Pub Date : 2025-02-10DOI: 10.1016/j.compfluid.2025.106569
Deepu Dinesan, Bibin John
The control of shock wave boundary layer interaction (SWBLI) by means of surface arc plasma actuator (SAPA) is the focus of current work. The primary objective is to explore the potential of short-duration pulse energy deposition in mitigating the separation zone that develops ahead of a cylindrical blunt body placed in a supersonic Mach 2.5 field. The research delves into the fundamental physics of BW generation and propagation, both in quasi-static fields and supersonic flows. Additionally, it elucidates how BWs interact with the separated shear layer, ultimately reducing the size of the separation zone. The numerical framework implemented for the replication of real time surface arc plasma energy addition is validated against the literature reported experimental and analytical data. Additional parametric studies demonstrating the effect of plasma actuation duration, energy magnitude/pulse and number of SAPAs are presented. Notably, the findings reveal that an array of SAPAs with five energy pulse locations can minimize the separation size to just 56% of the base flow, with one time actuation of SAPAs by depositing of energy.
{"title":"Mitigation of Shock wave boundary layer interaction using surface arc plasma energy actuators: A computational study","authors":"Deepu Dinesan, Bibin John","doi":"10.1016/j.compfluid.2025.106569","DOIUrl":"10.1016/j.compfluid.2025.106569","url":null,"abstract":"<div><div>The control of shock wave boundary layer interaction (SWBLI) by means of surface arc plasma actuator (SAPA) is the focus of current work. The primary objective is to explore the potential of short-duration pulse energy deposition in mitigating the separation zone that develops ahead of a cylindrical blunt body placed in a supersonic Mach 2.5 field. The research delves into the fundamental physics of BW generation and propagation, both in quasi-static fields and supersonic flows. Additionally, it elucidates how BWs interact with the separated shear layer, ultimately reducing the size of the separation zone. The numerical framework implemented for the replication of real time surface arc plasma energy addition is validated against the literature reported experimental and analytical data. Additional parametric studies demonstrating the effect of plasma actuation duration, energy magnitude/pulse and number of SAPAs are presented. Notably, the findings reveal that an array of SAPAs with five energy pulse locations can minimize the separation size to just 56% of the base flow, with one time actuation of SAPAs by depositing <span><math><mrow><mn>240</mn><mi>m</mi><mi>J</mi></mrow></math></span> of energy.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106569"},"PeriodicalIF":2.5,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395075","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}
Pub Date : 2025-02-07DOI: 10.1016/j.compfluid.2025.106568
Donovan Blais, Siva Nadarajah, Calista Biondic
Modern aircraft design involves a large number of design parameters from a multitude of disciplines. Obtaining high-fidelity solutions for all combinations of such parameters is computationally unfeasible. Although the solution to a large-scale system of equations is generally an element of a large-dimensional space, the solution may actually lie on a reduced-order subspace induced by parameter variation. In order to capture this subspace, samples of the high-dimensional system called snapshots are used to build a reduced-order model. These models have generated interest as a means to compute high-fidelity solutions at a much lower computational cost. However, little value can be placed in a reduced-order solution without some quantification of its error. The dual-weighted residual can be used to obtain error estimates between the outputs of different models. Using dual-weighted residual error estimates in conjunction with a radial basis function interpolation, this work introduces a novel adaptive sampling method that chooses snapshots iteratively such that a prescribed output error tolerance is estimated to be met on the entirety of a parameter space. The adaptive sampling procedure is demonstrated on a one-dimensional Burgers’ equation and two-dimensional inviscid flows.
