Distensible Tube Research Articles

Mathematical Models on Mechanics of Biofluids

In this work, we study the mathematical models of flows for some biofluids. In biomechanics, peristaltic flow plays an important role in which the motion generated in the fluid contained in a distensible tube when a progressive wave of area contraction and expansion travels along the wall of the tube. We consider the effect of elasticity of the tube wall in the flow through the progressive wave travelling along its length without its direct calculation. Since the no – slip condition has used on a moving undulating wall surface, it determines the sinusoidal boundary conditions on the upper and lower wall of the tube. The wide occurrence of peristaltic motion gives its result physiologically from neuro-muscular properties of any tubular smooth muscle.

MODELING AND OPTIMIZATION OF PERISTALTIC FLUID TRANSPORT IN AXISYMMETRIC, POROUS STRUCTURES

Peristaltic transport, a fundamental physiological and engineering process, involves the movement of fluid through a distensible tube via sequential compression and relaxation. This study investigates the peristaltic transport of an incompressible Newtonian fluid in an axisymmetric, porous, corrugated tube, emphasizing the interplay between fluid dynamics and the tube's structural characteristics. Utilizing lubrication theory and perturbation analysis within a wave frame of reference, we explore the effects of hydraulic resistivity, geometric parameters of the corrugation, and porous layer thickness on the phenomena of trapping and circulation. Our findings reveal that hydraulic resistivity significantly influences the development of circulation regions within the fluid core, which has implications for the efficiency of mixing and nutrient absorption in biological and industrial applications. Additionally, the geometric configuration of the wavy porous layer—specifically its amplitude and thickness—critically impacts the formation of trapping and circulation regions, thereby affecting fluid transport efficiency. This work not only advances our understanding of peristaltic pumping mechanisms but also highlights the potential for optimizing fluid transport processes in both biological systems and industrial applications. The insights gained from this study contribute to the design of more efficient peristaltic pumps and offer a valuable framework for future research aimed at enhancing substance delivery and mixing through peristaltic transport.

Assessing the efficiency of a distensible-tube wave attenuator at three different scales considering aero and hydro-elastic effects

A water-filled floating distensible tube connected to a forward-bent oscillating water column is here considered in the context of harnessing energy from sea waves. Based on wave-tank experiments conducted at three different scales, under intermediate and deep-water incident regular waves of small and finite amplitudes, the present study addresses important aspects that determine the energy capture-width of the system. The comparison between the results obtained at the three scales reveals non-linear and aero-hydroelastic scale effects inherent in modelling the device. The following issues are also tackled: (i) the occurrence of various working modes of the floating tube and their contribution to its performance; (ii) the compressibility of the airflow through the orifice power take-off system; (iii) the viscous-effects associated with the Reynolds and Keulegan-Carpenter numbers. The parameters that govern the system's efficiency are the tube's length, the OWC natural period and the bulge wave tuning period. The system becomes very efficient not only at the OWC resonance, but also when the incident wavelength is equal to or twice the tube's length. Video frames further provide evidence of the relationship between the tube's working modes and its performance. An iterative algorithm based on Buckingham's formula, with an empirical expansibility factor, provides adequate estimates of the compressible flow through the power take-off. Viscous losses closely related to the Reynolds and Keulegan-Carpenter numbers are found to be important even for waves with moderate steepness. Finally, the experiments suggest that a single distensible-tube system in open sea has a maximum capture-width of no more than 2 tube-diameters.

Wave-attenuation efficiency of a floating distensible tube at different Keulegan–Carpenter numbers

A water-filled floating rubber tube is tested in a wave flume under regular waves of different steepness. The wave excited pressure bulges in the tube induce periodic oscillations of a forward-bent water column at its stern, which in turn activate a pneumatic power take-off system. The purpose of the experiment is to better understand how the tube’s working modes contribute to the wave energy absorption and to quantify the power extracted from the incident waves. By applying Bernoulli’s equation for incompressible airflow, the water column free-surface displacement measurements deliver the pneumatic chamber pressure and the volume flow through the power take-off. Video captions help to reveal the interactions of the tube with the incident waves and further relate them to the system’s efficiency. Additionally, an energy balance enables the assessment of the internal friction and flow separation losses, at different Reynolds and Keulegan–Carpenter numbers. The hydrodynamic and overall efficiencies of the system are ultimately provided.

