In this work, we present a new monolithic finite element strategy for solving fluid-structure interaction problems involving a compressible fluid and a hyperelastic structure. In the Lagrangian limit, the time-steppin...
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In this work, we present a new monolithic finite element strategy for solving fluid-structure interaction problems involving a compressible fluid and a hyperelastic structure. In the Lagrangian limit, the time-stepping strategy that we propose conserves the total energy, and linear and angular momenta. Detailed proofs with numerical validations are provided. We use a displacement-based Lagrangian formulation for the structure, and a velocity-based arbitrary Lagrangian-Eulerian mixed formulation with appropriately chosen interpolations for the various field variables to ensure stability of the resulting numerical procedure. A hybrid formulation is used to prevent locking of thin structures. Apart from physical variables such as displacement, velocity, and so forth, no new variables are introduced in the formulation. The use of the exact tangent stiffness matrix ensures that the algorithm converges quadratically within each time step. A number of benchmark examples have been solved to illustrate the good performance of the proposed method.
Recirculation in venovenous extracorporeal membrane oxygenation (VV ECMO) leads to reduction in gas transfer efficiency. Studies of the factors contributing have been performed using in vivo studies and computational ...
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Recirculation in venovenous extracorporeal membrane oxygenation (VV ECMO) leads to reduction in gas transfer efficiency. Studies of the factors contributing have been performed using in vivo studies and computational models. The fixed geometry of previous computational models limits the accuracy of results. We have developed a finite element computational fluid dynamics model incorporating fluid-structure interaction (FSI) that incorporates atrial deformation during atrial filling and emptying, with fluid flow solved using large eddy simulation. With this model, we have evaluated an extensive number of factors that could influence recirculation during two-site VV ECMO, and characterized their impact on recirculation, including cannula construction, insertion depth and orientation, VV ECMO configuration, circuit blood flow, and changes in volume, venous return, heart rate, and blood viscosity. Simulations revealed that extracorporeal blood flow relative to cardiac output, ratio of superior vena caval (SVC) to inferior vena caval (IVC) blood flow, position of the SVC cannula relative to the cavo-atrial junction, and orientation of the return cannula relative to the tricuspid valve had major influences (>20%) on recirculation fraction. Factors with a moderate influence on recirculation fraction (5%-20%) include heart rate, return cannula diameter, and direction of extracorporeal flow. Minimal influence on recirculation (<5%) was associated with atrial volume, position of the IVC cannula relative to the cavo-atrial junction, the number of side holes in the return cannula, and blood viscosity.
We consider a loosely-coupled algorithm for fluid-structure interaction based on a Robin interface condition for the fluid problem (explicit Robin-Neumann scheme). We study the dependence of the stability of this meth...
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We consider a loosely-coupled algorithm for fluid-structure interaction based on a Robin interface condition for the fluid problem (explicit Robin-Neumann scheme). We study the dependence of the stability of this method on the interface parameter in the Robin condition. In particular, for a model problem we find sufficient conditions for instability and stability of the method. In the latter case, we find a stability condition relating the time discretization parameter, the interface parameter, and the fluid and structure densities. Numerical experiments confirm the theoretical findings and highlight optimal choices of the interface parameter that guarantee accurate solutions.
Atherosclerotic plaque in the femoral is the leading cause of peripheral artery disease (PAD), the worse consequence of which may lead to ulceration and gangrene of the feet. Numerical studies on fluid-structure inter...
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Atherosclerotic plaque in the femoral is the leading cause of peripheral artery disease (PAD), the worse consequence of which may lead to ulceration and gangrene of the feet. Numerical studies on fluid-structure interactions (FSI) of atherosclerotic femoral arteries enable quantitative analysis of biomechanical features in arteries. This study aims to investigate the hemodynamic performance and its interaction with femoral arterial wall based on the patient-specific model with multiple plaques (calcified and lipid plaques). Three types of models, calcification-only, lipid-only and calcification-lipid models, are established. Hyperelastic material coefficients of the human femoral arteries obtained from experimental studies are employed for all simulations. Oscillation of WSS is observed in the healthy downstream region in the lipid-only model. The pressure around the plaques in the two-plaque model is lower than that in the corresponding one-plaque models due to the reduction of blood flow domain, which consequently diminishes the loading forces on both plaques. Therefore, we found that stress acting on the plaques in the two-plaque model is lower than that in the corresponding one-plaque models. This finding implies that the lipid plaque, accompanied by the calcified plaque around, might reduce its risk of rupture due to the reduced the stress acting on it.
