Introduction Abdominal aortic aneurysm (AAA) is a life-threatening disease marked by localized dilatations of the infrarenal aortic wall. While clinical guidelines often use the aneurysm diameter as an indicator for s...
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Introduction Abdominal aortic aneurysm (AAA) is a life-threatening disease marked by localized dilatations of the infrarenal aortic wall. While clinical guidelines often use the aneurysm diameter as an indicator for surgical intervention, this metric alone may not reliably predict rupture risks, underscoring the need for detailed biomechanical analyses to improve risk *** We investigate the effects of the multi-layered tissue architecture and the intraluminal thrombus (ILT) on the wall stress distribution of AAA. Using fluid-structure interaction, we analyze the biomechanical responses of fusiform and saccular AAAs under three conditions: without ILT, with ILT but no tissue degradation, and with both ILT and tissue *** The findings show that the media is the primary load-bearing layer, and the multi-layered model yields a more accurate stress profile than the single-layered tissue model. The ILT substantially reduces overall stress levels in the covered tissue, although its impact on the location of peak stress varies across different scenarios. Media degradation increases the stress in the intima and adventitia, but the cushioning effect of ILT largely mitigates this *** The results underscore the importance of incorporating the multi-layered tissue architecture and ILT in patient-specific analyses of AAA. These factors may improve the predictive capabilities of biomechanical assessments for rupture risk.
Brush seals in gas turbine engines offer effective sealing performance but may encounter instability at high swirl velocities, potentially leading to seal failure. This investigation employs fluid-structure interactio...
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Brush seals in gas turbine engines offer effective sealing performance but may encounter instability at high swirl velocities, potentially leading to seal failure. This investigation employs fluid-structure interaction (FSI) analysis to examine the deformation of bristle packs under swirling flow conditions and evaluates the influence of geometric parameters through a design of experiments (DOE) methodology. The critical parameters encompass the bristle diameter, length, inclined angle, number of rows, radial clearance, and spacing between bristles. The findings of this study indicate that circumferential slip, associated with the normal-to-axial force ratio on the bristle pack, precipitates instability at elevated ratios. The spacing between the bristles and their inclination angle substantially affect the aerodynamic force ratio, with contributions of 26.5 % and 23.6 %, respectively. Radial clearance emerges as the predominant factor influencing leakage, explaining 74 % of its variability, with leakage increasing linearly with radial clearance. Structural optimization of the brush seal enhances aerodynamic stability and achieves a reduction in leakage of approximately 90 %.
This work introduces a numerical framework for addressing fluid-structure interaction problems involving thin structures subject to finite strain deformations. The proposed approach utilizes an embedded mesh method to...
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This work introduces a numerical framework for addressing fluid-structure interaction problems involving thin structures subject to finite strain deformations. The proposed approach utilizes an embedded mesh method to establish a coupling interface between the fluid and structural domains. The novelty of the work is the incorporation of a recently developed locking-free stabilized formulation of solid-shell elements to handle the structural domain. The framework employs established techniques to handle pressure jumps in the fluid domain across the embedding interface and enforce boundary conditions, such as discontinuous shape functions for the pressure unknowns designed to segregate nodal contributions of the cut elements, and Nitsche's method for the weak imposition of transmission conditions in the fluid. The present approach is validated through a series of benchmark cases in both 2D and 3D environments, progressively increasing in complexity. The results demonstrate good agreement with existing literature, establishing the presented framework as a viable method for addressing fluid-structure interaction problems involving thin structures subject to large strains.
This study examines fluid-structure interaction (FSI)-induced flow and heat transfer phenomena in a double-sided shear-driven, that is, lid-driven cavity filled with non-Newtonian power-law fluids. A flexible thin hea...
