Orifice Diameter Research Articles

NUMERICAL SIMULATION OF A FLUID FLOW IN THE CYLINDRICAL DUCT CONTAINING TWO DIAPHRAGMS WITH ORIFICES OF DIFFERENT DIAMETERS

The flow of a viscous incompressible fluid in a cylindrical duct with two serial diaphragms with orifices of different diameters was studied based on the numerical solution of the unsteady Navier-Stokes equations. The solution algorithm was based on the finite volume method using second-order accurate difference schemes in both space and time. The TVD (Total-Variation Diminishing) form of a central-difference scheme with a flux limiter was used for the interpolation of the convective terms. The combined evaluation of the velocity and pressure fields was carried out using the PISO (Pressure Implicit Split Operator) procedure. The problem was solved using OpenFOAM (Open-source Field Operation And Manipulation) open-source toolkit libraries using the computing power of the cluster supercomputer of the V.M. Glushkov Institute of Cybernetics of the National Academy of Sciences of Ukraine. It was shown that within a certain range of the diameter ratio of the orifices of the diaphragms, a circulation movement is established in the cavity between the diaphragms. The boundary layer breaks off from the surface of the first diaphragm and forms an annular shear layer. When approaching the second diaphragm, a sequence of ring vortices is formed in it, which interact with the surface of the diaphragm and lead to the emergence of tonal sound. When the ratio of the orifice diameter of the second diaphragm to the first decreases, the share of the jet’s kinetic energy, which participates in the circulation in the middle of the cavity between the diaphragms, increases. As a result, the amplitude of velocity fluctuations in the orifice of the second diaphragm decreases. When the ratio of the diameters of the orifices increases, the share of energy involved in the circulation decreases, and when a certain value of the ratio is reached, the interaction between the vortices in the shear layer and the surface of the diaphragm does not occur. As a result, the excitation of the tonal sound stops. The Strouhal number of self-oscillations practically does not change when the diameter ratio of the orifices changes. During the calculations, two different modes of self-oscillation were obtained, which is consistent with previous works.

The investigation of hydrogen released on the mixed jets with an axisymmetric jet and an asymmetric jet

Hydrogen released from complex multi-pipeline leakage sources can increase the difficulty of predicting the risk region of hydrogen and the probability of explosion accident. To investigate the collision and mixing features of subsonic hydrogen jets released from multi-pipeline leakage sources, an experimental platform for gas visualization and quantitative measurement is constructed. The differences in flow field structure and concentration distribution of vertical axisymmetric hydrogen jet, vertical asymmetric hydrogen jet and mixed hydrogen jets are compared and analyzed. Furthermore, the effects of multiple factors on the jet centerline, concentration decay, hazardous volume and diffusion height of the mixed region are predicted. The numerical simulation results are verified by the experimental data. Results indicate that the asymmetric hydrogen jet causes the mixed region centerline of hydrogen to deviate from the vertical axis under the combined effect of momentum-dominant and buoyancy. With the increase of the volumetric flow rate, the slope of the mixed region centerline initially decreases and then increases, with the smallest slope occurring at a volumetric flow rate of 159 NL/min. Either the increase of the leakage orifice diameter or the decrease of the distance between two leakage orifices can cause the slope of the mixed region centerline to decrease. Among three factors, the leakage orifice diameter has the most obvious effect on the concentration decay. The hydrogen diffusion height gets the highest when the ratio of leakage orifice diameter to pipeline inner diameter is 0.4 among five leakage orifice diameters. The distance between two leakage orifice has no significant influence on the hazardous volume. The investigation provides valuable data to support the prediction of the dangerous range of hydrogen leakage in complex multi-pipeline leakage sources.

Investigating Effect of Geometric Differences on Fluid Behavior in Synthetic Jets

A synthetic jet is a flow that is created by an actuator vibrating at a specific frequency and amplitude. In this study the velocities and propagation of synthetic jets have been measured using both circular and single-wave orifice geometries. Axial velocity measurements in the direction of flow have been taken using the PCE 423 model hot wire anemometer. Also flow visualization has been performed using TiO2 surface oil visualization to determine velocity distributions in the radial direction. The measurements have been conducted at different H/D values, representing the ratio between the axial distance (H) and the orifice diameter (D). The excitation frequency has been varied between 4 Hz and 5 Hz with a sinusoidal signal type. The results have shown that circular orifice geometry have higher velocities in the axial direction. However, When the axial velocity was measured at 4 Hz, it has been observed that the single wave geometry provided results close to a circle at H/D = 13 and 14 values, and at 5 Hz for H/D = 12 and 13 values. This suggests that the geometric shape is not very important at high H/D ratios. In addition, the axial velocity values for a single wave orifice geometry show almost the close results for both excitation frequency values. The flow visualization results have indicated that the single-wave orifice geometry with H/D=12 ratio perform better and provides a more accurate and well-distributed velocity field. In conclusion, the findings of this study suggest that synthetic jets could be potentially useful for industrial applications, especially in heat transfer applications with their extended flow field implications.

