Circular Obstruction Research Articles

Efficacy for aspiration prevention through thickening of liquid foods evaluated using a swallowing model apparatus

Abstract An apparatus simulating the swallowing process of liquid foods was constructed using a flow channel. In the channel, a circular cylindrical obstruction was fixed to serve as an epiglottis in the mesopharynx. The apparatus was designed with an adjustable gate for flow control to represent the processes of healthy swallowing and dysphagia. The parameters considered were the holding time and flow resistance controlled by the gate, which were assumed to indicate the swallowing reflex and power, respectively. When a Newtonian liquid with relatively low viscosity was used, the flow experiment performed using the apparatus under conditions of shorter holding time and larger flow resistance successfully reproduced a phenomenon similar to aspiration in a patient with dysphagia. In addition to a Newtonian liquid with high viscosity, non-Newtonian liquids thickened to various concentrations using commercially available thickeners were used. In flow experiments with these test liquids, the efficacy for aspiration prevention was inferred based not only on the viscosity of the liquid but also its elasticity, depending on its viscosity.

Flow manipulation of a nematic liquid crystal in a Hele-Shaw cell with an electrically controlled viscous obstruction

The flow of a nematic liquid crystal in a Hele-Shaw cell with an electrically controlled viscous obstruction is investigated using both a theoretical model and physical experiments. The viscous obstruction is created by temporarily electrically altering the viscosity of the nematic in a region of the cell across which an electric field is applied. The theoretical model is validated experimentally for a circular cylindrical obstruction, demonstrating user-controlled flow manipulation of an anisotropic liquid within a heterogeneous single-phase microfluidic device.

Empagliflozin in children with glycogen storage disease-associated inflammatory bowel disease: a prospective, single-arm, open-label clinical trial

Glycogen storage disease type Ib (GSD-Ib) is a rare inborn error of glycogen metabolism caused by mutations in SLC37A4. Patients with GSD-Ib are at high risk of developing inflammatory bowel disease (IBD). We evaluated the efficacy of empagliflozin, a renal sodium‒glucose cotransporter protein 2 (SGLT2) inhibitor, on colonic mucosal healing in patients with GSD-associated IBD. A prospective, single-arm, open-label clinical trial enrolled eight patients with GSD-associated IBD from Guangdong Provincial People's Hospital in China from July 1, 2022 through December 31, 2023. Eight patients were enrolled with a mean age of 10.34 ± 2.61 years. Four male and four female. The endoscopic features included deep and large circular ulcers, inflammatory hyperplasia, obstruction and stenosis. The SES-CD score significantly decreased at week 48 compared with before empagliflozin. Six patients completed 48 weeks of empagliflozin therapy and endoscopy showed significant improvement or healing of mucosal ulcers, inflammatory hyperplasia, stenosis, and obstruction. One patient had severe sweating that required rehydration and developed a urinary tract infection. No serious or life-threatening adverse events. This study suggested that empagliflozin may promote colonic mucosal healing and reduce hyperplasia, stenosis, and obstruction in children with GSD-associated IBD.

On drag and lift coefficient computations by using hybrid meshing of physical domain rooted with regular obstacles

The study of drag and lift forces on natural or manmade physical objects in confined domains owns both practical and theoretical importance in the field of general sciences, which particularly includes physical science. In this regard, this work is the numerical effort to examine drag and lift coefficients for the moving liquid stream at a low Reynolds number in the Convergent–Divergent (CD) channel. The liquid stream flows with the parabolic profile from the inlet and interacts with the case-wise infinite cylinders as barriers in the right vicinity of CD throat. The differential formulation is designed toward CD channel for the flow area, and the numerical solution is stated using the hybrid meshed finite element method. The contour and line graph analysis was conducted for a greater understanding of the involved flow variables. The comparative analysis is enclosed by setting a fixed Reynolds number for the hydrodynamic forces against mounted obstacles in a CD throat. It is seen that the square-shaped cylinder experienced the greater drag force as compared to the circular obstruction.