Aortic valve replacement(AVR)remains a major treatment option for patients with severe aortic valve *** outcome of AVR is strongly dependent on implanted prosthetic valve ***-structureinteraction(FSI)aortic root mode...
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Aortic valve replacement(AVR)remains a major treatment option for patients with severe aortic valve *** outcome of AVR is strongly dependent on implanted prosthetic valve ***-structureinteraction(FSI)aortic root models were constructed to investigate the effect of valve size on hemodynamics of the implanted bioprosthetic valve and optimize the outcome of AVR *** models with 4 sizes of bioprosthetic valves(19(No.19),21(No.21),23(No.23)and 25 mm(No.25))were *** ventricle outflow track flow data from one patient was collected and used as model flow *** Mooney–Rivlin models were used to describe mechanical properties of aortic valve *** flow pressure,velocity,systolic valve orifice pressure gradient(SVOPG),systolic cross-valve pressure difference(SCVPD),geometric orifice area,and flow shear stresses from the four valve models were *** results indicated that larger valves led to lower transvalvular pressure gradient,which is linked to better post AVR *** SVOPG,mean SCVPD and maximum velocity for Valve No.25 were 48.17%,49.3%,and 44.60%lower than that from Valve No.19,*** orifice area from Valve No.25 was 52.03%higher than that from Valve No.19(1.87 cm2 vs.1.23 cm2).Implantation of larger valves can significantly reduce mean flow shear stress on valve *** initial results suggested that larger valve size may lead to improved hemodynamic performance and valve cardiac function post *** patient studies are needed to validate our findings.
In the present study, the harmonic movement of fluid flow and the behaviour of elastic structure under this movement are investigated. Accordingly, a recently developed fluid-structure interaction method in which flui...
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In the present study, the harmonic movement of fluid flow and the behaviour of elastic structure under this movement are investigated. Accordingly, a recently developed fluid-structure interaction method in which fluid and structure are simulated with smoothed particle hydrodynamics (SPH) and finite element method (FEM) is used. The interaction between fluid and the structure is satisfied with the contact mechanics. In order to validate the numerical model under harmonic movement, different experiments are used. First, the structure is assumed to be rigid and the pressures calculated on the structure are compared with the experimental data available in the literature. Similarly, free-surfaces are also validated with novel experiments carried out in the context of this study. In addition, the interaction between an elastic structure and fluid is investigated in the novel experiments in which a water tank having an elastic buffer in the middle is moved under harmonic horizontal movement and the deflection of the elastic buffer and free-surface profiles are measured. Comprehensive results are given for all validation cases. According to the results, the numerical method is successful and can be used in these types of problems.
We recently developed the open-source library tIGAr, which extends the FEniCS finite element automation framework to isogeometric analysis. The present contribution demonstrates the utility of tIGAr in complex problem...
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We recently developed the open-source library tIGAr, which extends the FEniCS finite element automation framework to isogeometric analysis. The present contribution demonstrates the utility of tIGAr in complex problems by applying it to immersogeometric fluid-structure interaction (FSI) analysis. This application is implemented as the new open-source library CouDALFISh (Coupling, via Dynamic Augmented Lagrangian, of fluids with Immersed Shells, pronounced "cuttlefish"), which uses the dynamic augmented Lagrangian (DAL) method to couple fluid and shell structure subproblems. The DAL method was introduced previously, over a series of papers largely focused on heart valve FSI, but an open-source implementation making extensive use of automation to compile numerical routines from high-level mathematical descriptions brings newfound transparency and reproducibility to these earlier developments on immersogeometric FSI analysis. The portions of CouDALFISh that do not use code generation also illustrate how a framework like FEniCS remains useful even when some functionality is outside the scope of its standard workflow. This paper summarizes the workings of CouDALFISh and documents a variety of benchmarks demonstrating its accuracy. Although the implementation emphasizes transparency and extensibility over performance, it is nonetheless demonstrated to be sufficient to simulate 3D FSI of an idealized aortic heart valve. Source code will be maintained at https://***/david-kamensky/CouDALFISh. (C) 2020 Elsevier Ltd. All rights reserved.
