Computers & Fluids最新文献_第4页

From simplex to mixed element: Extension of a vertex-centered discretization, focus on accuracy analysis and 3D RANS applications

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-19 DOI: 10.1016/j.compfluid.2024.106526

Cosimo Tarsia Morisco , Frédéric Alauzet , Guillaume Puigt

Standard unstructured-grid CFD simulations generally rely on a cell-centered Finite Volume discretization applied to mixed-element grids. The interest in such approach is using elements that are aligned along a privileged direction in the region close to the boundary, and at the same time unstructured elements near complex geometrical details or in farfield regions. This paper proposes a novel version of the mixed Finite Element/Finite Volume approximation (Debiez and Dervieux 2000), which is a vertex-centered method known to produce second-order accurate solutions even on highly anisotropic adapted meshes composed of simplex elements (i.e., triangles and tetrahedra) (Alauzet and Loseille, 2010; Barral et al., 2017; Alauzet et al., 2018; Belme et al., 2019). The extension of this approach for two-dimensional mixed-element meshes was proposed in Tarsia Morisco et al. (2024) and involves the APproximated Finite Element -APFE- method (Puigt et al., 2010) to discretize diffusion. In this work we make the definitive step forward to handle three-dimensional mixed-element meshes: designing a second-order accurate scheme for smooth meshes involving tetrahedra, prisms and pyramids.

The present work focuses on two key aspects. One concerns the 3D extension of the APFE method. A detailed error analysis of this vertex-centered approach is provided for prisms and pyramids. The second ingredient deals with an innovative algorithm to compute the truncation error for linear problems. In contrast to usual methods, the one proposed here permits to compute exactly the coefficients related to each terms of error for any mesh, and can be implemented in any solver with a low development effort.

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引用次数: 0

A critical comparison of the implementation of granular pressure gradient term in Euler–Euler simulation of gas–solid flows

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-18 DOI: 10.1016/j.compfluid.2024.106523

Yige Liu , Mingming He , Jianhua Chen , Wen Li , Bidan Zhao , Ji Xu , Junwu Wang

Numerical solution of Euler–Euler model using different in-house, open source and commercial software can generate significantly different results, even when the governing equations and the initial and boundary conditions are exactly same. Unfortunately, the underlying reasons have not been identified yet. In this article, three methods for calculating the granular pressure gradient term are presented for two-fluid model of gas–solid flows and implemented implicitly or explicitly into the solver in OpenFOAM®: Method

I

assumes that the granular pressure gradient is equal to the elastic modulus plus the solid concentration gradient; Method

I I

directly calculates the gradient using a difference scheme; Method

I I I

, which is proposed in this work, calculates the gradient as the sum of two partial derivatives: one related to the solid volume fraction and the other related to the granular energy. Obviously, only Methods

I I

and

I I I

are consistent with kinetic theory of granular flow. It was found that the difference between all methods is small for bubbling fluidization. While for circulating fluidization, both Methods

I I

and

I I I

are capable of capturing non-uniform structures and producing superior results over Method

I

. The contradictory conclusions made from the simulation of different fluidization regimes is due to the different contribution of the term related to the granular energy gradient. Present study concludes that the implementation method of granular pressure gradient may have a significant impact on the hydrodynamics of gas–solid flows and is probably a key factor contributing to the observed differences between different simulation software.

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引用次数: 0

Incompressible Navier–Stokes solve on noisy quantum hardware via a hybrid quantum–classical scheme

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-18 DOI: 10.1016/j.compfluid.2024.106507

Zhixin Song , Robert Deaton , Bryan Gard , Spencer H. Bryngelson

Partial differential equation solvers are required to solve the Navier–Stokes equations for fluid flow. Recently, algorithms have been proposed to simulate fluid dynamics on quantum computers. Fault-tolerant quantum devices might enable exponential speedups over algorithms on classical computers. However, current and foreseeable quantum hardware introduce noise into computations, requiring algorithms that make judicious use of quantum resources: shallower circuit depths and fewer qubits. Under these restrictions, variational algorithms are more appropriate and robust. This work presents a hybrid quantum–classical algorithm for the incompressible Navier–Stokes equations. A classical device performs nonlinear computations, and a quantum one uses a variational solver for the pressure Poisson equation. A lid-driven cavity problem benchmarks the method. We verify the algorithm via noise-free simulation and test it on noisy IBM superconducting quantum hardware. Results show that high-fidelity results can be achieved via this approach, even on current quantum devices. Multigrid preconditioning of the Poisson problem helps avoid local minima and reduces resource requirements for the quantum device. A quantum state readout technique called HTree is used for the first time on a physical problem. Htree is appropriate for real-valued problems and achieves linear complexity in the qubit count, making the Navier–Stokes solve further tractable on current quantum devices. We compare the quantum resources required for near-term and fault-tolerant solvers to determine quantum hardware requirements for fluid simulations with complexity improvements.