Effects of geometric parameters on flow and atomization characteristics of swirl nozzles for artificial snowmaking

With the worldwide popularity of skiing, artificial snow technology has been gradually developed. Atomization is the key process for snowmaking, and swirl nozzles are applied as the core atomization components in snowmakers. In this research, the effects of nozzle geometric parameters on the flow and atomization characteristics are explored to improve snowmaking performance. The flow and atomization process in swirl nozzle is simulated by VOF-DPM approach after experimental validation. The results show that appropriate increase of orifice diameter and swirl slot area can effectively reduce the atomization droplet size and increase the spray flow rate. As the diameter ratio of swirl chamber to orifice decreases from 6.67 to 2.5, Sauter Mean Diameter (SMD) decreases by 54.9%, and mass flow rate increases by 168.2%. When orifice diameter is 4.0 mm, as the atomizer constant increases from 0.1688 to 0.3797, SMD decreases by 65.8% and mass flow rate increases by 114.3%. Furthermore, the reduction in SMD and the increase in spray flow rate are attributed to high discharge velocity. The swirl nozzles have the best atomization droplet size and maximum flow rate, as the inlet pressure is 0.6 -1.4 MPa, orifice diameter is 4.0 mm and swirl slot width is 2.25 mm.

Design Optimization Methods for Forced Lubrication System Used in Automotive Transmissions

<div>Lubrication has been a major area of interest in engineering. Especially in vehicle transmissions, lubrication plays a very crucial role because gears and bearings are constantly subjected to heavy loads. Proper lubrication is essential for maintaining system performance and ensuring endurance life. Insufficient lubrication can lead to excessive wear, increased friction, and eventually, failures in the transmission components. However, excess lubrication can result in power losses due to the resistance offered by the excessive lubricant. Therefore, achieving effective lubrication using optimized lubrication system design is vital for ensuring the longevity and efficiency of the transmission system.</div> <div>Majorly, two types of lubrication methods are used in transmissions: splash lubrication and forced lubrication. This article focuses on forced lubrication, where the lubrication system actively delivers the required flow of lubricant to specific locations within the transmission. Pump outflow, orifice diameters, and channel dimensions are a few of the critical design parameters of the forced lubrication system. This article presents two design optimization methods: one using ANSYS DX (3D) and the other using GT-Suite (1D) tool. In the 3D method, ANSYS Fluent is used for CFD (computational fluid dynamics) simulations and subsequently ANSYS DesignXplorer (DX) is leveraged for design optimization. Predictions from CFD simulations are validated against physical test data and show good agreement (>90% match for flow rate). GT-SUITE is used in the 1D method, which is validated with predictions from 3D CFD method. The optimized designs obtained from both methods are effective in achieving the desired flow rate distribution, demonstrating their reliability. The ANSYS DX method provides an advantage in terms of reduced overall turnaround time (50% less) for the optimization. On the other hand, co-simulation (CFD+1D) approach can prove beneficial if it is required to perform minor routing changes on the lube system layout.</div>

Assessment of design and location of an active prechamber igniter to enable mixing-controlled combustion of ethanol in heavy-duty engines

This numerical study focuses on assessing the key design parameters of interest for use of an active prechamber igniter as an ignition assistance device to enable mixing-controlled combustion (MCC) of ethanol (E100) in a heavy-duty Caterpillar C9.3B engine. Computational fluid dynamic (CFD) simulations of a baseline diesel and prechamber retrofitted C9.3B at a gross indicated mean effective pressure (IMEPg) of 5 bar and 1800 rpm are carried out using CONVERGE. In particular, the sizing of the prechamber volume, sizing of total orifice cross sectional area (orifice diameter), and location of the prechamber relative to a centrally mounted common rail direct injector are varied to discern the appropriate operational and design characteristics to achieve robust ignition assistance at the selected conditions. Simulation results indicate that use of an active prechamber igniter with E100 as a standalone fuel source can replicate ignition delays and thermal efficiencies similar to diesel combustion at the same engine boundary conditions, thus not requiring any changes to the engine’s air handling system. Igniter mounting location, orifice sizing, and jet targeting were found to have the strongest influence on ignition assistance with preference toward larger orifice diameters that appropriately located heating contributions in near vicinity to the direct injector.

