Fluid flow stagnation point

Figure 4.1.2 is a photograph of a coimterflow burner assembly. The experimental particle paths in this cold, nonreacting, counterflow stagnation flow can be visualized by the illumination of a laser sheet. The flow is seeded by submicron droplets of a silicone fluid (poly-dimethylsiloxane) with a viscosity of 50 centistokes and density of 970 kg/m, produced by a nebulizer. The well-defined stagnation-point flow is quite evident. A direct photograph of the coimterflow, premixed, twin flames established in this burner system is shown in Figure 4.1.3. It can be observed that despite the edge effects.

The pitot tube is a device for measuring v(r), the local velocity at a given position in the conduit, as illustrated in Fig. 10-1. The measured velocity is then used in Eq. (10-2) to determine the flow rate. It consists of a differential pressure measuring device (e.g., a manometer, transducer, or DP cell) that measures the pressure difference between two tubes. One tube is attached to a hollow probe that can be positioned at any radial location in the conduit, and the other is attached to the wall of the conduit in the same axial plane as the end of the probe. The local velocity of the streamline that impinges on the end of the probe is v(r). The fluid element that impacts the open end of the probe must come to rest at that point, because there is no flow through the probe or the DP cell this is known as the stagnation point. The Bernoulli equation can be applied to the fluid streamline that impacts the probe tip ... 

At all values of the particle Reynolds number Rep, the fluid is brought to rest relative to the particle at A, which is therefore a stagnation point where the pressure is higher than in the flowing fluid (see equation 1.19 in... 

In the opposed jets design fluid is sucked or pumped into a beaker. The profile which develops is dominantly extensional. In the profiled slot design a rectangular channel is designed such that in the total slip condition an extensional flow develops with a constant rate. The pressure is measured at the stagnation point. Other designs include the open syphon, where fluid is sucked from a beaker through a nozzle which is... 

T.W. Chapman and G.L. Bauer. Stagnation-Point Viscous Flow of an Incompressible Fluid between Porous Plates with Uniform Blowing. Appl. Sci. Res., 31 223-239, 1975. 

O. G. Harlen, E. J. Hinch, and J. M. Rallison, Birefringent pipes The steady flow of a dilute polymer solutions near a stagnation point, J. Non-Newt. Fluid Mech., 44, 229 (1992). 

As discussed in the previous section, the convective droplet vaporization case has yet to be analyzed completely. The major difficulty lies with describing the fluid mechanical aspect of the phenomena, particularly for large Reynolds number flow when separation and reverse flow occur towards the rear stagnation point in both the gas and liquid phases. The difficulty is further compounded when the components in the droplet are not completely miscible, as is the case for emulsified fuels. The drop-... 

Besides ellipsometry, reflectometry has proven its value. By this technique adsorbed masses can conveniently be obtained and. if the measurements are carried out with polarized light, also the orientation of the adsorbed molecules. Experiments are usually done at near-normal Incidence, when // Another variant, pertaining to adsorption from solution and sketched in fig. 2.15, can be made fast enough for the kinetics of adsorption to be followed. In the mode shown, fluid is admitted to the surface from bottom to top ("impinging jet") equations are available for the rate of supply in the stagnation point (the "core" of the fluid flow, which hits the surface perpendicularly). The quotient of the reflected Intensities = S is obtained by electronic division, it is... 

Cross-flow over a cylinder exhibits complex flow patterns, as shown in Fig. 7-16, The fluid approaching the cylinder branches out and encircles the cylinder, forming a boundary layer that wraps around the cylinder. The fluid particles on Ihe inidplane strike Ihe cylinder at Ihe stagnation point, bringing the fluid to a complete stop and ihus raising the pressure at that point. The pressure decreases in the flow direction while the fluid velocity increases. 

Let us consider a solid spherical particle of radius o in a translational Stokes flow with velocity U and dynamic viscosity /i (Figure 2.1). We assume that the fluid has a dynamic viscosity /z. We use the spherical coordinate system. R, 9, ip with origin at the center of the particle and with angle 0 measured from the direction of the incoming flow (that is, from the rear stagnation point on the particle surface). In view of the axial symmetry, only two components of the fluid velocity, namely, Vr and Vg, are nonzero, and all the unknowns are independent of the third coordinate [Pg.58]

Figure 4.2. (a) The flow pattern near the surface of a particle in a neighborhood of stagnation points or lines onflow (with coordinate %) and run-off (with coordinates rik+i), arrows show the direction of the fluid velocity vector, (b) Distribution of the tangential component of the fluid velocity near stagnation points or lines on the surface of the body... 

Freely rotating cylinder. Now let us consider convective mass transfer to the surface of a circular cylinder freely suspended in an arbitrary linear shear Stokes flow (Re -> 0). In view of the no-slip condition, the cylinder rotates at a constant angular velocity equal to the angular velocity of the flow at infinity. The fluid velocity distribution is described by formulas (2.7.11). The streamline pattern qualitatively differs from that for the case of a fixed cylinder. For 0 0, there are no stagnation points on the surface of the cylinder and there exist two qualitatively different types of flow. For 0 < Ifigl < 1, there are both closed and open streamlines in the flow, the region filled with closed streamlines is adjacent to the surface of the cylinder, and streamlines far from the cylinder are open (Figure 2.11). For Ifl l > 1, all streamlines are open. 

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