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引用次数: 0

A new temperature evolution equation that enforces thermodynamic vapour–liquid equilibrium in multiphase flows - application to CO2 modelling

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-18 DOI: 10.1016/j.compfluid.2024.106524

Pardeep Kumar , Benjamin Sanderse , Patricio I. Rosen Esquivel , R.A.W.M. Henkes

This work presents a novel framework for numerically simulating the depressurization of tanks and pipelines containing carbon dioxide (

CO 2

). The framework focuses on efficient solution strategies for the coupled system of fluid flow equations and thermodynamic constraints. A key contribution lies in proposing a new set of equations for phase equilibrium calculations which simplifies the traditional vapour–liquid equilibrium (VLE) calculations for two-phase

CO 2

mixtures. The first major novelty resides in the reduction of the conventional four-equation VLE system to a single equation, enabling efficient solution using a non-linear solver. This significantly reduces computational cost compared to traditional methods. Furthermore, a second novelty is introduced by deriving an ordinary differential equation (ODE) directly from the UV-Flash equation. This ODE can be integrated alongside the governing fluid flow equations, offering a computationally efficient approach for simulating depressurization processes.

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引用次数: 0

Integration of Lattice Boltzmann-overset method with non-conforming quadtree mesh based on the combination of spatial and Lagrangian-link interpolated streaming technique

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-11 DOI: 10.1016/j.compfluid.2024.106522

Abdallah ElSherbiny, Sébastien Leclaire

This study integrates the two-dimensional Lattice Boltzmann overset approach with a non-conforming quadtree mesh to address fluid flow problems involving dynamic boundaries. The Lattice Boltzmann overset method employs two grids, one fixed and one movable, which can be computationally intensive due to the dual grid setup. A quadtree mesh is employed to reduce the number of nodes to mitigate this resource-demanding issue. Nonetheless, the use of the quadtree introduces challenges related to varying cell levels and spatial displacements. One of the approaches to address these challenges involves the use of an interpolated particle distribution function streaming technique. This study introduces an interpolation method, which initially applies spatial interpolation as a predictor step. Subsequently, this spatial predictor-interpolated value is utilized for a Lagrangian-link corrector interpolation. Furthermore, the study introduces a node-splitting technique aimed at enhancing the efficiency of the proposed interpolation scheme. The method's order of accuracy is maintained without any degradation as a second order, and the flow around a rotating cylinder validates the method as the results align with previously published data.

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引用次数: 0

A comparative computational study of different formulations of the compressible Euler equations for mesoscale atmospheric flows in a finite volume framework

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-11 DOI: 10.1016/j.compfluid.2024.106510

M. Girfoglio , A. Quaini , G. Rozza

We consider three conservative forms of the weakly compressible Euler equations, called CE1, CE2 and CE3, with the goal of understanding which leads to the most accurate and robust pressure-based solver in a finite volume environment. Forms CE1 and CE2 are both written in density, momentum, and specific enthalpy, but employ two different treatments of the buoyancy and pressure gradient terms: for CE1 it is the standard pressure splitting implemented in open-source finite volume solvers (e.g., OpenFOAM®), while for CE2 it is the typical pressure splitting found in computational atmospheric studies. Form CE3 is written in density, momentum, and potential temperature, with the buoyancy and pressure terms addressed as in CE2. For each formulation, we adopt a computationally efficient splitting approach. The three formulations are thoroughly assessed and compared through six benchmark tests involving dry air flow over a flat terrain or orography. We found that all three models are able to provide accurate results for the tests with a flat terrain, although the solvers based on the CE2 and CE3 forms are more robust. As for the mountain tests, CE1 solutions become unstable, while the CE2 and CE3 models provide results in very good agreement with data in the literature, the CE3 model being the most accurate. Hence, even when using a pressure-based approach and space discretization by a finite volume method, the CE3 model is the most accurate, reliable, and robust for the simulation of mesoscale atmospheric flows.

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引用次数: 0

Very high order finite volume solver for multi component two-phase flow with phase change using a posteriori Multi-dimensional Optimal Order Detection

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-11 DOI: 10.1016/j.compfluid.2024.106509

Michael Deligant , Carlos-Jesús Romero-Casado , Xesús Nogueira , Luis Ramírez , Mathieu Specklin , Farid Bakir , Sofiane Khelladi

In this work we propose a very high-order compressible finite volume scheme with a posteriori stabilization for the computation of multi-component two-phase flow with phase change. It is based on finite volume approach using moving least squares (MLS) reproducing kernels for high order reconstruction of the Riemann states. Increased robustness is achieved by using the multi-dimensional optimal order detection (MOOD) method to get a high-accurate and low-dissipation scheme while maintaining boundedness and preventing numerical oscillations at interfaces and strong gradient zones. The properties of the proposed framework are demonstrated on classical test problems starting with convergence order verification on simple scalar advection test cases. More complex shock and more stringent tube tests with various water, steam and air concentration are then simulated and compared with available references in the literature. Finally, the ability of the proposed approach to compute multi-component flows with phase change is illustrated with the simulation of a liquid oxygen jet in gaseous hydrogen.

