Annular Geometry Research Articles

Septal annular dilation in chronic ovine functional tricuspid regurgitation

IntroductionAnnular reduction with prosthetic rings represents the current surgical treatment of functional tricuspid regurgitation (FTR). However, alterations of annular geometry and dynamics associated with FTR are not well characterized. MethodsFTR was induced in 29 adult sheep with either 8 weeks of pulmonary artery banding (PAB, n = 15) or 3 weeks of tachycardia-induced cardiomyopathy (TIC, n = 14). Eight healthy sheep served as controls (CTL). At the terminal procedure, all animals underwent sternotomy, epicardial echocardiography, and implantation of sonomicrometry crystals on the tricuspid annulus (TA) and right ventricular free wall while on cardiopulmonary bypass. Simultaneous hemodynamic, sonomicrometry, and echocardiographic data were acquired after weaning from cardiopulmonary bypass and stabilization. Annular geometry and dynamics were calculated from 3-dimensional crystal coordinates. ResultsMean FTR grade (0-4) was 3.2 ± 1.2 and 3.2 ± 0.5 for PAB and TIC, respectively, with both models of FTR associated with similar degree of right ventricular dysfunction (right ventricular fractional area contraction 38 ± 7% and 37 ± 9% for PAB and TIC, respectively). Left ventricular ejection fraction was significantly reduced in TIC versus baseline (33 ± 9%, vs 58 ± 4%, P = .0001). TA area was 651 ± 109 mm2, 881 ± 242 mm2, and 995 ± 232 mm2 for CTL, FTR, and TIC, respectively (P = .006) with TA area contraction of 16.6 ± 4.2%, 11.5 ± 8.0%, and 6.0 ± 4.0%, respectively (P = .003). Septal annulus increased from 33.8 ± 3.1 mm to 39.7 ± 6.4 mm and 43.1 ± 3.2 mm for CTL, PAB, and TIC, respectively (P < .0001). ConclusionsOvine FTR was associated with annular dilation and reduced annular area contraction. Significant dilation of septal annulus was observed in both models of FTR. As tricuspid rings do not completely stabilize the septal annulus, continued remodeling may contribute to recurrent FTR after repair.

Transmission properties of thue-morse, fibonacci and fixed length photonic crystals: comparing the planar and annular geometries

Transmission properties of thue-morse, fibonacci and fixed length photonic crystals: comparing the planar and annular geometries

Transient pressure-driven electrokinetic slip flow and heat transfer through a microannulus

To guarantee the transporting efficiency of microdevices associated with fluid transportation, mixing, or separation and to promote the heat transfer performance of heat exchangers in microelectronics, the hydrodynamic behaviors at the unsteady state as well as the thermal characteristics at the steady state in a pressure-driven electrokinetic slip flow through a microannulus are studied. To present a more reliable prediction, the slip phenomenon at walls is incorporated. The Cauchy momentum equation applicable to all time scales is analytically solved by the integral transform method; thereby, the physical picture of how the flow is initiated and accelerated to the steady state is provided. The energy equation and entropy generation for the steady flow are numerically solved. Consequently, the temperature profile, heat transfer rate, and entropy generation rate are computed at different electrokinetic widths, slip lengths, Joule heating parameters, and Brinkman numbers; thereby, the coupling effect of the slip hydrodynamics, annular geometry, viscous dissipation, and Joule heating on thermal behaviors is explored. The unsteady flow takes a longer time to achieve the steady state for a smaller radius ratio. The slip length not only accelerates the flow but also alters the velocity and temperature profiles. Compared to the outer one, the inner slip length plays a more significant role on the entropy generation rate. The relevant discussion can serve as a theoretical guide for the operation and thermal management of flow actuation systems related to annular geometries.