Longitudinal wall motion during peristalsis and its effect on reflux

In this study, for the first time, we consider longitudinal motion of the walls during peristalsis in a distensible tube and how this affects backward (or retrograde) flow, i.e. peristaltic reflux. Building on the analytical model developed by Shapiro et al. (J. Fluid Mech., vol. 37, no. 4, 1969, pp. 799–825) based on lubrication theory, we model peristalsis as a two-dimensional infinite sinusoidal wavetrain. We develop an objective function with high mechanical pumping efficiency and low reflux to find optimal peristalsis conditions. We show that optimal wall longitudinal motion contributes substantially to limiting reflux during peristalsis. The results suggest that the optimal form of wall longitudinal velocity is a linear function of the wall transverse coordinate, moving forward with the wave when the tube is distended and retracting when contracted. Our results are in general agreement with clinical observations of ureteral peristalsis.

Peristaltic flow of Buongiorno model nanofluids within a sinusoidal wall surface used in drug delivery

AbstractThe current paper deals with the radiative heat transfer of the peristaltic flow of the Buongiorno model nanofluid through a two‐dimensional channel with a sinusoidal wall surface. A particular form of fluid transport occurring through progressive wave of expansion or contraction generating along a distensible tube containing fluid is known as peristaltic pumping, which takes place from the lower pressure region to the higher pressure region. Peristaltic transport finds several applications, such as blood pumping in heart, lung, and pharmacological delivery systems, and industrial applications—sanitary fluid transport, corrosive fluids transport, and so on. An approximate analytical solution is employed for the solution of the system of transformed differential equations with prescribed boundary conditions. The influences of physical parameters characterizing the flow phenomena are obtained and presented via graphs. The result warrants a good correlation with earlier studies in particular case. The following are the main findings: thermophoresis is favorable to enhance the fluid temperature near the channel center and also the axial velocity increases as an increase in the thermal buoyancy parameter. However, the main findings are elaborated in Section 3.

Comparison between multi-channel LDV and PWI for measurement of pulse wave velocity in distensible tubes: Towards a new diagnostic technique for detection of arteriosclerosis

The aim of this work, was to compare pulse wave velocity (PWV) measurements using Laser Doppler vibrometry (LDV) and the more established ultrasound-based pulse wave imaging (PWI) in smooth vessels. Additionally, it was tested whether changes in phantom structure can be detected using LDV in vessels containing a local hardening of the vessel wall.Results from both methods showed good agreement illustrated by the non-parametric Spearman correlation analysis (Spearman-ρ= 1 and p< 0.05) and the Bland–Altman analysis (mean bias of −0.63m/s and limits of agreement between −0.35 and −0.90m/s).The PWV in soft phantoms as measured with LDV was 1.30±0.40m/s and the PWV in stiff phantoms was 3.6±1.4m/s. The PWV values in phantoms with inclusions were in between those of soft and stiff phantoms.However, using LDV, given the low number of measurement beams, the exact locations of inclusions could not be determined, and the PWV in the inclusions could not be measured. In conclusion, this study indicates that the PWV as measured with PWI is in good agreement with the PWV measured with LDV although the latter technique has lower spatial resolution, fewer markers and larger distances between beams. In further studies, more LDV beams will be used to allow detection of local changes in arterial wall dynamics due to e.g. small inclusions or local hardenings of the vessel wall.

Wave–structure interactions for the distensible tube wave energy converter

A comprehensive linear mathematical model is constructed to address the open problem of the radiated wave for the distensible tube wave energy converter. This device, full of sea water and located just below the surface of the sea, undergoes a complex interaction with the waves running along its length. The result is a bulge wave in the tube which, providing certain criteria are met, grows in amplitude and captures the wave energy through the power take-off mechanism. Successful optimization of the device means capturing the energy from a much larger width of the sea waves (capture width). To achieve this, the complex interaction between the incident gravity waves, radiated waves and bulge waves is investigated. The new results establish the dependence of the capture width on absorption of the incident wave, energy loss owing to work done on the tube, imperfect tuning and the radiated wave. The new results reveal also that the wave–structure interactions govern the amplitude, phase, attenuation and wavenumber of the transient bulge wave. These predictions compare well with experimental observations.

Fluid friction and wall viscosity of the 1D blood flow model

We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity.