{"title":"Goal-oriented adaptive sampling for projection-based reduced-order models","authors":"Donovan Blais, Siva Nadarajah, Calista Biondic","doi":"10.1016/j.compfluid.2025.106568","DOIUrl":"10.1016/j.compfluid.2025.106568","url":null,"abstract":"<div><div>Modern aircraft design involves a large number of design parameters from a multitude of disciplines. Obtaining high-fidelity solutions for all combinations of such parameters is computationally unfeasible. Although the solution to a large-scale system of equations is generally an element of a large-dimensional space, the solution may actually lie on a reduced-order subspace induced by parameter variation. In order to capture this subspace, samples of the high-dimensional system called snapshots are used to build a reduced-order model. These models have generated interest as a means to compute high-fidelity solutions at a much lower computational cost. However, little value can be placed in a reduced-order solution without some quantification of its error. The dual-weighted residual can be used to obtain error estimates between the outputs of different models. Using dual-weighted residual error estimates in conjunction with a radial basis function interpolation, this work introduces a novel adaptive sampling method that chooses snapshots iteratively such that a prescribed output error tolerance is estimated to be met on the entirety of a parameter space. The adaptive sampling procedure is demonstrated on a one-dimensional Burgers’ equation and two-dimensional inviscid flows.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106568"},"PeriodicalIF":2.5,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395719","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}
Pub Date : 2025-02-07DOI: 10.1016/j.compfluid.2025.106571
Shunsuke Kurioka , Changhong Hu
This paper proposes an improved Particle Level Set (PLS) method that enhances accuracy and mass conservation by correcting the position information of Lagrangian particles placed on the interface using high-order kernel functions. This method, referred to as the PLS/KC (improved Particle Level Set method with high-order Kernel function Correction), accurately captures moving interfaces in multiphase flow simulations on fixed Eulerian grids. The innovation and practical significance of the proposed method are highlighted as follows: (1) correction values for the level set function are calculated with high precision using high-order kernel functions instead of conventional linear interpolation, (2) advection of the level set function is achieved with compact low-order schemes rather than computationally complex high-order advection schemes traditionally recommended, (3) the correction process using kernel functions is easily extendable to three-dimensional applications, and (4) fine interface tracking below the mesh resolution is performed with high accuracy while maintaining mass conservation. The proposed method was validated through numerical experiments using widely adopted two-dimensional and three-dimensional rigid body rotation and interface stretching tests. The numerical results demonstrated that the new method outperforms conventional techniques in accurately capturing moving interfaces and improving mass conservation. Additionally, the proposed method was implemented into a fluid simulation code and evaluated using a dam break benchmark. The results showed good agreement with experimental data, demonstrating the method's effectiveness for practical applications in free-surface interface capturing.
{"title":"Improved particle level set method with higher-order kernel function correction: Enhancing accuracy and conservation","authors":"Shunsuke Kurioka , Changhong Hu","doi":"10.1016/j.compfluid.2025.106571","DOIUrl":"10.1016/j.compfluid.2025.106571","url":null,"abstract":"<div><div>This paper proposes an improved Particle Level Set (PLS) method that enhances accuracy and mass conservation by correcting the position information of Lagrangian particles placed on the interface using high-order kernel functions. This method, referred to as the PLS/KC (improved Particle Level Set method with high-order Kernel function Correction), accurately captures moving interfaces in multiphase flow simulations on fixed Eulerian grids. The innovation and practical significance of the proposed method are highlighted as follows: (1) correction values for the level set function are calculated with high precision using high-order kernel functions instead of conventional linear interpolation, (2) advection of the level set function is achieved with compact low-order schemes rather than computationally complex high-order advection schemes traditionally recommended, (3) the correction process using kernel functions is easily extendable to three-dimensional applications, and (4) fine interface tracking below the mesh resolution is performed with high accuracy while maintaining mass conservation. The proposed method was validated through numerical experiments using widely adopted two-dimensional and three-dimensional rigid body rotation and interface stretching tests. The numerical results demonstrated that the new method outperforms conventional techniques in accurately capturing moving interfaces and improving mass conservation. Additionally, the proposed method was implemented into a fluid simulation code and evaluated using a dam break benchmark. The results showed good agreement with experimental data, demonstrating the method's effectiveness for practical applications in free-surface interface capturing.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"291 ","pages":"Article 106571"},"PeriodicalIF":2.5,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421506","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}
Pub Date : 2025-02-06DOI: 10.1016/j.compfluid.2025.106567
Jeffrey S. Horner , David J. Kemmenoe , Gustav J. Bourdon , Scott A. Roberts , Edward R. Arata , Jaideep Ray , Anne M. Grillet
Brazing and soldering are metallurgical joining techniques that use a wetting molten metal to create a joint between two faying surfaces. The quality of the brazing process depends strongly on the wetting properties of the molten filler metal, namely the surface tension and contact angle, and the resulting joint can be susceptible to various defects, such as run-out and underfill, if the material properties or joining conditions are not suitable. In this work, we implement a finite element simulation to predict the formation of such defects in braze processes. This model incorporates both fluid–structure interaction through an arbitrary Eulerian–Lagrangian technique and free surface wetting through conformal decomposition finite element modeling. Upon validating our numerical simulations against experimental run-out studies on a silver-Kovar system, we then use the model to predict run-out and underfill in systems with variable surface tension, contact angles, and applied pressure. Finally, we consider variable joint/surface geometries and show how different geometrical configurations can help to mitigate run-out. This work aims to understand how brazing defects arise and validate a coupled wetting and fluid–structure interaction simulation that can be used for other industrial problems.
