Computationally determined just suspended speed using multiphase mean age theory

Abstract

Mean age theory was applied towards predicting just suspended speed in mixing tanks by evaluating multiphase mean age near the bottom surface through strategic zone selection. Multiphase mean age equations were solved only in a thin section along the bottom of the vessel (~1% of the vessel height), allowing the mean age in proximity to the bottom to be computed. A rigorously defined method for open systems and a modified method for closed systems using modified boundaries provided equivalent results. The technique was accurate within 1-3% of experimental values across a range of solid densities, solid fractions, and particle sizes while using multiple impeller types and vessel geometries.

Blood residence time to assess significance of coronary artery stenosis

“…Rather than measuring or computing pressure loss to quantify physiological significance, we have presented a new approach which directly quantifies altered flow trajectories through residence time, a well-established mixing metric that quantifies variations in time spent in a given volume due to variations in paths through the same volume. While mean age theory has primarily been demonstrated in industrial systems 22,25,26,36 , it can also be useful for characterizing flow within vessels and human organs or their model counterparts. In this study, we employed mean age theory to characterize blood flow characteristics in coronary segments.…”

“…Once the flow field was established, mean residence time was computed according to previously described CFD applications using "mean age theory" [25][26][27] . The general theory is briefly summarized here.…”

“…Further, conventional residence time theory is a measure of flow distribution at the exit of a continuous system whereas mean age theory provides spatial resolution throughout the interior of the flow domain. Since then, mean age has been demonstrated in a variety of applications for both single phase 24,25 and multiphase flow 26,27 . Multiphase modeling would be beneficial if, for example, one wanted to determine the age of blood components such as cells, platelets, and plasma, etc.…”

Non-invasive detection and assessment of coronary stenosis from blood mean residence times.

“…Conventional residence time theory is a measure of flow distribution at the exit of a continuous system whereas mean age theory provides spatial resolution throughout the interior of the flow domain. Mean age has been demonstrated in a variety of applications for both single phase [62,63] and multiphase flow [66,67]. Multiphase would be beneficial if, for example, one sought to determine the age of blood components such as cells, platelets, and plasma, etc.…”

“…While the main objective was to determine the BloodRT threshold for diagnostic accuracy, there was also a strong correlation between pressure-wire FFR and BloodRT values (r=0.75, P< 0.001). While mean age theory has primarily been demonstrated in industrial systems [60,63,67,93], it can also be useful for characterizing flow within vessels and human organs or their model counterparts. In this study, we employed mean age theory to characterize The threshold between a hemodynamically significant or non-significant stenosis was also determined for our new BloodRT metric.…”