Computers & Fluids最新文献

{"title":"A new temperature evolution equation that enforces thermodynamic vapour–liquid equilibrium in multiphase flows - application to CO2 modelling","authors":"Pardeep Kumar ,&nbsp;Benjamin Sanderse ,&nbsp;Patricio I. Rosen Esquivel ,&nbsp;R.A.W.M. Henkes","doi":"10.1016/j.compfluid.2024.106524","DOIUrl":"10.1016/j.compfluid.2024.106524","url":null,"abstract":"<div><div>This work presents a novel framework for numerically simulating the depressurization of tanks and pipelines containing carbon dioxide (<span><math><mrow><mi>CO</mi><mn>2</mn></mrow></math></span>). 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 <span><math><mrow><mi>CO</mi><mn>2</mn></mrow></math></span> 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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"289 ","pages":"Article 106524"},"PeriodicalIF":2.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integration of Lattice Boltzmann-overset method with non-conforming quadtree mesh based on the combination of spatial and Lagrangian-link interpolated streaming technique","authors":"Abdallah ElSherbiny,&nbsp;Sébastien Leclaire","doi":"10.1016/j.compfluid.2024.106522","DOIUrl":"10.1016/j.compfluid.2024.106522","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"289 ","pages":"Article 106522"},"PeriodicalIF":2.5,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A comparative computational study of different formulations of the compressible Euler equations for mesoscale atmospheric flows in a finite volume framework","authors":"M. Girfoglio ,&nbsp;A. Quaini ,&nbsp;G. Rozza","doi":"10.1016/j.compfluid.2024.106510","DOIUrl":"10.1016/j.compfluid.2024.106510","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106510"},"PeriodicalIF":2.5,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Very high order finite volume solver for multi component two-phase flow with phase change using a posteriori Multi-dimensional Optimal Order Detection","authors":"Michael Deligant ,&nbsp;Carlos-Jesús Romero-Casado ,&nbsp;Xesús Nogueira ,&nbsp;Luis Ramírez ,&nbsp;Mathieu Specklin ,&nbsp;Farid Bakir ,&nbsp;Sofiane Khelladi","doi":"10.1016/j.compfluid.2024.106509","DOIUrl":"10.1016/j.compfluid.2024.106509","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106509"},"PeriodicalIF":2.5,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Boundary treatment for variational quantum simulations of partial differential equations on quantum computers","authors":"Paul Over ,&nbsp;Sergio Bengoechea ,&nbsp;Thomas Rung ,&nbsp;Francesco Clerici ,&nbsp;Leonardo Scandurra ,&nbsp;Eugene de Villiers ,&nbsp;Dieter Jaksch","doi":"10.1016/j.compfluid.2024.106508","DOIUrl":"10.1016/j.compfluid.2024.106508","url":null,"abstract":"<div><div>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 <em>polylog</em> 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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106508"},"PeriodicalIF":2.5,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Python-based flow solver for numerical simulations using an immersed boundary method on single GPUs","authors":"M. Guerrero-Hurtado ,&nbsp;J.M. Catalán ,&nbsp;M. Moriche ,&nbsp;A. Gonzalo ,&nbsp;O. Flores","doi":"10.1016/j.compfluid.2024.106511","DOIUrl":"10.1016/j.compfluid.2024.106511","url":null,"abstract":"<div><div>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., <span><math><mrow><mo>×</mo><mn>1</mn><mo>.</mo><mn>6</mn><mo>−</mo><mn>3</mn></mrow></math></span> 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).</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106511"},"PeriodicalIF":2.5,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LES study of turbulent flow fields over a three-dimensional steep hill considering the effects of thermal stratification","authors":"Tong Zhou,&nbsp;Takeshi Ishihara","doi":"10.1016/j.compfluid.2024.106521","DOIUrl":"10.1016/j.compfluid.2024.106521","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106521"},"PeriodicalIF":2.5,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A FEM computational approach for gas-liquid flow in pipelines using a two-fluid model","authors":"Xiaowei Li ,&nbsp;Ruichao Tian ,&nbsp;Limin He ,&nbsp;Yuling Lv ,&nbsp;Shidong Zhou ,&nbsp;Yaqiang Li","doi":"10.1016/j.compfluid.2024.106520","DOIUrl":"10.1016/j.compfluid.2024.106520","url":null,"abstract":"<div><div>Two-phase flow is typically observed in gas-liquid pipelines across diverse domains, including nuclear, petroleum, and chemical industries. As accurate prediction of flow characteristics is crucial for engineering applications, one-dimensional two-fluid models with various treatments have been extensively employed to mathematically describe the gas-liquid variations in the pipelines through a set of non-linear partial differential equations (PDEs). This paper presents a modularly designed algorithm that incorporates an implicit scheme coupled with the finite element method (FEM) to solve the one-dimensional two-fluid model with gas-liquid stratified calculation. To validate the accuracy of this algorithm, four cases utilizing varying mesh sizes, inlet