Navier–Stokes flow in converging–diverging distensible tubes

We use a method based on the lubrication approximation in conjunction with a residual-based mass-continuity iterative solution scheme to compute the flow rate and pressure field in distensible converging–diverging tubes for Navier–Stokes fluids. We employ an analytical formula derived from a one-dimensional version of the Navier–Stokes equations to describe the underlying flow model that provides the residual function. This formula correlates the flow rate to the boundary pressures in straight cylindrical elastic tubes with constant-radius. We validate our findings by the convergence toward a final solution with fine discretization as well as by comparison to the Poiseuille-type flow in its convergence toward analytic solutions found earlier in rigid converging–diverging tubes. We also tested the method on limiting special cases of cylindrical elastic tubes with constant-radius where the numerical solutions converged to the expected analytical solutions. The distensible model has also been endorsed by its convergence toward the rigid Poiseuille-type model with increasing the tube wall stiffness. Lubrication-based one-dimensional finite element method was also used for verification. In this investigation five converging–diverging geometries are used for demonstration, validation and as prototypes for modeling converging–diverging geometries in general.

The flow of power law fluids in elastic networks and porous media

The flow of power law fluids, which include shear thinning and shear thickening as well as Newtonian as a special case, in networks of interconnected elastic tubes is investigated using a residual-based pore scale network modeling method with the employment of newly derived formulae. Two relations describing the mechanical interaction between the local pressure and local cross-sectional area in distensible tubes of elastic nature are considered in the derivation of these formulae. The model can be used to describe shear dependent flows of mainly viscous nature. The behavior of the proposed model is vindicated by several tests in a number of special and limiting cases where the results can be verified quantitatively or qualitatively. The model, which is the first of its kind, incorporates more than one major nonlinearity corresponding to the fluid rheology and conduit mechanical properties, that is non-Newtonian effects and tube distensibility. The formulation, implementation, and performance indicate that the model enjoys certain advantages over the existing models such as being exact within the restricting assumptions on which the model is based, easy implementation, low computational costs, reliability, and smooth convergence. The proposed model can, therefore, be used as an alternative to the existing Newtonian distensible models; moreover, it stretches the capabilities of the existing modeling approaches to reach non-Newtonian rheologies.

The yield condition in the mobilization of yield-stress materials in distensible tubes

AbstractIn this paper we investigate the yield condition in the mobilization of yield-stress materials in distensible tubes. We discuss the two possibilities for modeling the yield-stress materials prior to yield: solid-like materials and highly-viscous fluids and identify the logical consequences of these two approaches on the yield condition. Our results reveal that these two modeling approaches have far reaching consequences on the yield bottleneck and hence should be critically examined in the light of experimental evidence. As part of this investigation we derive an analytical expression for the pressure field inside a distensible tube with a Newtonian flow using a one-dimensional Navier-Stokes flow model in conjunction with a pressurearea constitutive relation based on elastic tube wall characteristics. This analytical expression has wider applicability than in the identification of the yield condition of yield-stress material.

7&amp;#148; long knife for 7 years in the duodenum: a rare case report and review of literature

Foreign body ingestion is a common occurrence both in sane and insane population. Quite a good number of interesting and unusual cases of foreign body ingestion has been reported in the surgical literature from time to time. Ingested foreign bodies varying widely in number, size and character, may travel through a distensible tube of comparatively small diameter causing mechanical insult to the intestinal wall without producing symptoms or permanent tissue damage. Accidental ingestion of the foreign body is by far the most common. Deliberate ingestion may result from an act of insanity, a dare, a habit or medicinal therapy. Retention of elongated or pointed objects in the duodenum is a frequent problem. Long, sharp, objects may perforate the duodenum and have been known to migrate widely in the abdomen. Early removal of such objects has been advised. This case forms rarity due to the fact that the 7 inches knife remained in the Duodenum for 07 long years without causing major catastrophe. From Medline as well as Medical library search we failed to find such a case report till date where the metallic foreign body has remained in the GIT for such a long time.

Predictions of aneurysm formation in distensible tubes: Part B—Application and comparison of alternative approaches

The theoretical treatise of the companion paper produced three distinct approaches of increasing complexity. Just as the presented theory is equally applicable to other medical, scientific or engineering applications, so the systematic numerical investigation now reported is relevant to these fields of study. An independently developed finite element analysis (FEA) solution is used to show that the commercial package selected provides critical pressure predictions of a consistent order of magnitude. The FEA sensitivity analysis considers five distinct elements with up to seven alternative strain-energy functions and different combinations of uniaxial, equi-biaxial and pure shear data sets to identify the effect on critical pressure prediction and overall behaviour of a pressurised distensible tube. This represents the most comprehensive comparative study available in the open literature. For a selected strain-energy function the impact of the variation of length to initial radius and wall thickness to initial radius are investigated. Thereafter it is demonstrated that these two ratios rather than actual dimensions are the driving factors behind pressurised tube behaviour.

