Cross Section Of Tube Research Articles

Inertial focusing of red blood cells in square tube flows

Red blood cells flowing through square capillary tubes were observed to migrate towards four points located on the diagonal in the tube cross-section, owing to their deformability and inertia.

Excitation of pipe bending modes by internal pressure: A phenomenon present in refrigerators with skin condenser

The concept of skin condenser refrigerators has been increasingly explored for its capacity to provide a larger internal cabinet volume. However, the discharge pulsation of the cooling gas has become a significant source of noise because it directly excites the cabinet. This paper analyzes the mechanisms of cabinet vibration excitation by gas pulsation in the condenser tubes. Initial tests were performed with vibration measurements on a refrigerator and on segments of the cabinet excited by pulsation only. The results showed that bending modes of cabinet segments were excited by the pulsation in the condenser tube. A theoretical analysis showed that asymmetry in the condenser tube cross section is responsible for bending moment generation and numerical evaluations confirmed this effect for different types of asymmetries.

Biomedical simulations of nanoparticles drug delivery to blood hemodynamics in diseased organs: Synovitis problem

PurposeSynovial fluid is an ultra-viscous plasma filtration that lubricates joint movement. During acute accidents or a cartilage repair surgical intervention, blood is introduced into the joint and mixed with variable amounts of synovial fluid. The hypothesis of this study was that mixing the blood with the synovial fluid, forming a mixture of them, can change the rheological properties of the blood and the mechanical properties of the stenosis formed. Design/methodology/approachIn this work we have presented a theoretical study to a mixture of synovial and blood nanofluid with heat distribution, concentration and volume fraction effects through concentric tube when the outer tube contain stenosis. Two models of synovial fluid that depend on viscosity are debated, in model I the viscosity depend exponentially on the concentration while model II shear tensor is considered as a function of concentration. The mathematical model has been studied in cylindrical coordinates. The solution of mathematical model was also obtained numerically using finite difference method after using a domain transformation to transform the variable cross-section of the concentric tube to a uniform cross section. We approaches to the synovial fluid improves the velocity of blood in the areas of atherosclerosis due to the nature of synovial fluid, which has less friction forces. Also, the velocity of mixture blood and synovial for model I is higher than that for model II. Realistic implicationsThis problem with synovial lining is called synovitis. Originality/valueTo the authors’ information, no such research has been performed in the literature.

On the computer simulation of the forced vibration characteristics of the microtubes using a couple of von-Kármán and modified couple stress theories

The present article investigates the forced vibration behavior of axially functionally graded (AFG) tubes under external dynamic load using a pair of Euler-Bernoulli and von-Kármán equations in combination with the modified couple stress theory. The Hamilton principle is used to obtain the linear and nonlinear partial differential (PD) governing equations and the boundary conditions. Functionally graded materials (FGMs) are utilized to produce tube constructions that alter gradually throughout the length of the tube. The cross-section of the cylindrical tube was considered to be nonuniform throughout the tube length, and the porosity distribution in the radius direction was assumed to be nonuniform, resulting in the bi-directional material characteristics function. In order to solve the nonlinear motion equation, the generalized differential quadrature method (GDQM) was connected to the iteration technique. Following that, the computed linear and nonlinear results are thoroughly explained in order to explore the different effects on the resonance, natural frequency, and dynamic deflection.

Dependence of the Piezoelectric Micropump Operating Mode on Its Geometry

A mathematical and computer axisymmetric models in which periodic oscillations of ring piezoelectric actuators placed on an elastic tube of circular cross-section leads to radial deformations of the tube is constructed. The result of these displacements is a local compression of the microchannel, which leads to changes in its volume and the corresponding pushing of the fluid. If a non-symmetrical oscillation scheme is used, the average fluid flow over the period will be non-zero and the device can be used as a micropump. The aim of the work is a computer study of the geometric features of an axisymmetric piezoelectric micropump, taking into account the processes of heat transfer by a fluid in the channel. The dependence of the average fluid flow rate on the channel parameters and the frequency of oscillations of the piezoelectric actuators is determined by the method of factorial experiment. The parameters preventing heat backflow have been determinate, which makes it possible to use a device for supplying coolant to a microgripper cooling system.