flows, and outlet pressures are conducted to scrutinize numerical steady-state gas-liquid flow characteristics, and the consistency between the numerical variations computed through this algorithm and those from OLGA simulator is used to analyze transient gas-liquid behaviors. The steady-state flow fields reveal two distinct zones along the pipe: an intense momentum exchange zone influenced by the inlet nonequilibrium state and a gentle momentum exchange zone influenced by the gas compressibility. Notably, a finer mesh will yield more accurate descriptions of flow parameters in the intense zone, while a relatively sparser mesh suffices for the gentle zone. Additionally, the transient results reveal that the gas-liquid variations in the pipe under initial condition of single-phase gas can be divided into three stages: the gas expansion stage determined by gas compressibility, the gas spread stage influenced by the gas propulsion, and the liquid filling stage decided by the liquid kinetic motion. The consistent identification of the three stages in gas-liquid variations under initial conditions of different static fluids highlights the effectiveness and accuracy of the proposed numerical method in describing transient features.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106520"},"PeriodicalIF":2.5,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parallel large eddy simulations with curvilinear immersed boundary method for high-speed flows","authors":"Amir M. Akbarzadeh,&nbsp;Iman Borazjani","doi":"10.1016/j.compfluid.2024.106495","DOIUrl":"10.1016/j.compfluid.2024.106495","url":null,"abstract":"<div><div>A sharp-interface immersed boundary method is developed to simulate turbulent compressible flows through large-eddy simulations (LES) on curvilinear grids. The curvilinear grid enables increasing the grid resolution near regions of interest such as solid walls. To capture both shocks and turbulence, the equations are discretized using a hybrid discretization comprising a fourth-order skew-central scheme and a third-order weighted essentially nonoscillatory (WENO) scheme. A switch function is incorporated to switch between WENO in the vicinity of shocks to central far away from shocks. A dynamics Smagornisky model is used to model the subgrid scales for the central scheme. The interpolation for the immersed boundary is modified to incorporate wall functions. The code is parallelized to efficiently run on thousands of CPU cores for highly resolved grids. The method is verified and validated against several test cases including a decaying isotropic turbulent flow, turbulent channel flow, supersonic flow and shock diffraction over a cylinder. The results show that the LES can properly resolve the inertial subrange and the hybrid scheme can effectively capture shocks over the immersed bodies. It is observed that highly refined grids and low-dissipation hybrid scheme are necessary to capture fine turbulence features such as shear instabilities and shock boundary layer interaction over immersed bodies. In fine grids, however, the importance of explicit LES modeling decreases as most scales are resolved and the WENO scheme provides the dissipation implicitly. In such cases, the results are most sensitive to wall modeling which demonstrate the need for development of wall models for high-speed flows.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106495"},"PeriodicalIF":2.5,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using Delayed Detached Eddy Simulation to create datasets for data-driven turbulence modeling: A periodic hills with parameterized geometry case","authors":"Davide Oberto ,&nbsp;Davide Fransos ,&nbsp;Stefano Berrone","doi":"10.1016/j.compfluid.2024.106506","DOIUrl":"10.1016/j.compfluid.2024.106506","url":null,"abstract":"<div><div>Despite the emerging field of data-driven turbulence models, there is a lack of systematic high-fidelity datasets at flow configurations changing continuously with respect to geometrical/physical parameters. In this work, we investigate the possibility of using Delayed Detached Eddy Simulation (DDES) to generate reliable datasets in a significantly cheaper manner compared to the DNS or LES counterparts. To do that, we perform 25 simulations of the geometrically-parameterized periodic hills test case to deal with different hills steepnesses. We firstly check the accuracy of our results by comparing one simulation with the benchmark case of Xiao et al. Then, we use such database to train the turbulent viscosity-Vector Basis Neural Network (<span><math><msub><mrow><mi>ν</mi></mrow><mrow><mi>t</mi></mrow></msub></math></span>-VBNN) data-driven turbulence model. The latter outperforms the classic <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> SST RANS model, proving that our generated dataset can be useful for data-driven turbulence modeling and opening the opportunity to exploit DDES to create systematic datasets for data-driven turbulence modeling.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"288 ","pages":"Article 106506"},"PeriodicalIF":2.5,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}