Inlet Dimensions Research Articles

BOLSA CHICA WETLANDS RESTORATION INLET DESIGN

Bolsa Chica Wetlands is one of a few recently restored large wetlands in Southern California of the United States. The project required restoration of tidal flooding of some isolated wetlands while minimizing impacts to the shoreline adjacent to the new inlet and maintenance costs, preserving endangered species on site, and maintaining oil field operations along the periphery of the project. The project created a direct connection to the ocean through wetland basins that included a full tidal basin, muted tidal basins and seasonal ponds linked by a series of ocean jetties, levees, water control structures, culverts, and channels. The inlet is a key project feature and has been the focus of numerous technical studies and numerical modeling tasks. As part of theses analyses, a pre-filled ebb bar was designed and about 1 million cubic yards of clean sand from the lowlands dredging was placed offshore to minimize the anticipated impacts of the inlet opening to the shoreline. This paper presents the inlet location selection, inlet and wetland hydrodynamics, inlet dimension optimization, inlet stability analyses, and jettied inlet entrance design. It also discusses findings of comparison between model predictions and field measurements of tidal elevations and sediment accumulations in the wetland basin since the completion of the project in August 2006. This project received the first Project Excellence Award from COPRI (Coasts, Oceans, Ports and Rivers Institute) of the American Society of Civil Engineers in 2008.

The Pyrocarbon Deposition Techniques of Mechanical Heart Valve Prostheses

The structure and property of pyrocarbon varies widely with different deposition conditions. The isotropic carbon which can only been deposited in the bed of fluidized particles is very important in biomedical fields, for instance, it is often used as the coating of artificial heart valve components. The deposition of isotropic pyrocarbon containing silicon is experimented in fluidized bed over a wide range of deposition conditions. The results show that bed temperature influences strongly average coating rate, coating density, silicon content and coating micro-hardness. Propane concentration has a much effect on coating density, carbon matrix density and isotropic characteristics. Total gas flow rate and inlet dimension of fluidized bed affect the formation of fluidized bed.

The effect of cyclone inlet dimensions on the flow pattern and performance

The effect of the cyclone inlet dimensions on the performance and flow field pattern has been investigated computationally using the Reynolds stress turbulence model (RSM) for five cyclone separators. The results show that, the maximum tangential velocity in the cyclone decreases with increasing the cyclone inlet dimensions. No acceleration occurs in the cyclone space (the maximum tangential velocity is nearly constant throughout the cyclone). Increasing the cyclone inlet dimensions decreases the pressure drop. The cyclone cut-off diameter increases with increasing cyclone inlet dimension (consequently, the cyclone overall efficiency decreases due to weakness of the vortex strength). The effect of changing the inlet width is more significant than the inlet height especially for the cut-off diameter. The optimum ratio of inlet width to inlet height b/ a is from 0.5 to 0.7.

Optimization of the cyclone separator geometry for minimum pressure drop using mathematical models and CFD simulations

The response surface methodology has been performed based on the Muschelknautz method of modeling (MM) to optimize the cyclone geometrical ratios. Four geometrical factors have significant effects on the cyclone performance viz., the vortex finder diameter, the inlet width and inlet height, and the cyclone total height. There are strong interactions between the effect of inlet dimensions and vortex finder diameter on the cyclone performance. CFD simulations based on Reynolds stress model are also used in the investigation. A new set of geometrical ratios (design) has been obtained (optimized) to achieve minimum pressure drop. A comparison of numerical simulation of the new design and the Stairmand design confirms the superior performance of the new design compared to the Stairmand design.

