125,503 research outputs found
On in-situ visualization for strongly coupled partitioned fluid-structure interaction
We present an integrated in-situ visualization approach for partitioned
multi-physics simulation of fluid-structure interaction. The simulation itself is treated
as a black box and only the information at the fluid-structure interface is considered,
and communicated between the fluid and solid solvers with a separate coupling tool.
The visualization of the interface data is performed in conjunction with the fluid solver.
Furthermore, we present new visualization techniques for the analysis of the interrelation
of the two solvers , with emphasis on the involved error due to discretization in space and
time and the reconstruction. Our visualization approach also enables the investigation of
these errors with respect of their mutual influence on the two simulation codes and their
space-time discretization. For efficient interactive visualization, we employ the concept
of explorable spatiotemporal images, which also enables finite-time temporal navigation
in an in-situ context. We demonstrate our overall approach and its utility by means of
a fluid-structure simulation using OpenFOAM that is coupled by the preCICE software
layer
Fluid-Structure Interaction for a Deformable Anisotropic Cylinder: A Case Study
For a structure designed to interact with the surrounding fluid, structural deformation under loads induced by fluid flows is an important factor to consider, and one which is traditionally difficult to account for analytically. Coupling the finite element method for structural analysis with the finite volume method for the determination of fluid response allows for accurate simulation of the pressure and shearing loads applied by the fluid onto the fluid-structure interface, while also determining localized structural displacements that would cause changes to the geometry of the interface. This work seeks to simulate the behavior of cylinders with varying heights and stiffnesses under external flows with low Reynolds numbers. To address structural deformation accurately in the simulation, a morphing and remapping algorithm is applied to the fluid-structure interface. With additional consideration for anisotropy in the structure\u27s elasticity, these analyses could potentially support the development of flexible components that deform in predetermined ways under anticipated fluid loads, allowing for simpler and more efficient solutions to control flow scenarios that traditionally require moving components and control surfaces
Coupling different discretizations for fluid structure interaction in a monolithic approach
In this thesis we present a monolithic coupling approach for the simulation of phenomena involving interacting fluid and structure using different discretizations for the subproblems. For many applications in fluid dynamics, the Finite Volume method is the first choice in simulation science. Likewise, for the simulation of structural mechanics the Finite Element method is one of the most, if not the most, popular discretization method. However, despite the advantages of these discretizations in their respective application domains, monolithic coupling schemes have so far been restricted to a single discretization for both subproblems. We present a fluid structure coupling scheme based on a mixed Finite Volume/Finite Element method that combines the benefits of these discretizations. An important challenge in coupling fluid and structure is the transfer of forces and velocities at the fluidstructure interface in a stable and efficient way. In our approach this is achieved by means of a fully implicit formulation, i.e., the transfer of forces and displacements is carried out in a common set of equations for fluid and structure. We assemble the two different discretizations for the fluid and structure subproblems as well as the coupling conditions for forces and displacements into a single large algebraic system. Since we simulate real world problems, as a consequence of the complexity of the considered geometries, we end up with algebraic systems with a large number of degrees of freedom. This necessitates the use of parallel solution techniques. Our work covers the design and implementation of the proposed heterogeneous monolithic coupling approach as well as the efficient solution of the arising large nonlinear systems on distributed memory supercomputers. We apply Newton’s method to linearize the fully implicit coupled nonlinear fluid structure interaction problem. The resulting linear system is solved with a Krylov subspace correction method. For the preconditioning of the iterative solver we propose the use of multilevel methods. Specifically, we study a multigrid as well as a two-level restricted additive Schwarz method. We illustrate the performance of our method on a benchmark example and compare the afore mentioned different preconditioning strategies for the parallel solution of the monolithic coupled system
Efficient Simulation of Fluids
Fluid simulation is based on Navier-Stokes equations. Efficient simulation codes may rely on the smooth particle hydrodynamic toolbox (SPH), a method that uses kernel density estimation. Many variants of SPH have been proposed to optimize the simulation, like implicit incompressible SPH (IISPH) or predictive-corrective incompressible SPH (PC-ISPH). This chapter recalls the formulation of SPH and focuses on its effective parallel implementation using the Nvidia common unified device architecture (CUDA), while message passing interface (MPI) is another option. The key to effective implementation is a dedicated accelerating structure, and therefore some well-chosen parallel design patterns are detailed. Using a rough model of the ocean, this type of simulation can be used directly to simulate a tsunami resulting from an underwater earthquake
