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 predict...
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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 fluidstructureinteraction (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.
We propose a monolithic fluid-structure interaction (FSI) method that presents the advantages of both the reference map technique (RMT) and the Lagrangian Markers approach on a unified, cell-centered finite volume Eul...
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We propose a monolithic fluid-structure interaction (FSI) method that presents the advantages of both the reference map technique (RMT) and the Lagrangian Markers approach on a unified, cell-centered finite volume Eulerian framework. Full Eulerian methods that use a Cartesian mesh are attractive for FSI problems that require large-scale computing and involve complex geometries and large solid deformations. However, conventional full Eulerian methods use the velocity gradient to evaluate solid deformations, hence they suffer from numerical instability caused by the discontinuity of the velocity gradient near the interface. In this work, we develop a novel algorithm that interpolates and transfers a reference mapping information field between a collection of Lagrangian Markers and a Eulerian finite volume framework. As a result of integrating these approaches, our method is able to (1) evaluate solid deformations without computing the velocity gradient in the Eulerian framework thanks to RMT, and (2) remove the numerical dissipation of interfaces and internal variables caused by advection in the full Eulerian RMT, thanks to the use of the Lagrangian Markers to compute the constitutive equations. We illustrate with numerical examples that the proposed method preserves geometrical features and yields more accurate results for the deformation and energy than conventional Eulerian FSI method and the full Eulerian RMT.
In this paper, we present a novel fluid-structure interaction framework based on the smoothed particle hydrodynamics model for fluids and a recently developed constitutively informed particle dynamics model for solids...
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In this paper, we present a novel fluid-structure interaction framework based on the smoothed particle hydrodynamics model for fluids and a recently developed constitutively informed particle dynamics model for solids. We develop a new method for coupling these approaches to expand the fluid-structure simulation framework to include crack propagation failure in the solid. Several benchmark problems have been simulated to validate the fluid and solid models separately as well as the coupled model. We then apply this coupled approach to model brittle failure of a notched bar impacted by a fluid. We study the effect of various parameters such as height of the obstacle and location of the notch on its fracture.
This paper focuses on a fluid-structure interaction topic-the determination of added effects caused by fluid forces acting on a body, considering the standard linear equation of motion. We present various problems tha...
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This paper focuses on a fluid-structure interaction topic-the determination of added effects caused by fluid forces acting on a body, considering the standard linear equation of motion. We present various problems that assume small-displacement oscillations of single and multiple bodies in inviscid irrotational (potential) flow or viscous incompressible flow in both closed domain and external flow. For inviscid flow, effects of geometric parameters on the added effects were studied. The presented results extend results known from the literature. For viscous flow, frequency dependence of the added effects was studied for a wide range of frequency. The added effects were computed from data from numerical simulations of fluid flow, where the body oscillations were modeled using the dynamic mesh approach. Effects of the phase shift caused by the dynamic mesh were addressed. The added mass was compared with the corresponding value determined for inviscid flow where applicable. The results show strong dependence of the added effects on many parameters, making their proper computation challenging even for simplified cases.
The centrifugal pump is a prevalent power equipment widely used in different engineering patterns,and the impeller blade wrap angle significantly impacts its performance.A numerical investigation was conducted to anal...
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The centrifugal pump is a prevalent power equipment widely used in different engineering patterns,and the impeller blade wrap angle significantly impacts its performance.A numerical investigation was conducted to analyze the influence of the blade wrap angle on flow characteristics and energy distribution of a centrifugal pump evaluated as a low specific speed with a value of *** study investigates six impellermodels that possess varying blade wrap angles(95°,105°,115°,125°,135°,and 145°)that were created while maintaining the same volute and other geometrical *** investigation of energy loss was conducted to evaluate the values of total and entropy generation rates(TEG,EGR).The fluid-structure interaction was considered numerically using the software tools ANSYS Fluent and *** elastic structural dynamic equation was used to estimate the structural response,while the shear stress transport k–ωturbulence model was utilized for the fluid domain *** findings suggest that the blade wrap angle has a significant influence on the efficiency of the *** impeller featuring a blade wrap angle of 145°exhibits higher efficiency,with a notable increase of 3.76%relative to the original *** in the blade wrap angle impact the energy loss,shaft power,and pump *** model with a 145°angle exhibited a maximum equivalent stress of 14.8MPa and a total deformation of 0.084 *** results provide valuable insights into the intricate flow mechanism of the centrifugal pump,particularly when considering various blade wrap angles.
This paper investigates the dynamic characteristics of a multi-degree-of-freedom (multi-DOF) acoustic resonant system involving highly viscous fluids. First, a fluid-structure interaction (FSI) model is established to...
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This paper investigates the dynamic characteristics of a multi-degree-of-freedom (multi-DOF) acoustic resonant system involving highly viscous fluids. First, a fluid-structure interaction (FSI) model is established to describe the interaction between the multi-DOF acoustic resonant system and the two-phase fluids, and then the effects of various excitation parameters on the dynamic response of the coupled system are studied. Under the influence of vertical acoustic vibration, the fluid in the container undergoes violent and irregular motions, which leads to a decrease and fluctuation in the equivalent mass of the fluid. The reduction in fluid equivalent mass causes the excitation frequency to deviate from the natural frequency of the multi-DOF acoustic resonant system, thus significantly reducing the dynamic response of the coupled system. Furthermore, the fluctuation of the fluid equivalent mass induces a quasi-periodic motion pattern of the acoustic resonant system. Although increasing the excitation amplitude can effectively increase the dynamic response of the coupled system, it can also increase the fluctuation level of the dynamic response to a certain extent. By appropriately increasing the excitation frequency, the coupled system can operate at a new resonant frequency, thereby reducing the influence of fluid motion on the dynamic response of the system.
