A coupling algorithm between two open-source numerical toolboxes, i.e., OpenFOAM and Code_Aster, is implemented for fluid-structure interaction analysis of submerged nets. This algorithm is developed to handle the wak...
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A coupling algorithm between two open-source numerical toolboxes, i.e., OpenFOAM and Code_Aster, is implemented for fluid-structure interaction analysis of submerged nets. This algorithm is developed to handle the wake effects of thin, flexible and highly permeable structures with complex geometries. Compared to previous approaches, the present algorithm simplifies the procedures of the model preparation by removing additional data-fitting processes for porous coefficients, and improves the accuracy of structural responses by employing a fluid solver to calculate the flow field and a superior Screen model to calculate the hydrodynamic forces. The coupling algorithm is comprehensively described and validated with published experiments for both fixed and flexible nets. Different solidities, inflow angles, incoming velocities and dimensions of nets are also considered. The comparisons of flow velocity in the wake, deformation of flexible nets and drag force on the full-scale fish cage show that the numerical results obtained from the present coupling algorithm are in good agreement with published experimental data.
The numerical simulation of airbags is receiving an increasing attention for the remarkable advantages in terms of cost, efficiency, flexibility and amount of data that can be extracted from the analysis. This work pr...
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The numerical simulation of airbags is receiving an increasing attention for the remarkable advantages in terms of cost, efficiency, flexibility and amount of data that can be extracted from the analysis. This work proposes an advanced fluid-structure interaction (FSI) numerical technique for the simulation of airbag deployment. The fluid subproblem, described by weakly compressible Navier-Stokes equations, is solved exploiting the advanced features of the Particle Finite Element Method (PFEM) while the solid subproblem is addressed using standard Finite Element method. A domain decomposition approach with a special treatment of the fluid-structure interface conditions has been implemented to couple fluid and structural solvers allowing for non-conforming meshes at the interface and different time step size in the two subdomains. A peculiar feature of the proposed methodology is the explicit time integration, mandatory for the solution of very fast dynamics problems, like the airbag deployment: an explicit fluid solver is coupled explicitly with an explicit structural solver. The proposed technique is first tested on a inflation of a balloon, showing very good agreements and then it has been applied to the real case of airbag deployment.
The present work extends a recently developed quasi-2D flow model for fluid tran-sients in elastic pipes to accommodate fluid-structure interaction mechanisms. In this context, the primary goal of the proposed approac...
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The present work extends a recently developed quasi-2D flow model for fluid tran-sients in elastic pipes to accommodate fluid-structure interaction mechanisms. In this context, the primary goal of the proposed approach is to analyze energy transfer and dissipative effects in the fluid-pipe system. The fluid-structure interaction couples the flow dynamics with the axial movement of the tube, giving rise to friction, Poisson, and junction coupling mechanisms to take place. The mechanical model mathematical structure forms a quasi-linear hyperbolic system of partial differential equations for which approximated solutions are sought by employing the method of characteristics. The proposed model reproduces classical benchmark solutions and presents a good agreement with experimental data. In addition, the whole thermomechanical consistent framework in which the model is established allows an accurate description of the flow's internal structure. This feature allows a better comprehension of the phenomenon when compared to the classic frictionless and quasi-steady-friction-based four-equation models. The present approach allows a better description of the friction coupling mechanism and unveils uneven shear stress distributions in the unsteady flow. As a result, the energy dissipation in the fluid is captured with accuracy. Due to the absence or limited ability to describe these dispersive and dissipative effects, the traditional approaches are proved to lose their accuracy as the fluid transient goes. The coupled and uncoupled models are also analyzed and are proven to respond differently due to localized pipe-fluid interface effects in addition to the bulk mechanisms of transfer of energy that occur differently in both approaches. (c) 2022 Elsevier Ltd. All rights reserved.
Bulb turbine units are widely used in run-of river or dam projects with relatively low head, and can also be used for tidal energy utilization. Some types of bulb turbines have excessive vibration and fatigue failure ...
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Bulb turbine units are widely used in run-of river or dam projects with relatively low head, and can also be used for tidal energy utilization. Some types of bulb turbines have excessive vibration and fatigue failure problems, which threats their fatigue life. The model analyzed in this paper is a prototype bulb turbine rotor which suffered cracks, probably due to erosion and welding defects. The dynamic stress characteristics are analyzed under not only the non-cracked shaft condition but also the cracked one, to find possible causes of the failure. The computational fluid dynamics (CFD) simulation is performed to obtain reliable hydraulic load on the runner for performing the FEM analysis. The CFD results are verified by comparing with the site test for the prototype one. The linear elastic fracture mechanics theory combined with the fluid-structural interaction theory is applied to developing a cracked FEM model, to obtain the dynamic stress characteristics for the runner, shaft and rotor. The results reveal that the change in dynamic stress level on the shaft flange root significantly depends on the operating conditions Based on the numerical calculations and site inspection, it could be concluded that the insufficient sealing could lead to leakage flows with specific flow rates in flange root, which resulted in the occurrence of erosion;in addition, the welding at the flange root probably generated tiny defects. These two factors are likely lead to fatigue cracks and major failure of the shaft. Suggestions for solutions for the problems of the shaft are also discussed. Results of this study helps to find the reasons of the shaft fatigue failure. Furthermore, the analysis method could be used for an accurate calculation of fatigue life and providing guidance in future designs and operations of bulb turbine units.
Based on expert system theory and fluid-structure interaction (FSI), this paper suggests an intelligent design optimization system to derive the optimal shape of both the fluid and solid domain of flow channels. A par...
