Two-dimensional Tube Research Articles

Fallopian tube assessment of the peristaltic-ciliary flow of a linearly viscous fluid in a finite narrow tube

The present theoretical assessment deals with the peristaltic-ciliary transport of a developing embryo within a fallopian tubal fluid in the human fallopian tube. A mathematical model of peristalsis-cilia induced flow of a linearly viscous fluid within a fallopian tubal fluid in a finite two-dimensional narrow tube is developed. The lubrication approximation theory is used to solve the resulting partial differential equation. The expressions for axial and radial velocities, pressure gradient, stream function, volume flow rate, and time mean volume flow rate are derived. Numerical integration is performed for the appropriate residue time over the wavelength and the pressure difference over the wavelength. Moreover, the plots of axial velocity, the appropriate residue time over wavelength, the vector, the pressure difference over wavelength, and the streamlines are displayed and discussed for emerging parameters and constants. Salient features of the pumping characteristics and the trapping phenomenon are discussed in detail. Furthermore, a comparison between the peristaltic flow and the peristaltic-ciliary flow is made as the special case. Relevance of the current results to the transport of a developing embryo within a fallopian tubal fluid from ampulla to the intramural in the fallopian tube is also explored. It reveals the fact that cilia along with peristalsis helps to complete the required mitotic divisions while transporting the developing embryo within a fallopian tubal fluid in the human fallopian tube.

Computation of Micro-Strains in Cold Formed Steels- FEA Approach

This paper describes the computations of micro-strains at inner corner of cold formed rectangular hollow sections (CFRHS) made up of structural steels using finite element analysis. In order to obtain the micro-strains, distortion test is simulated by modeling two-dimensional structural steel tubes in ANSYS software. Two dimensional linear static analyses are performed by defining elastic properties of steel. These simulations were performed for tubes with outer radius to thickness (<i>r_o/t</i>) ratios of 3. In real distortion tests, the direction of force at outer corner of the tube may vary in terms of angle. Therefore, this fact is taken into account while performing simulations. One more aspect is taken into consideration which is related to strain gauge placement during distortion testing. This problem is analyzed by modeling three-dimensional structural tubes and performing linear static analyses to investigate the variations in strains at inner bent section of the tube with different strain gauge locations.

Physiological Flow of Jeffrey Six Constant Fluid Model due to Ciliary Motion

The main purpose of this article is to present a mathematical model of ciliary motion in an annulus. In this analysis, the peristaltic motion of non-Newtonian Jeffrey six constant fluid is observed in an annulus with ciliated tips in the presence of heat and mass transfer. The effects of viscous dissipation are also considered. The flow equations of non-Newtonian fluid for the two-dimensional tube in cylindrical coordinates are simplified using the low Reynolds number and long wave-length approximations. The main equations for Jeffrey six constant fluid are considered in cylindrical coordinates system. The resulting nonlinear problem is solved using the regular perturbation technique in terms of a variant of small dimensionless parameter α. The results of the solutions for velocity, temperature and concentration field are presented graphically. Bk is Brinkman number, ST is soret number, and SH is the Schmidth number. Outcome for the longitudinal velocity, pressure rise, pressure gradient and stream lines are represented through graphs. in the history, the viscous-dissipation effect is usually represented by the Brinkman number.

Numerical analysis of the forced convective heat transfer on Al2O3–Cu/water hybrid nanofluid

A numerical investigation to elucidate thermal behavior of hybrid nanofluids consisting of Al2O3 and Cu nanoparticles at ratio of 90:10 was conducted. Numerical domain of a two-dimensional axisymmetric copper tube with a length of 1000 and 10 mm in diameter is used. A uniform axial velocity is assigned at the velocity inlet based on the Reynolds number. The outer wall of the tube consists of non-slip wall condition with a constant heat flux. The assumptions of this numerical analysis are; (1) there is a steady state analysis, (2) effective thermo-physical properties of the nanofluid are depend on the volume concentration, and (3) fluid is continuum. It is found that the dominant nanoparticle in the hybrid nanofluids strongly influences the thermal behavior of the hybrid nanofluids. It was also found that the heat transfer coefficient increases as the volume concentration of the hybrid nanoparticle increases in base fluids and the Reynolds number.

Current of loaded particle in two-dimensional tube with varying width

The current of a loaded particle along a two-dimensional (2D) tube with non-straight midline and is investigated. It is found that in the case of a load with an asymmetric unbiased external force, the limits of temperature and asymmetric external force for particle directed moving become smaller as the load increased. The directed current is a peaked function of temperature and amplitude of the asymmetric unbiased external force. As the channel width is decreased, the directed current decreases with the increase of the load.

