Executive Summary
*In this report, we have examined some of the fundamental mechanisms expected to be at work during mobilization of the waste within the double-shell tanks at Hanford. The motivation stems from the idea that in order to properly apply correlations derived from scaled tests, one would have to ensure that appropriate scaling laws are utilized. Further, in the process of delineating the controlling mechanisms during mobilization, the currently used computational codes are being validated and strengthened based on these findings.Experiments were performed at 1/50-scale, different from what had been performed in the previous fiscal years (i.e., 1/12-and 1/25-scale). It was anticipated that if the current empirical correlations are to work, they should be scale invariant. The current results showed that linear scaling between the 1/25-scale and 1/50-scale correlations do not work well.Several mechanisms were examined in the scaled tests which might have contributed to the discrepancies between the results at these two scales. No deficiencies in the experimental approach and the data were found. Cognizant of these results, it was concluded that the use of the current empirical correlations for ECR should be done cautiously taking into account the appropriate properties of the material for yielding.To better understand some of the fundamental mechanisms within the "separate-effect" processes during mobilization, theoretical analysis was carried out, supported by careful laboratory measurements of turbulence within Newtonian and non-Newtonian jets. It was concluded that most of the mechanisms related to scaling of turbulent Newtonian jets and pseudoplastic jets are considered to be unimportant. It was found that as long as geometric scaling was properly maintained, the fluid did not develop any yield stress, and the jet Reynolds numbers were maintained above 10,000, then the dynamics within the jets scaled well. However, the jet turbulence studies were performed from a normal jet -sludge interaction point of view. It was concluded that the reason the 1/50-scale and 1/25-scale (and perhaps 1/12-scale) results did not scale was because of off-normal jet -sludge interactions. We do not believe that the material property variance played a significant role in the scaled experiments. Once the effect of off-normal interaction is included, then the results from various scales should collapse onto a unique set of curves.
A combined experimental and computational study was carried out to investigate the laminar flow of a nonlinear viscoplastic fluid through an axisymmetric sudden expansion. The yield-stress, power-law index, and the consistency index of the yield shear-thinning test fluid were 0.733 Pa, 0.68, and 0.33 Pa · s0.68, respectively, resulting in a Hedstrom number of 1.65. The Reynolds number ranged between 1.8 and 58.7. In addition, the flow of a Newtonian fluid through the same expansion was also studied to form a baseline for comparison. Velocity vectors were obtained on the vertical center plane using a digital particle image velocimeter (PIV). From these measurements. two-dimensional distributions of axial and radial velocity as well as the stream function were calculated covering the separated, reattached and redeveloping flow regions. These results were compared to finite difference numerical solutions of the governing continuity and fully-elliptic momentum equations. The calculations were found to be in good agreement with the experimental results. Both computational and experimental results indicate the existence of two distinct flow regimes. For low Reynolds numbers, a region of nonmoving fluid is observed immediately downstream of the step and no separated flow zone exists. For the higher Reynolds numbers, a recirculating flow zone forms downstream of the expansion step, which is followed by a zone of stagnant fluid adjacent to pipe wall characterizing reattachment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.