Influence of heterogeneous thermal conductivity on the long-term evolution of the lower-mantle thermochemical structure: implications for primordial reservoirs

Abstract. The long-term evolution of the mantle is simulated using 2D spherical annulus geometry to examine the effect of heterogeneous thermal conductivity on the stability of reservoirs of primordial material. Often in numerical models, purely depth-dependent profiles emulate mantle conductivity (taking on values between 3 and 9 Wm-1K-1). This approach synthesizes the mean conductivities of mantle materials at their respective conditions in situ. However, because conductivity also depends on temperature and composition, the effects of these dependencies on mantle conductivity are masked. This issue is significant because dynamically evolving temperature and composition introduce lateral variations in conductivity, especially in the deep mantle. Minimum and maximum variations in conductivity are due to the temperatures of plumes and slabs, respectively, and depth dependence directly controls the amplitude of conductivity (and its variations) across the mantle depth. Our simulations allow assessing the consequences of these variations on mantle dynamics, in combination with the reduction in thermochemical pile conductivity due to its expected high temperatures and enrichment in iron, which has so far not been well examined. The mean conductivity ratio from bottom to top indicates the relative competition between the decreasing effect with increasing temperature and the increasing effect with increasing depth. We find that, when depth dependence is stronger than temperature dependence, a mean conductivity ratio &gt;2 will result in long-lived primordial reservoirs. Specifically, for the mean conductivity profile to be comparable to the conductivity often assumed in numerical models, the depth-dependent ratio must be at least 9. When conductivity is underestimated, the imparted thermal buoyancy (from heat-producing element enrichment) destabilizes the reservoirs and influences core–mantle boundary coverage configuration and the onset of dense material entrainment. The composition dependence of conductivity only plays a minor role that behaves similarly to a small conductivity reduction due to temperature. Nevertheless, this effect may be amplified when depth dependence is increased. For the cases we examine, when the lowermost mantle's mean conductivity is greater than twice the surface conductivity, reservoirs can remain stable for very long periods of time, comparable to the age of the Earth.

Unsteady Pressure-Driven Electrokinetic Slip Flow and Heat Transfer of Power-Law Fluid through a Microannulus

To guarantee the transporting efficiency of microdevices associated with fluid transportation, mixing, or separation and to promote the heat transfer performance of heat exchangers in microelectronics, the hydrodynamic behaviors at unsteady and steady states, as well as the thermal characteristics at the steady state in a pressure-driven electrokinetic slip flow of power-law fluid in a microannulus are studied. To present a more reliable prediction, the slip phenomenon at walls and nonlinear rheology of liquid are incorporated. The modified Cauchy momentum equation applicable to all time scales and energy equations, are analytically solved in the limiting case of a Newtonian fluid and numerically solved for power-law fluids. The transient velocity profile, time evolution of flow rate, temperature profile, and heat transfer rate are computed at different flow behavior indices, electrokinetic width, slip lengths, and Brinkman numbers, thereby, the coupling effect of nonlinear rheology, slip hydrodynamics, and annular geometry on flow and thermal behaviors is explored. The unsteady flow takes a longer time to achieve the steady state for shear thinning fluids or greater slip lengths. The flow behavior index and slip length play a significant role in the flow rate and heat transfer performance. The relevant discussion can serve as a theoretical guide for the operation and thermal management of annular geometry-related flow actuation systems.

Dynamic assessment of the tricuspid annulus in a healthy Asian population: A four-dimensional echocardiography study.

Tricuspid annulus (TA) geometry and function reference values are limited, especially for Asian populations. We aimed to explore TA using four-dimensional echocardiography (4DE) in a healthy Asian population. A total of 355 healthy Asian volunteers (median age 34 years; 52% males) were prospectively enrolled. TA geometry and function were analyzed using 4DE throughout the cardiac cycle. The TA area, perimeter, and dimensions were smallest at end systole (ES) and largest at late diastole (LD). Normal TA parameters at end diastole (ED) in different sex and age groups were obtained. TA areas, perimeters, and dimensions in males were significantly larger than those in females at ED; BSA-indexed perimeters and BSA-indexed dimensions in males were significantly smaller than those in females at ED. TA parameters correlated well with tricuspid valve (TV) tenting, right ventricle (RV), and right atrium (RA) parameters. Reference values of TA parameters were obtained by 4DE in an Asian population. Quantitative data on TA geometry and function are essential for TA pathology and therapeutics.