{"title":"Predictive dynamic wetting, fluid–structure interaction simulations for braze run-out","authors":"Jeffrey S. Horner , David J. Kemmenoe , Gustav J. Bourdon , Scott A. Roberts , Edward R. Arata , Jaideep Ray , Anne M. Grillet","doi":"10.1016/j.compfluid.2025.106567","DOIUrl":"10.1016/j.compfluid.2025.106567","url":null,"abstract":"<div><div>Brazing and soldering are metallurgical joining techniques that use a wetting molten metal to create a joint between two faying surfaces. The quality of the brazing process depends strongly on the wetting properties of the molten filler metal, namely the surface tension and contact angle, and the resulting joint can be susceptible to various defects, such as run-out and underfill, if the material properties or joining conditions are not suitable. In this work, we implement a finite element simulation to predict the formation of such defects in braze processes. This model incorporates both fluid–structure interaction through an arbitrary Eulerian–Lagrangian technique and free surface wetting through conformal decomposition finite element modeling. Upon validating our numerical simulations against experimental run-out studies on a silver-Kovar system, we then use the model to predict run-out and underfill in systems with variable surface tension, contact angles, and applied pressure. Finally, we consider variable joint/surface geometries and show how different geometrical configurations can help to mitigate run-out. This work aims to understand how brazing defects arise and validate a coupled wetting and fluid–structure interaction simulation that can be used for other industrial problems.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106567"},"PeriodicalIF":2.5,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386527","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}
This study delves into the complexities of modelling dense gases near thermodynamic critical points, where conventional gas dynamic assumptions prove inadequate. Within this unique regime, non-linear waves exhibit behaviours divergent from classical phenomena, like expansion shocks which remain consistent with entropy conditions. Accurately capturing these phenomena mandates sophisticated equation of state (EoS) that surpasses the ideal gas assumptions, presenting challenges for numerical simulations. In this paper, we propose a simple modification to the Boltzmann equation (with the BGK framework), which, upon taking moments, leads to Euler equations for dense gas flows. We consider van der Waals EoS. Further, we develop a three-velocity model based Kinetic Flux Difference Splitting (KFDS) scheme for the Euler system, with adaptable diffusion coefficients suitable to capture compressible flow phenomena specific to ideal and dense gases. This innovative approach diverges from traditional algorithms, which are tailored for ideal gas EoS and struggle to accommodate the inherent variations. A comparative analysis with macroscopic efficient central solvers designed to be independent of the eigen-structure, such as MOVERS+ and RICCA, is conducted to validate the results against benchmark tests from the data in the literature. It is important to note that the kinetic schemes also possess the advantage of being independent of the eigen-structure, a feature that distinguishes them from traditional Riemann solvers. This effort significantly enhances computational modelling capabilities and fosters deeper insights into the behaviour of dense gases. The proposed advancements enhance numerical methods tailored for real gas EoS simulations by ensuring precise capture of grid-aligned steady discontinuities and effectively mitigating numerical diffusion across these discontinuities in inviscid compressible flows.
