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The supersonic variable Mach number wind tunnel can operate at multiple Mach numbers during a single operation, which has unique advantages for studying supersonic maneuvering process and scramjet starting. The supersonic variable Mach number nozzle is the core component for adjusting Mach number during wind tunnel operation, and its design quality directly determines the flow field quality of the experimental section. The research progress of nozzle design in supersonic variable Mach number wind tunnels both domestically and internationally in recent years is reviewed in this paper, and four typical variable Mach number wind tunnel nozzle schemes（flexible wall, semi-flexible wall, profile rotation, asymmetric）are introduced, as well as their numerical simulation and experimental calibration results. The key considerations in the design of different variable Mach number nozzle schemes are summarized, and the application ofvariable Mach number wind tunnel nozzle in specific tests is prospected.

A detailed study of the effect of coarctation on the blood flow of the thoracic aorta was carried out by modeling the interaction between blood and the aortic wall. Fluid-structure interaction (FSI) simulations were performed on the thoracic aorta geometries of healthy and diseased patients obtained from medical images. The pulsating flow of non-Newtonian blood was set by the boundary condition for the velocity in the form of a periodic physiological wave depending on time. As a result, the parameters of blood flow and vessel deformation were evaluated. It is shown that the velocity value at the site of aortic narrowing increases and falls after the narrowing. In addition, it can be noted that the value of pressure in the healthy aorta was higher than in the aorta with CoA, but at the same time, the pressure in the CoA model increased after the coarctation zone. It was noted that the shear stresses for the two models showed little difference and WSS was overestimated in the diseased aorta. As can be seen from the obtained data, using numerical simulation, important characteristics were determined to assess the influence of the fluid-structure interaction during blood flow in the flexible stenotic thoracic aorta. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To enhance flow stability and reduce hydrodynamic noise caused by fluctuating pressure, a quasi-periodic elastic support skin composed of flexible walls and elastic support elements is proposed for fluid noise reduction. The arrangement of the elastic support element is determined by the equivalent periodic distance and quasi-periodic coefficient. In this paper, a dynamic model of skin in a fluid environment is established. The influence of equivalent periodic distance and quasi-periodic coefficient on flow stability is investigated. The results suggest that arranging the elastic support elements in accordance with the quasi-periodic law can effectively enhance flow stability. Meanwhile, the hydrodynamic noise calculation results demonstrate that the skin exhibits excellent noise reduction performance, with reductions of 10 dB in the streamwise direction, 11 dB in the spanwise direction, and 10 dB in the normal direction. The results also demonstrate that the stability analysis method can serve as a diagnostic tool for flow fields and guide the design of noise reduction structures.

Boosting the mixed convection in vented cavities using a moving wall results in a disturbed strong circulation. This study investigates the mitigation of the disturbed circulation to promote the transfer of heat by providing additional size to the circulation. The use of deformable walls with different thicknesses, lengths and modulus of elasticity is suggested for this problem. The top wall of the cavity is adiabatic and moves in the positive direction, and four speeds were studied; 0.5, 1, 2 and 4 times the fluid velocity at the inlet vent. The ratio of the natural to forced convection is controlled by ranging Richardson number by 0.01 ≤ Ri ≤ 100. Three aspect ratios are studied; AR = 0.5 (horizontal cavity), 1 and 2 (tall cavity). The problem is treated numerically using the finite element method. Results indicate that the fluid flow inside the vented square cavity changes from major single vortices into multi vortices at high (Ri = 100). Results affirm that a flexible wall yields a higher Nusselt number than the rigid wall, it's about 12 %, and 20 % for Ri = 0.01 and 10, respectively. A thicker flexible wall augments the Nusselt number for Ri ≤ 10. For specified conditions, the Nusselt number of the horizontal cavity is 17.7 % greater than the tall cavity. The lid speed of u Lid = 4 u in exhibits a competent role in raising the Nusselt number for low Richardson number. [ABSTRACT FROM AUTHOR]