Partitioning strategies for the interaction of a fluid with a poroelastic material based on a Nitsche's coupling approach
We develop a computational model to study the interaction of a fluid with a
poroelastic material. The coupling of Stokes and Biot equations represents a
prototype problem for these phenomena, which feature multiple facets. On one
hand it shares common traits with fluid-structure interaction. On the other
hand it resembles the Stokes-Darcy coupling. For these reasons, the numerical
simulation of the Stokes-Biot coupled system is a challenging task. The need of
large memory storage and the difficulty to characterize appropriate solvers and
related preconditioners are typical shortcomings of classical discretization
methods applied to this problem. The application of loosely coupled time
advancing schemes mitigates these issues because it allows to solve each
equation of the system independently with respect to the others. In this work
we develop and thoroughly analyze a loosely coupled scheme for Stokes-Biot
equations. The scheme is based on Nitsche's method for enforcing interface
conditions. Once the interface operators corresponding to the interface
conditions have been defined, time lagging allows us to build up a loosely
coupled scheme with good stability properties. The stability of the scheme is
guaranteed provided that appropriate stabilization operators are introduced
into the variational formulation of each subproblem. The error of the resulting
method is also analyzed, showing that splitting the equations pollutes the
optimal approximation properties of the underlying discretization schemes. In
order to restore good approximation properties, while maintaining the
computational efficiency of the loosely coupled approach, we consider the
application of the loosely coupled scheme as a preconditioner for the
monolithic approach. Both theoretical insight and numerical results confirm
that this is a promising way to develop efficient solvers for the problem at
hand
An Investigation of Micro-Surface Shaping on the Piston/Cylinder Interface of Axial Piston Machines
Presently, axial piston machines of the swash plate type are commonly used in industry due to their many benefits. However, with recent technological advancements in hydraulic hybrid powertrains and displacement-controlled actuation, the application of such machines has been broadened demanding a more cost-effective reliable and efficient, yet versatile machine. The fluid film geometry of the lubricating interfaces is a very complex and sensitive phenomena that must simultaneously fulfill a competing bearing and sealing function. Therefore, the design process of such machines is a difficult process while tightly constrained manufacturing tolerances are essential thereby increasing the initial production costs. Accordingly, virtual prototyping through analytical simulation in this field has emerged as an ideal tool not only to improve the performance of existing units, but to also design new and innovative axial piston machines that fulfill the demands of advanced technology.
The aim of this dissertation is to investigate more efficient and reliable designs of the piston/cylinder interface of an axial piston machine over a broad range of operating conditions. Primarily, an extensive simulation study was conducted in which the design of a commercially available machine was modified to accommodate piston micro-surface shaping where the relative improvements were then quantified in comparison. This study utilizes a novel fully-coupled fluid structure interaction model considering both thermal and pressure deformations of the solid bodies to accurately predict the dynamic behavior of the lubricating interface. Having analyzed the phenomena of the lubricating gap and the effects of micro-surface shaping, an optimization technique was utilized to design this interface. The optimization scheme determines the best balance between improving the sealing function while maintaining or even improving the bearing function. A surface shaped piston was then measured and compared back to the simulation results realizing the capabilities of such a novel methodology. Ultimately, this cost-effective design process demonstrated that micro-surface shaping is beneficial as it allows for reduced clearances, achieving a reduction in volumetric losses, while increasing fluid film support, resulting in superior efficiency as well as enhanced reliability and overall performance
Fluid-Structure Interaction Simulation of a Coriolis Mass Flowmeter using a Lattice Boltzmann Method
In this paper we use a fluid-structure interaction (FSI) approach to simulate
a Coriolis mass flowmeter (CMF). The fluid dynamics are calculated by the open
source framework OpenLB, based on the lattice Boltzmann method (LBM). For the
structural dynamics we employ the open source software Elmer, an implementation
of the finite element method (FEM). A staggered coupling approach between the
two software packages is presented. The finite element mesh is created by the
mesh generator Gmsh to ensure a complete open source workflow. The Eigenmodes
of the CMF, which are calculated by modal analysis are compared with
measurement data. Using the estimated excitation frequency, a fully coupled,
partitioned, FSI simulation is applied to simulate the phase shift of the
investigated CMF design. The calculated phaseshift values are in good agreement
to the measurement data and verify the suitability of the model to numerically
describe the working principle of a CMF
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