Experimental research on the detonation behavior in annular combustors utilizing liquid hypergolic propellants

The development of rotating detonation engine utilizing hypergolic propellants is necessary for practical application of detonation-based rocket engines, but this liquid-liquid rotating detonation has been rarely researched due to its difficulty of well atomization and mixing in very short time. This study aims to experimentally investigate the propagation characteristics of rotating detonations using non-premixed hypergolic propellants in annular combustors. Here the monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) have been used as oxidizer and fuel, respectively. Twenty-four unlike impinging elements have been used for injection and mixing of liquid propellants. The orifice diameter is 0.4 mm for oxidizer and 0.3 mm for fuel. Three typical combustion modes such as deflagration mode, one-wave rotating detonation mode and two-wave collision mode have been captured by dynamic pressure transducers and the high-speed camera. The influence of many factors, such as mass flow rate, mixing ratio, annular combustor width and chamber throat, on rotating detonation behaviors have been investigated. The propagation velocity of rotating detonations is around 1328 m/s∼1405 m/s, including one-wave rotating detonation mode and two-wave collision mode. When the mass flow rate and mixing ratio is not appropriate, the hypergolic combustion becomes obviously unstable and combustion modes vary very quickly, especially at the start-up stage. The chamber throat plays a negative role on rotating detonation which suppresses the detonation propagation and can lead to detonation fail. Besides, the wider annular combustor width is beneficial for rotating detonation propagating, which can eliminate the negative influence of the chamber throat on the detonation propagation. In addition, increasing mass flow rate would lead to higher injection velocity and thus better impinging injection, atomization and mixing, which is positive for increasing the stable operation range of mixing ratio for rotating detonations.

Successful surgical treatment of omphalocele with umbilical evagination of the bladder: an extremely rare presentation of neonatal case

BackgroundA few cases of small omphalocele with umbilical evagination of the bladder have been reported. However, its embryology is yet to be elucidated. Only a few reports have indicated the existence of urachal anomalies and umbilical cysts related to bladder evagination. The incidence of urachal anomalies at birth is reported to be 1 in 5000–8000 live birth, and urachal aplasia is rare. Herein, we report a rare, novel case of urachal aplasia.Case presentationWe encountered a small omphalocele with bladder evagination associated with urachal aplasia for which the neonate underwent surgery one day after birth. The patient was a one-day-old boy with a prenatally diagnosed omphalocele. A fetal magnetic resonance image (MRI) scan (25 weeks of gestation) revealed a 30 × 33 mm (approximately 1.3 in.) cystic lesion which was suspected to be an umbilical cyst. The baby was born vaginally at 38 weeks, weighing 2956 g. An omphalocele (hernial orifice diameter, 4 cm × 3 cm) with bladder prolapse was recognized. After sac excision, the prolapsed bladder was resected and closed with two-layer sutures. In order to secure sufficient bladder capacity, we estimated the minimum residual volume as 21 ml after bladder plasty. The remaining bladder capacity was confirmed to be 30 ml by injecting a contrast dye and saline into the bladder. The neonate had no associated cardiac urogenital or skeletal anomalies. Postoperative course was uneventful. The patient was regularly followed up for two years after surgery and underwent umbilicoplasty. He had no trouble with urinary function.ConclusionIn this case, we experienced extremely rare condition of a small omphalocele with bladder evagination associated with urachal aplasia and reviewed 7 case reports of anomalies similar to those in the present case. Umbilical cord cysts may be an informative indicator of these symptoms in utero. Therefore, ultrasonography scans should be conducted until delivery, despite the spontaneous disappearance of cord cysts.

The Research on Performance Characteristics of the Sliding Relief Valve

Based on the software AMESim, this paper introduced the operating principle and established the system models of relief valves. The effects on dynamic characteristics under the different parameters, including the number of overflow orifices, overflow orifice diameter and spring stiffness, were analyzed by the AMESim batch processing method. This paper compared and analyzed the curves and summarized the parameters which affect the performance characteristics of the relief valves. The result helps optimize the structure parameters and improve the performance characteristics of the relief valves.