MULTIDIMENSIONAL OPEN SYSTEM FOR VALVELESS PUMPING

In this study, we present a multidimensional open system for valveless pumping (VP). This system consists of an elastic tube connected to two open tanks filled with a fluid under gravity. The two-dimensional elastic tube model is constructed based on the immersed boundary method, and the tank model is governed by a system of ordinary differential equations based on the work-energy principle. The flows into and out of the elastic tube are modeled in terms of the source/sink patches inside the tube. The fluid dynamics of this system is generated by the periodic compress-and-release action applied to an asymmetric region of the elastic tube. We have developed an algorithm to couple these partial differential equations and ordinary differential equations using the pressure-flow relationship and the linearity of the discretized Navier-Stokes equations. We have observed the most important feature of VP, namely, the existence of a unidirectional net flow in the system. Our computations are focused on the factors that strongly influence the occurrence of unidirectional flows, for example, the frequency, compression duration, and location of pumping. Based on these investigations, some case studies are performed to observe the details of the ow features.

Effect of viscosity and wall heat conduction on shock attenuation in narrow channels

In the present work, the effects due to viscosity and wall heat conduction on shock propagation and attenuation in narrow channels are numerically investigated. A two-dimensional viscous shock tube configuration is simulated, and heat conduction in the channel walls is explicitly included. The simulation results indicate that the shock attenuation is significantly less in the case of an adiabatic wall, and the use of an isothermal wall model is adequate to take into account the wall heat conduction. A parametric study is performed to characterize the effects of viscous forces and wall heat conduction on shock attenuation, and the behaviour is explained on the basis of boundary layer formation in the post-shock region. A dimensionless parameter that describes the shock attenuation is correlated with the diaphragm pressure ratio and a dimensionless parameter which is expressed using the characteristic Reynolds number and the dimensionless shock travel.

Cannabinoids inhibit angiogenic capacities of endothelial cells via release of tissue inhibitor of matrix metalloproteinases-1 from lung cancer cells

Cannabinoids inhibit tumor neovascularization as part of their tumorregressive action. However, the underlying mechanism is still under debate. In the present study the impact of cannabinoids on potential tumor-to-endothelial cell communication conferring anti-angiogenesis was studied. Cellular behavior of human umbilical vein endothelial cells (HUVEC) associated with angiogenesis was evaluated by Boyden chamber, two-dimensional tube formation and fibrin bead assay, with the latter assessing three-dimensional sprout formation. Viability was quantified by the WST-1 test. Conditioned media (CM) from A549 lung cancer cells treated with cannabidiol, Δ9-tetrahydrocannabinol, R(+)-methanandamide or the CB2 agonist JWH-133 elicited decreased migration as well as tube and sprout formation of HUVEC as compared to CM of vehicle-treated cancer cells. Inhibition of sprout formation was further confirmed for cannabinoid-treated A549 cells co-cultured with HUVEC. Using antagonists to cannabinoid-activated receptors the antimigratory action was shown to be mediated via cannabinoid receptors or transient receptor potential vanilloid 1. SiRNA approaches revealed a cannabinoid-induced expression of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) as well as its upstream trigger, the intercellular adhesion molecule-1, to be causally linked to the observed decrease of HUVEC migration. Comparable anti-angiogenic effects were not detected following direct exposure of HUVEC to cannabinoids, but occurred after addition of recombinant TIMP-1 to HUVEC. Finally, antimigratory effects were confirmed for CM of two other cannabinoid-treated lung cancer cell lines (H460 and H358). Collectively, our data suggest a pivotal role of the anti-angiogenic factor TIMP-1 in intercellular tumor-endothelial cell communication resulting in anti-angiogenic features of endothelial cells.

An Analysis of Peristaltic Flow of Finitely Extendable Nonlinear Elastic- Peterlin Fluid in Two-Dimensional Planar Channel and Axisymmetric Tube

We have investigated the peristaltic motion of a non-Newtonian fluid characterized by the finitely extendable nonlinear elastic-Peterlin (FENE-P) fluid model. A background for the development of the differential constitutive equation of this model has been provided. The flow analysis is carried out both for two-dimensional planar channel and axisymmetric tube. The governing equations have been simplified under the widely used assumptions of long wavelength and low Reynolds number in a frame of reference that moves with constant wave speed. An exact solution is obtained for the stream function and longitudinal pressure gradient with no slip condition. We have portrayed the effects of Deborah number and extensibility parameter on velocity profile, trapping phenomenon, and normal stress. It is observed that normal stress is an increasing function of Deborah number and extensibility parameter. As far as the velocity at the channel (tube) center is concerned, it decreases (increases) by increasing Deborah number (extensibility parameter). The non-Newtonian rheology also affect the size of trapped bolus in a sense that it decreases (increases) by increasing Deborah number (extensibility parameter). Further, it is observed through numerical integration that both Deborah number and extensibility parameter have opposite effects on pressure rise per wavelength and frictional forces at the wall. Moreover, it is shown that the results for the Newtonian model can be deduced as a special case of the FENE-P model

