To discuss clogging phenomena quantitatively, the relative rates of deposition and fine formation were defined as the ratios of the total deposition rate and fines formation rate to the circulation rate of solid in the annulus.
The solid phase of annulus ground substance and nucleus were represented as Neo-Hookean hyperelastic material and parameters were chosen based on literature [ 20, 21, 32].
Moreover, a newly developed CFB model accounting for the downflow of both the gas and solids in the annulus was applied to the fast fluidization regime.
Overall, the results presented show that relatively high viscosities, high polymer relaxation times under shear flow and non-zero residual shear stresses are desired rheological characteristics for a drilling fluid to obtain a uniform solids distribution in the annulus, as well as high solids carrying capacity.
Key anatomic landmarks: Native aortic valve annulus plane (solid black arrow), left main coronary emanating from left coronary sinus of Valsalva (solid white arrow), sinotubular junction (dotted white arrow), Edwards SAPIEN valve (double-headed arrow) and mitral valve annular calcifications.
They investigated the TOF offset calibration on a clinical system using a stationary solid source, with an annulus shape and a diameter only a few centimeters smaller than the diameter of the FOV (Fig. 4 c).
The numerical results were carefully processed and several key gas solid hydrodynamic properties, such as the jet height, the bubble size and the amount of solids entrained from the annulus to the jet were validated against literature correlations.
Also, due to the importance of the hole-cleaning during drilling operations, the effects of different controlling parameters on the solid volume fraction distribution during annulus are discussed.
The transition to DSU conditions could be distinguished by means of variations of net solids flow direction at the wall, annulus thickness approaching zero and flattening of the solids holdup versus Gs trend.
The experimental results show that the lateral distribution of time-averaged local solid fraction is a core-annulus or heterogeneous structure in the three regions (draft tube, bottom region, particle diffluence region), but a uniform lateral distribution in the annulus.
A cylindrical annulus with an inner solid circular cylinder (CC) of equivalent heat generation is also studied for the purpose of comparison.