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引用次数: 0

Boundary treatment for variational quantum simulations of partial differential equations on quantum computers

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-10 DOI: 10.1016/j.compfluid.2024.106508

Paul Over , Sergio Bengoechea , Thomas Rung , Francesco Clerici , Leonardo Scandurra , Eugene de Villiers , Dieter Jaksch

The paper presents a variational quantum algorithm to solve initial–boundary value problems described by second-order partial differential equations. The approach uses hybrid classical/quantum framework that is well suited for quantum computers of the current noisy intermediate-scale quantum era. The partial differential equation is initially translated into an optimal control problem with a modular control-to-state operator (ansatz). The objective function and its derivatives required by the optimizer can efficiently be evaluated on a quantum computer by measuring an ancilla qubit, while the optimization procedure employs classical hardware. The focal aspect of the study is the treatment of boundary conditions, which is tailored to the properties of the quantum hardware using a correction technique. For this purpose, the boundary conditions and the discretized terms of the partial differential equation are decomposed into a sequence of unitary operations and subsequently compiled into quantum gates. The accuracy and gate complexity of the approach are assessed for second-order partial differential equations by classically emulating the quantum hardware. The examples include steady and unsteady diffusive transport equations for a scalar property in combination with various Dirichlet, Neumann, or Robin conditions. The results of this flexible approach display a robust behavior and a strong predictive accuracy in combination with a remarkable polylog complexity scaling in the number of qubits of the involved quantum circuits. Remaining challenges refer to adaptive ansatz strategies that speed up the optimization procedure.

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引用次数: 0

A Python-based flow solver for numerical simulations using an immersed boundary method on single GPUs

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-09 DOI: 10.1016/j.compfluid.2024.106511

M. Guerrero-Hurtado , J.M. Catalán , M. Moriche , A. Gonzalo , O. Flores

We present an efficient implementation for the simulation of three-dimensional, incompressible flow around moving bodies with complex geometries on single GPUs, based on Nvidia CUDA through Numba and Python. The flow is solved in this framework through an implementation of the Immersed Boundary Method tailored for the GPU, where different GPU grid architectures are exploited to optimize the overall performance. By targeting a single-GPU, we eliminate the need for both intra- and inter-node communication, which can potentially introduce overheads. With this approach, all simulation data remains in the GPU’s global memory at all times. We provide details about the numerical methodology, the implementation of the algorithm in the GPU and the memory management, critical in single-GPU implementations. Additionally, we verify the results comparing with our analogous CPU-based parallel solver and assess satisfactorily the efficiency of the code in terms of the relative computing time of the different operations and the scaling of the CPU code compared to a single GPU case. Overall, our tests show that the single-GPU code is between 34 to 54 times faster than the CPU solver in peak performance (96–128 CPU cores). This speedup mainly comes from the change in the method of solution of the linear systems of equations, while the speedup in sections of the algorithm that are equivalent in the CPU and GPU implementations is more modest (i.e.,

\times 1.6 - 3

speedup in the computation of the non-linear terms). Finally, we showcase the performance of this new GPU implementation in two applications of interest, one for external flows (i.e., bioinspired aerodynamics) and one for internal flows (i.e., cardiovascular flows), demonstrating the strong scaling of the code in two different GPU cards (hardware).

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引用次数: 0

LES study of turbulent flow fields over a three-dimensional steep hill considering the effects of thermal stratification

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2024-12-09 DOI: 10.1016/j.compfluid.2024.106521

Tong Zhou, Takeshi Ishihara

In this study, large-eddy simulations are performed to elucidate the spatiotemporal characteristics and physical mechanisms of turbulent boundary layers over hilly terrain under stable, neutral, and unstable stratification. The impact of thermal stratification on turbulent flows over a steep three-dimensional hill is clarified through flow patterns and statistical characteristics. Compared to neutral stratification, the separation bubble downstream of the hill crest is reduced under unstable stratification, while it is enlarged under stable stratification. In addition, turbulent eddy motions in the wake region are enhanced in the unstable condition but are suppressed in the stable condition. Both mean velocities and turbulence fluctuations over steep hilly terrain are amplified by unstable stratification and attenuated by stable stratification. The flow characteristics on the hill crest are comprehensively determined by the topography and thermal stratification, whereas the flow dynamics in the hill wake are predominantly influenced by terrain-induced turbulence. Moreover, the mechanisms driving the formation of flow fields over steep hilly topography under different thermal stratification are investigated through force balance analysis using the time-averaged Navier–Stokes equations. The results indicate that turbulence plays a negligible role in the force balance upstream of the hill, while it becomes the dominant factor for the force balances downstream of the hill.

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引用次数: 0