Systematic analysis of the heat exchanger arrangement problem using multi-objective genetic optimization

A two-dimensional cross-flow tube bank heat exchanger arrangement problem with internal laminar flow is considered in this work. The objective is to optimize the arrangement of tubes and find the most favorable geometries, in order to simultaneously maximize the rate of heat exchange while obtaining a minimum pressure loss. A systematic study was performed involving a large number of simulations. The global optimization method NSGA-II was retained. A fully automatized in-house optimization environment was used to solve the problem, including mesh generation and CFD (computational fluid dynamics) simulations. The optimization was performed in parallel on a Linux cluster with a very good speed-up.The main purpose of this article is to illustrate and analyze a heat exchanger arrangement problem in its most general form and to provide a fundamental understanding of the structure of the Pareto front and optimal geometries. The considered conditions are particularly suited for low-power applications, as found in a growing number of practical systems in an effort toward increasing energy efficiency. For such a detailed analysis with more than 140 000 CFD-based evaluations, a design-of-experiment study involving a response surface would not be sufficient. Instead, all evaluations rely on a direct solution using a CFD solver.

Intestinal Flow of a Couple Stress Nanofluid in Arteries

The current article discusses the influence of nanofluid on the peristaltic flow of an incompressible couple stress fluid in a two-dimensional uniform tube. The problem formulation is accessible in an upsurge structure of orientation for equations of momentum, energy, and concentrations. The continuity, linear momentum, energy, and nanoparticle equations lead to the mathematical development. HPM is used to get the solutions for velocity, temperature, nanoparticle, and pressure gradient. The solutions contain the Brownian motion number N(b), thermophoresis number N(t), local temperature Grashof number B(r), and local nanoparticle Grashof number G(r). The physical features of different embedded parameters are analyzed and discussed physically in detail.

A meshless scheme for incompressible fluid flow using a velocity–pressure correction method

A meshless point collocation method is proposed for the numerical solution of the steady state, incompressible Navier–Stokes (NS) equations in their primitive u–v–p formulation. The flow equations are solved in their strong form using either a collocated or a semi-staggered “grid” configuration. The developed numerical scheme approximates the unknown field functions using the Moving Least Squares approximation. A velocity, along with a pressure correction scheme is applied in the context of the meshless point collocation method. The proposed meshless point collocation (MPC) scheme has the following characteristics: (i) it is a truly meshless method, (ii) there is no need for pressure boundary conditions since no pressure constitutive equation is solved, (iii) it incorporates simplicity and accuracy, (iv) results can be obtained using collocated or semi-staggered “grids”, (v) there is no need for the usage of a curvilinear system of coordinates and (vi) it can solve steady and unsteady flows. The lid-driven cavity flow problem, for Reynolds numbers up to 5000, has been considered, by using both staggered and collocated grid configurations. Following, the Backward-Facing Step (BFS) flow problem was considered for Reynolds numbers up to 800 using a staggered grid. As a final example, the case of a laminar flow in a two-dimensional tube with an obstacle was examined.

Response Probability Analysis of Random Acoustic Field Based on Perturbation Stochastic Method and Change-of-Variable Technique

To calculate the probability density function of the response of a random acoustic field, a change-of-variable perturbation stochastic finite element method (CVPSFEM), which integrates the perturbation stochastic finite element method (PSFEM) and the change-of-variable technique in a unified form, is proposed. In the proposed method, the response of a random acoustic field is approximated as a linear function of the random variables based on a first order stochastic perturbation analysis. According to the linear relationship between the response and the random variables, the formal expression of the probability density function of the response of a random acoustic field is obtained by the change-of-variable technique. The numerical examples on a two-dimensional (2D) acoustic tube and a three-dimensional (3D) acoustic cavity of an automobile cabin verify the accuracy and efficiency of the proposed method. Hence, the proposed method can be considered as an effective method to quantify the effects of the parametric randomness of a random acoustic field on the sound pressure response.