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Based on expert system theory and fluid-structure interaction (FSI), this paper suggests an intelligent design optimization system to derive the optimal shape of both the fluid and solid domain of flow channels. A parametric modeling scheme of flow channels is developed by design for additive manufacturing (DfAM). By changing design parameters, a series of flow channel models can be obtained. According to the design characteristics, the system can intelligently allocate suitable computational models to compute the flow field of a specific model. The pressure-based normal stress is abstracted from the results and transmitted to the solid region by the fluid-structure (FS) interface to analyze the strength of the structure. The design space is obtained by investigating the simulation results with the metamodeling method, which is further applied for pursuing design objectives under constraints. Finally, the improved design is derived by gradient-based optimization. This system can improve the accuracy of the FSI simulation and the efficiency of the optimization process. The design optimization of a flow channel in a simplified hydraulic manifold is applied as the case study to validate the feasibility of the proposed system.
This paper investigates the fluid-structure interaction in the transfer of heat through natural convection within an L-shaped wavy enclosure featuring a flexible baffle. Through numerical simulations through Comsol Mu...
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A hydroelastic fluid-structure interaction (FSI) solver entirely based on the Riemann-SPH method is proposed. In this scheme, the Riemann-SPH method is incorporated to model elastic structures, which is performed by p...
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A hydroelastic fluid-structure interaction (FSI) solver entirely based on the Riemann-SPH method is proposed. In this scheme, the Riemann-SPH method is incorporated to model elastic structures, which is performed by proposing a new treatment on Cauchy stress. The present structure solver can avoid the use of the artificial viscous force and can obtain good results. For the fluid, the conventional Riemann-SPH with a low-dissipation limiter is adopted to simulate incompressible free surface flows. The structure solver is coupled with the fluid solver by a simple coupling way considering the force balance. The developed structure solver is verified by three benchmarks, namely a free oscillating cantilever plate, stress concentration problem of a plate and wave propagation in a cable. Subsequently, through several 2D and 3D typical hydroelastic FSI tests, the accuracy and robustness of the present FSI solver are verified/validated by comparing with analytical solutions and experimental results.(c) 2021 Elsevier B.V. All rights reserved.
Quasi-Newton methods have proven to be an efficient way to couple partitioned solvers in fluid-structure interaction problems, as they are able to stabilize cases with high added-mass, as well as accelerate the conver...
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Quasi-Newton methods have proven to be an efficient way to couple partitioned solvers in fluid-structure interaction problems, as they are able to stabilize cases with high added-mass, as well as accelerate the convergence. However, these methods assume that the coupled system is a complete black-box, whereas often, its behavior is well approximated by a surrogate model. Such a model may be obtained by coarsening the system, simplifying the physics, reverting to analytical approximations or considering the system at a previous point in time. The principal idea of this work is to use an initial solution and a Jacobian provided by the surrogate model, to expedite the convergence even further. This article presents a new framework for the inclusion of surrogate models in quasi-Newton methods and positions several existing methods with respect to it. (C) 2021 Elsevier Ltd. All rights reserved.
The capability of a computational fluid-structure interaction method for simulating thin shell structures with an immersed boundary method and a nonlinear structural dynamics solver is extended in order to simulate su...
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The capability of a computational fluid-structure interaction method for simulating thin shell structures with an immersed boundary method and a nonlinear structural dynamics solver is extended in order to simulate supersonic spacecraft parachutes. Methodologies for the representation and motion tracking of thin, sub-grid resolution, thickness Lagrangian geometries in a static Eulerian background mesh are presented in detail. Logical functions for constructing reliable near-wall finite difference operators in the presence of thin geometries and trapped/concave volumes of space are presented. The Darcy-Forchheimer momentum equation is solved as a jump condition at the immersed interface in order to model the porosity of parachute broadcloth. A parallel contact identification and enforcement strategy based on first principles is introduced and validated. The coupled method is then used to simulate wind tunnel experiments conducted to support the Mars Science Laboratory (MSL) mission. In these experiments, a sub-scale MSL disk-gap-band parachute is inflated in a range of Mach numbers and dynamic pressures. The computational method shows good agreement with the experimental data, and where available, other simulation and empirical data, in terms of the opening load magnitude at various Mach numbers and the sustained aerodynamic performance measured by the coefficient of drag. Following quantitative comparison, a qualitative analysis is performed to investigate the effect of freestream Mach number, material porosity, and the bluff upstream payload on the main flow features. (C) 2022 Elsevier Ltd. All rights reserved.
In this paper, a fluid-structure interaction (FSI) using the model-order reduction (MOR) of dynamic grids is proposed. Within the interface problem between the fluid and the structure, the grid deformation is based on...
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In this paper, a fluid-structure interaction (FSI) using the model-order reduction (MOR) of dynamic grids is proposed. Within the interface problem between the fluid and the structure, the grid deformation is based on the spring analogy, and it is further extended in order for the efficient computation. In this procedure, the projection-based MOR technique is employed. The relevant MOR technique is realized by using the proper orthogonal decomposition and the discrete empirical interpolation method (POD/DEIM). The resulting FSI framework is based on a semi-implicit coupling approach. In order to achieve this, a characteristic-based split (CBS) scheme is used for an arbitrary Lagrangian-Eulerian (ALE) formulation of the two-dimensional Navier-Stokes equation. Also, a structural analysis is based on the co rotational (CR) formulation in order to simulate the geometrically nonlinear behavior. Both the fluid and structural analyses are combined with the semi-implicit coupling approach, and the relevant algorithm is embedded in the ALE/CBS scheme. Then, the present FSI analysis is verified using three examples, and the computational efficiency is evaluated. The resulting numerical data demonstrated the validity of the present analysis, and it is found that a significant reduction in the computational cost is possibly achieved with the proposed approach. (c) 2022 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).
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