Stagnation point flow cell

FIG. 3 Schematic representation of a reflectometer with a stagnation-point flow cell. (Adapted from Ref. 41.)... 

Dijt et al. [41] have studied the kinetics of polymer adsorption on a flat silica surface in a stagnation-point flow cell with a fixed-angle reflectometer. The effect of solution concentration, flow rate, and molar mass on the rate of adsorption of... 

Although contact-based methods have proved useful for biological studies, there is a strong need for contact-free, flow-based methods for precise confinement and manipulation of biomolecules and cells. To this end, a number of contact-free fluid flow-based trapping and manipulation methods have been developed. These methods rely on microvortices, microeddies, stagnation point flows, or stagnant regions within a fluid stream to confine particles for further analysis. 

W. G. Bessler. Gas concentration impedance of solid oxide fuel cell anodes. I. Stagnation point flow geometry. J. Electrochem. Soc. (in press). 

As can be seen in Figs. 15a and 15b, the extension of the region where the fluid flow can be approximated by Eq. (104) deereases with the increase in Reynolds number. This can be better seen in Fig. 16, which presents the dependence of C(r) on the radial distance from the cell center. This function describes directly the deviation form the stagnation point flow expressed by Eq. (103). One can note that the C(r) function can be well approximated for r/k < 1 by the simple relationship... 

FIG. 2 Geometry of some flow cells with simple well-defined flow patterns (a) impinging jet with a stagnation-point flow (h) a slab (c) a cylindrical capillary. 

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 ... 

The measured pressure difference AP is the difference between the stagnation pressure in the velocity probe at the point where it connects to the DP cell and the static pressure at the corresponding point in the tube connected to the wall. Since there is no flow in the vertical direction, the difference in pressure between any two vertical elevations is strictly... 

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