Heat Transfer Enhancement for Internal Flows with a Centrally Located Circular Obstruction and the Impact of Buoyancy

Numerical simulations have been carried out for gas flow through a horizontal pipe. Accounting is made of buoyancy effects, changes to the thermophysical properties, and the presence of a blockage. It was found that for low-to-moderate Reynolds numbers, the combined effects on heat transfer and pressure loss lead to an improved performance with the obstruction. On the other hand, the influence of heating on properties is shown to have a significant effect on the Nusselt number in both the laminar and the turbulent regions. Property variations increase the laminar Nusselt number and decrease the turbulent values. The results also show that a blockage has a much bigger impact on laminar flows than on turbulent flows and can inhibit downstream buoyant motion and convective heat transfer.

460 Alianza Barbed Pharyngoplasty in Moderate to Severe OSAS Patients

Abstract Introduction Alianza barbed pharyngoplasty is a recent non-resective surgical tecnique, indicated for patients with obstructive sleep apnea syndrome (OSAS) with circular retropalatal obstruction pattern. It has the aim of stabilizing and reducing the collapsibility of the palato-pharyingeal area during sleep. It uses barbed absorbable sutures that allow to suspend palato-pharyngeal structures to anatomical non-collapsable landmarks (posterior nasal spine, pterigoideal hamulus, pterigomandibular raphe). The aim of this study is to evaluate efficacy and safety of Alianza barbed pharyngoplasty in moderate to severe OSAS. Methods Thirty-six consecutive patients with moderate to severe OSAS underwent Alianza barbed pharyngoplasty. Preoperatively all patients presented with palatal hypertrophy, concentric collapse and retropalatal flatter during drug induced sleep endoscopy (DISE) and did not tolerate CPAP and/or MAD therapies. All patients underwent clinical examination, polysomnography, and subjective evaluation of snoring with visual analogue scale (VAS) and Epworth Sleepiness Scale (ESS) both pre-operatively (T0) and at 6 months postoperatively (T1). Results There was a significant reduction of AHI at T1, from 32.49 ± 14.55 to 12.1 ± 12.16 (p< 0.05) of AHI. Mean AHI gain was of 20.39 ± 11.58, in particular 13.34 ± 5.48 in moderate OSAS patients and 30.18 ± 9.34 in severe OSAS patients. There was also a significant ODI reduction, from 27.57 ± 15.68 to 12.97 ± 13.25 (p< 0.05). There was a significant reduction of ESS, from 8.75 ± 4.51 to 4.05 ± 2.39 (p< 0.05) and a significant reduction of snoring VAS from 7.85 ± 1.23 to 3.2 ± 1.7 (p< 0.05). Conclusion Alianza barbed pharyngoplasty led to significant improvement both in objective parameters measured with polysomnography (AHI and ODI), and in subjective parameters (ESS and snoring VAS) in moderate to severe OSAS patients. Support (if any):

Domain walls in vertically vibrated monolayers of cylinders confined in annuli

Liquid-crystalline ordering in vertically vibrated granular monolayers confined in annuli of different sizes is examined. The annuli consist of circular cavities with a central circular obstruction. In the absence of the central obstruction cylinders of low aspect-ratio exhibit tetratic order, except for the existence of four defects which restore the symmetry broken by the circular confinement. This behaviour is demanded by topology in systems with strong anchoring properties at the surface. By contrast, topology dictates that the annular geometry is compatible with a distorted tetratic phase without point defects. However, the effect of restricted geometry and limited size on phases possessing finite anchoring energy at the wall and elastic stiffness leads to different configurations, showing finite ordered regions separated by domain walls. We argue that highly packed nonequilibrium vibrated granular monolayers respond to geometrical frustration and extreme confinement as corresponding equilibrium systems of particles do, and that the former can be analysed in terms of surface free energies, elastic distortions and defects, much as equilibrium liquid crystals. Therefore, selective confinement of vertically-vibrated monolayers of rods could be used with advantage as a new tool to study the creation and dynamics of various types of defects in ordered systems.