Cooling of two parallel surfaces with different temperatures is encountered in marine equipment. This requires a compact heat exchanger of two separated fluids, which counts on the double-passage channel. The present study uses a flexible separator to isolate two vertical passages, each partially filled with a porous layer. The permeability of the porous layers (Darcy number, Da), Reynolds number of each passage, temperature ratio, and the modulus of elasticity of the separator are scrutinized. Finite element method with the coupled ALE approach is employed in the numerical treatises. Results show that the strain energy of the elastic separator promotes the overall performance of the heat transfer, where at Da = 10−4, the left wall Nusselt number elevates by 10.4% and that of the right wall by 16.25% when the separator is changed from rigid to a flexible one. As the porous layers meet high permeability, energy transfer from the hot surfaces to the cold fluid upgrades notably, where the Nusselt number increases by 138% for the left wall and 96% for the right wall when Da is increased from 10−5 to 10−1. It is found in a high permeable layer, the flexible separator showcases higher performance than the rigid separator. • The paper investigates the energy exchange through a double-passage channel. • Each passage composed of clear and porous layers. A flexible strained wall separates the passages. • The elastic separator promotes the performance of the heat transfer in the channel. • The higher permeability porous layer promotes the Nusselt number. • The encountered buoyancy within the right passage lowers the Nusselt number in this passage. [ABSTRACT FROM AUTHOR]

The static and dynamic interaction of a normal shock wave (upstream Mach number 1.35) with a compliant wall is characterized experimentally by schlieren visualizations and an optical displacement sensor. Depending on the location of the shock wave along the compliant wall, three different regimes of interaction are found: large-amplitude synchronized regime, small-amplitude synchronized regime and unsynchronized regime. The regime of large-amplitude synchronized oscillations is found for shock locations close to the mid-point of the compliant wall along the streamwise direction; at this location, the coupled system locks to the second vibration frequency of the structure. Three regimes of small-amplitude synchronized oscillations are found depending on the shock position. When the shock is located upstream the center of the compliant wall, the shock may oscillate either periodically at the frequency of the first vibration mode or quasi-periodically with highest amplitudes at the three frequencies of the vibration modes. When the shock is located downstream the center of the compliant wall, the shock oscillates periodically at the frequency of the third vibration mode. Finally, close to the trailing edge of the compliant wall, the shock oscillation is not synchronized with the compliant wall which oscillates with a very small amplitude. An empirical model is proposed to investigate the energy exchange between the flow and the compliant wall during the limit cycle oscillations. A negative aerodynamic damping – and, hence, the possibility of a limit cycle – is observed when a sufficiently extended separation is considered in the model for the pressure distribution at the wall. • Experimental characterization of transonic shock and compliant wall interaction. • Three interaction regimes: large, small synchronized, non-synchronized oscillations. • Empirical model of energy exchange between the flow and the structure. • Explanation of the observed coupled limit cycle oscillations. [ABSTRACT FROM AUTHOR]

The aim of this study is to understand the relationship between blood flow and vascular mechanics in stenotic and healthy arteries and use this understanding to improve the accuracy of computational models for predicting blood flow in human arteries. The article considers four models: a flexible and rigid model of a healthy artery and two flexible arteries with stenoses of various shapes. The deformation of a blood vessel is modeled as a fluid-structure interaction (FSI). The arterial wall is modeled as an isotropic, linearly elastic material, and wall shear stress (WSS) is calculated in order to explore the correlation between induced flow stress and the shape of the artery geometry. Blood is considered as an incompressible non-Newtonian fluid, described by the Carreau viscosity model. Signals of physiological pressure and velocity are used as boundary conditions, which ensure the pulsating nature of the flow. Numerical results show that the developed model predicts vessel deformations and describes their influence on pressure distribution, pressure drop and wall shear stresses. The results of the healthy FSI model are compared with the results of the rigid wall model in order to evaluate the effect of wall elasticity on wall shear stress distribution. Thus, under pathological conditions, the maximum speed value was observed in the model with 40% stenosis and reached 2.16 m/s, while the model with 30% stenosis had a speed of 2.06 m/s. In this case, the maximum displacement of the walls during the cardiac cycle was observed in the artery with 40% stenosis. The deformation value exceeded the wall thickness by 3.3 times and reached 1.66 mm. [ABSTRACT FROM AUTHOR]