Geometric changes after tricuspid annuloplasty and predictors of residual tricuspid regurgitation: a real-time three-dimensional echocardiography study

We sought to demonstrate geometric changes in the tricuspid valve (TV) apparatus after tricuspid annuloplasty (TAP) and to identify predictors of residual tricuspid regurgitation (TR) in patients with functional TR using real-time three-dimensional echocardiography (RT3DE). RT3DE and two-dimensional colour Doppler echocardiography were performed in 59 consecutive patients before and 4.7 ± 2.1 days after TAP. The tenting angles of the three leaflets were significantly increased, whereas tenting volume, annulus diameters, and septal-lateral right ventricular inlet dimension decreased after TAP. By multiple stepwise linear regression analysis, tenting volume (P < 0.001) and antero-posterior annulus diameter (P = 0.043) before TAP were major predictors of residual TR assessed using distal jet area. When TR severity was quantified by vena contracta width, tenting volume (P < 0.001) before TAP was the only independent predictor. Pre-TAP tenting volume ≥1.68 mL (sensitivity of 86%, specificity of 73%), and ≥2.30 mL (sensitivity of 100%, specificity of 84%) were the best cut-off values predicting severe residual TR quantified using distal jet area and vena contracta width, respectively. After TAP, tenting volume and pulmonary artery systolic pressure were major determinants of residual TR. Tenting angles of all three leaflets increase, whereas annulus diameters decrease, after TAP. Pre-TAP tenting volume and antero-posterior annulus diameter measured using RT3DE are independent predictors of residual TR severity, and measurement of these parameters may help to identify patients at high risk for severe residual TR, for whom TV replacement should possibly be initially considered.

Right Ventricular Remodeling Determines Tricuspid Valve Geometry and the Severity of Functional Tricuspid Regurgitation: A Real-Time 3-Dimensional Echocardiography Study

Background and ObjectivesRight ventricle (RV) remodeling can determine tricuspid valve (TV) geometry and the severity of functional tricuspid regurgitation (TR).Subjects and MethodsIn 53 patients with various degrees of functional TR and in sinus rhythm, RV and TV geometries were analyzed using real-time 3-dimensional echocardiography, including tenting angles of 3 leaflets, septal-lateral and antero-posterior tricuspid annulus diameters and inlet RV dimensions, mid-RV septal-lateral dimension, and the distance between annulus and apex. A mid-systole frame when the TV tenting is smallest was selected for the analysis. RV end-diastolic and end-systolic volumes were measured. The severity of functional TR was determined by distal jet area.ResultsTR distal jet area was mainly determined by septal-lateral annulus diameter (p<0.001) RV inlet dimension (p=0.015), RV end-systolic volume (p=0.010), septal (p=0.019), and anterior leaflet tenting angles (p=0.045) by multiple stepwise linear regression analysis. Leaflet tenting angles were mainly determined by septal-lateral RV inlet dimension. Septal-lateral annulus diameter was determined by septal-lateral RV inlet dimension (p<0.001) and mid RV dimension (p=0.033), whereas antero-posterior annulus diameter was determined by antero-posterior RV inlet dimension (p<0.001).ConclusionFunctional TR severity is determined by septal-lateral annulus and RV dilation, and tenting of septal and anterior leaflets. TV leaflet tenting is mainly determined by septal-lateral RV inlet dilation, and tricuspid annulus dilation is closely linked with inlet RV dilation.

Numerical simulation of effects of reactor dimensions on isothermal CVI process of C/SiC composites

A two-dimensional axisymmetrical mathematical model taking into account the transport phenomena of momentum, energy and mass in conjunction with the infiltration induced changes of the preform structure were implemented to simulate the effects of the reactor dimension on the isothermal CVI process of C/SiC composites. The effects of the reactor inlet dimension and the reactor diameter on the concentration distribution and the time-dependent densification behaviors of C/SiC composites were studied. The reactor inlet dimension was found to impose trivial effects on the ICVI process of C/SiC composites. Calculation results show that the mean MTS molarity in preform and the global density increase firstly and then decrease with the elevating reactor diameter at any given infiltration time though the MTS molarity gradients drops gradually with the elevating reactor diameter. The preferable reactor diameter is implied to be 90 mm for the preform taken. Calculation results of the densification behavior of C/SiC composites during the ICVI process imply that the reactor diameter does not evidently influence both the rules of densification and the absolute values of the density.