Enhancement of axial force of optical tweezers by utilizing a circular stop at the back focal plane of the objective

Optical tweezers are indispensable force spectroscopes. The trap stiffness and the linear force range of the instrument determine the working force range of the instrument. Here we show both theoretically and experimentally that utilizing a circular obstruction at the back focal plane of the objective can significantly increase the maximum linear force. For instance, utilizing a disk with an obstruction ratio of 0.773 could increase the maximum linear force by a factor of ∼39 when a 3.4 μm polystyrene bead is trapped. We also show that this simple beam shaping method can significantly improve the maximum applicable force per unit power of the laser entering the objective lens.

Thermal Analysis of a Commercial Plate Fin Heat Exchanger With Nonuniform Inlet Flow Conditions

In studies using computational fluid dynamics software, very often a uniform air stream is applied as an inlet boundary condition of a heat exchanger. In actual applications, however, the inlet flow conditions are not uniform. Therefore, the effect of nonuniformities on the thermal performance is characterized in a wind tunnel for a commercially available plate water/air heat exchanger. Three nonuniform flow conditions are investigated. The heat exchanger is 275 mm wide and 295 mm high. Three nonuniformities are created by placing a plate 10 cm upstream of the heat exchanger: The first one covers the right-hand side of the heat exchanger, the second one covers the top half of the heat exchanger, and the last obstruction consists of a circular hole of 150 mm diameter in the middle of a plate. Only the circular obstruction has a significant influence on the heat transfer rate: The external convective resistance is up to 25% higher compared to the uniform case. The measurement results presented in this study can be used by other researchers to validate numerical simulations with nonuniform inlet conditions.

Numerical study of the heater length effect on the heating of a solid circular obstruction centered in an open cavity

The steady vortex formation and thermal behavior in a two-dimensional square ventilated cavity is numerically studied. The governing equations of mass, momentum and energy are solved with a finite element method combined with an operator splitting scheme. We analyze the flow occurring inside the enclosure with a centered circular obstruction and a heater plate located at the center of the lower wall of the cavity. The size of the heater is varied for five different lengths. The simulations are obtained for Richardson and Prandtl numbers of 0.01 to 10.0 with a Reynolds number of 400. Results are reported in the form of streamlines, isotherms, average Nusselt number, average bulk fluid and obstruction temperatures. The effects of the heater length, Richardson number and Prandtl number on the hydrodynamics and thermal behavior have been investigated. Four vortex formation mechanisms are identified: (a) the inertial effect of the inlet jet which moves from the lower left sidewall to the upper right sidewall, (b) the detachment of the boundary layer from the wall located above of the entrance of the cavity and from the obstruction, (c) the rolling up of the fluid when this meets with the corners of the cavity and (d) the thermal boundary layer formed on the heater which originates a thermal plume with instabilities traveling upward. It is observed that for low Prandtl numbers with large heater sizes and high Richardson numbers the temperature of the obstruction is increased.

An efficient method for the incompressible Navier–Stokes equations on irregular domains with no-slip boundary conditions, high order up to the boundary

Common efficient schemes for the incompressible Navier–Stokes equations, such as projection or fractional step methods, have limited temporal accuracy as a result of matrix splitting errors, or introduce errors near the domain boundaries (which destroy uniform convergence to the solution). In this paper we recast the incompressible (constant density) Navier–Stokes equations (with the velocity prescribed at the boundary) as an equivalent system, for the primary variables velocity and pressure. equation for the pressure. The key difference from the usual approaches occurs at the boundaries, where we use boundary conditions that unequivocally allow the pressure to be recovered from knowledge of the velocity at any fixed time. This avoids the common difficulty of an, apparently, over-determined Poisson problem. Since in this alternative formulation the pressure can be accurately and efficiently recovered from the velocity, the recast equations are ideal for numerical marching methods. The new system can be discretized using a variety of methods, including semi-implicit treatments of viscosity, and in principle to any desired order of accuracy. In this work we illustrate the approach with a 2-D second order finite difference scheme on a Cartesian grid, and devise an algorithm to solve the equations on domains with curved (non-conforming) boundaries, including a case with a non-trivial topology (a circular obstruction inside the domain). This algorithm achieves second order accuracy in the L ∞ norm, for both the velocity and the pressure. The scheme has a natural extension to 3-D.

