جستجوی مقالات مرتبط با کلیدواژه « برهم کنش سیال-سازه » در نشریات گروه « مکانیک »

There are many engineering applications of pipes at different scales for conveying fluid. The dynamic characteristics of a spinning pipe conveying fluid in vertical configuration equipped with piezoelectric patches are analyzed in this study. Based on Euler–Bernoulli beam theory, the governing equations of the system are derived by applying Hamilton’s variational principle. In this equations, the gyroscopic coupling, electromechanical coupling and gravitational effects are considered. The Galerkin’s method is used to discretize the governing equations of motions. Numerical results are investigated to predict the influences of the piezoelectric layer spanning angle, spinning speed, pipe length and flow velocity, on the unbalance response of the system. The results indicate that, depending on excitation frequency, the vibration amplitude can be decreased or increased by increasing the piezoelectric layer spanning angle. The results of this research can be used to conduct piezoelectric pipe design and performance predictions for future pipe vibration control and energy harvesting applications.

In the recent years, double-walled carbon nanotubes (DWCNTs) have been used for different indusrial applications such as separation and purification technology. So, the main purpose of this paper is to analyze the bifurcation behavior of double-walled carbon nanotubes conveying fluid with considering van der Waals nonlinear forces. The internal flow is considered to be pulsating. In the framework of the Von Karman's theory and the Euler-Bernoulli beam model, the nonlinear governing equations of motion are developed using the Hamilton's principle. The governing partial differential equations are discretized by means of the assumed modes method and solved by the Rung-Kutta method. Then, the effects of flow velocity and pulsation frequency on the dynamic behavior of the system are investigated by the bifurcation diagrams, phase plan portrait, time series and Poincar'e maps. The results indicate that the flow velocity and pulsation frequency have significant effects on the dynamic responses of the system. Also, the results of analysis reveal a variety of nonlinear behavior such as periodic, multi-periodic and chaotic motions that can give some insight to researchers in designing and studying these systems in the future.

The study of axonal behavior under different environmental conditions can provide a better insight into the development of therapeutic approaches for healing after nerve damages. By modeling of sublayer in the form of a hyperelastic material and applying different pressures, the amount of strains tolerated by the axon was calculated. Strains were applied at three different time intervals to examine the effects of different strain rates. For axon, a model containing microtubules with linear elastic properties, neurofilament, and axolemma with linear viscoelastic properties was considered. The finite element method and COMSOL software were used for the discretization of the sublayer and the substructures of the axon. It was observed that the fluid regime in the channel did not affect the mechanical response of the axon. The strain was close to zero (at most 0.0001) and the stress was also negligible (at most, 70 N/m2). The results showed the major effect of microtubules on resisting mechanical forces and on the overall integrity of the axons. Most of the strains were seen inside the axolemma, indicating the importance of its mechanical response to injury. Regarding the response to the strain rate, the most probable damage to the axon, comparable with the former corresponding reports will occur at the strain of 42% and strain rate of 19.1 s-1, respectively.

Primary Cilia is appendage that extrudes from cell surface into the extracellular matrix .These organelles play a sensor role for mechanical stimulation in the cell and due to stretch ion channels in its base, play critical role in induce osteogenic differentiation of stem cells. Primary cilia deflected under fluid flow passing through the surface of the cell, which deflection causes tensile ion channels to be opened. In this study, cilia is assumed as linear elastic. The innovative aspect of this research is exerting of oscillatory fluid flow to the primary cilia and evaluating the response of cilia to the fluid flow. The results show that under conditions of exerting the oscillatory fluid flow, maximum strain occur in the base of the cilia which is experienced by tensile ion channels, is 0.5 and in the condition of steady flow is 0.3, Accordingly, mechanical stimuli are sensed by the tensile ionic channels during oscillatory flow higher than steady flow. osteogenic differentiation of stem cells, in addition, the result showed that by using the oscillatory fluid flow the mechanical stimulation better senses by cilia and It is anticipated that exerting oscillatory fluid flow facilitate osteogenic differentiation of stem cell.

Pulmonary embolism (PE) is one of the most prevalent diseases amid hospitalized patients and takes many people lives annually. However, this phenomenon has not been investigated in the field of biomechanics so far and insufficient information is available about hemodynamic factors affecting this phenomenon. Inexplicit signs and symptoms of this illness make it intricate to be diagnosed. In this research, a patient-specific anatomical model of pulmonary arteries has been constructed from computed tomography images (CT images). The fluid-structure interactions method was used to simulate motion of the blood clot. In addition, Navier-Stokes equations, as the governing equations, have been solved in an arbitrary Lagrangian-Eulerian (ALE) formulation. Furthermore, viscoelastic parameters were adopted in accordance with the red blood clot (stemmed from deep veins) properties for the structure model (emboli). Results revealed that the maximum shear stress magnitude applied on the embolus equals 957.56 Pa at 0.46841 s that was occurred when the clot plow into the wall of the artery. Based on the residence time of high magnitudes of stress in the clot, some predictions on clot lysis or development may be elaborated. In addition, the average shear stress of the arterial wall was reduced from 1.7697 to 1.02761 Pa due to the presence of the embolus. This reduction may lead to such phenomena as high pulmonary arterial resistance, low pulmonary arterial compliance, endothelial dysfunction, and consequently cause right heart dysfunction and pulmonary arterial hypertension (PAH) if different clots repeatedly pass through the arteries.

The present study aims to address the effect of the presence of a flexible fin on the natural convection heat transfer inside a square cavity. A flexible fin is placed on the left vertical wall by initial tilted angle 30o from the horizontal direction. An Arbitrary Lagrangian-Eulerian method for fluid-structure (fluid-flexible fin) interaction is utilized. Based on this method, the governing system of equations for laminar fluid and heat transfer is formulated into a non- dimensional form and then solved using the finite element method and then results accuracy evaluated against previous valid studies. The results are plotted for an enclosure containing a flexible fin as well as a solid fin in the non-dimensional time interval of 0 to 0.07 and in the Rayleigh number range of 106 to 2×107 and the fin tilted angle of -10° to °. The results show that the presence of a flexible fin deteriorates the heat transfer compared to a solid fin. In other words, using an insulated fin instead of a conductive fin makes different patterns for average Nusselt number curve in a range time and causes a reduction of the rate of heat transfer. Also, the presence of a flexible fin mounted on the hot wall especially affects the average Nusselt number in the areas above the fin location and induces oscillating heat transfer patterns.