Hydrodynamic Modelling of Estuarine Flood Defence Realignment as an Adaptive Management Response to Sea-Level Rise

A numerical hydrodynamic model is used to investigate the sensitivity of a morphologically complex and heavily “engineered” mesotidal estuary to idealized sea-level rise scenarios and to evaluate the appropriateness of managed realignment as an adaptive response to sea-level rise. The hydrodynamic regime of the Blyth estuary (Suffolk, eastern England) is governed by a distinctive morphology that has resulted from the abandonment of a reclaimed midestuary tidal floodplain in the 1920s and 1940s. Hypsometric characteristics (extensive intertidal area and constricted inlet dimensions) make the outer estuary potentially sensitive to sea-level rise. Model results indicate that a sea-level rise of 0.3 m (as a best estimate scenario for 2050) could increase peak tidal current velocities and discharges by up to 20% and 28%, respectively. Extensive areas of potential tidal floodplain remain protected by embankments that will require upgrading to cope with sea-level rise. Realignment (or “managed retreat”) of these defences can reduce local flood defence costs by eliminating unsustainable seawall but needs to be evaluated in the light of wider impacts. Modelling of hypothetical realignment scenarios shows that restoration of tidal exchange to the largest flood compartments could have an immediate effect on outer estuary hydrodynamics that is larger than worst case scenarios for half a century of accelerated sea-level rise (peak velocity and discharge increased by up to 35% and 32%, respectively). More generally, incompatibilities are apparent between flood defence and habitat restoration objectives, such that the appropriateness and feasibility of large-scale flood defence realignment could be questionable in estuarine contexts.

Evolving Role of Multidetector Computed Tomography in Evaluation of Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

The purpose of this study was to report 1 center's experience with multidetector computed tomography (MDCT) in the evaluation of patients suspected to have arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C). RV dilatation/dysfunction is 1 of the most important criteria for establishing the diagnosis of ARVD/C. Cardiac magnetic resonance imaging (MRI) is the most preferred imaging modality for the diagnosis of ARVD/C. However, many patients with suspected ARVD/C have implantable cardioverter-defibrillators, prohibiting the use of MRI. Thirty-one patients (19 men; mean age 41 +/- 12 years) referred for evaluation of known or suspected ARVD/C had a complete reevaluation including contrast-enhanced cardiac MDCT at the center. Two patients underwent both cardiac MRI and MDCT. Seventeen of 31 patients met Task Force criteria for ARVD/C and were confirmed to have ARVD/C. Multidetector computed tomographic images were analyzed for qualitative and quantitative characteristic findings of ARVD/C. Increased RV trabeculation (p <0.001), RV intramyocardial fat (p <0.001), and scalloping (p <0.001) were significantly associated with the final diagnosis of ARVD/C. RV volumes, RV inlet dimensions, and RV outflow tract surface area were increased in patients with ARVD/C compared with patients who did not meet the criteria. RV and left ventricular functional analysis was performed in 2 patients. In conclusion, cardiac MDCT has a strong potential to detect many qualitative and quantitative abnormalities of the right ventricle in patients with ARVD/C. Limitations include implantable cardioverter-defibrillators and motion artifacts, along with well-known radiation and contrast-induced reaction.