{"title":"Kinetic and macroscopic modelling for dense gas flow simulations","authors":"K.S. Shrinath , Ramesh Kolluru , S.V. Raghurama Rao , Vasudeva Rao Veeredhi , Sekhar G.N.","doi":"10.1016/j.compfluid.2024.106539","DOIUrl":"10.1016/j.compfluid.2024.106539","url":null,"abstract":"<div><div>This study delves into the complexities of modelling dense gases near thermodynamic critical points, where conventional gas dynamic assumptions prove inadequate. Within this unique regime, non-linear waves exhibit behaviours divergent from classical phenomena, like expansion shocks which remain consistent with entropy conditions. Accurately capturing these phenomena mandates sophisticated equation of state (EoS) that surpasses the ideal gas assumptions, presenting challenges for numerical simulations. In this paper, we propose a simple modification to the Boltzmann equation (with the BGK framework), which, upon taking moments, leads to Euler equations for dense gas flows. We consider van der Waals EoS. Further, we develop a three-velocity model based <em>Kinetic Flux Difference Splitting</em> (KFDS) scheme for the Euler system, with adaptable diffusion coefficients suitable to capture compressible flow phenomena specific to ideal and dense gases. This innovative approach diverges from traditional algorithms, which are tailored for ideal gas EoS and struggle to accommodate the inherent variations. A comparative analysis with macroscopic efficient central solvers designed to be independent of the eigen-structure, such as MOVERS+ and RICCA, is conducted to validate the results against benchmark tests from the data in the literature. It is important to note that the kinetic schemes also possess the advantage of being independent of the eigen-structure, a feature that distinguishes them from traditional Riemann solvers. This effort significantly enhances computational modelling capabilities and fosters deeper insights into the behaviour of dense gases. The proposed advancements enhance numerical methods tailored for real gas EoS simulations by ensuring precise capture of grid-aligned steady discontinuities and effectively mitigating numerical diffusion across these discontinuities in inviscid compressible flows.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106539"},"PeriodicalIF":2.5,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395720","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}
Pub Date : 2025-01-30DOI: 10.1016/j.compfluid.2025.106559
Biswajit Basu , Andrea Staino , Frank Gaitan
In this paper, we solve for shocks and travelling waves in advection, inviscid Burgers’ and Burgers’ equations by implementing a recently established quantum algorithm in the literature. The quantum algorithm has been successful in solving Navier–Stokes, flow generated by Burgers’ and submarine tephra flow equations under certain initial and boundary conditions. Here, we further study the efficacy of the quantum algorithm by extending the application to advection, inviscid Burgers’ and Burgers’ equations under different kinds of initial and boundary conditions. In addition to central differencing and upwinding, Lax–Wendroff discretization scheme has also been introduced in the quantum algorithm to observe how numerical dissipation and dispersion are affected. We recover known travelling waves, and shocks with rarefaction and expansion.
{"title":"On solving for shocks and travelling waves using a quantum algorithm","authors":"Biswajit Basu , Andrea Staino , Frank Gaitan","doi":"10.1016/j.compfluid.2025.106559","DOIUrl":"10.1016/j.compfluid.2025.106559","url":null,"abstract":"<div><div>In this paper, we solve for shocks and travelling waves in advection, inviscid Burgers’ and Burgers’ equations by implementing a recently established quantum algorithm in the literature. The quantum algorithm has been successful in solving Navier–Stokes, flow generated by Burgers’ and submarine tephra flow equations under certain initial and boundary conditions. Here, we further study the efficacy of the quantum algorithm by extending the application to advection, inviscid Burgers’ and Burgers’ equations under different kinds of initial and boundary conditions. In addition to central differencing and upwinding, Lax–Wendroff discretization scheme has also been introduced in the quantum algorithm to observe how numerical dissipation and dispersion are affected. We recover known travelling waves, and shocks with rarefaction and expansion.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106559"},"PeriodicalIF":2.5,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395721","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}
Pub Date : 2025-01-25DOI: 10.1016/j.compfluid.2025.106558
Marius M. Neamtu-Halic , Stefano Brizzolara , George Haller , Markus Holzner
Lagrangian coherent structures (LCSs) are widely recognized as playing a significant role in turbulence dynamics since they can control the transport of mass, momentum or heat. However, the methods used to identify these structures are often based on ambiguous definitions and arbitrary thresholding. While LCSs theory provides precise and frame-indifferent mathematical definitions of coherent structures, some of the commonly used extraction algorithms employed in the literature are still case-specific and involve user-defined parameters. In this study, we present a new, unsupervised extraction algorithm that enables the extraction of rotational LCSs based on Lagrangian average vorticity deviation from an arbitrary 3D velocity field. The algorithm utilizes two alternative methods for the identification of the LCS core (ridge): an unsupervised clustering method and a streamline-based method. In a subsequent step, the ridge curve is parametrized through a pruning procedure of minimum spanning tree graphs. To assess the effectiveness of the algorithm, we test it on two cases: (i) direct numerical simulations of forced homogeneous and isotropic turbulence and (ii) three-dimensional Particle Tracking Velocimetry experiments of a turbulent gravity current.
