The aerostatic spindle is made up of the structure components and the fluid film. The interaction between them has important influence on the comprehensive performance of the spindle. This paper presents a new design ...
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The aerostatic spindle is made up of the structure components and the fluid film. The interaction between them has important influence on the comprehensive performance of the spindle. This paper presents a new design method of aerostatic spindle based on the fluid-structure interaction method. The changes of bearing clearance caused by the structure deformation under high-pressure fluid film are considered, and the static performances of the bearing are obtained. In order to improve the performance of the spindle, the structural parameters of the bearing are optimized. The proposed design method is implemented through a self-developed aerostatic spindle.
A new three-dimensional (3D) matrix-free implicit unstructured multigrid finite volume (FV) solver for structural dynamics is presented in this paper. The solver is first validated using classical 2D and 3D cantilever...
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A new three-dimensional (3D) matrix-free implicit unstructured multigrid finite volume (FV) solver for structural dynamics is presented in this paper. The solver is first validated using classical 2D and 3D cantilever problems. it is shown that very accurate predictions of the fundamental natural frequencies of the problems can be obtained by the solver with fast convergence rates. This method has been integrated into our existing FV compressible solver [X. Lv, Y. Zhao, et al., An efficient parallel/unstructured-multigrid preconditioned implicit method for simulating 3d unsteady compressible flows with moving objects, Journal of Computational Physics 215(2) (2006) 661-690] based on the immersed membrane method (IMM) [X Lv, Y. Zhao, et al., as mentioned above]. Results for the interaction between the fluid and an immersed fixed-free cantilever are also presented to demonstrate the potential of this integrated fluid-structure interaction approach. (c) 2006 Elsevier Inc. All rights reserved.
The coupling of lightweight and often thin-walled structures to fluids in an incompressible regime is a recurring theme in biomechanics. There are many fluidstructureinteraction (FSI) solution schemes to address the...
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The coupling of lightweight and often thin-walled structures to fluids in an incompressible regime is a recurring theme in biomechanics. There are many fluidstructureinteraction (FSI) solution schemes to address these kinds of problem, each one with its costs and benefits. Here, we attempt a comparison of the most important FSI schemes in the context of biomechanical problems, that is a comparison of different fixed-point schemes and a block preconditioned monolithic scheme. The emphasis of this study is on the numerical behavior of these FSI schemes to gain an understanding of their effectiveness in comparison with each other. To this end a simplified benchmark problem is studied to show its applicability for more involved biomechanical problems. Two such examples with patient-specific geometries are also discussed. The monolithic scheme proved to be much more efficient than the partitioned schemes in biomechanical problems. Copyright (C) 2009 John Wiley & Sons, Ltd.
This paper investigates the leakage characteristics of brush seals including the flow field characteristic of brush seal and the effects of structural parameters on the leakage characteristic of brush seals with the c...
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This paper investigates the leakage characteristics of brush seals including the flow field characteristic of brush seal and the effects of structural parameters on the leakage characteristic of brush seals with the consideration of bristle deflection. The flow field characteristic of brush seal was discussed based on three-dimensional (3-D) computational model of brush seal, two-way fluid-structure interaction and moving grid technique. Then the effect of structural parameters on the leakage characteristic of brush seals was investigated from theoretical and numerical simulation perspectives with the emphasis on an improved prediction formula of leakage flow rate of brush seals. As illustrated in the analysis of the leakage characteristics of brush seals, (1) the leakage with the influence of bristle deflection is closer to the results of experiment relative to that without bristle deflection, and increases with the increasing inlet/outlet pressure ratios, which validate the developed 3-D computational model with bristle deflection to be more reasonable;(2) the flow field characteristics (pressure and velocity) of brush seal are revealed reasonably;(3) with the increasing of the height of backing plate fence, the clearance of brush wire and the axial clearance between brush bristle and back plate, the leakage factor rises and then reaches a stable value when the clearance of brush is larger than 0.3 mm;moreover, (4) with the increase of brush wire diameter, the leakage factor decreases firstly and then tends to stabilization, while rapidly decreases at first, then slowly decreases, and lastly tends to a value when the bristle row number increases;(5) the reliability and accuracy of the proposed prediction equation for brush seals is validated to be high by the CFD computational results. The efforts of this paper provide a useful theoretical and numerical method to clearly understand the leakage characteristics of brush seal, which is beneficial to improve the desig
A two-dimensional fully nonlinear potential flow model is employed to investigate non-linear stochastic responses of an experimental fluid-structure interaction system that includes both single-degree-of-freedom surge...
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A two-dimensional fully nonlinear potential flow model is employed to investigate non-linear stochastic responses of an experimental fluid-structure interaction system that includes both single-degree-of-freedom surge-only and two-degree-of-freedom surge-heave coupled motions. Sources of nonlinearity include free surface boundary, fluid-structure interaction, and large geometry in the structural restoring force. Random waves performed in the tests include nearly periodic, periodic with band-limited noise, and narrow band. The structural responses observed can be categorized as nearly deterministic (harmonic, sub- and super-harmonic), noisy periodic, and random. Transition phenomena between coexisting response attractors are also identified. An implicit boundary condition upholding the instantaneous equilibrium between the fluid and structure using a mixed Eulerian-Lagrangian method is employed. Numerical model predictions are calibrated and validated via the experimental results under the three types of wave conditions. Extensive simulations are conducted to identify the response characteristics and the effects of random perturbations on nonlinear responses near primary and secondary resonances.
We present a monolithic approach to large-deformation fluid-structure interaction (FSI) problems that allows for choosing fully implicit, single-step and single-stage time integration schemes in the structure and flui...