Effect of Reynolds and Prandtl Numbers on Mixed Convection in an Obstructed Vented Cavity

A numerical investigation is conducted to analyze the steady flow and thermal fields as well as heat transfer characteristics in a vented square cavity with a built-in heat conducting horizontal solid circular obstruction. Hydrodynamic behavior, thermal characteristics and heat transfer results are obtained by solving the couple of Navier-Stokes and energy equations by using a weighted residuals Finite element method. The computation was made for different Reynolds number, Prandtl number ranging from 50 to 200 and from 0.71 to 7.1 at the three different convective regimes. Three different regimes are observed with increasing Ri: forced convection (with negligible free convection), mixed convection (comparable free and forced convection) and free convection dominated region (with higher free convection). The results are presented to show the effects of the Reynolds number, Prandtl number on flow pattern, thermal field and heat transfer characteristics at the three convective regimes. It is found that the flow and thermal field strongly depend on the Reynolds number, Prandtl number as well as Richardson number. As the Reynolds number and Prandtl number increase, the heat transfer rate increases but average fluid temperature in the cavity and temperature at the cylinder center decrease at the three convective regimes.Keywords: Mixed convection; Finite element method; Obstructed vented cavity; Prandtl number.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i2.4344 J. Sci. Res. 3 (2), 271-281 (2011)

Numerical simulation of pedestrian flow past a circular obstruction

In this paper, a revisiting Hughes’ dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to destination, under the consideration of the current traffic conditions and the tendency to avoid a high-density region and an obstruction. An algorithm for the pedestrian flow model is based on a cellcentered finite volume method for a scalar conservation law equation, a fast sweeping method for an Eikonal-type equation and a second-order TVD Runge-Kutta method for the time integration on unstructured meshes. Numerical results demonstrate the effectiveness of the algorithm. It is verified that density distribution of pedestrian flow is influenced by the position of the obstruction and the path-choice behavior of pedestrians.

Formation of speckle images formed for diffusers illuminated by modulated apertures (circular obstruction)

An amplitude modulation of circular aperture is used for the illumination of a numerical object having a randomly distributed function. In this study, a central obstruction for the aperture is assumed. The modulated speckle image is obtained using the MATLAB program and compared with that obtained in the case of an uniform circular aperture for the illumination. We have considered coherent illumination obtained from a laser beam in order to facilitate the computation of the Fourier transform of the defined computed speckle intensity corresponding to this novel aperture. Finally, the autocorrelation function of the randomly distributed object is calculated in all cases.

Wavelength dependent propagation and reconstruction of white light Bessel beams

Bessel beams are propagation invariant light fields. It has very recently been shown that they may be created with temporally incoherent (white) light. Such fields may have applications in low coherence interferometric imaging for biomedicine and optical micromanipulation. White light Bessel beams may be deemed at first glance to generate a white focal line of light at the beam centre due to the absence of chromatic aberration. We investigate the spectral characteristics of the reformation or self-healing of this light field in the presence of a circular obstruction and reveal that the spectral characteristics of the beam generation and reformation results in a dispersive focal line at the beam centre which is 'white' only over a certain region.