{"title":"Unsupervised extraction of rotational Lagrangian coherent structures","authors":"Marius M. Neamtu-Halic , Stefano Brizzolara , George Haller , Markus Holzner","doi":"10.1016/j.compfluid.2025.106558","DOIUrl":"10.1016/j.compfluid.2025.106558","url":null,"abstract":"<div><div>Lagrangian coherent structures (LCSs) are widely recognized as playing a significant role in turbulence dynamics since they can control the transport of mass, momentum or heat. However, the methods used to identify these structures are often based on ambiguous definitions and arbitrary thresholding. While LCSs theory provides precise and frame-indifferent mathematical definitions of coherent structures, some of the commonly used extraction algorithms employed in the literature are still case-specific and involve user-defined parameters. In this study, we present a new, unsupervised extraction algorithm that enables the extraction of rotational LCSs based on Lagrangian average vorticity deviation from an arbitrary 3D velocity field. The algorithm utilizes two alternative methods for the identification of the LCS core (ridge): an unsupervised clustering method and a streamline-based method. In a subsequent step, the ridge curve is parametrized through a pruning procedure of minimum spanning tree graphs. To assess the effectiveness of the algorithm, we test it on two cases: (i) direct numerical simulations of forced homogeneous and isotropic turbulence and (ii) three-dimensional Particle Tracking Velocimetry experiments of a turbulent gravity current.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106558"},"PeriodicalIF":2.5,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143237931","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}
Pub Date : 2025-01-17DOI: 10.1016/j.compfluid.2025.106555
R. Ruyssen , R. Cottereau , P. Boivin
This paper introduces a method for the numerical approximation of solutions of the mono-kinetic Radiative Transfer Equation, adapting some of the Lattice Boltzmann Method features. The main difference between the Radiative Transfer Equation and the Boltzmann Equation, used in the classical Lattice Boltzmann Method framework, lies in the constrained norm of the velocity field appearing in the advection operator. This small difference leads to off-grid propagation if one uses a regular lattice, as classically done for efficiency reasons. To recover on-grid propagation, this paper introduces a specific time discretization along each propagation directions and an original traversal algorithm to allow for scattering between different directions at common times. The algorithm involves only linear time interpolations so as to preserve the local nature of the Lattice Boltzmann Method. The direction quadrature follows the principles of the Discrete Ordinate Method. The relevance of the approach is illustrated on different two-dimensional problems and the results are compared to previously published numerical test-cases.