Dobutamine Stress-Induced Ischemic Right Ventricular Dysfunction and Its Relation to Cardiac Output in Patients With Three-Vessel Coronary Artery Disease With Angina-Like Symptoms

We investigated markers of ischemic dysfunction and their relation to overall right ventricular (RV) performance during dobutamine stress echocardiography in patients who had coronary artery disease. Thirty-three patients (58 +/- 10 years old) who had 3-vessel coronary artery disease were compared with 17 age-matched controls (58 +/- 11 years old). RV long-axis amplitude (M mode), systolic and diastolic myocardial tissue Doppler velocities, and filling and ejection velocities were measured, and cardiac output (CO) was calculated at rest and during peak stress. There was no difference in RV size (inlet dimension <3.5 cm), RV systolic long-axis amplitude, systolic and diastolic velocities, peak early/late diastolic velocity ratio, and RV CO between patients and controls at rest. During stress, RV systolic long-axis amplitude increased in controls (from 24 +/- 6 to 30 +/- 5 mm) and CO increased significantly (from 4.9 +/- 1.2 to 12.5 +/- 2.1 L/min, p <0.001 for the 2 items). In contrast, RV amplitude did not change with stress in patients (from 24 +/- 5 to 22 +/- 6 mm, p = NS), and the stress-increment in CO was augmented (from 4.2 +/- 1.2 to 8.3 +/- 2.0 L/min, p <0.001 vs control stress increment). Failure to increase RV systolic amplitude >2 mm was 79% sensitive and 88% specific for detecting ischemic RV dysfunction, and there was a close correlation between stress-induced change in RV systolic amplitude and change in CO in patients (r = 0.56, p <0.001). Early diastolic velocity increased in controls (from 10.8 +/- 3.2 to 13.1 +/- 3.6 cm/s, p <0.01) but did not change in patients (from 11.5 +/- 3.7 to 11.3 +/- 4.8 cm/s, p = NS). RV shortening after ejection did not appear in any control subject but did develop in 8 of 33 patients, thus contributing to the decrease in RV peak early/late diastolic velocity ratio in patients (from 1.1 +/- 0.3 to 0.76 +/- 0.4, p <0.001) compared with that in controls (1.3 +/- 0.3 to 1.0 +/- 0.2, p <0.001). In conclusion, markers of RV dysfunction are not related to left ventricular wall motion score index or long-axis changes with stress.

Fluid Dynamics in Airway Bifurcations: III. Localized Flow Conditions

Localized flow conditions (e.g., backflows) in transition regions between parent and daughter airways of bifurcations were investigated using a computational fluid dynamics software code (FIDAP) with a Cray T90 supercomputer. The configurations of the bifurcations were based on Schreck's (1972) laboratory models. The flow intensities and spatial regions of reversed motion were simulated for different conditions. The effects of inlet velocity profiles, Reynolds numbers, and dimensions and orientations of airways were addressed. The computational results showed that backflow was increased for parabolic inlet conditions, larger Reynolds numbers, and larger daughter-to-parent diameter ratios. This article is the third in a systematic series addressed in this issue; the first addressed primary velocity patterns and the second discussed secondary currents.

Fluid Dynamics in Airway Bifurcations: I. Primary Flows

The subject of fluid dynamics within human airways is of great importance for the risk assessment of air pollutants (inhalation toxicology) and the targeted delivery of inhaled pharmacologic drugs (aerosol therapy). As cited herein, experimental investigations of flow patterns have been performed on airway models and casts by a number of investigators. We have simulated flow patterns in human lung bifurcations and compared the results with the experimental data of Schreck (1972). The theoretical analyses were performed using a third-party software package, FIDAP, on the Cray T90 supercomputer. This effort is part of a systematic investigation where the effects of inlet conditions, Reynolds numbers, and dimensions and orientations of airways were addressed. This article focuses on primary flows using convective motion and isovelocity contour formats to describe fluid dynamics; subsequent articles in this issue consider secondary currents (Part II) and localized conditions (Part III). The agreement between calculated and measured results, for laminar flows with either parabolic or blunt inlet conditions to the bifurcations, was very good. To our knowledge, this work is the first to present such detailed comparisons of theoretical and experimental flow patterns in airway bifurcations. The agreement suggests that the methodologies can be employed to study factors affecting airflow patterns and particle behavior in human lungs.