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This study examines fluid-structure interaction (FSI)-induced flow and heat transfer phenomena in a double-sided shear-driven, that is, lid-driven cavity filled with non-Newtonian power-law fluids. A flexible thin heater positioned at the center of the cavity serves as the heat source, while the moving side walls maintained at constant low temperature perform as a heat sink. The numerical approach adopts the finite element Galerkin method, integrating the Arbitrary Lagrangian-Eulerian framework with moving mesh technique to solve the associated flow, thermal, and stress fields. The thermoelastodynamic system behavior is analyzed through streamline, isothermal, and heater deformation visualizations, along with an evaluation of heat transfer performance, namely, the average Nusselt number. FSI-induced internal stress scenario in the heater is also studied in terms of maximum von Mises stress. Variation of system conditions necessarily includes mixed convection strength, shearing effect, fluid rheology, and flexibility of the heater manifested by four governing system parameters, namely, the Richardson number (0.1 <= Ri <= 10), Reynolds number (100 <= Re <= 300), power-law index (0.6 <= n <= 1.4), and Cauchy number (10(-4) <= Ca <= 10(-8)). The findings of this study reveal a significant improvement in heat transfer for shear-thinning fluids, with the most notable enhancement occurring at the highest Richardson number (Ri), where the heat transfer rate shows an increase of up to 33.33% compared with Newtonian fluids. The insights of this study might be helpful in heat transfer enhancement of industrial process equipment, particularly in applications such as food processing, electronics cooling, and chemical engineering, where non-Newtonian fluids are extensively used in reactors and related thermofluid systems.
The effect of the intraglottal vortices on the glottal flow waveform was explored using flow-structure-interaction (FSI) modeling. These vortices form near the superior aspect of the vocal folds during the closing pha...
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The effect of the intraglottal vortices on the glottal flow waveform was explored using flow-structure-interaction (FSI) modeling. These vortices form near the superior aspect of the vocal folds during the closing phase of the folds' vibration. The geometry of the vocal fold was based on the well-known M5 model. The model did not include a vocal tract to remove its inertance effect on the glottal flow. Material properties for the cover and body layers of the folds were set using curve fit to experimental data of tissue elasticity. A commercially available FSI solver was used to perform simulations at low and high values of subglottal input pressure. Validation of the FSI results showed a good agreement for the glottal flow and the vocal fold displacement data with measurements taken in the excised canine larynx model. The simulations result further support the hypothesis that intraglottal vortices can affect the glottal flow waveform, specifically its maximum flow declination rate (MFDR). It showed that MFDR occurs at the same phase when the highest intraglottal vortical strength and the negative pressure occur. It also showed that when MFDR occurs, the magnitude of the aerodynamic force acting on the glottal wall is greater than the elastic recoil force predicted in the tissue. These findings are significant because nearly all theoretical and computational models that study the vocal fold vibrations mechanism do not consider the intraglottal negative pressure caused by the vortices as an additional closing force acting on the folds.
The flow of fluid in collapsible channels is a topic of great interest with numerous physiological applications, including blood flow during sports and exercise. This paper presents a fluid- structureinteraction (FSI...
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The flow of fluid in collapsible channels is a topic of great interest with numerous physiological applications, including blood flow during sports and exercise. This paper presents a fluid- structureinteraction (FSI) model for the study of single-phase fluid flow through a micro- channel with a two-sided collapsible wall. The model considers the viscoelastic properties of the fluid and incorporates a moving mesh approach to analyze the deformation of the channel walls. Three distinct modes of motion are observed in the elastic walls involving the elastic walls bulge outward, they undergo a mode-2 deformation characterized by two half-wavelengths along the elastic walls, and the walls indent inward towards the channel. Furthermore, the study shows that as the Weissenberg number increased, there is an associated increase in pressure on the central part of the plate, particularly the major portion. This increase in pressure leads to a decrease in the deflection of the plate. Additionally, the results reveals that the thickness of the plate influences the wall deformations. Thicker plates exhibites minimal deformation compared to thinner plates, which display more pronounced deformations. Moreover, an increase in plate thickness results in a gradual upward (downward) movement of the lowest point of the upper wall (the highest point of the down wall), eventually shifting towards the midpoint of the elastic walls.
We propose a suite of strategies for the parallel solution of fully implicit monolithic fluid-structure interaction(FSI).The solver is based on a modeling approach that uses the velocity and pressure as the primitive ...