{"title":"A Staggered Lattice Boltzmann Method for the Radiative Transfer Equation","authors":"R. Ruyssen , R. Cottereau , P. Boivin","doi":"10.1016/j.compfluid.2025.106555","DOIUrl":"10.1016/j.compfluid.2025.106555","url":null,"abstract":"<div><div>This paper introduces a method for the numerical approximation of solutions of the mono-kinetic Radiative Transfer Equation, adapting some of the Lattice Boltzmann Method features. The main difference between the Radiative Transfer Equation and the Boltzmann Equation, used in the classical Lattice Boltzmann Method framework, lies in the constrained norm of the velocity field appearing in the advection operator. This small difference leads to <em>off-grid</em> propagation if one uses a regular lattice, as classically done for efficiency reasons. To recover on-grid propagation, this paper introduces a specific time discretization along each propagation directions and an original traversal algorithm to allow for scattering between different directions at common times. The algorithm involves only linear time interpolations so as to preserve the local nature of the Lattice Boltzmann Method. The direction quadrature follows the principles of the Discrete Ordinate Method. The relevance of the approach is illustrated on different two-dimensional problems and the results are compared to previously published numerical test-cases.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"290 ","pages":"Article 106555"},"PeriodicalIF":2.5,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143166250","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}
Pub Date : 2025-01-15DOI: 10.1016/j.compfluid.2025.106556
Joaquín López
A high-order accurate, efficient and easy-to-implement method is presented for computing the fluid volume bounded by an arbitrary polyhedron, whether it is convex or non-convex, and an implicitly-defined fluid body. This method is an improved version of a previous one that used a recursive local grid refinement of the polyhedron and linear interpolations to determine the intersections of the interface that delimits the fluid body (or simply fluid-body interface) with the polyhedron boundaries. The proposed method first determines the volume of a polyhedral approximation of the bounded fluid region by using a general clipping-lookup and capping procedure valid for arbitrary polyhedra, where the points of intersection between the polyhedron and the fluid-body interface are obtained using a root-finding method rather than linear interpolations. The approximated polyhedral volume is subsequently corrected by using simple Gaussian quadrature rules over a triangulated approximation of the intersected fluid-body interface to achieve high-order accuracy. Recursive local grid refinement of the polyhedron also enables reductions in fluid volume errors. The proposed method requires no assumption of any particular local parametrization of the fluid-body interface, whether paraboloidal or of any other type, or deriving any complex analytical expressions to compute the volume of fluid contained within the polyhedron, thereby making the method easy to implement and generally applicable to any implicitly-defined function. A detailed assessment shows global fourth-order convergent accuracies on structured and unstructured grids even for complex fluid-body interfaces of a high degree. Speedups of several orders of magnitude with respect to the previous refinement method with linear interpolations are achieved even for relatively coarse grids. Comparisons with other methods are also presented, and the software with the implemented method and tests used for the assessment is freely available.
{"title":"High-order, refinement-based computation of the volume of an arbitrary polyhedron intersected by an implicitly defined fluid body","authors":"Joaquín López","doi":"10.1016/j.compfluid.2025.106556","DOIUrl":"10.1016/j.compfluid.2025.106556","url":null,"abstract":"<div><div>A high-order accurate, efficient and easy-to-implement method is presented for computing the fluid volume bounded by an arbitrary polyhedron, whether it is convex or non-convex, and an implicitly-defined fluid body. This method is an improved version of a previous one that used a recursive local grid refinement of the polyhedron and linear interpolations to determine the intersections of the interface that delimits the fluid body (or simply fluid-body interface) with the polyhedron boundaries. The proposed method first determines the volume of a polyhedral approximation of the bounded fluid region by using a general clipping-lookup and capping procedure valid for arbitrary polyhedra, where the points of intersection between the polyhedron and the fluid-body interface are obtained using a root-finding method rather than linear interpolations. The approximated polyhedral volume is subsequently corrected by using simple Gaussian quadrature rules over a triangulated approximation of the intersected fluid-body interface to achieve high-order accuracy. Recursive local grid refinement of the polyhedron also enables reductions in fluid volume errors. The proposed method requires no assumption of any particular local parametrization of the fluid-body interface, whether paraboloidal or of any other type, or deriving any complex analytical expressions to compute the volume of fluid contained within the polyhedron, thereby making the method easy to implement and generally applicable to any implicitly-defined function. A detailed assessment shows global fourth-order convergent accuracies on structured and unstructured grids even for complex fluid-body interfaces of a high degree. Speedups of several orders of magnitude with respect to the previous refinement method with linear interpolations are achieved even for relatively coarse grids. Comparisons with other methods are also presented, and the software with the implemented method and tests used for the assessment is freely available.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"289 ","pages":"Article 106556"},"PeriodicalIF":2.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147869","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}