A novel multi-component model is introduced for studying interaction between blood flow and deforming aortic wall with intramural hematoma (IMH). The aortic wall is simulated by a composite structure submodel representing material properties of the three main wall layers. The IMH is described by a poroelasticity submodel which takes into account both the pressure inside hematoma and its deformation. The submodel of the hematoma is fully coupled with the aortic submodel as well as with the submodel of the pulsatile blood flow. Model simulations are used to investigate the relation between the peak wall stress, hematoma thickness and permeability in patients of different age. The results indicate that an increase in hematoma thickness leads to larger wall stress, which is in agreement with clinical data. Further simulations demonstrate that a hematoma with smaller permeability results in larger wall stress, suggesting that blood coagulation in hematoma might increase its mechanical stability. This is in agreement with previous experimental observations of coagulation having a beneficial effect on the condition of a patient with the IMH.

In this paper, the flow around a square block in a two-dimensional channel with flexible walls and steady laminar flow is analysed by the one-way fluid-structure interaction numerical method. Flow analysis is carried out by FLUENT and the wall deformations are studied with the assistance of finite element software ANSYS. The study aims to investigate the effects of Poisson's ratio, blockage ratio, channel wall thickness, and elastic modulus on hydrodynamic parameters and ultimately the deformation of channel walls. The results show that an increase in the blockage ratio increases the wall displacement, the total drag coefficient and the friction coefficient on the block. In contrast, an increase in the elastic modulus or Poisson's ratio decreases the displacement of the walls. [ABSTRACT FROM AUTHOR]

The hydraulic conductivity is known as the soil properties that mostly vary over an order of magnitude. There are many laboratory test methods to determine the hydraulic conductivity of the soil. Each test has its own merits, drawbacks and limitations. One of these methods is the measurement using a rigid wall permeameter (RWP), which is a common practice to obtain the fluid transmissibility characteristics of the soil matrix. This type of permeameter has the advantages of low cost, simplicity of test equipment, and adaptability to many different types of permeant liquids. Another method is the measurement through a flexible wall permeameter (FWP). The hydraulic conductivity measured using the FWP is conducted in a confined cylinder in which water flow is forced into one direction. The main disadvantage of this type is being relatively more expensive and needs more time to perform the test compared to the RWP. This study is aimed at comparing three testing conditions to obtain an adjustment factor for the hydraulic conductivity test normally carried out in practice in order to cut down the time needed to perform the test as well as its cost. Different mixtures of sand and expansive clay addition were considered to examine the effect of expansive clay content on the values of the hydraulic conductivity. Tests results revealed that the clay content had a significant effect on the swelling potential, which was attributed to structural changes in the mixtures. The hydraulic conductivity of mixtures decreases with the increase in clay content. The hydraulic conductivity of mixtures tested using FWP was observed to be lower than that of mixtures tested using RWP at similar clay contents. The tests conducted enabled establishing a correction factor to adjust the hydraulic conductivity normally obtained in practice using rigid wall cells.

Abstract Despite the extensive literature on liquid falling films, the majority of them have focused on clean falling films on rigid walls. In this study, the falling film contaminated with insoluble surfactant on a flexible substrate is considered in the numerical simulations. The flow dynamics of film is studied by using the Navier–Stokes equations coupled with interface tracking approach. The surfactant concentration is calculated according to the ratio between surfactant mass and the surface area of film. The fully developed solitary-like wave accompanied with front capillary ripples is obtained. The results show that the presences of interfacial surfactant and flexible substrate have a considerable influence upon the dynamics of falling film. The surfactant, which acts to reduce the celerity of interfacial wave, can suppress the dispersion as well. The wall damping plays a role to deplete the deformation energy of short-wavelength deflection. As the wall damping coefficient increases, the proceeding capillary ripples of the interfacial humps can be suppressed, and the secondary circulation flow is intensified. The wall tension, which can inhibit the flexible wall fluctuation, tends to strengthen the proceeding capillary ripples and promote the celerity of interfacial solitary-like wave. [ABSTRACT FROM AUTHOR]