A mechanistic model for minimizing pressure loss in the wellbore during drilling by considering the effects of cuttings

Because of the existence of cuttings in the flow, the pressure loss in the wellbore can increase significantly. Minimization of the flow pressure loss greatly benefits the drilling process. This work investigates the most important factors to the pressure loss in the wellbore during the hole cleaning process. It is found that, for the solid–liquid, two-phase flow, the fluid flow rate is not always proportional to annular pressure loss as the single-phase flow. The mechanisms behind this effect are studied, and a mechanistic model based on the solid–liquid, two-phase flow is proposed to simulate the hole cleaning process and predict the critical fluid flow rate, which gives the minimum pressure loss in the wellbore. The effect of the inclination angle, fluid rheological parameters, annulus geometry, and the rate of penetration on the critical value are investigated by using the proposed model. Results show that the critical flow rate value increases as the inclination angle increases under 60° and decreases once the inclination angle goes beyond 60°. The critical flow rate increases as the fluid viscosity and the wellbore geometry increase. This proposed model can be used to minimize the pressure loss in the wellbore in the given operational conditions and optimize the drilling parameters.

An experimental study on bubble growth and departure in pool boiling on wire with annular geometry and providing empirical relations

An experimental study on bubble growth and departure in pool boiling on wire with annular geometry and providing empirical relations

From disks to channels: dynamics of active nematics confined to an annulus.

Confinement can be used to systematically tame turbulent dynamics occurring in active fluids. Although periodic channels are the simplest geometries to study confinement numerically, the corresponding experimental realizations require closed racetracks. Here, we computationally study 2D active nematics confined to such a geometry-an annulus. By systematically varying the annulus inner radius and channel width, we bridge the behaviors observed in the previously studied asymptotic limits of the annulus geometry: a disk and an infinite channel. We identify new steady-state behaviors, which reveal the influence of boundary curvature and its interplay with confinement. We also show that, below a threshold inner radius, the dynamics are insensitive to the presence of the inner hole. We explain this insensitivity through a simple scaling analysis. Our work sheds further light on design principles for using confinement to control the dynamics of active nematics.

Imprinting Persistent Currents in Tunable Fermionic Rings

Persistent currents in annular geometries have played an important role in disclosing the quantum phase coherence of superconductors and mesoscopic electronic systems. Ultracold atomic gases in multiply connected traps also exhibit long-lived supercurrents, and have attracted much interest both for fundamental studies of superfluid dynamics and as prototypes for atomtronic circuits. Here, we report on the realization of supercurrents in homogeneous, tunable fermionic rings. We gain exquisite, rapid control over quantized persistent currents in all regimes of the BCS-BEC crossover through a universal phase-imprinting technique, attaining on-demand circulations $w$ as high as 9. High-fidelity read-out of the superfluid circulation state is achieved by exploiting an interferometric protocol, which also yields local information about the superfluid phase around the ring. In the absence of externally introduced perturbations, we find the induced metastable supercurrents to be as long-lived as the atomic sample. Conversely, we trigger and inspect the supercurrent decay by inserting a single small obstacle within the ring. For circulations higher than a critical value, the quantized current is observed to dissipate via the emission of vortices, i.e., quantized phase slips, which we directly image, in good agreement with numerical simulations. The critical circulation at which the superflow becomes unstable is found to depend starkly on the interaction strength, taking its maximum value for the unitary Fermi gas. Our results demonstrate fast and accurate control of quantized collective excitations in a macroscopic quantum system, and establish strongly interacting fermionic superfluids as excellent candidates for atomtronic applications.