Predictions of aneurysm formation in distensible tubes: Part A—Theoretical background to alternative approaches

Pressurised distensible tubes are subject to aneurysms. Aneurysm inception will take place at a location along the tube when a critical pressure, relative to tube wall thickness at that location, is reached. Parents will recognise the existence of critical pressure when endeavouring to inflate a party balloon. Another example of aneurysm is the thoracic aortic aneurysm corresponding to permanent dilation of the aorta in such proportions that it can be life threatening. Corrective procedures for aortic aneurysms involve the introduction of stiff materials to prevent aneurysm. Similarly in a proposed distensible tube based wave energy device aneurysm inception is partially controlled through the use of alternative longitudinal strips of inextensible material and appropriate rubber strips. Here we consider distensible tubes made of one material.Having reviewed the aneurysm based literature some inconsistencies were observed between the material properties used in a non-linear finite element analysis and the material properties of the specimen used to provide experimental measurements for comparison. To appreciate the inconsistencies the authors decided to investigate aneurysm development using both non-linear finite element analyses and distinct alternative formulations and solution techniques. Rather than restrict strain-energy function to a subset of Neo-Hookean, Mooney–Rivlin and Ogden forms, the authors have implemented several alternative strain-energy models in parallel, also exploring for the first time the impact of using different combinations of uniaxial, equi-biaxial and pure shear experimental data for different rubbers.This paper addresses the needs (necessary considerations, such as the Valanis–Landel hypothesis, Maxwell equal area rule and data selection criteria) for a realistic approach to modelling a distensible tube to provide predictions of critical pressure. In common with all other cited references a static analysis is used.

Delay or removal of aneurysm formation in the Anaconda wave energy extraction device

Any distensible tube inflated beyond a critical pressure will experience aneurysm formation. The Anaconda wave energy device consists of a pressurised flooded tube, which when excited with an external incident wave of appropriate frequency, for the set inflation pressure, permits generation of internal bulge waves that provide the mechanism for more efficient wave energy extraction. The distensible tube must be designed to have structural integrity and to facilitate the bulge wave matching the incident wave. The bulge wave speed is governed by internal fluid density and tube distensibility. The latter is readily shown to be dependent upon volume–pressure gradient within the tube. With application of a displacement–pressure based finite element formulation the likelihood of aneurysm and its delay or avoidance can be investigated. The strain energy functions selected for use with the finite element analysis are the Yeoh and third-order Ogden model as these formulations have been previously shown by the authors to satisfy the required Maxwell equal area rule and provide the most consistent predictions when using different mixes of experimental stress-strain data. After summarising a representative set of known wave energy extraction devices, to appreciate how different Anaconda is, the paper looks at the extent and mode of deployment of an outer inextensible reinforcement to provide bulge waves of appropriate speed whilst also overcoming the onset of aneurysms within the Anaconda tube.

Morphological adaptations of digestive tract according to food and feeding habits of the broomtail wrasse, Cheilinus lunulatus

The present study deals with the morphological adaptations of digestive tract according to food and feeding habits of the broomtail wrasse, Cheilinus lunulatus. The highest rate of feeding activity was recorded during spring and the lowest during summer. In the older and younger fish, the rates of feeding activity are nearly similar. The fish is mainly carnivorous benthic feeder. This fish plays an important role as a predator of invertebrates of reef fauna. It consumes a wide range of animal food. Molluscs, echinoderms and small fishes were the main food items consumed by these fish. Molluscs increased and echinoderms decreased in the food with the increasing length of the fish. The mouth is relatively large, terminal in position, usually with prominent lips. Jaws are extremely protrusible to make the fish able to get food between branches of coral reef. The jaws teeth are conical canine in shape and composed of outer uni-serial pointed teeth. Two enlarged teeth are present in the front of the upper and lower jaws. They are specialized for catching and holding the prey and preventing its escape out of the buccal cavity. The pharyngeal teeth are molar in shape with blunt or round edge and arranged in two rows, usually 7 - 17 in each row of the floor. The teeth in the roof are developed and haphazard distributed. These molariform teeth are adapted for crushing and grinding of hard body preys. 11 gill rakers are present on the bowshaped gill arch and conical in shape with tapering tips adapted for binding the prey. Oesophagus is a short muscular distensible tube with few number of large mucosal folds adapted for facilitating conduction of food to the stomach. The Jshaped stomach is of the siphon type with large number of small mucosal folds adapted for food retention to be digested. The intestine is a short uncomplicated tube which recognized by the presence of ileo-rectal valve modified to prevent the passage of food particles into the posterior part before intestinal digestion and absorption is completed. It contains very large number of mucosal folds adapted for facilitating lubrication of feces towards the anus.