Numerical study of mixed convection in a lid-driven 3D flexible walled trapezoidal cavity with nanofluids was performed by using Galerkin weighted residual finite element method. Effects of various pertinent parameters such as Richardson number (between 0.05 and 50), elastic modulus of the side surfaces (between 1000 and 10 5 ), side wall inclination angle (between 0° and 20°) and solid particle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer characteristics in a 3D lid-driven-trapezoidal cavity were numerically examined. It was observed that these characteristics are influenced when the pertinent parameters change. Flexible side surface can be used as control element for heat transfer rate. Increment and reduction in the space which are provided by the flexible side walls result in heat transfer enhancement and deterioration for side wall inclination angle of 0° and 10°. Average Nusselt number enhances by about 9.80 % when the value of the elastic modulus is increased from 1000 to 10 5 for side wall inclination angles of θ = 0°. Adding nanoparticles to the base fluid results in linear increment of heat transfer and at the highest volume fraction, 25.30 % of heat transfer enhancement is obtained. A polynomial type correlation for the average Nusselt number along the hot wall was proposed and it has a fourth order polynomial dependence upon the Richardson number and first order dependence upon the solid particle volume fraction. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze the influence of wall flexibility and Joule heating on the peristaltic transport of a conducting nanofluid in uniform/non-uniform porous channel. The exact solutions are obtained for stream function and velocity. Further, R-K-Fehlberg integration scheme is applied to solve the energy and concentration equations. Results obtained and discussed for the flow over uniform and non-uniform geometries at different values of relevant parameters. Moreover, the trapping phenomena are investigated with the help of streamlines. Non-uniform geometry parameter, magnetic parameter, and permeability parameter have a strong impact on trapping phenomena. The fluid velocity is high in the diverging channel when compared to the uniform channel, while the situation is reversed for temperature and concentration fields. [ABSTRACT FROM AUTHOR]

A flexible cylinder launcher based on compressed gas mute launch was developed in order to realize to do work in changing distance to ejection object in the case of constraint and non-blasting.The dynamic characteristics of flexible cylinder launcher is studied through the analysis of catapult theory,simulation calculation and experimental verification.Results indicate that the flexible cylinder launcher can catapult the projectiles when it is folded,compressed,inflated and unfolded,and no blasting phenomenon exists during catapulting.The catapult ability of launcher is affected by the initial length of the flexible cylinder,the contact area of flexible cylinder and projectile,the pressure in flexible cylinder and other factors.The catapult ability of flexible cylinder with different initial lengths is researched.It is found that the longer the initial length is,and the more the fold number of flexible cylinder is,the longer the its catapult distance is,and the stronger its catapult ability is.Under the action of the pressure 2 MPa,a φbl 000 mm x 2 000 mm four flexible cylinder group which catapults a 60 t projectile can produce 4.6 MJ energy.It reflects that flexible cylinder launcher can realize to catapult large mass object. [ABSTRACT FROM AUTHOR]

In this study MHD flow in a lid driven nanofluid filled square cavity with a flexible side wall is numerically investigated. The top wall of the cavity is colder than the bottom wall and it moves in the + x direction with constant speed. Other walls of the cavity are insulated. The finite element formulation is utilized to solve the governing equations. The Arbitrary-Lagrangian-Eulerian method is used to describe the fluid motion with the flexible wall of the cavity in the fluid–structure interaction model. The influence of the Young’s modulus of the flexible wall on the flow and heat transfer characteristics are numerically investigated for the following parameters: ( 10 4 N / m 2 ≤ E ≤ 2.5 × 10 5 N / m 2 ), with a Richardson number of ( 0.01 ≤ R i ≤ 5 ), a Hartmann number of ( 0 ≤ H a ≤ 50 ) and a volume fraction of the solid particles given by ( 0 ≤ ϕ ≤ 0.04 ). The effect of Brownian motion on the effective thermal conductivity of the nanofluid is taken into account. Averaged heat transfer decreases with increasing Hartmann number and decreasing Richardson numbers. As the Young’s modulus of the flexible wall decreases, the averaged heat transfer increases and 66.5% of the heat transfer enhancement is obtained for E = 10 4 N/m 2 compared with E = 2.5 × 10 5 N/m 2 . An averaged heat transfer enhancement of 33.87% is obtained for a solid volume fraction of 4% compared to the base fluid for the fluid–structure model coupled with the magnetic field. [ABSTRACT FROM AUTHOR]

