Flow Tagging

Shelby, J.P., Chiu, D.T., Mapping fast flows over micrometer-length scales using flow-tagging velocimetry and single-molecule detection. Anal. Chem. 2003, 75, 1387-1392. 

Solid/liquid flows are commonly found in industrial processes to avoid flow obstruction, nonintrusive flowmeters are generally preferred. Flowmeters based on ultrasonic techniques are ideal nonintrusive instruments because, in most applications, the ultrasonic transducers are simply clamped on the outside pipe wall. In this section, we describe two ultrasonic flowmeters based on the Doppler and cross-correlation methods. Both require an inherent flow tag thus both are directly applicable to solid/liquid flows because of the presence of solid particles. Both flowmeters measure mainly particle velocity liquid-phase velocity, if different from the particle velocity, is not determined. 

The cross-correlation technique measures the time of flight of an inherent flow tag passing through two sensors separated by a known distance. The technique has been used successfully to monitor single-phase fluid flows in which turbulent eddies modulate the interrogating ultrasonic beams. This type of correlation flowmeter has also been developed for solid/liquid and gas/liquid flows, in which the density fluctuation, caused by clusters of solids and by gas bubbles, is the prime inherent flow tag. 

FIGURE 8-13a LIPA optical configuration for flow tagging velocity measurements (Hill and Klewicki 1996). (Reprinted by permission of Springer-Verlag.)... 

Hill, R.B., and Klewicki, J.C., Data reduction methods for flow tagging velocity measurements, Exps. in Fluids, 2Q, 142-152 (1996). 

Lempert WR, Magee K, Ronney P, Gee KR, Haugland RP (1995) Flow tagging velocimetry in incompressible flow using photoactivated nonintrusive tracking of molecular motion (PHANTOMM). Exp Fluids 18 249-257... 

Flow profiling Flow tagging Laser-induced molecular tagging Laser-induced photochemical anemometiy Photo-activated nonintrusive tracking of molecular motion Photobleached fluorescence... 

If. eq. (4) is not satisfied for step-up and step-down tracer tests, then the proper distribution functions have not been obtained by the tracer test. The cause might be either that the system was not at steady state, or that the tracer did not behave perfectly and underwent a nonlinear process within the system. Another requirement for establishing the F(t) curve correctly from tracer step-up or step-down experiments, which is particularly important for systems with laminar flow, is that tracer must be introduced proportionally to flow (flow tagging) and that its mixing cup concentration must be monitored at,the outflow (18-21). 

Maynes and Webb (2002) presented pressure drop, velocity and rms profile data for water flowing in a tube 0.705 mm in diameter, in the range of Re = 500-5,000. The velocity distribution in the cross-section of the tube was obtained using the molecular tagging velocimetry technique. The profiles for Re = 550,700,1,240, and 1,600 showed excellent agreement with laminar flow theory, as presented in Fig. 3.2. The profiles showed transitional behavior at Re > 2,100. In the range Re = 550-2,100 the Poiseuille number was Po = 64. 

Fig. 1.18 A film of silicone oil of 1 mm thickness is flowing along a vertically oriented planer sheet of PMMA. In a tagging experiment, a horizontal slice of 2 mm thickness is marked and its deformation is recorded as a function of the separation time A between the...

Fig. 2.6.9 Visualization of gas flow through a cylindrical surface represents the rock, (b) Only porous sandstone rock. A 3D phase encoding a slice through the center of the rock is sequence with a hard encoding pulse was used, displayed, showing the origin of the gas that is (a) 3D representation of an isochronal surface flowing through the detector at different times at different times after the encoding step. The after the tagging [figure taken from 43].

Fig. 3.3.10 Tagging of water flow in a bed packed with 7 mm diameter beads. The width of the grid line is 2 mm.

M. V. Icenogle, A. Caprihan, E. Fu-kushima 1992, (Mapping flow streamlines by multistripe tagging), J. Magn. Reson. 100, 376. 

Fig. 4.4.2 The discrete data points represent Taylor-Couette-Poiseuille flow regimes observed with MRI for r = 0.5 [41]. The curved boundaries were obtained for r = 0.77 with optical techniques [38]. The two inserts show MRI spin-tagging FLASH images of the SHV and PTV hydrodynamic modes.

Fig. 4.4.5 Gradual blurring (staring on locations marked by arrow) of MRI spin-tagging spin-echo images of Taylor—Couette—Poiseuille flow as the axial flow is increased (from left to right). The images correspond to longitudinal sections of the flow and the axial flow is upwards. The dashed line marks the location of one of the stationary helical vortices which characterize the SHV mode. This flow regime corresponds to the transition from the SHV (steady) to partial PTV (unsteady) regimes as Re increases, as shown in Figure 4.4.2.

---