Development of a cardiopulmonary mathematical model incorporating a baro–chemoreceptor reflex control system

This article describes the development of a comprehensive mathematical model of the human cardiopulmonary system that combines the respiratory and cardiovascular systems and their associated autonomous nervous control actions. The model is structured to allow the complex interactions between the two systems and the responses of the combined system to be predicted under different physiological conditions. The cardiovascular system model contains 13 compartments, including the heart chambers operating as a pump and the blood vessels represented as distensible tubes configured in a serial and parallel arrangement. The accurate representation of the hemodynamics in the system and the good fit to published pressure and flow waveforms gave confidence in the modelling approach adopted for the cardiovascular system prior to the incorporation of the baroreflex control and the respiratory models. An improved baroreceptor reflex model is developed in this research, incorporating afferent, central and efferent compartments. A sigmoid function is included in the efferent compartment to produce sympathetic and parasympathetic nerve outflow to the effector sites. The baroreflex action is modelled using physiological data, its interaction with the chemoreflex control is explained and the simulation results presented show the ability of the model to predict the static and dynamic hemodynamic responses to environmental disturbances. A previously published respiratory model that includes the mechanics of breathing, gas exchange process and the regulation of the system is then combined with the cardiovascular model to form the cardiopulmonary model. Through comparison with published data, the cardiopulmonary model with the baro-chemoreflex control is validated during hypoxia and hypercapnia. The percentage difference between the predicted and measured changes in the heart rates and the mean arterial pressures are within 3% in both cases. The total peripheral resistance correlates well for hypoxia but is less good for hypercapnia, where the predicted change from normal condition is around 7% compared with a measured change of 23%. An example showing the application of the proposed model in sport science is also included.

Laboratory testing the Anaconda

Laboratory measurements of the performance of the Anaconda are presented, a wave energy converter comprising a submerged water-filled distensible tube aligned with the incident waves. Experiments were carried out at a scale of around 1:25 with a 250 mm diameter and 7 m long tube, constructed of rubber and fabric, terminating in a linear power take-off of adjustable impedance. The paper presents some basic theory that leads to predictions of distensibility and bulge wave speed in a pressurized compound rubber and fabric tube, including the effects of inelastic sectors in the circumference, longitudinal tension and the surrounding fluid. Results are shown to agree closely with measurements in still water. The theory is developed further to provide a model for the propagation of bulges and power conversion in the Anaconda. In the presence of external water waves, the theory identifies three distinct internal wave components and provides theoretical estimates of power capture. For the first time, these and other predictions of the behaviour of the Anaconda, a device unlike almost all other marine systems, are shown to be in remarkably close agreement with measurements.

Suppression of absolute instabilities in the flow inside a compliant tube

AbstractThe stability of the steady flow of a viscous liquid through a thick‐wall, three‐layer, viscoelastic tube with different rheological parameters for each layer is studied. The temporal and spatial eigenvalues of the system are found. Influence of the material parameters of the layers and the Reynolds number on the spatial and temporal amplification rate of the most unstable mode is investigated. It is shown that the system can be in both absolute and convective unstable states. Effects of the rheological parameters of each layer on the amplification rate of the most unstable mode that represents an absolute instability are examined. It is shown that the absolute instability of the system can be converted into a convective instability, and in some cases the system can even be stabilized with an appropriate choice of the rheological parameters. The rheological parameters of the tube layers influence the system stability in different ways. While some of those parameters destabilize the system, others stabilize it. It is found that an anisotropic tube composed of layers possessing distinct rheological values can completely eliminate all absolute instability modes. The present model can be applied to blood vessels that are composed of three viscoelastic layers with distinct rheological properties and to distensible tubes conveying fluids in different technical devices. Copyright © 2009 John Wiley &amp; Sons, Ltd.