889 ATRIOVENTRICULAR BLOCK, AN UNUSUAL CLINICAL PRESENTATION OF CALCIFIED BICUSPID AORTIC VALVE

Abstract Background Bicuspid aortic valve (BAV) is the most frequent congenital valve disease in adults. It is often associated with other congenital cardiac defects. Sometimes it is associated with aortic dilatation. BAV is an heterogeneous disease with varying valve morphology (asymmetrical cusp size and rafe), annulus geometry and size, asymmetrical calcification of the aortic valve and left ventricular outflow tract. Case Report A 32 year-old male patient was diagnosed with bicuspid aortic valve after several cardiologic visits for eligibility to competitive sport. Since April 2021 he developed a progressive exertional dyspnea for strenuous efforts. In February 2022, he was referred to our department after a Holter ECG showed a bradyarrhythmia with complete atrioventricular block. The echocardiography evaluation demonstrated a preserved ejection fraction and a bicuspid aortic valve with a mild-moderate regurgitation. The coronary computed tomography showed a thick and calcified bicuspid aortic valve with a coarse calcification of the anterior cuspid that involve the pars membranacea of the interventricular septum. The ergometric exercise demonstrated chronotropy incompetence. The tomography confirmed the mildy aortic root dilatation. Therefore, an MRI was performed and reported a small laminar LGE on the infero-lateral wall of the left ventricle, of unclear significance. He underwent Dual-Chamber permanent pacemaker implantation. A conservative approach was preferred over valvular replacement, considering the mild aortic root dilatation on a background of mild-to- moderate aortic insufficiency. Conclusion Our case is unusual given the bicuspid aortic valve concomitant with atrioventricular block, which was connected with the location of the calcification. Thus, the aim of our case report is, to describe a complication to this condition which, although rare, represents a different clinical presentation of the pathology itself in a young adult.

Experimental investigation on critical heat flux enhancement by mixing-vanes spacer grid in a vertical annular geometry

In this paper, critical heat flux (CHF) experiment was carried out in a vertical single-rod channel using R-134a as working fluid to study the effect of mixing-vanes spacer grid (MVSG) on CHF enhancement. The single-rod channel had a rectangular geometry with a uniformly heated rod centrally installed. The test conditions were pressure from 1.8 to 2.7 MPa, mass fluxes from 600 to 2100 kg·m−2·s−1 and subcooling temperature from 10 to 40 ℃, which was determined by Katto’s fluid-to-fluid modeling method with reference to the operation condition of Pressurized Water Reactors (PWRs). The effects of flow parameter and downstream distance on CHF enhancement by MVSG were investigated. In addition, visualization study on flow regime during CHF occurrence and bubble behavior when passing though MVSG was observed by a high-speed camera, which contributed to improving better understanding on the mechanism of CHF enhancement by MVSG.

A Comparative Study of Entropy Generation Analysis Through Cartesian and Cylindrical Annulus Geometries

Abstract This research paper presents a comparative study dealing with entropy generation analysis in Cartesian and cylindrical annulus geometries. This numerical investigation involves heat and mass transfer coupled with forced convection and gas radiation in a semitransparent medium during the evaporation of a thin liquid film. The systems of equations are solved with interfacial and boundary conditions using an implicit finite volume method by the tridiagonal matrix algorithm method. The radiative transfer equation (RTE) was solved by the Ray tracing model. The statistical narrow band correlated-K model with the updated model parameters was applied to calculate the gas transmissivity. The main intent of this paper is to compare the entropy generation components in two different configurations. The result shows that the entropy generation related to heat and mass transfer in the channel is higher than that estimated for the cylindrical annulus. Regarding optimal design selection, the entropy generation analysis, detailed in this paper, suggests a preference for the cylindrical annulus geometry. Our results may guide designers to select from the studied configuration.

Entropy and energy analysis of MHD nanofluid thermal transport in a non-uniformly heated annulus

In this analysis, nanoliquid motion and thermal dissipation rate along with the associated entropy production of water-based nanoliquid have been numerically investigated in an annular geometry. The vertical boundaries are imposed with sinusoidal thermal profiles with different phase deviations, while the top and bottom are retained as insulators, and an inclined external magnetic force has also been considered. The numerical experiments reveal that the change in phase deviation produces severe nanoliquid movement due to the shifting of hot and cold regions along with the outer cylinder. The enhancement of phase deviation produces higher thermal transport rates with minimal entropy production. The influence of magnetic field angle strongly depends on the magnitude of and also the thermal performance could be improved with a proper choice of magnetic tilt angle. Further, the entropy production in the annulus greatly depends on the intensity of the applied magnetic field. An increase in the nanoparticle concentration induces the thermal conductivity of nanoliquid and in turn improves the thermal transport. Through the present analysis, we identified a set of parameters to increase the thermal transport with minimum entropy production.