Theoretical validation of the respiratory benefits of helium-oxygen mixtures

A theoretical analysis of convective gas transport validates the clinically demonstrated advantage of using helium-oxygen mixtures in treating patients with respiratory problems. Previous studies have attributed that advantage to the ability of helium-oxygen to stay laminar at higher velocities than nitrogen-oxygen. The present work shows that helium-oxygen does not need to be laminar to provide higher flow rates and that its benefits persist under turbulent conditions. The analysis is applied to steady flow through the lungs and through a circular airway obstruction. A simplified model of the lungs gives pressure-flow relations that show a significant increase in oxygen flow rate when nitrogen is substituted by helium. A similar improvement is found for flow through an obstruction. For a given pressure difference across the lungs or across an obstruction, the turbulent flow rate of oxygen increases by approximately 50% when nitrogen is replaced by helium in a mixture containing 20% oxygen.

An algorithm for the shallow water equations with body fitted meshes

An efficient algorithm based on flux difference splitting is presented for the solution of the two-dimensional shallow water equations in a generalised coordinate system. The scheme is based on solving linearised Riemann problems approximately and in more than one dimension incorporates operator splitting. The scheme has good jump capturing properties and the advantage of using body-fitted meshes. Numerical results are shown for flow past a circular obstruction.

Electron wavelike behavior: A historical and experimental introduction

Following the Fresnel theory of light and the consequent scientific debate that his formulation generated, two key experiments with electrons, diffraction by means of a circular hole and a circular obstruction, have been realized to show the existence of the Fresnel zones and of the so-called ‘‘Poisson spot.’’ The basic arguments concerning the quantum mechanical nature of electrons can be introduced by taking advantage of the vivid impression stimulated by the experimental images.

The spot of Arago: New relevance for an old phenomenon

The ‘‘spot of Arago’’ has been a controversial topic since its inception in 1818 when Poisson predicted its existence in an attempt to discredit Fresnel’s wave theory of light. Arago performed the experiment and found the surprising prediction was true, thus putting Fresnel’s theory on a firm technical foundation. In recent years, the spot of Arago, which exists as a bright spot at the center of the geometrical shadow of a circular obstruction, has caused substantial grief in various high-energy laser applications and has come to be considered more of a nuisance than a curiosity. This paper suggests that the size and shape of the spot of Arago is characteristic of the wave-front aberrations of the incident beam and can therefore be used to advantage as a beam sample for wave-front analysis of annular beams. The implementation of this wave-front sampling scheme would eliminate the requirement for a special beam-sampling optical component and thus reduce to a minimum the deleterious effects upon the beam frequently accompanying the use of such components. Both experimental and numerical results are presented along with a discussion of the capabilities and limitations of this particular beam sample for diagnostic purposes.

An experimental study of the effects of upstream obstructions upon subsonic jet noise

Results obtained for noise produced by two obstructions—one circular (1 inch diameter x 2·84 inch long) and another rectangular (0·4 inch thick x 1 inch wide x 2·84 inch long) in shape—immersed in both “clean” and turbulent flows 4·8 inches upstream of the nozzle exit are described. Variations of overall sound pressure levels (OASPL's) and power Watt levels (PWL's) with jet exit velocity (Vj) and the directivities of OASPL's are considered in detail. Considerable care was taken to ensure that any comparison of the obstruction generated noise with the “clean” jet noise is for the same mean jet exit velocity and thrust. The mean jet exit velocity was derived from the measured velocity profile at the nozzle exit in each case. For the same mean exit velocity and nozzle diameter, the noise levels with the circular obstruction were measured to be as much as 40 dB higher than the “clean” jet noise. The rectangular obstruction increased the noise by up to 10 dB. Flow over these obstructions generated discrete tones as well. The velocity index for the obstruction generated noise were between 8 and 9 between Vj=350 ft/s and 1000 ft/s. This contradicts the traditional V6 law. The main reason for the discrepancy has been attributed to the variation of the coefficient of fluctuating lift, C L 2 ¯ , with Reynolds number. The angle of peak overall sound pressure levels (OASPL's) was between 45° and 60°, as compared to between 0° and 20° for the clean jet noise. When the obstructions were immersed in turbulent flows most of the discrete tones which were obtained from the obstructions in smooth flows disappeared. The high frequency noise levels, however, increased by as much as 20 dB.