Современный метод хирургического лечения стриктуры протока околоушной слюнной железы

INTRODUCTION: A modern principle of treatment for obstructive pathologies of salivary glands is saving the gland itself and its functions using minimally invasive methods. This article describes a clinical case of elimination of the stricture of the parotid salivary gland duct and compensation for its expanded section behind the gland with intraoperative visualization using ultrasound. Under US control, the expanded portion was punctured from external access; a conductor was inserted, which passed into the oral cavity through the natural orifice. Through the formed opening, a catheter was installed, which expanded the narrowed area and prevented the reappearance of the stricture. Control examinations in 1, 6 and 12 months showed the functioning of the orifice with release of clear saliva in the satisfactory amount. The patient noted absence of enlargement of the parotid salivary gland and absence of pain at rest and in chewing. Control US in 6 and 12 months showed absence of any signs of stricture and reduction of the orifice diameter to 2 mm. CONCLUSION: The developed method of elimination of stricture of the parotid salivary gland duct can lead to reduction of duration and the scope of surgical intervention, of the risk of re-stricture, postoperative and rehabilitation periods, frequency of using costly equipment, which makes the procedure available.

Liquid jet dispersion after impact on a highly curved surface

A liquid jet impacting on a wire mesh is a phenomenon that occurs in such industrial applications as rotating packed beds or agricultural spraying. To derive a fundamental understanding of the behaviour of a dispersion generated by the whole mesh, a simple geometric case needs to be studied. This paper focuses on the dispersion of a liquid jet impacting on a single stainless steel rod studied with a high-speed visualisation. It is found that two liquid sheets are formed with sheet characteristics described by a dispersion angle αe, a sheet velocity vs, and a breakup length Lb. Three stages of the angular development of the dispersion are observed based on the liquid flow rate and the exit orifice diameter. A correlation for the dispersion angle growth is proposed based on the experimental results. Perforated, segmented and wave-assisted sheet breakup regimes are found in the recorded images with their presence dependent on the impact velocity. A correlation for the breakup length is proposed for the sheets based on similarities with flat fan nozzle theory.

Numerical Investigation of Effect of Structural Parameters on the Performance of a Combustion-Driven Sparkjet Actuator

With the aim of increasing the momentum jet and obtaining better environmental adaptability, this study designs a new type of actuator combining a sparkjet actuator and a combustion-driven actuator. Numerical simulation shows that the combustion-driven sparkjet actuator has a higher velocity and mass rate compared to the sparkjet actuator when the length and orifice diameter are 6.5 mm and 1.3 mm, respectively, while the saturation work frequency is almost the same. A parameter study shows that as the volume increases, the pressure, orifice velocity, and mass rate of the combustion-driven sparkjet actuator increase. By contrast, the saturation work frequency decreases. Moreover, as the orifice diameter decreases, the orifice peak velocity, temperature, and pressure increase, whereas the mass flow rate and saturation work frequency decrease.

Droplet spatial distribution of oil-based emulsion spray

Introduction Oil-based emulsion solution is a common pesticide formulation in agricultural spraying, and its spray characteristics are different from that of water spraying. The well understanding of its spray characteristics is the theoretical basis to improve the pesticide spraying technology. The objective of the present study is to deepen the understanding of the spray characteristics of oil-based emulsion. Method In this paper, the spatial distribution characteristics of spray droplets of oil-based emulsion were captured visually using the high-speed photomicrography. On the basis of image processing method, the droplet size and distribution density of spray droplets at different spatial locations were analyzed quantitatively. The effects of nozzle configuration and emulsion concentration on spray structures and droplet spatial distribution were discussed. Results Oil-based emulsion produced a special perforation atomization mechanism compared with water spray, which led to the increase of spray droplet size and distribution density. Nozzle configuration had a significant effect on oil-based emulsion spray, with the nozzle changed from ST110-01 to ST110-03 and ST110-05; the sheet lengths increased to 18 and 28 mm, respectively, whereas the volumetric median diameters increased to 51.19% and 76.00%, respectively. With emulsion concentration increased from 0.02% to 0.1% and 0.5%, the volumetric median diameters increased to 5.17% and 14.56%, respectively. Discussion The spray droplet size of oil-based emulsion spray can be scaled by the equivalent diameter of discharge orifice of nozzles. The products of volumetric median diameters and corresponding surface tensions were nearly constant for the oil-based emulsion spray of different emulsion concentrations. It is expected that this research could provide theoretical support for improving the spraying technology of oil-based emulsion and increasing the utilization of pesticide.