Effect of Pubic Symphysiodesis on Pelvic Development in the Skeletally Immature Greyhound

To evaluate the effect of pubic symphysiodesis (PS) on pelvic development in skeletally immature dogs. Prospective randomized clinical trial. Eight 4 month-old, sexually intact female Greyhounds. Initial PS was performed at 4 months of age using a powered stapling device. Because of failure of the initial surgery, a second PS was performed 1 month later by resecting the pubic symphysis with a rongeur followed by placement of handmade bone staples in four dogs. Sham PS was performed in four control dogs at 4 months of age. Pubic growth rate and pelvic development were evaluated using standard plane radiography and computed tomography. Specific measurements included acetabular ventroversion, Norberg angle, lateral center-edge angle, and pelvic inlet dimensions. Hip distraction indices were determined as well. PS at 4 months of age using a stapling device failed. Pubic symphysiodesis using hand made staples was successful at 5 months of age and did not result in any clinically significant intraoperative or postoperative complications. Pubic symphysiodesis markedly decreased pubic symphysis growth in the treatment group. Hip distraction indices and pelvic inlet circumference, area, and width significantly decreased in treated dogs compared to those in the control group. Acetabular ventroversion was significantly increased in treated dogs compared to those in the control group. PS decreases pelvic canal size, increases acetabular ventroversion, and does not appear to have any clinically significant complications. PS performed in skeletally immature dogs with hip dysplasia may provide an effect similar to a triple pelvic osteotomy and warrants further investigation.

Relationship between scooping of the ventricular septum, morphology of the inferior bridging leaflet and electrocardiographic findings in atrioventricular septal defect with common valvar orifice

AbstractWe described previously that the degree of deficiency of the ventricular septum (scooping) affects electrocardiographic findings in atrioventricular septal defect with separate right and left atrioventricular orifices. The aim of this study was to clarify the clinicomorphological relationships of the degree of scooping, the precise morphology of the atrioventricular valve, and electrocardiographic findings in hearts having a common atrioventricular orifice. In 63 patients with usual atrial arrangement, the outlet, scoop and inlet dimensions of the ventricular septum were measured by biplanar cineangiography and were compared with the body surface area. The scoop/outlet ratio and inlet/outlet ratio were also compared with the body surface area, atrioventricular valvar morphology, electrocardiographic findings, and severity of regurgitation of the atrioventricular valve. The results showed that the three individual dimensions of the septum correlated significantly with the body surface area, even though the scoop/outlet ratio and inlet/outlet ratio did not. A correlation was found between the scoop/outlet ratio and the degree of left axis deviation on the electrocardiogram (r=0.74, p&lt;0.001). In 16 patients with division of the inferior bridging leaflet, there was a lower scoop/outlet ratio than in the remaining 37 with an undivided bridging leaflet (p&lt;0.01). Of 24 patients with counterclockwise rotation in the horizontal loop of the vectorcardiogram, 22 had an undivided inferior bridging leaflet (p&lt;0.01). The morphology of the superior bridging leaflet, in contrast, was not associated with the scoop/outlet ratio, and neither was the severity of valvar regurgitation. We conclude that the degree of scooping of the ventricular septum is related not only to electrocardiographic findings, but also to the morphology of the inferior bridging leaflet in atrioventricular septal defect with common atrioventricular orifice.

The degree of scooping of the interventricular septum influences electrocardiographic findings in atrioventricular septal defect

AbstractThe aim of this study was to clarify those morphological features and hemodynamic stress factors which influence the electrocardiographic findings in atrioventricular septal defect. In 64 patients with the incomplete form of atrioventricular septal defect (separate valvar orifices) with usual atrial arrangement, the length from the left ventricular apex to the aortic valve (outlet dimension), to the so-called cleft (scoop dimension), and to the lowest point of the left atrioventricular valve (inlet dimension) were measured by biplanar cineangiography. The size of the ostium primum defect, the ventricular pressure ratio, and the pulmonary/systemic flow ratio were also evaluated. The results showed that the lower the scoop/outlet ratio (r=0.60, p&lt;0.001), or the higher the ventricular pressure ratio (r= −0.55, p&lt;0.001), the more deviated to the left and superior was the mean frontal QRS axis. These factors also had significant correlation with the QRS patterns in the Frank vectorcardiogram. We conclude that the scoop/outlet ratio, supposedly reflecting the degree of scooping of the interventricular septum, is one of the most significant factors which influence the electrocardiographic findings in atrioventricular septal defect.