Estimation of local heat flux for turbulent flow in a helical coil tube by conjugate gradient method

Estimation of local heat flux is challenging in a helical coil tube heat exchanger due to the complex flow field developed by tube curvature. The heat flux has uneven distribution in the angular direction of the tube cross-section. The current research aims to estimate the local heat flux at the fluid-solid interface for the turbulent flow of water in a helical coil tube by solving the inverse heat conduction problem (IHCP). Conjugate gradient method (CGM) with an adjoint problem is used as an inverse algorithm. First, the commercial CFD software ANSYS FLUENT is used for solving the governing equations of continuity, momentum, and energy for turbulent flow to obtain the heat flux at the fluid-solid interface. This heat flux is used to determine the temperature distribution at the outer surface of the tube. The heat flux is then considered unknown and it is estimated by CGM algorithm with the developed in-house code in MATLAB. The result shows that the estimation of heat flux by CGM is very accurate.

Dual-effect evaluation of heat transfer deterioration of supercritical carbon dioxide in variable cross-section horizontal tubes under heating conditions

Heat transfer characteristics analysis of supercritical carbon dioxide (sCO2) in variable cross-section tubes is critical for its promotion and application. This paper proposed three horizontal heat exchange tubes, i.e., straight tube, converging tube, and diverging tube. On this basis, we used numerical simulation to analyze the convective heat transfer performance of sCO2 in the horizontal tube with variable cross-section under heating conditions. The diverging tube effectively enhances the overall heat transfer performance compared with the uniform cross-section tube, and the heat transfer rate is increased by 19.26% compared with that of the straight tube. In contrast, the converging tube weakens the heat transfer ability. Moreover, we proposed quasi-air film and eddy blockage concepts to reveal the fluid's heat transfer deterioration mechanism near the top bus. Wherein the quasi-air film is full of sCO2, which has a low thermal conductivity close to that of air at room temperature, and generates near the top bus. Besides, the criterion factor, But was proposed by double corrections of density and temperature for judging the occurrence of eddy blockage, and the Nu-based evaluation shows that the eddy blockage can deteriorate the heat transfer performance at the top of the horizontal tube by 17%. The physical mechanism of heat transfer deterioration under the heating condition is clarified by the dual-effect of quasi-air film and eddy blockage on this account.

Design assessment of a horizontal shell and tube latent heat storage system: Alternative to fin designs

In the present study, the charging and discharging performances of a horizontal shell and tube latent heat storage (LHS) system are analysed. The effective heat capacity approach is adopted to develop a numerical model using sodium nitrate as the phase change material (PCM) and air as the heat transfer fluid (HTF). The study proposes design alternatives to conventional shell and tube LHS systems by varying the PCM volume distribution and the surface area of heat transfer along the length. A novel design methodology is proposed, wherein, the outer shell of the LHS system is optimized into a cone and the cross-section of the HTF tube is varied. Based on the optimal shell dimensions, seven different designs having cylindrical/converging conical/diverging conical shells and cylindrical/converging/diverging cross-sections of the inner HTF tube are developed for a fixed PCM volume and heat transfer surface area. The LHS system with converging shell and converging cross-section HTF tube is found to have optimal performance with 37% and 47.3% reduction in charging and discharging times over the conventional cylindrical shell and tube system. The system is also compared with a fin and non-finned cylindrical shell and tube system at different inlet charging and discharging temperatures. The melting and solidification contours and melt fraction plots show a more uniform rate of natural convection and conduction heat transfer along the length of the proposed optimal design which is projected as an alternative to longitudinal fin design due to similar charging/discharging performances.