Rotordynamic Analysis and Operating Test of an Externally Pressurized Gas Bearing Turbo Expander for Cryogenic Applications

This study designed an externally pressurized bearing and analyzed the rotordynamics of a turbo expander for a hydrogen liquefaction plant. The turbo expander, comprising a turbine and compressor wheel assembled to a shaft, lowered the temperature of the helium refrigerant. Its rated speed was 75,000 rpm, and an externally pressurized gas bearing was selected to support the rotor. Pressurized helium was used as the lubricant for the bearing operation. To design the rotor–bearing system, we conducted a bearing performance analysis and rotordynamic characteristic prediction using the developed numerical model. We calculated the bearing stiffness and flow rate of the bearing gas for various feed parameters and selected the appropriate orifice diameter for maximum stiffness. The predicted Campbell diagram showed that the system had a sufficient separation margin with the critical speed, and the predicted critical speed correlated well with the nonlinear orbit simulation. A successful operation was achieved with the manufactured turbo expander within the rated speed. The shaft vibration was monitored during the operation test, and the test results revealed two critical speeds below the rated speed, as predicted by the analytical model. In addition, the shaft vibration was maintained at <3 μm.

Pericardial effusion following percutaneous left atrial appendage closure using the LAmbre device.

Pericardial effusion (PE) is an uncommon but serious complication that occurs following percutaneous left atrial appendage closure (LAAC). There are few data regarding PE following implantation of the LAmbre device for LAAC. Patients with nonvalvular atrial fibrillation (AF) undergoing percutaneous LAAC using the LAmbre device at the Arrhythmia Center of Ningbo First Hospital from October 2017 to March 2021 were retrospectively reviewed (n = 133). PE was defined as acute if diagnosed ≤7 days post LAAC (n = 3, 2.3%) or delayed if diagnosed >7 days post LAAC (n = 3, 2.3%). The clinical characteristics and procedural data were compared between patients with PE (PE group, n = 6) and without PE (non-PE group, n = 127). The predictors of PE were analyzed by logistic regression. All patients with PE recovered following treatment by pericardiocentesis. Patients with PE were found to have a higher incidence of congestive heart failure (50.0% vs. 13.4%, P = 0.044) and had larger measured LAA orifice diameters (33.5 mm ± 6.0 mm vs. 28.3 mm ± 5.2 mm, P = 0.018) and landing zone diameters (27.8 mm ± 4.8 mm vs. 23.9 mm ± 4.8 mm, P = 0.054) compared with those without PE. The diameters of the device umbrellas (31.7 mm ± 5.6 mm vs. 26.9 mm ± 5.0 mm, P = 0.026) and covers (36.3 mm ± 4.6 mm vs. 33.4 mm ± 4.0 mm, P = 0.075) implanted were larger in the PE group compared to the non-PE group. Univariate logistic regression revealed that congestive heart failure (OR = 6.47, 95% CI = 1.21-34.71, P = 0.029) and LAA maximal orifice diameter (OR = 1.22, 95% CI = 1.02-1.45, P = 0.027) were both associated with PE following LAmbre device implantation. In this single-center experience, both acute and delayed PE were uncommon in patients with AF following LAmbre device implantation. Congestive heart failure and a larger LAA orifice were identified as predictors for the occurrence of PE.

Theoretical and experimental study on the stability of water lubricated high speed journal bearing with lobe pockets

The stability problem prevents the application of water lubricated journal bearing in high speeds conditions. To improve the bearing performance, the lobe pocket with Archimedes helix profile is designed in the water lubricated hydrostatic and hydrodynamic hybrid journal bearing. Bearing stiffness coefficients, damping coefficients and threshold speed are investigated with considering turbulence. Effects of radius clearance, pocket parameters, water supply pressure, restriction parameter and external load are analyzed. The results indicate that decreasing radius clearance and increasing pocket depth both improve the bearing stability, while there are optimal values for pocket widths. The water supply pressure and orifice diameter increase the threshold speed at low speeds. The results obtained provide useful information for designing high stability journal bearings.

Augmented flow and reduced clogging of particles passing through small apertures by addition of fine grains

The effect on the flow and clogging of a sample of particles passing through an orifice due to the addition of a second fine-graded species is investigated. The flow rate of the main species is measured for various parameters: the mass ratio of the big species, the particle size ratio and the orifice diameter. We show that when the fine grains are added into the system the flow rate of the larger species can be increased and its clogging significantly reduced. In particular, we were able to flow (without clogging) the big species through an orifice only 1.5 times its particle diameter. This allows for applications such as the alignment of particles in a narrow tube without clogging. A simple state diagram is presented to describe the clogging transition for these binary mixtures. The experimental results are compared with various existing models for the flow rate of binary mixtures.