Investigation of heat transfer performance within annular geometries with swirl-inducing fins using clove-treated graphene nanoplatelet colloidal suspension

The paper investigated the benefits of having fins that induce swirling flow within an annular passage. The importance of the vortical structures produced using different fin angles and flow velocities in heat transfer was studied. The combination of swirling fluid with recirculation on heat transfer within an annular domain was not fully understood, and this paper aims to address that gap. The 10°, 20°, 30° and 40° angled fins were investigated to understand the changes in heat transfer performance as fluid recirculation becomes more dominant as angles become steeper. The usage of CGNP colloidal suspension was investigated for its potential benefits in heat transfer in a domain with angled fins. The CGNP concentrations of 0.025, 0.075 and 0.1 mass % were used as part of this investigation. Higher concentrations of CGNP increased the overall heat transfer coefficient. A more compact fin spacing improved heat transfer performance at the expense of increased pressure drop. Fin angles of 20° and 30° yielded poor heat transfer performance in the transitional flow regime (2000 < Re < 3000) due to the smaller swirling longitudinal vortices being insufficient in promoting fluid mixing from the thermal boundary layer into the freestream.

Thermal Performance in Convection Flow of Nanofluids Using a Deep Convolutional Neural Network

This study develops a geometry adaptive, physical field predictor for the combined forced and natural convection flow of a nanofluid in horizontal single or double-inner cylinder annular pipes with various inner cylinder sizes and placements based on deep learning. The predictor is built with a convolutional-deconvolutional structure, where the input is the annulus cross-section geometry and the output is the temperature and the Nusselt number for the nanofluid-filled annulus. Profiting from the proven ability of dealing with pixel-like data, the convolutional neural network (CNN)-based predictor enables an accurate end-to-end mapping from the geometry input and the desired nanofluid physical field. Taking the computational fluid dynamics (CFD) calculation as the basis of our approach, the obtained results show that the average accuracy of the predicted temperature field and the coefficient of determination R2 are more than 99.9% and 0.998 accurate for single-inner cylinder nanofluid-filled annulus; while for the more complex case of double-inner cylinder, the results are still very close, higher than 99.8% and 0.99, respectively. Furthermore, the predictor takes only 0.038 s for each nanofluid field prediction, four orders of magnitude faster than the numerical simulation. The high accuracy and the fast speed estimation of the proposed predictor show the great potential of this approach to perform efficient inner cylinder configuration design and optimization for nanofluid-filled annulus.

3D mitral annulus echocardiography assessment in patients affected by degenerative mitral regurgitation who underwent mitral valve repair with flexible band.

Degenerative mitral valve (MV)regurgitation (DMR) shows significative mitral annulus (MA) alterations; mitral valve repair (MVR) seeks to restore annular geometry and function, and the current use of flexible band seams to respect most annular mobility reducing parietal stress. Parameters of MV geometry obtained by 3D transesophageal echocardiography (3D-TTE) analysis are crucial for surgical planning and postoperative success. The aim of this study was to assess, by means of a dedicated software, the variations of MA geometry and function in patients affected by DMR compared to controls and after MVR with flexible band. We enrolled 32 patients (cases) with severe DMR who underwent MVR using flexible band; we compare this group with 20 controls. The TEE with 3D MV images acquisition was performed in both groups and then analyzed in postprocessing by using a dedicated software. There were no anthropometrics differences between cases and controls, both presented normal left ventricular ejection fraction. DMR group showed a significant increase of annulus dimensional parameters (p = .001) and alteration of nonplanarity comparing to controls (p < .05). The annuloplasty with flexible band induces a considerable reduction of MV dimensions comparing to preoperative data and restores physiological mobility and nonplanarity. There were no statistical differences between postoperative DMR and controls data, except for nonplanarity parameters (p ~.05), maybe influenced by hemodynamic settings. MVR with annuloplasty using flexible band appears able to reinstate a more physiological anatomic conformation of the MA, without compromising its dynamic properties.

Narrow, Fast, and “Cool” Mantle Plumes Caused by Strain‐Weakening Rheology in Earth's Lower Mantle