In modern times, electro-kinetics-based microfluidic pumping procedures find wide implementations in multifarious branches of biomedical and physiological manifestations. In this context, our main intention in this research work is to outline a mathematical framework for the hemodynamical characterization of blood circulation loaded with trihybrid nanoparticles inside an eccentric endoscopic arterial canal with a flexible wall under the interference of buoyancy and electro-osmotic forces. The subsequent rescaled equations are solved by employing an analytical approach with the help of Mathematica coding. The changes in the hemodynamical profiles in the endoscopic arterial duct against the preeminent parameters are overlooked via graphical demonstrations. Our graphical inspection proves that blood mobility across the endoscopic arterial tract gets more intense for elevated electro-osmotic parameter values and wall slip factor values. The use of unlike shapes of trihybrid nanoparticles attains the desired heat flow rate in surgical procedures. The lower temperature distribution is recorded for higher loading of trihybrid nanoparticles injected into the bloodstream. Overall, noteworthy findings of this modelling would find an effective way to design tools or devices for medication administration issues and electrotherapies. • Mathematical modelling of electroosmosis-based trihybrid nano-blood motion in an endoscopic arterial tract are performed. • Analytical methodology via Mathematica coding is deployed to acquire the closed-form solutions. • Electro-osmotic force significantly amends blood circulation loaded with trihybrid nanoparticles in the endoscopic space. • Loading trihybrid nanoparticles into the bloodstream are more effective in controlling hemodynamical features. • Our model gives pivotal information to medical students about how to control blood circulation during endoscopic operations. [ABSTRACT FROM AUTHOR]

In this numerical study, magnetohydrodynamics natural convection in a flexible sided triangular cavity with internal heat generation is investigated. The inclined wall of the cavity is cooled and flexible while the left vertical wall is partially heated. Galerkin weighted residual finite element method is used to solve the governing equations. The effects of pertinent parameters such as external Rayleigh number (between 10 4 and 10 6 ), internal Rayleigh number (between 10 4 and 10 7 ), elastic modulus of flexible wall (between 500 and 10 5 ), Hartmann number (between 0 and 40) and inclination angle of the magnetic field (between 0° and 90°) on the fluid flow and heat transfer characteristics were numerically investigated. It was observed local and averaged Nusselt number enhance with external Rayleigh number but in the vicinity of the upper location of the heater local heat transfer deteriorates due to the inclined wall deformation with increasing external Rayleigh number. Heat transfer reduces with internal Rayleigh number and Hartmann number. Averaged heat transfer decreases 13.25% when internal Rayleigh number is increased from 10 4 to 10 7 and decreases 40.56% when Hartmann number is increased from 0 to 10. The reduction in the convection with magnetic field is effective for higher values of external Rayleigh numbers and averaged heat transfer increases with magnetic field inclination angle. [ABSTRACT FROM AUTHOR]

The flow dynamics of an upper-convected-Maxwell (UCM) falling film down a flexible vertical wall is studied in the limit of weak viscoelasticity. A set of Benney-like weakly nonlinear equations for the film thickness and wall deflection, which is valid for small flow rate, is derived based on the long-wave theory. It shows that the unstable role of liquid viscoelasticity is equivalent to that of the flow inertia. A set of asymptotic evolution equations valid for moderate flow rate is obtained based on the integral theory. The linear instability property of the system is examined by using a normal-mode analysis. It shows that the liquid viscoelasticity acts to destabilize the falling film even for the flow with inertia being negligible. The nonlinear evolution equations for the moderate flow rate are solved numerically. The spatio-temporal evolutions of the liquid-air interface and flexible wall are examined. It is concluded that the liquid viscoelasticity plays a role to strengthen the dispersion of the initial imposed perturbation. It can promote the traveling speed of the solitary-like humps and suppress the front-running ripples at the same time. Both the wall damping and wall tension acts to suppress the fluctuations of the flexible wall. However, they play different roles in the evolution of the liquid-air interface. [ABSTRACT FROM AUTHOR]