Bioprosthetic heart valve (BHV), the most widely and commonly used valves in clinical practice, are susceptible to fatigue damage. Biological valves are always in one or fewer body postures before sampling in pigs and...
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Bioprosthetic heart valve (BHV), the most widely and commonly used valves in clinical practice, are susceptible to fatigue damage. Biological valves are always in one or fewer body postures before sampling in pigs and bovines. Nevertheless, human body positions are far more than them. Variations in body position significantly affect the intrinsic environment of blood pressure (BP), heart rate (HR), and peripheral resistance (PR). Such boundary condition changes will inevitably affect the implanted biological valve. In this paper, the immersed boundary method was used to simulate the motion of the aortic valve during the entire cardiac cycle in five postural blood flow environments: upright, sitting, prone, supine and orthostatic hypotension (OH). Several hemodynamic and biomechanical parameters, including the transvalvular pressure gradient and valve displacement, were evaluated. The results showed that the OH group exhibited the worst performance of the valves, accompanied by the greatest regurgitation and high-frequency flutter, predisposing patients to thrombosis and fatigue calcification. For BHVs to serve longer, patients implanted with BHV should avoid OH in their daily routine.
The study on arterial stenosis has gained rapid interest among researchers in the last decade because of its chronic consequences. Several researchers have tried to investigate stenosis and plaque progression in the c...
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The study on arterial stenosis has gained rapid interest among researchers in the last decade because of its chronic consequences. Several researchers have tried to investigate stenosis and plaque progression in the carotid artery with different simulation models. In this study, a realistic 3-D geometry of the carotid artery has been used to analyze the effect of varying degrees of stenosis present at different locations of the carotid artery on various hemodynamic parameters. An extensive range of stenosis degrees, starting from a healthy artery(0 %stenosis) to 10%, 30%, 50%, 75%, and 90% stenosis, have been studied. These degrees of stenosis were planted at different locations of the artery grown simultaneously. The whole study was done under the realm of fluid-structure interaction multiphysics. The change in velocity profiles at the areas of stenosis has been found along with the wall shear stress and arterial displacement. The magnitude of velocity and wall shear stress in the case of multiple stenosis locations has been found to be dependent on each other. The presence or absence of one stenosis affects the other, and given the regular and irregular patterns of the velocity profile, wall shear stress, and displacement, their inclusion in blood flow simulation studies having multiple stenoses should be considered.
Background and Objective: Prosthetic heart valve interventions such as TAVR have surged over the past decade, but the associated complication of long-term, life-threatening thrombotic events continues to undermine pat...
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Background and Objective: Prosthetic heart valve interventions such as TAVR have surged over the past decade, but the associated complication of long-term, life-threatening thrombotic events continues to undermine patient outcomes. Thus, improving thrombogenic risk analysis of TAVR devices is crucial. In vitro studies for thrombogenicity are typically difficult to perform. However, revised ISO testing standards include computational testing for thrombogenic risk assessment of cardiovascular implants. We present a fluid-structure interaction (FSI) approach for assessing thrombogenic risk of transcatheter aortic valves. Methods: An FSI framework was implemented via the incompressible computational fluid dynamics multi-physics solver of the ANSYS LS-DYNA software. The numerical modeling approach for flow analysis was validated by comparing the derived flow rate of the 29 mm CoreValve device from benchtop testing and orifice areas of commercial TAVR valves in the literature to in silico results. Thrombogenic risk was analyzed by computing stress accumulation (SA) on virtual platelets seeded in the flow fields via ANSYS EnSight. The integrated FSIthrombogenicity methodology was subsequently employed to examine hemodynamics and thrombogenic risk of TAVR devices with two approaches: 1) engineering optimization and 2) clinical assessment. Results: Simulated effective orifice areas for commercial valves were in reported ranges. In silico cardiac output and flow rate during the positive pressure differential period matched experimental results by approximately 93 %. The approach was used to analyze the effect of various TAVR leaflet designs on hemodynamics, where platelets experienced instantaneous stresses reaching around 10 Pa. Post-TAVR deployment hemodynamics in patient-specific bicuspid aortic valve anatomies revealed varying degrees of thrombogenic risk with the highest median SA around 70 dyn & sdot;s/cm2- nearly double the activation threshold- despite those being cli
In this paper, the effects of the gradient form, peak pressure and decaying time on the fluid-structure interaction of composite auxetic re-entrant honeycomb structures was experimentally and numerically investigated....
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In this paper, the effects of the gradient form, peak pressure and decaying time on the fluid-structure interaction of composite auxetic re-entrant honeycomb structures was experimentally and numerically investigated. The specimens for this experiment were manufactured by hot-press molding method. The acrylic transparent tube was utilized to accommodate water medium, pistons and specimen during experiment. The exponential decaying shock wave was simulated by accelerating the fly plate to impact the piston based on the one-stage light gas gun system. The incident velocity of the fly plate and process of the fluid-structure interaction response were monitored by high frame rate camera. In addition, the velocity of the shock wave in water was measured by transducers installed at different measuring points. The voltage signal of the dynamic overpressure collected by transducers was amplified by the charge amplifier and recorded by the oscilloscope. On the other hand, finite element software Abaqus/Explicit was applied to simulate the cavitation process of water domain and dynamic response of specimens. The experimental results and numerical results were in good agreement. The results indicated that the increase of the thickness of the fly plate had a certain effect on the propagation velocity of the shock wave, and the increase of the peak pressure would make the cavitation generation position close to the fluid-structure interface and make the cavitation duration longer. And the average structure which has a minimum transformation of 8.12 mm shows better underwater impact resistance than the gradient structure.
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