Microcomputer technique for optimum design of centrifugal pumps

A microcomputer technique is devised for the selection of the optimum design of centrifugal pumps. It gives full information about data, such as pumping speed, power requirements, impeller outlet and inlet dimensions, casing throat area and cavitation limits. It can be used as an effective tool in the study of the parameters governing the characteristics of pump performance, such as suction head for maximum lift and shut valve to manometric head ratio for stability at large demand fluctuations and load variations. When tested in designing an actual pumping unit, for a specified duty, the technique yielded good results and proved to be valid, reliable, and easy to use.

Feed Rate of a Rotary Feeder

The revolution characteristic of feed rate of a rotary feeder is examined theoretically and experimentally when back pressure is not applied to the feeder outlet. The revolution giving the maximum feed rate is dependent on the inlet dimension, the total volume of wheel rooms and the number of wheel rooms of the feeder and on the relaxation time of solid particle. For solids having large relaxation time the maximum feed rate becomes independent of the relaxation time. Discrepancy between experimental results and a theory is largely due to irregular outflow of solids from a hopper to the feeder inlets.

TIDE-INDUCED MASS TRANSPORT; A FLUSHING MECHANISM FOR SHALLOW LAGOONS

Based on the one-dimensional long wave equations a discussion of the physics underlying the tide-induced mass transport in lagoons is presented. It follows from the dynamic equation that the bottom stress associated with the mass transport serves to balance the gradient of the radiation stress and the net bottom stress associated with the (tidal) waves. The mass transport is at best of 0(a/h) (a = tidal amplitude, h = depth). It is shown that inlets can play an important role in the mass transport and that by properly selecting the inlet dimensions that mass transport can be considerably increased. Numerically computed values show that the tide-induced mass transport can be an important mechanism in renewing the waters of shallow lagoons.

TIDE-INDUCED MASS TRANSPORT IN LAGOON-INLET SYSTEMS

This paper examines the tide-induced net discharge in lagoon-inlet systems. In particular, attention is given to the role inlets play in inducing a steady current. The flow in the lagoon is described by the one-dimensional long wave equations, the flow in the inlets is described by a semi-empirical equation. Both numerical and analytical techniques are employed to solve for the net discharge. The results of the study indicate that 1) the net discharge can be significant provided the tidal amplitude to depth ratio is not small 2) the net discharge can be considerably increased by the proper selection of the inlet dimensions.

The effect of varying inlet geometry on the collection characteristics of a 10-millimeter nylon cyclone.

Inlet dimensions of the 10-mm nylon cyclone are such that at a 2-liter/min sampling rate particles of 1- to 10-μm aerodynamic equivalent diameter (AED) may not be representatively sampled. Samples of a coal dust aerosol were collected simultaneously with two filter holders: one designed to sample representatively 1- to 10-μm AED particles at 2 liters/min in calm conditions, and one with smaller inlet dimentions corresponding to those of the 10-mm nylon cyclone. No differences in mass concentration or size distribution were observed. Standard 10-mm nylon cyclones were modified to conform to theory by installing entries of plexiglas and aluminum. A coal dust aerosol with 3.3-μm geometric mean AED was simultaneously sampled with modified and unmodified cyclones. Differences in the mass concentration of respirable dust collected were observed with the plastic entries and were attributed to pairticle deposition within the entry caused by static charge. No differences were observed with the aluminum entry.