A theoretical study of condensation heat transfer in tubes with novel cross-sections

This paper presents a numerical study of stratified flow condensation heat transfer in tubes with novel cross-section designs. A design framework of the novel cross-section geometry was developed by first studying and analyzing the condensate film distribution in a circular tube. It was found that the circular arc diameter and orientation have effects on the condensate film thickness. Based on this understanding, four different cross-section designs (models N1, N2, N3 and N4) formed by connecting circular arcs of different curvatures at various orientations were proposed. The heat transfer performances of these models were compared to a circular tube of the same perimeter. Our simulations show that all models possess higher average heat transfer coefficients than a circular tube when no accumulated condensate layer is present. Among all the models proposed, model N4 exhibits the largest heat transfer enhancement ratio of 1.42 at ∊ = 0.96. The design of model N4 utilizes small circular arcs which are arranged in an orientation that increases the effect of the gravitational force, providing significant condensate film thickness reduction over a large area. This study not only demonstrates the possibility of enhancing condensation heat transfer by simply varying the tube curvature but also provided a design guideline which can be employed for the development of novel cross-section tubes that can be fabricated by advanced manufacturing techniques such as selective laser melting.

RELIABILITY ANALYSIS OF AXIAL BEARING CAPACITY OF CONCRETE FILLED STEEL TUBULAR STUB COLUMNS WITH DIFFERENT CROSS SECTIONS BASED ON SIMPLIFIED FOURTH-MOMENT METHOD

A new point estimate method and a simplified fourth-moment method are used to analyze the reliability of bearing capacity formula (proposed by Ding Faxing) of concrete-filled steel tubular stub columns (CFST) under axial compression considering the shape constraint coefficient of different steel tube cross sections. The influences of different section shapes, different strengths of concrete and steel, two load combinations and different load ratios on the reliability index are considered. The results show that: the reliability indexes of the bearing capacity formulas of CFST with different cross sections are higher than 3.7, which meets the requirements of target reliability index of 3.2; When the ratio of office live load to dead load is 1.0, the higher the concrete strength, the larger the reliability index.

Seismic behavior of a novel beam to reinforced concrete-filled steel tube column joint

This paper presents an experimental investigation of a novel beam to reinforced concrete-filled steel tube (RCFST) column joint. Four beam-to-RCFST-column specimens, varying with a cross-section of middle steel tube (250 × 250 × 6, 300 × 300 × 9, 350 × 350 × 12) and transfer sleeves (with or without), were tested under the cyclic loading to clarify the main seismic indicators, such as failure modes, hysteretic performances, stiffness degradation, strength degradation, energy dissipation capacity and the strain responses of the novel beam-to-RCFST-column joint. The hysteretic curves of the tested beam-to-RCFST-column joint show obvious pinch phenomena because of the slip around the transfer sleeve. Transfer sleeve is the key factor to affect the strength of the tested beam-to-RCFST-column joint. The finite element analysis (FEA) shows a reliable prediction of mechanical properties and failure modes.

Analytical and numerical study for oscillatory flow of viscoelastic fluid in a tube with isosceles right triangular cross section

Abstract A theoretical investigation is carried out to analyze the oscillatory flow of second-grade fluid under the periodic pressure gradient in a long tube of isosceles right triangular cross section in the present study. The analytical expressions for the velocity profile and phase difference are obtained. The numerical solutions are calculated by using the finite difference method with Crank–Nicolson (C–N) scheme. In comparison with the Newtonian fluid (λ = 0), the effects of retardation time, Deborah number and Womersley number on the velocity profile and phase difference are discussed numerically and graphically. For smaller Womersley number, the behavior of second-grade fluid is dominated by viscosity. For larger Womersley number α = 20, the flow becomes more difficult to be generated under periodic pressure gradient with increasing retardation time. Furthermore, the analytical expressions of the mean velocity amplitude and phase difference are given explicitly for discussing.