In this article, we derive an adjoint fluid-structure interaction (FSI) system in an arbitrary Lagrangian-Eulerian (ALE) framework, based upon a one-field finite element method. A key feature of this approach is that ...
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In this article, we derive an adjoint fluid-structure interaction (FSI) system in an arbitrary Lagrangian-Eulerian (ALE) framework, based upon a one-field finite element method. A key feature of this approach is that the interface condition is automatically satisfied and the problem size is reduced since we only solve for one velocity field for both the primary and adjoint system. A velocity (and/or displacement)-matching optimisation problem is considered by controlling a distributed force. The optimisation problem is solved using a gradient descent method, and a stabilised Barzilai-Borwein method is adopted to accelerate the convergence, which does not need additional evaluations of the objective functional. The proposed control method is validated and assessed against a series of static and dynamic benchmark FSI problems, before being applied successfully to solve a highly challenging FSI control problem.
Effectively controlling the deformation and temperature of heated structures is crucial for achieving highperformance active cooling through fluid flow. In this study, the topology optimization design of structures co...
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Effectively controlling the deformation and temperature of heated structures is crucial for achieving highperformance active cooling through fluid flow. In this study, the topology optimization design of structures considering fluid-structure interactions and heat transfer performance was investigated, and then optimized designs of two-dimensional/three-dimensional cooling impingement systems obtained using the proposed method were obtained. In the optimization model, the objective function was constructed as a weighted combination of the mechanical deformations at specific locations and the average temperature within the designated solid channel structures. Additionally, explicit functional interpolation models were introduced to establish connections between the thermal, fluid, and solid properties, along with the element densities. In the analysis model, the strongly coupled structural mechanical deformation and fluid velocity field were analyzed via a dynamic-grid-based finite element model with a Winslow elliptic smoother to automatically track the fluid-structure interface during the process of optimization. To solve the optimization problems, the globally convergent moving asymptotic optimizer method was used to adjust the design variables on the basis of the sensitivity analysis. A demonstration of the efficacy of the proposed algorithm is provided through the presentation of several optimization examples. Furthermore, two-and three-dimensional cooling impingement systems were designed with the proposed method.
We analyze the steady non-Newtonian fluid-structure interaction between the flow of an Oldroyd-B fluid and a deformable channel. Specifically, we provide a theoretical framework for calculating the leading-order effec...
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We analyze the steady non-Newtonian fluid-structure interaction between the flow of an Oldroyd-B fluid and a deformable channel. Specifically, we provide a theoretical framework for calculating the leading-order effect of the fluid's viscoelasticity on the flow rate-pressure drop relation and on the deformation of the channel's elastic wall. We first identify the characteristic scales and dimensionless parameters governing the fluid- structureinteraction in slender and shallow channels. Applying the lubrication approximation for the flow and employing a perturbation expansion in powers of the Deborah number De, we derive a closed-form expression for the pressure as a function of the non-uniform shape of the channel in the weakly viscoelastic limit up to O(De). Coupling the hydrodynamic pressure to the elastic deformation, we provide the leading-order effect of the interplay between the viscoelasticity of the fluid and the compliance of the channel on the pressure and deformation fields, as well as on the flow rate-pressure drop relation. For the flow-rate-controlled regime and in the weakly viscoelastic limit, we show analytically that both the compliance of the deforming top wall and the viscoelasticity of the fluid decrease the pressure drop. Furthermore, we reveal a trade-off between the influence of compliance of the channel and the fluid's viscoelasticity on the deformation. While the channel's compliance increases the deformation, the fluid's viscoelasticity decreases it.
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