AbstractThe rheological properties of Earth's lower mantle are key for mantle dynamics and planetary evolution. The main rock‐forming minerals in the lower mantle are bridgmanite (Br) and smaller amounts of ferropericlase (Fp). Previous work has suggested that the large differences in viscosity between these minerals greatly affect the bulk rock rheology. The resulting effective rheology becomes highly strain‐dependent as weaker Fp minerals become elongated and eventually interconnected. This implies that strain localization may occur in Earth's lower mantle. So far, there have been no studies on global‐scale mantle convection in the presence of such strain‐weakening (SW) rheology. Here, we present 2D numerical models of thermo‐chemical convection in spherical annulus geometry including a new strain‐dependent rheology formulation for lower mantle materials, combining rheological weakening and healing terms. We find that SW rheology has several direct and indirect effects on mantle convection. The most notable direct effect is the changing dynamics of weakened plume channels as well as the formation of larger thermochemical piles at the base of the mantle. The weakened plume conduits act as lubrication channels in the mantle and exhibit a lower thermal anomaly. SW rheology also reduces the overall viscosity, notable in terms of increasing convective vigor and core‐mantle boundary heat flux. Finally, we put our results into context with existing hypotheses on the style of mantle convection and mixing. Most importantly, we suggest that the new kind of plume dynamics may explain the discrepancy between expected and observed thermal anomalies of deep‐seated mantle plumes on Earth.

On‐line melt temperature measurements for polymer injection molding through an instrumented annular duct

AbstractPolymer processing requires reliable monitoring equipment to ensure product quality, improve energy efficiency and apply advanced control strategies. This work tests an instrumented annular duct as a nozzle on the downstream side of the screw‐barrel to analyze the thermal behavior of the polymer flow in an injection molding machine. The plasticization step is first studied, and then virtual injection molding cycles are performed. The measurements via the instrumented annular duct show that the melt temperature decreases during fast production, due to the lack of residence time in the barrel for the material to be sufficiently heated by conduction. The instrumented annular duct also enables detection of changes in melt temperature over time during a single injection. Moreover, the experiments prove the robustness of the temperature measurements in an annular geometry for process monitoring.

Reference ranges of tricuspid annulus geometry in healthy adults using a dedicated three-dimensional echocardiography software package.

BackgroundTricuspid annulus (TA) sizing is essential for planning percutaneous or surgical tricuspid procedures. According to current guidelines, TA linear dimension should be assessed using two-dimensional echocardiography (2DE). However, TA is a complex three-dimensional (3D) structure.AimIdentify the reference values for TA geometry and dynamics and its physiological determinants using a commercially available three-dimensional echocardiography (3DE) software package dedicated to the tricuspid valve (4D AutoTVQ, GE).MethodsA total of 254 healthy volunteers (113 men, 47 ± 11 years) were evaluated using 2DE and 3DE. TA 3D area, perimeter, diameters, and sphericity index were assessed at mid-systole, early- and end-diastole. Right atrial (RA) and ventricular (RV) end-diastolic and end-systolic volumes were also measured by 3DE.ResultsThe feasibility of the 3DE analysis of TA was 90%. TA 3D area, perimeter, and diameters were largest at end-diastole and smallest at mid-systole. Reference values of TA at end-diastole were 9.6 ± 2.1 cm2 for the area, 11.2 ± 1.2 cm for perimeter, and 38 ± 4 mm, 31 ± 4 mm, 33 ± 4 mm, and 34 ± 5 mm for major, minor, 4-chamber and 2-chamber diameters, respectively. TA end-diastolic sphericity index was 81 ± 11%. All TA parameters were correlated with body surface area (BSA) (r from 0.42 to 0.58, p < 0.001). TA 3D area and 4-chamber diameter were significantly larger in men than in women, independent of BSA (p < 0.0001). There was no significant relationship between TA metrics with age, except for the TA minor diameter (r = −0.17, p < 0.05). When measured by 2DE in 4-chamber (29 ± 5 mm) and RV-focused (30 ± 5 mm) views, both TA diameters resulted significantly smaller than the 4-chamber (33 ± 4 mm; p < 0.0001), and the major TA diameters (38 ± 4 mm; p < 0.0001) measured by 3DE. At multivariable linear regression analysis, RA maximal volume was independently associated with both TA 3D area at mid-systole (R2 = 0.511, p < 0.0001) and end-diastole (R2 = 0.506, p < 0.0001), whereas BSA (R2 = 0.526, p < 0.0001) was associated only to mid-systolic TA 3D area.ConclusionsReference values for TA metrics should be sex-specific and indexed to BSA. 2DE underestimates actual 3DE TA dimensions. RA maximum volume was the only independent echocardiographic parameter associated with TA 3D area in healthy subjects.