The hydraulic conductivity is known as the soil properties that mostly vary over an order of magnitude. There are many laboratory test methods to determine the hydraulic conductivity of the soil. Each test has its own merits, drawbacks and limitations. One of these methods is the measurement using a rigid wall permeameter (RWP), which is a common practice to obtain the fluid transmissibility characteristics of the soil matrix. This type of permeameter has the advantages of low cost, simplicity of test equipment, and adaptability to many different types of permeant liquids. Another method is the measurement through a flexible wall permeameter (FWP). The hydraulic conductivity measured using the FWP is conducted in a confined cylinder in which water flow is forced into one direction. The main disadvantage of this type is being relatively more expensive and needs more time to perform the test compared to the RWP. This study is aimed at comparing three testing conditions to obtain an adjustment factor for the hydraulic conductivity test normally carried out in practice in order to cut down the time needed to perform the test as well as its cost. Different mixtures of sand and expansive clay addition were considered to examine the effect of expansive clay content on the values of the hydraulic conductivity. Tests results revealed that the clay content had a significant effect on the swelling potential, which was attributed to structural changes in the mixtures. The hydraulic conductivity of mixtures decreases with the increase in clay content. The hydraulic conductivity of mixtures tested using FWP was observed to be lower than that of mixtures tested using RWP at similar clay contents. The tests conducted enabled establishing a correction factor to adjust the hydraulic conductivity normally obtained in practice using rigid wall cells. [ABSTRACT FROM AUTHOR]

Abstract: This study concerns an evaluation of pulsatile flow and arterial wall behavior in a real world model of a stenosed abdominal aorta and iliac arteries. Two different geometries of a healthy and severly stenosed abdominal aorta, extracted from CT scan images and simulations of fluid flow and tissue interaction (Fluid Solid Interaction), are carried out. The blood is taken as incompressible, non-Newtonian, and the arterial wall tissue is treated as isotropic, elastic material with uniform mechanical properties. The results of using two models with rigid and flexible walls are presented and compared. The computed pressure at the abdominal aorta for a flexible healthy wall is consistent with measured values in vivo conditions. Results show that the computed pressure is lower by 15% for the flexible model, as compared to the rigid and complaint models. Although results obtained from the FSI study of pulsatile healthy and stenosed models show a similar trend for Wall Shear Stress (WSS) patterns, considerable differences in magnitude exist. It is shown that for the cases presented here, the effects of wall flexibility and actual stenosed geometry on the flow performance of veins are noticeable. [Copyright &y& Elsevier]

Abstract: Studies showed that vascular diseases were prone to occur in curved arteries. In this paper, biomechanical behaviors of curved artery with flexible wall subjected to physiological flow were presented. Fluid–structure interaction effect was considered. The Von Mises stress variation and distribution patterns, the influence of artery curvature and flexibility on peak wall Von Mises stress, diameter change and cross sectional shape variation of the curved artery in the cardiac cycle were studied in detail. We believe that the findings may provide important implications for individualized treatment for patients with cardiovascular disease. [Copyright &y& Elsevier]

Abstract: Turbulent pulsatile flow and wall mechanics were studied numerically in an axisymmetric three-layered wall model of a descending aorta. The transport equations were solved using the finite element formulation based on the Galerkin method of weighted residuals. A fully-coupled fluid–structure interaction (FSI) analysis was utilized in this investigation. We calculated Von Mises wall stress, streamlines and fluid pressure contours. The findings of this study show that peak wall stress and maximum shear stress are highest in the media layer. The difference in the elastic properties of contiguous layers of the wall of the aorta probably determines the occurrence of dissection in the media layer. Moreover, the presence of aortic intramural hematoma is found to have a significant effect on the peak wall stress acting on the inner layer. [Copyright &y& Elsevier]