Numerical investigation of supercritical heat transfer of water flowing in vertical and horizontal tube with emphasis of gravity effect

Over a decade, coal-based thermal power plants are upgraded to operate at supercritical pressure conditions due to its high efficiency and low emissions. Water wall panels of a typical supercritical boiler are structured spirally in the lower furnace and vertically placed in the upper furnace. The spiral tubes are inclined at 19 to 22 degrees in which fluid behaves as in horizontal tubes. The design of water wall panels plays the key role in designing a supercritical boiler. The present work aims to numerically investigate the heat transfer behavior of both vertical and horizontal tubes at the supercritical conditions. Since the temperature distribution across the cross-section of vertical tube is uniform, a 2D axis symmetry tube has been considered for analyzing the vertical tube. Unlike vertical tube, the heat transfer characteristics is different for horizontal tubes. Therefore, a 3D tube has been modelled for the computation of horizontal tubes. In order to gain confidence, the present simulations are validated with experiments results available in the literature. Ansys-Fluent has been used in the present simulation. SST k-ω turbulence model is used in this analysis. In the present work, 10 mm diameter of 4m length of vertical tube has been chosen and simulated at low heat flux to mass flux ratio 0.27 and high heat flux to mass flux ratio 0.67 with pressure 241 bar. The effect of heat flux (q) to mass flux (G) ratio which is responsible for heat transfer enhancement and heat transfer deterioration has been studied for both vertical and horizontal tubes. The wall temperature has been plotted along the length of the tube for both top and bottom portion of horizontal tube and compared with wall temperature of vertical tube. The effect of buoyancy plays a vital role in the heat transfer behavior of horizontal tube compared to vertical tube. Heat transfer deterioration occurs due to buoyancy which has a direct linkage with gravity. Three cases were studied, one with full gravity (factor 1), half gravity (factor 0.5) and zero gravity (factor 0). It has been observed that, sudden rise in wall temperature occurs for the case gravity factor 1.0, i.e, considering the gravity effect. For the case of zero gravity, no sudden peak of local wall temperature is observed due to the absence of buoyancy term in the Navier-Stokes equations. Some of the thermo-physical properties like velocity, turbulent kinetic energy, density, wall temperature and turbulent viscosity are analyzed for three cases.

Experimental Investigation of Heat Transfer of Nanofluid in Elliptical and Circular Tubes

The paper presents experimental comparison of forced convection for steady state turbulent flow of nanofluid (Al2O3-distilled water) inside circular and elliptical (aspect ratio of 0.75) cross section tubes of identical circumference and tube surface area. Convection coefficient, pressure change, and fiction factor were compared at different Reynolds number (3,000-9,230) with different nanoparticles volume concentration (0.5%, 1.0%, and 1.5%). The results showed that Nusselt number increases with increasing Reynolds number and nanoparticle volume concentration. The pressure drops and friction factor of nanofluid are higher than the distilled water and are increasing as the volume concentration increases. Furthermore, the elliptical tube provided small increase in Nusselt number compared to that of circular cross sectional tube. However, the friction factor in the elliptical tube was slightly higher.

Experimental Study and Mechanism Analysis of Concrete-Filled Square Steel Tubular Columns Reinforced by Rhombic Stirrups Under Axial Compression