Numerical simulations of detonation-containing flows have emerged as crucial tools for designing next-generation power and propulsion devices. As these tools mature, it is important for the combustion community to properly understand and isolate grid resolution effects when simulating detonations. To this end, the objective of this work is to provide a comprehensive analysis of the numerical convergence of unsteady detonation simulations, with focus on isolating the impacts of chemical timescale modifications on convergence characteristics in the context of operator splitting. With the aid of an AMReX-based adaptive mesh refinement flow solver (Sharma et al., 2024)—which enables resolutions up to cells-per-induction length—the convergence analysis is conducted using two kinetics configurations: (1) the simplified three-step Arrhenius-based model mechanism of Short and Quirk (1997), where chemical timescales in the detonation are modified by adjusting activation energies in the initiation and branching reactions, and (2) a detailed hydrogen-air mechanism (Mével et al. (2009), Shepherd (2018)), where the chemical timescales are adjusted by varying the ambient pressure. The convergence of unsteady self-sustained detonations in one-dimensional channels is then analyzed with reference to steady-state theoretical baseline solutions using these mechanisms. The goal of the analysis is to provide a detailed comparison of the effects of grid resolution on both macroscopic (peak pressures and wave speeds) and microscopic (wave structure) quantities of interest, drawing connections between the deviations from steady-state baselines and minimum chemical timescales. In particular, chemical timescale reductions were found to have minimal impact on the convergence of macroscopic properties. However, analyses of microscopic convergence trends, particularly in the reaction front location, revealed a key insight: maintaining the induction time while eliminating prohibitive chemical timescales through mechanism simplifications and combustion modeling can significantly enhance detonation convergence properties. Ultimately, this work uncovers resolution-dependent unsteady detonation convergence regimes and highlights the important role played by not only the chemical timescales, but also the ratio between the chemical timescale and induction time on the numerical convergence of the detonation wave structure.
{"title":"Chemical timescale effects on detonation convergence","authors":"Shivam Barwey , Michael Ullman , Ral Bielawski , Venkat Raman","doi":"10.1016/j.compfluid.2025.106550","DOIUrl":"10.1016/j.compfluid.2025.106550","url":null,"abstract":"<div><div>Numerical simulations of detonation-containing flows have emerged as crucial tools for designing next-generation power and propulsion devices. As these tools mature, it is important for the combustion community to properly understand and isolate grid resolution effects when simulating detonations. To this end, the objective of this work is to provide a comprehensive analysis of the numerical convergence of unsteady detonation simulations, with focus on isolating the impacts of chemical timescale modifications on convergence characteristics in the context of operator splitting. With the aid of an AMReX-based adaptive mesh refinement flow solver (Sharma et al., 2024)—which enables resolutions up to <span><math><mrow><mi>O</mi><mrow><mo>(</mo><mn>1000</mn><mo>)</mo></mrow></mrow></math></span> cells-per-induction length—the convergence analysis is conducted using two kinetics configurations: (1) the simplified three-step Arrhenius-based model mechanism of Short and Quirk (1997), where chemical timescales in the detonation are modified by adjusting activation energies in the initiation and branching reactions, and (2) a detailed hydrogen-air mechanism (Mével et al. (2009), Shepherd (2018)), where the chemical timescales are adjusted by varying the ambient pressure. The convergence of unsteady self-sustained detonations in one-dimensional channels is then analyzed with reference to steady-state theoretical baseline solutions using these mechanisms. The goal of the analysis is to provide a detailed comparison of the effects of grid resolution on both macroscopic (peak pressures and wave speeds) and microscopic (wave structure) quantities of interest, drawing connections between the deviations from steady-state baselines and minimum chemical timescales. In particular, chemical timescale reductions were found to have minimal impact on the convergence of macroscopic properties. However, analyses of microscopic convergence trends, particularly in the reaction front location, revealed a key insight: maintaining the induction time while eliminating prohibitive chemical timescales through mechanism simplifications and combustion modeling can significantly enhance detonation convergence properties. Ultimately, this work uncovers resolution-dependent unsteady detonation convergence regimes and highlights the important role played by not only the chemical timescales, but also the ratio between the chemical timescale and induction time on the numerical convergence of the detonation wave structure.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"289 ","pages":"Article 106550"},"PeriodicalIF":2.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147858","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}
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