On-demand heart valve manufacturing using focused rotary jet spinning

On-demand heart valve manufacturing using focused rotary jet spinning

Visualization investigation of jet ignition ammonia-methanol by an ignition chamber fueled H2

Ammonia is an ideal carbon-free fuel if the burning velocity problem can be successfully addressed. Blending ammonia with high-activity fuels and utilizing high-energy ignition are both suitable solutions for accelerating ammonia combustion. In this study, jet-controlled compound ignition (JCCI) by an ignition chamber fueled H2 was proposed to accelerate the premixed ammonia /methanol combustion. Visualization experiments were applied to evaluate the combustion performance. The effects of hydrogen energy substitution ratios (Ri) in the ignition chamber, methanol blend (Rm) in the main chamber, and orifice diameters (d) between the ignition chamber and main chamber on the combustion were investigated. By utilizing JCCI, it achieved a combustion duration of 85 ms, which is 47.7% shorter than spark ignition (SI) under an equivalent ratio of 1.0. Furthermore, JCCI produced excellent lean burn performance. At the equivalent ratio of 0.8 and 1.0 in the main chamber, JCCI model shortened the combustion duration by 20.9% and 52.2% respectively, compared with SI ignition. Additionally, it is necessary to adapt the appropriate hydrogen energy substitution ratio for different equivalent ratios of ammonia blends. For the equivalent ratio of 1.0 and 0.8 in the main chamber, the Ri = 1% and Ri = 2% achieved shorter jet delay and combustion duration, respectively. In addition, when the equivalent ratio was 1.0 and the methanol blend ratio Rm = 10%, Rm = 30% and Rm = 50%, the combustion duration reduced by 11.9%, 28.0%, and 42.1%, respectively, compared to Rm = 0%. This reduction resulted mainly from changes in the jet flow and flame structures due to the various hydrogen energy substitution ratios and methanol blend ratios. Furthermore, using a 3 mm orifice diameter, compared to a 6 mm orifice diameter, caused the combustion duration to decline by 63.4% and 54.3% for equivalent ratios of 1.0 and 0.8, respectively.

Left atrial appendage anatomical changes following radiofrequency-based ostial isolation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial appendage (LAA) electrical isolation (ei) may be achieved via radiofrequency (RF) energy applications at the level of the appendage ostium targeting the sites of earliest activation recorded by a mapping catheter. Notably, RF has long been used in vascular, orthopedic, and aesthetic surgery to promote thermal-induced collagen matrix contraction, fibrosis, and tissue retraction. LAA anatomical changes associated to RF-induced tissue retraction have never been reported. Purpose To quantify the anatomical changes of the LAA ostium following RF-based LAAei. Methods Thirty-four consecutive patients requiring AF ablation with LAAei underwent transesophageal echocardiography (TEE) within 7 days before (baseline TEE) and apx 6 months after (follow-up TEE) ablation. The diameter of LAA orifice and landing zone were measured at 4 different views (0°, 45°, 90°, 135°). Measurements were performed by two independent reviewers blinded to the patient’s identity. Results Among 43 AF patients (67±6yrs, 72.1% males), the LAA morphology was classified as chicken wing in 19 (44.2%) patients, windsock in 12 (27.9%), cactus in 8 (18.6%), and cauliflower in 4 (9.3%). At baseline TEE, the mean maximum and mean minimum ostial diameters were 25±4mm and 22±4mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 26±4mm and 23±3mm, respectively. On average, LAAei was achieved after 17±6 minutes of RF at a power of 45W. Follow-up TEE was performed 294±136 days after LAAei. The median LAA contraction velocity was 0.1 m/s (IQR: 0.02-0.18) and was significantly impaired in all patients. At follow-up TEE, the mean maximum and mean minimum ostial diameters were 19±4mm and 17±3mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 20±4mm and 18±4mm, respectively. The mean relative reduction of the ostium and the landing zone was -24.4% and -22.5%, respectively. Box-Whisker plots of the maximum and minimum ostial diameters before and after LAAei are reported in Fig.1. Conclusion RF led to a >20% reduction of the diameters of the ostium and the landing zone. These changes may have important implications for a successful percutaneous occlusion procedure and justify a staged approach of isolation and occlusion.