The square steel tube component has a beautiful appearance, simple joint connection, and it is widely available. However, the uneven distribution of effective constraints in the cross-section of a square steel tube hinders its application. A novel concrete-filled square steel tubular column was tested under axial compression. There were 11 specimens [10 concrete-filled square steel tube columns reinforced with rhombic stirrups with 90-degree internal angle (SSSC specimens) and 1 concrete-filled square steel tube column (SC specimen)]. The load-displacement curves, the law of failure process, failure mode, mechanism analysis, energy consumption, ductility, and stiffness degradation were described, we then investigated the influence of stirrup diameter, stirrup side length, stirrup spacing, steel tube thickness, aspect ratio, and steel ratio on the mechanical properties of the specimens. The results show that the failure process of the SSSC specimens was basically the same. The ultimate failure mode of the specimens with an aspect ratio of 4 was local buckling failure. The specimens with an aspect ratio of 5 and 6 failed due to bending failure in the plastic stage. The steel tube bulged out in different degrees in most of the debonding areas. The longitudinal bars also produced outward bending deformation in the larger bulging area of the steel tube. Some of the stirrups were broken in the later stage of loading. The characteristics of load-displacement curve changed with the changing of stirrup spacing. The strength of longitudinal constraint had an obvious influence on the bearing capacity. In a certain range of steel ratio (ρs = 8.97% ∼ 9.05%), the weakening of the lateral restraint of the stirrup cage had a greater adverse effect on the bearing capacity than the weakening of the effective restraint of the corner. In a certain range of steel ratio (ρs = 8.97% ∼ 9.49%), strengthening the effective corner constraint of stirrups improved the stiffness of the specimen, however, the ductility performance was reduced. The opposite was true for strengthening the lateral constraint of the stirrup cage.

Dispersion of Slow Magnetoacoustic Waves in the Active Region Fan Loops Introduced by Thermal Misbalance

Slow magnetoacoustic waves observed in the solar corona are used as seismological probes of plasma parameters. It has been shown that the dispersion properties of such waves can vary significantly under the influence of the wave-induced thermal misbalance. In the current research, we study the effect of misbalance on waves inside the magnetic-flux tube under the second-order thin-flux-tube approximation. Using the parameters of active-region-fan coronal loops, we calculated wave properties such as the phase speed and decrement. It is shown that neglecting thermal misbalance may be the reason for the substantial divergence between seismological and spectrometric estimations of plasma parameters. We also show that the frequency dependence of the phase speed is affected by two features, namely the geometric dispersion and the dispersion caused by the thermal misbalance. In contrast to the phase speed, the wave decrement primarily is affected by the thermal misbalance only. The dependencies of the phase speed and decrement of the slow wave on the magnetic field and tube cross-section are also analysed.

Theoretical analysis of water absorption kinetics of recycled aggregates immersed in water

Water absorption kinetics of recycled aggregates (RAs) is closely connected with the effective water to cement ratio (w/c), which influences the workability of concrete mixture and the performance of hardened concrete. However, experimental methods are talentless to uncover the detail of the process, especially the initial stage of the water absorption of RAs. In order to explore the mechanism of water absorption of RAs, theoretical analysis is conducted based on the experimental data. Firstly, a non-uniform cross-sectional capillary tube is introduced to investigate the mechanism of water–air displacement in RAs, which are immersed in water. Secondly, based on the Terzaghi capillary water rise model, a theoretical model is established to describe the initial stage of water absorption of RAs. Thirdly, the mechanism of water absorption of RAs during the second stage (slow water absorption stage) is analyzed theoretically. The results show that the process of water absorption of RAs can be divided into two stages: rapid water absorption stage and slow water absorption stage. The rapid water absorption rate during the first stage is caused by the high capillary pressure in small pores and large contact area of RAs with water. The slow water absorption rate during the second stage is mainly caused by two reasons: the bubbles adhered on the surfaces of RAs are not separated timely and the capillary pressure in big pores, which act as the exhaust passage during the first stage, is low.

Magnetic Reconnection in a Sheared Magnetic Flux Tube: Slippage Versus Tearing

AbstractThe process of magnetic reconnection in a flux tube can occur in a time‐stationary fashion as slippage reconnection or in a time‐dependent manner based on, for example, the tearing instability. However, it is not well known under which conditions a system can sustain slippage reconnection. Likewise, it is unclear whether systems can exhibit slippage reconnection and time‐dependent reconnection simultaneously. In order to investigate these questions, we employ a set of 3D magnetohydrodynamic simulation. Using these simulations, we model a twisted flux tube with a spatially localized resistive region in the center of the simulation box, and an applied driver on one end plane of the simulation box. As a result, the Poynting flux injected at the boundary propagates to the resistive region and dissipates there. If the driver is nearly circular, we find a predominance of slippage reconnection, which decouples the applied driver entirely from one half of the flux tube. Second, a tearing‐like instability occurs with slippage reconnection in the resistive region when the resistivity is strong enough and the cross section of the flux tube, as defined by the shape of the applied velocity perturbation, is elliptical enough. In this case we find the surprising feature that magnetic field perturbation generated by the tearing‐like instability radiates away from the resistive region to influence the entire flux tube shape.