Numerical simulation of forced convective evaporation in thermal desalination units with vertical tubes

The subject of present study is a numerical simulation of transient solution of evaporation on upward flow in a two-dimensional vertical tubes by using the water as the working fluid. The heat transfer mechanisms are energy and mass transfer during the phase change based on volume of fluid model in commercial CFD software, with a user defined function. Operating conditions are specified in saturation temperature of water flow boiling. The physical properties of water are determined using inlet temperature and pressure system in saturation conditions. The characteristic of water flow boiling such as void fraction, heat transfer coefficient, and wall temperature distribution are investigated in the range of various heat fluxes. Due to agitation of vapor bubbles, the flow is turbulent which is simulated based on SST K–ω model and also the pressure implicit with splitting of operators pressure–velocity coupling scheme is used to improve the efficiency of calculation.

Two-phase simulation of non-uniform magnetic field effects on biofluid (blood) with magnetic nanoparticles through a collapsible tube

In this paper, the behavior of a two-dimensional tube with an elastic segment containing ferrofluid (blood and 3vol% Fe3O4), in presence of non-uniform magnetic field is reported. Two cases of magnetic field including constant gradient (both positive and negative) and field of a wire, carrying electric current were examined. Surface tension of the membrane is considered to be fixed and constant along the elastic wall. Numerical solution of governing equations of the flow field has been obtained using the two-phase mixture model and control volume technique. Also, the membrane equation has been used to iterate and access the membrane position. Based on the obtained results, applying positive gradient magnetic field makes the tube narrower, but the negative one and magnetic field of electric wire opens the tube up.

Confined modes in two-dimensional tubes

We survey various numerical methods for finding solutions of quantum confined states. We especially consider states in two-dimensional (2D) tubes, or 2D surfaces that are confined in the transverse direction but are unconfined in the longitudinal direction. We first review existence proofs for bound states in long 2-D tubes. We then review various methods for finding such states and we discuss the significance of these eigenstates.

Transport of Brownian particles in a deformable tube

Directed transport of Brownian particles in a deformable two-dimensional tube is investigated in the presence of asymmetric unbiased fluctuations. It is found that the current can be enhanced by choosing appropriate noise intensity and deformation. There exists a value of deformation at which the current takes its maximum. For small deformable parameter, transport is dominated by noise intensity, and for very large deformable parameter, transport is dominated by deformation. The competition between the deformation and the asymmetric driving forces will induce rich phenomena in transport.

Numerical Analysis of Flame Behavior Near the Quenching Conditions During Passage from Wider to Narrower Tube Diameters

The present study numerically investigates the propagation of a laminar premixed flame front in two-dimensional tubes with a sudden contraction and isothermal cold walls. Navier–Stokes equations and species equations are solved with a single-step overall reaction model for a stoichiometric propane/air mixture. The finite volume method is applied in investigating flame behavior during the passage through a sudden contraction in tubes of various diameters. These investigations show that a flame can enter a smaller diameter tube from a wider one and propagate in a stable manner in all configurations of diameters of both tubes as long as the diameter of the narrow tube is far from the quenching diameter. By decreasing the diameter of the narrow tube, we approach conditions where the dimension of the wide tube decides if the flame will propagate or quench. This is associated with a temporarily increased ratio of heat losses to thermal energy generation caused by a greater heat loss area. It is also shown that a tulip-shaped flame occurring at large diameters of the wide tube is particularly exposed to quenching during propagation through the sudden contraction. This is due to a transition from a tulip-shaped flame to a mushroom-shaped one, which takes place at the entrance to the narrower tube.

Diffusion in a soft confining environment: Dynamic effects of thermal fluctuations

A dynamical model of a soft, thermally fluctuating two-dimensional tube is used to study the effect of thermal fluctuations of a confining environment on diffusive transport. The tube fluctuations in both space and time are driven by Brownian motion and suppressed by surface tension and the rigidity of the surrounding environment. The dynamical fluctuations modify the concentration profile boundary condition at the tube surface. They decrease the diffusive transport rate through the tube for two important cases: uniform tube fluctuations (wave vector, q=0 mode) for finite tube lengths and fluctuations of any wave vector for infinitely long tubes.

Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure

The Stokes equation with the varying viscosity is considered in a thin tube structure, i.e., in a connected union of thin rectangles with heights of order ɛ &amp;lt; &amp;lt; 1 and with bases of order 1 with smoothened boundary. An asymptotic expansion of the solution is constructed: it contains some Poiseuille type flows in the channels (rectangles) with some boundary layers correctors in the neighborhoods of the bifurcations of the channels. The estimates for the difference of the exact solution and its asymptotic approximation are proved.