Converging flow experiments

A series of tracer tests were performed at the Aspo hard rock laboratory in Sweden. The tests were performed in a well-characterised rock volume. In this paper two sets of converging flow experiments are discussed. One set is over a distance of about five meters, the TRUE-1 experiments. The other is over 14-33 m in the TRUE-block experiments. The site is in a drift at about 400 m below the ground (Byegard et al. 1998 and Andersson et al. 2001). 

Figure 51. Conductivity convergence (CUSUM graph) curves for the reference (no groundwater) and ground water flow experiment...

In order to observe a reaction in a stopped-flow experiment, data must be collected over the proper time window. Because the method spans some five orders of magnitude in time, it is easy to miss a reaction because it was either too fast or too slow to be observed on the time scale selected. The rule is to observe the reaction over six half-lives. An iterative method should be applied. Initial estimates of the rate are used to select the time over which to examine the reaction the measured rate is then used to adjust the time of data collection, eventually converging on the optimal time according to the rate of the reaction. 

A nearly i al situation of this type is found with the tubeless siphon of Fig. VI. 10b. (This ascending column is easily obtained with polymer solutions because of their ability to thread.) The interest of this geometry, from the present point of view, is to provide us with a simple convergent flow (not perturbed by walls) in the bulk of the fluid behw the siphon. (Chain behavior inside the siphon has been studied in experiments at Naples, but the analysis ignored possible elongations before entry.)... 

We have seen that rheometers capable of accurate measiuements of extensional flow properties are limited to use at low Hencky strain rates, usually well below 10 s . In order to reach higher strain rates, the drawdown of an extruded filament ( melt spinning ) and the converging flow into an orifice die or capillary have been used to determine an apparent extensional viscosity . Since the stress and strain are not imiform in these flows, it is necessary to model the flow in order to interpret data in terms of material functions or constants. And such a simulation must incorporate a rheological model for the melt under study, but if a reliable rheological model were available, the experiment would not be necessary. This is the basic problem with techniques in which the kinematics is neither controlled nor known with precision. It is necessary to make a rather drastically simplified flow analysis to interpret the data in terms of some approximate material function. 

Fig. 3a indicates that the bubble-rise velocity measured based on the displacement of the top surface of the bubble ( C/bt) quickly increases and approaches the terminal bubble rise velocity in 0.02 s. The small fluctuation of Ubt is caused by numerical instability. The bubble-rise velocity measured based on the displacement of the bottom surface of the bubble (Ubb) fluctuates significantly with time initially and converges to Ubt after 0.25 s. The overshooting of Ubb can reach 45-50 cm/s in Fig. 3a. The fluctuation of Ubb reflects the unsteady oscillation of the bubble due to the wake flow and shedding at the base of the bubble. Although the relative deviation between the simulation results of the 40 X 40 x 80 mesh and 100 x 100 x 200 mesh is notable, the deviation is insignificant between the results of the 80 x 80 x 160 mesh and those of the 100 X 100 x 200 mesh. The agreement with experiments at all resolutions is generally reasonable, although the simulated terminal bubble rise velocities ( 20 cm/s) are slightly lower than the experimental results (21 25 cm/s). A lower bubble-rise velocity obtained from the simulation is expected due to the no-slip condition imposed at the gas-liquid interface, and the finite thickness for the gas-liquid interface employed in the computational scheme.

The photoacoustic calorimeter of figure 13.6 can be divided into three subsets of instruments converging on the sample cell. The first set is used to initiate the photophysical process in the cell the second allows the detection and measurement of the photoacoustic signal produced the third is used to measure the solution transmittance. A flow line conducts the solution throughout the system. The calorimeter can operate under inert atmosphere conditions, and the temperature variation during an experiment is less than 0.5 K. 

Experiment also shows that there is no detectable (observable) 3-space EM energy flow that converges into the charge. Hence we are left with a quandary— experiment shows that there is a broken symmetry in the conservation of EM energy 3-flow, directly associated with the source charge. 

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