“DURYSTA” the first biodegradable sustained release implant for the treatment of open-angle glaucoma

A study for “DURYSTA” in the treatment of open angle glaucoma has been done in this work. A angle between the cornea and iris is open whereas the trabecular meshwork is partially blocked, that obstructs the outflow of aqeous humor and lead to vision loss and damage the optic nurve that is known as open angle glucoma. This model presented the study for outflow of watery clear liquid called aqueous humor from the eye through the trabacular meshwork into the Schlemm's Canal in the human eye. This circular lymphatic-like vessel which is called Canal of Schlemm is modeled as a permeable flexible canal with a trabecular meshwork that keeps it open. Aqueous humor seeps through trabacular meshwork and reaches to Schlemm's canal. The inner wall of the canal is porous and it is considered that between two collecting channels the segment of canal is assumed as a circular cross-section tube. In this model, the flow and pressure characteristics of the aqueous fluid are drawn, and the effect of the main limitations and parameters on these profiles is extracted and explained. The effects of “DURYSTA” on these parameter have also been extracted and shown.

Local behavior near triple point in a laminar two-phase flow in an arbitrary tube cross-section

In this study, we propose a simple approach for examining the local behavior of the velocity and shear stresses in the vicinity of a triple point (TP) in a two-phase flow. We assume a laminar steady, fully developed, stratified two-phase flow with any contact angle, α, independent of the shape of the tube’s cross-section. The axial component of the fluid’s velocity can be treated as a scalar function in two dimensions that obeys Poisson’s equation, together with the no-slip condition on the boundary (tube walls) and appropriate conditions on the interface between the phases. In our opinion, the exact solutions described in previous studies (for the special case of a cylindrical tube) are complicated and difficult to follow. Moreover, the approximated interface presented in previous studies predicts a geometric contact angle (αgeometry) that might not coincide with the physical contact angle, α, which is located at the real interface’s shape. The exact solutions numerically solve the global problem for a circular tube (i.e., they find the velocity and shear stresses) and analytically obtain results in the vicinity of the TP to solve the problem with the aid of the residue theorem. However, we begin in the vicinity of the TP and our entire analysis focuses within this domain. To simplify the calculations, three steps are suggested: 1) zooming in on the TP allows us to approximate the curved arcs of the walls and the interface as straight lines (the tangents of the arcs of the wall and the outward ray of the interface)11Intuitively, for a local observation up to first order in distance, a regular curve can be approximated as a straight line; i.e., an arc can be approximated to a cord. Up to second order, a curve can be approximated as a circle. For a formal proof that Laplace’s equation for the region is bounded by the wall circle (radius Rwall), the interface circle (radius Ri), and our radius R defined in Fig 2.2, a possible option is to Möbius-transform the wall circle and the interface circle into straight lines concurrent in the angle α (so the other meeting points of these circles are mapped onto the point at infinity), and to obtain the Laplace solution, thereby proving that when R/(min(Rwall,Rinterface))<<1, the deviation tends to zero.; 2) attaching a polar coordinate system where the origin of this coordinate system is located at the TP; and 3) suppressing the local driving forces and expressing distant driving forces as a function on the boundary, thereby leaving the velocity as a harmonic function.The proposed method can be converted for electromagnetism near a junction of several dielectric materials. Furthermore, the electromagnetic parallel problem can be extended to three dimensions; i.e., a junction point of prisms with different dielectric constants.