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We propose a suite of strategies for the parallel solution of fully implicit monolithic fluid-structure interaction(FSI).The solver is based on a modeling approach that uses the velocity and pressure as the primitive variables,which offers a bridge between computational fluid dynamics(CFD)and computational structural *** spatiotemporal discretization leverages the variational multiscale formulation and the generalized-αmethod as a means of providing a robust discrete *** particular,the time integration scheme does not suffer from the overshoot phenomenon and optimally dissipates high-frequency spurious modes in both subproblems of *** on the chosen fully implicit scheme,we systematically develop a combined suite of nonlinear and linear solver *** a block factorization of the Jacobian matrix,the Newton-Raphson procedure is reduced to solving two smaller linear systems in the multi-corrector *** first is of the elliptic type,indicating that the algebraic multigrid method serves as a well-suited *** second exhibits a two-by-two block structure that is analogous to the system arising in *** by prior studies,the additive Schwarz domain decomposition method and the block-factorization-based preconditioners are invoked to address the linear *** the number of unknowns matches in both subdomains,it is straightforward to balance loads when parallelizing the algorithm for distributed-memory *** use two representative FSI benchmarks to demonstrate the robustness,efficiency,and scalability of the overall FSI solver *** particular,it is found that the developed FSI solver is comparable to the CFD solver in several aspects,including fixed-size and isogranular scalability as well as robustness.
Submerged vegetation is becoming more and more relevant as a nature-based solution for coastal protection schemes, counteracting the effects of climate change and sea level rise. The numerical model REEF3D has been us...
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Submerged vegetation is becoming more and more relevant as a nature-based solution for coastal protection schemes, counteracting the effects of climate change and sea level rise. The numerical model REEF3D has been used to simulate the motion of and forces exerted on flexible vegetation under unidirectional currents. This study emphasizes the critical need for accurate solutions obtained by numerical models to investigate the complex ecosystem services, adopting a direct forcing approach using the immersed boundary method. The fluid- structureinteraction capability within the finite difference model is comprehensively evaluated for the simulation of stem motions and forces exerted on flexible vegetation under varying unidirectional flows. Thresholds for numerical parameters, including a minimum number of 25 rigid elements composing the stem, are identified for accurate solutions. The necessity of using large eddy simulations and a Smagorinsky constant of 0.1 to simulate the turbulent flow is demonstrated. The study confirms the accuracy of the implemented fluid-structure interaction model to replicate stem bending (less than 10 % deviation relative to the stem length) and forces across varying hydrodynamic conditions.
A variational formulation based on velocity and stress is developed for linear fluid-structure interaction problems. The well-posedness and energy stability of this formulation are established. A hybridizable disconti...
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A variational formulation based on velocity and stress is developed for linear fluid-structure interaction problems. The well-posedness and energy stability of this formulation are established. A hybridizable discontinuous Galerkin method is employed to discretize the problem. An hp-convergence analysis is performed for the resulting semi-discrete scheme. The Crank-Nicolson method is used for temporal discretization, and the convergence properties of the fully discrete scheme are examined. Numerical experiments are presented to validate the theoretical results and demonstrate the accuracy of the proposed method.
Buried pipes are widely used for submarine water transportation, but the complex operating conditions in the seabed pose challenges for the modeling of buried pipes. In order to more accurately capture the dynamic beh...
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Buried pipes are widely used for submarine water transportation, but the complex operating conditions in the seabed pose challenges for the modeling of buried pipes. In order to more accurately capture the dynamic behavior of the buried pipes in the seabed, in this study, considering the pipeline and soil as a systematic structure is proposed, improving the fluid-structure interaction four-equation model to make it applicable for the calculation of buried pipe system modes. After verifying the practicality of the model, considering the external seawater as uniform pressure, the coupling at the joints, and the Poisson coupling of submarine pipelines during transient processes are discussed, revealing that structural vibrations under both forms of coupling will cause greater hydraulic oscillations. The impact of soil elastic modulus on the system's response is further discussed, revealing that increasing the modulus from 0 to 1015 Pa raises the wave speed from 498 m/s to 1483 m/s, causing a 40% increase in the amplitude of pressure oscillations. Finally, the vibration modes of the combined structure of pipe wall and soil are discussed, revealing that the vibration modes are mainly dominated by water hammer pressure, with the superposition of pipeline stress waves and soil stress waves. In this study, the dynamic behavior of submarine pipelines is elucidated, providing a robust foundation for regulating and mitigating fatigue failures in such systems.
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