used to describe the pressure changes at a sudden expansion in turbulent flow (Fig. 21b). The control surface 2 is taken to be sufficiently far downstream that the flow is uniform but sufficiently close to surface 3 that wall shear is negligible. The additional important assumption is made that the pressure is uniform on surface 3. The conservation equations are then applied as follows ... [Pg.108]


See other pages where Velocity laminar is mentioned: [Pg.514]    [Pg.1437]    [Pg.579]    [Pg.158]    [Pg.633]    [Pg.34]    [Pg.415]    [Pg.514]    [Pg.1437]    [Pg.579]    [Pg.158]    [Pg.633]    [Pg.34]    [Pg.415]    [Pg.66]    [Pg.55]    [Pg.216]    [Pg.809]    [Pg.2]    [Pg.59]    [Pg.89]    [Pg.89]    [Pg.90]    [Pg.92]    [Pg.92]    [Pg.92]    [Pg.93]    [Pg.96]    [Pg.98]    [Pg.99]   
See also in sourсe #XX -- [ Pg.308 , Pg.341 ]




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