Abstract: A hybrid discrete–finite element model is introduced for simulation of mechanical behavior of geomaterials. The soil or rock is modeled as a system of discrete balls that interact through normal and shear springs. The balls can be bonded at the contact points to withstand the applied deviatoric stresses. The important feature of this model is that the confining walls that can be imagined for example as the surrounding membrane or the mold in a physical test are modeled by deformable finite elements. This allows simulation of laboratory test features more realistically compared to the situations where the surrounding walls are rigid. The relationships between micro- and macro-properties are investigated in this paper as well. These relationships and the corresponding curves are helpful tools in calibration of the numerical model for the macroscopic elastic properties. [Copyright &y& Elsevier]

Abstract: Pulsatile turbulent flow characteristics in an axisymmetric aortic aneurysm (AA) model were analyzed numerically using a simulated physiological waveform. The transport equations were solved using the finite element formulation based on the Galerkin method of weighted residuals. A fully-coupled fluid–structure interaction (FSI) analysis was utilized in this work. We investigated the effects of turbulent flow characteristics on the distribution of wall stress and flow patterns in AA models. Wall stress distributions were calculated by computational solid stress (CSS) model, which ignores the effect of the blood flow, and the FSI model that takes into account flow and solid mechanics. Our results showed that peak wall stress and peak deformation were found to occur shortly after peak systolic flow in the FSI model and at the peak luminal pressure condition in the CSS model. Further, CSS model underestimated wall stress calculations when compared to the FSI model. There were also significant differences in the structure of flow fields between the flexible and rigid wall aneurysm models. Contour plots of kinetic energy dissipation and the application of the Kolmogorov microscale suggest that the conditions that result in red blood cell damage and platelet activation most likely occur in the near-wall region of AA during turbulent flow. [Copyright &y& Elsevier]

Abstract: The interaction of two superposed inviscid liquids with a flexible side wall of a rectangular container is considered. The governing equations describing the behaviour of the system are analyzed using the concept of normal modes, and their solutions presented in the form of infinite series. The expansion coefficients for the velocity potentials are calculated by employing a new inner product which allows orthogonalizing the fluid shape modes. An eigenfrequency equation is then derived from the requirement for a nontrivial solution exists. The influence of the governing parameters on the coupled frequencies is illustrated in the case of water–mercury system. To cite this article: M. Amaouche, B. Meziani, C. R. Mecanique 336 (2008). [Copyright &y& Elsevier]

The problem of non-Newtonian and nonlinear pulsatile flow through an irregularly stenosed arterial segment is solved numerically where the non-Newtonian rheology of the flowing blood is characterized by the generalized Power-law model where both the shear-thinning and shear-thickening models of the streaming blood are taken into account. The combined influence of an asymmetric shape and surface irregularities (roughness) of the constriction has been explored in a study of blood flow with 48% areal occlusion. The vascular wall deformability is taken to be anisotropic, linear, viscoelastic, incompressible circular cylindrical membrane shell. The effect of the surrounding connective tissues on the motion of the arterial wall is also paid due attention. Results are obtained for a smooth stenosis model and also for a stenosis model represented by the cosine curve. The present analytical treatment has the potential to calculate the rate of flow, the resistive impedance and the wall shear stress without excessive computational complexity by exploiting the appropriate physiologically realistic prescribed conditions in nonuniform nonstaggered grids, and to estimate the effects of surface roughness as well as asymmetry of stenosis shape for both shear-thinning and shear-thickening models of Power-law fluid, representing the streaming blood through graphical representations in order to validate the applicability of the present improved mathematical model. [ABSTRACT FROM AUTHOR]

Abstract: Of concern in the paper is an analytical study of pulsatile blood flow in an irregular stenosed arterial segment through a mathematical model. The model is two-dimensional and axisymmetric with an outline of the stenosis obtained from a three-dimensional casting of a mildly stenosed artery [L. Back, Y. Cho, D. Crawford, R. Cuffel, Effect of mild atherosclerosis on flow resistance in a coronary artery casting of man, J. Biomech. Eng. 106 (1984) 48–53]. The combined influence of an asymmetric shape and surface irregularities of the constriction has been explored in a computational study of blood flow through arterial stenosis with 48% areal occlusion. The moving wall of the artery is included to be anisotropic, linear, viscoelastic, incompressible circular cylindrical membrane shell. The effect of the surrounding connective tissues on the motion of the arterial wall is also paid due attention. Results are also obtained for a smooth stenosis model and also for a stenosis model representative by the cosine curve. An extensive quantitative analysis has been performed in non-uniform non-staggered grids through numerical computations for the effect of surface irregularities on the flow velocity, the flux, the resistive impedance and on the wall shear stress through their graphical representations so as to validate the applicability of such an improved mathematical model. [Copyright &y& Elsevier]