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We present a monolithic approach to large-deformation fluid-structure interaction (FSI) problems that allows for choosing fully implicit, single-step and single-stage time integration schemes in the structure and fluid field independently, and hence is tailored to the needs of the individual field. The independent choice of time integration schemes is achieved by temporal consistent interpolation of the interface traction. To reduce computational costs, we introduce the possibility of field specific predictors in both structure and fluid field. These predictors act on the single fields only. Possible violations of the interface coupling conditions during the predictor step are dealt with within the monolithic solution procedure. We present full details of such a generalized monolithic solution procedure, which is fully consistent in its nonconforming temporal and spatial discretization. The incorporated mortar approach allows for nonmatching spatial discretizations of the fluid and solid domain at the fluid-structure interface and is fully integrated in the resulting monolithic system of equations. The method is applied to a variety of numerical examples. Thereby, temporal convergence rates, the special role of essential boundary conditions at the fluid-structure interface, and the positive effect of predictors are demonstrated and discussed. Emphasis is put on the comparison of different time integration schemes in fluid and structure field, for what the achieved freedom of choice of time integrators is fully exploited.
Heart valves play a critical role in maintaining proper cardiovascular function in the human heart;however, valve diseases can lead to improper valvular function and reduced cardiovascular performance. Depending on th...
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Heart valves play a critical role in maintaining proper cardiovascular function in the human heart;however, valve diseases can lead to improper valvular function and reduced cardiovascular performance. Depending on the extent and severity of the valvular disease, replacement operations are often required to ensure that the heart continues to operate properly in the cardiac system. Transcatheter aortic valve replacement (TAVR) procedures have recently emerged as a promising alternative to surgical replacement approaches because the percutaneous methods used in these implant operations are significantly less invasive than open heart surgery. Despite the advantages of transcatheter devices, the precise deployment, proper valve sizing, and stable anchoring required to securely place these valves in the aorta remain challenging even in successful TAVR procedures. This work proposes a parametric modeling approach for transcatheter heart valves (THVs) that enables flexible valvular development and sizing to effectively generate existing and novel valve designs. This study showcases two THV configurations that are analyzed using an immersogeometric fluid-structure interaction (IMGA FSI) framework to demonstrate the influence of geometric changes on THV performance. The proposed modeling framework illustrates the impact of these features on THV behavior and indicates the effectiveness of parametric modeling approaches for enhancing THV performance and efficacy in the future.
We study a nonconforming finite element approximation of the vibration modes of an acoustic fluid-structure interaction. Displacement variables are used for both the fluid and the solid. The numerical scheme is based ...
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We study a nonconforming finite element approximation of the vibration modes of an acoustic fluid-structure interaction. Displacement variables are used for both the fluid and the solid. The numerical scheme is based on an irrotational fluid displacement formulation and hence it is free of spurious eigen-modes. The method uses weakly continuous P-1 vector fields for the fluid and classical piecewise linear elements for the solid, and it has O(h(2)) convergence for the eigenvalues on properly graded meshes. The theoretical results are confirmed by numerical experiments.
This paper investigates the use of Gaussian processes to solve sail trimming optimization problems. The Gaussian process, used to model the dependence of the performance with the trimming parameters, is constructed fr...
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This paper investigates the use of Gaussian processes to solve sail trimming optimization problems. The Gaussian process, used to model the dependence of the performance with the trimming parameters, is constructed from a limited number of performance estimations at carefully selected trimming points, potentially enabling the optimization of complex sail systems with multiple trimming parameters. The proposed approach is tested on a two-parameter trimming for a scaled IMOCA mainsail in upwind sailing conditions. We focus on the robustness of the proposed approach and study especially the sensitivity of the results to noise and model error in the point estimations of the performance. In particular, we contrast the optimization performed on a real physical model set in a wind tunnel with a fully non-linear numerical fluid-structure interaction model of the same experiments. For this problem with a limited number of trimming parameters, the numerical optimization was affordable and found to require a comparable amount of performance estimation as for the experimental case. The results reveal a satisfactory agreement for the numerical and experimental optimal trimming parameters, considering the inherent sources of errors and uncertainties in both numerical and experimental approaches. Sensitivity analyses have been eventually performed in the numerical optimization problem to determine the dominant source of uncertainties and characterize the robustness of the optima.
To accelerate the convergence of strongly coupled partitioned fluid-structure interaction simulations, the manifold mapping algorithm is used which combines a high-fidelity model with a low-fidelity model. A computati...
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To accelerate the convergence of strongly coupled partitioned fluid-structure interaction simulations, the manifold mapping algorithm is used which combines a high-fidelity model with a low-fidelity model. A computationally inexpensive low-fidelity fluid-structure interaction (FSI) model is combined with a high-fidelity FSI model in order to accelerate the convergence of the coupling iterations of the high-fidelity FSI model. The manifold mapping algorithm is applied to the fluid-structure interaction problem in order to minimize the fluid-structure interface residual. Originating from multi-fidelity optimization, the manifold mapping algorithm is applied for the first time in a simulation context, instead of an optimization context. The manifold mapping algorithm is applied to an unsteady flow in a one-dimensional tube, incompressible laminar flow over a fixed cylinder with an attached flexible flap, and a wave propagation in a three-dimensional elastic tube problem. A reduction of approximately 50% in terms of high-fidelity iterations is achieved compared to the state-of-the-art Interface Quasi-Newton Inverse Least Squares algorithm. The convergence of the high-fidelity model is accelerated even further when information from previous time steps is reused. (C) 2015 Elsevier B.V. All rights reserved.
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