• This work shows the factors that affect wall pressure distributions in silos. • A validated finite element model is used for parametric study. • The importance of wall and solid stiffness is demonstrated. • A relationship for wall pressures and stiffness is presented. • This relationship can be used for more efficient structural design. An experimentally validated finite element model of filling pressures in rectangular silos with flexible walls is used to predict the stress regime in the stored solid in squat and intermediate aspect ratio silos. The model predicts the state of stress in the stored solid and the pressures imposed on the flexible walls of the silo. The non-uniform horizontal pressure distributions at each depth at the end of filling are explored. It is known that an empirical relation for the horizontal pressure variation on each straight wall derived from experimental observations in an earlier study closely matches the computational predictions. The coefficients of this relation are found to vary with depth below the stored solid surface, and depend on the relative stiffness of stored solid and the silo wall. Following many calculations involving different solids, an empirical relationship is derived that is suitable for practical design for a range of different stored solids for which relevant properties are known. The resulting expression is well suited to the practical determination of filling pressures in rectangular silos, and provides a silo design pressure proposal that is based on theoretical, rather than empirical findings. [ABSTRACT FROM AUTHOR]

• Unsteady forced convective with Fluid-structure interaction is been studied. • Parallel plates channel with two baffles and compliant wall is inserted. • Galerkin finite element method together with ALE technique is followed. • Higher and lower Re numbers cause positive and negative deflections, respectively. • The best length of the downstream baffle is 0.2 times the channel height. This paper investigates the fluid-structure interaction (FSI) and the forced convective heat transfer in a channel partly heated by constant heat flux. The FSI is represented by the 2-dimensional benchmarked geometry; a compliant segment wall. Two alternatives, upstream and downstream, baffles acting as vortex generators bound the compliant segment. The unsteady problem is formulated by arbitrary Lagrangian-Eulerian scheme based on finite element method. The thermal-hydraulic enhancement criterion is computed to evaluate the performance of the channel. Cauchy number and the length of the baffles respectively control the flexibility of the compliant segment and the force exerted on it, while Reynolds number is imposed to assess the competitive roles of the inertia and viscous forces. It is found that the Nusselt number of a certain compliant baffled channel enhances 94% compared with non-baffled channel at Re = 250, while the pressure drop increases by 210%. The thermal-hydraulic analysis shows that the best performance can be obtained at Cauchy number of 10−7 when the lengths of the upstream and downstream baffles are 0.6 and 0.2 times the channel height, respectively. The results show also that the compliant wall segment lowers the thermal performance of the non-baffled channel. [ABSTRACT FROM AUTHOR]

A novel multi-component model is introduced for studying interaction between blood flow and deforming aortic wall with intramural hematoma (IMH). The aortic wall is simulated by a composite structure submodel representing material properties of the three main wall layers. The IMH is described by a poroelasticity submodel which takes into account both the pressure inside hematoma and its deformation. The submodel of the hematoma is fully coupled with the aortic submodel as well as with the submodel of the pulsatile blood flow. Model simulations are used to investigate the relation between the peak wall stress, hematoma thickness and permeability in patients of different age. The results indicate that an increase in hematoma thickness leads to larger wall stress, which is in agreement with clinical data. Further simulations demonstrate that a hematoma with smaller permeability results in larger wall stress, suggesting that blood coagulation in hematoma might increase its mechanical stability. This is in agreement with previous experimental observations of coagulation having a beneficial effect on the condition of a patient with the IMH., Competing Interests: 7. Conflict of interest statement There is no conflict of interest., (Copyright © 2016 Elsevier Ltd. All rights reserved.)