Pub Date : 2022-03-16DOI: 10.1080/10618562.2022.2091776
Sashi Kumar Gadiyakari Nagendra, N. K. Maheshwari
Compressible multi species flow solver, developed by the authors Kumar and Maheshwari [May 15, 2020. “Viscous Multi-Species Lattice Boltzmann Solver for Simulating Shock-Wave Structure.” Computers and Fluids 203. Article ID 104539], has been extended further to non-continuum flows. The approach uses the Onsager-BGK model, which ensures Onsager's maximum entropy production principle is followed, thus avoids unphysical solutions. Equations for velocity slip and temperature jump have been derived. The viscous slip, thermal slip and diffusion slip coefficients have been successfully validated with 13-moment solver's and experimental data. The departure from equilibrium in such flows has been approximated by a collision probability function ( ), instead of using the complicated second order perturbation over the Knudsen number (that leads to Burnett equations). This provided the necessary reduction in (viscous, thermal, mass) dissipation and the developed approximate solver is able to predict the thermal and viscous profiles in a non-continuum regime and validates against DSMC simulations. Test cases consisting of flow through micro-channels demonstrated the ability of solver to handle monoatomic, diatomic and poly atomic gases. The developed non-continuum solver is in a finite volume framework and is easily adaptable to legacy in-house Navier–Stokes solvers.
{"title":"Multi-Species Compressible Solver for Non-Continuum Flow Through a Micro-Channel","authors":"Sashi Kumar Gadiyakari Nagendra, N. K. Maheshwari","doi":"10.1080/10618562.2022.2091776","DOIUrl":"https://doi.org/10.1080/10618562.2022.2091776","url":null,"abstract":"Compressible multi species flow solver, developed by the authors Kumar and Maheshwari [May 15, 2020. “Viscous Multi-Species Lattice Boltzmann Solver for Simulating Shock-Wave Structure.” Computers and Fluids 203. Article ID 104539], has been extended further to non-continuum flows. The approach uses the Onsager-BGK model, which ensures Onsager's maximum entropy production principle is followed, thus avoids unphysical solutions. Equations for velocity slip and temperature jump have been derived. The viscous slip, thermal slip and diffusion slip coefficients have been successfully validated with 13-moment solver's and experimental data. The departure from equilibrium in such flows has been approximated by a collision probability function ( ), instead of using the complicated second order perturbation over the Knudsen number (that leads to Burnett equations). This provided the necessary reduction in (viscous, thermal, mass) dissipation and the developed approximate solver is able to predict the thermal and viscous profiles in a non-continuum regime and validates against DSMC simulations. Test cases consisting of flow through micro-channels demonstrated the ability of solver to handle monoatomic, diatomic and poly atomic gases. The developed non-continuum solver is in a finite volume framework and is easily adaptable to legacy in-house Navier–Stokes solvers.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"59 1","pages":"207 - 231"},"PeriodicalIF":1.3,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89352223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-03-16DOI: 10.1080/10618562.2022.2094917
V. Casseau, Wenbo Zhang, Shrutakeerti Mallikarjun, W. Habashi, Song Gao, A. Karchani
This paper presents HALO3D, a CFD code simulating the wide range of Mach numbers a hypervelocity vehicle experiences. HALO3D is composed of (a) a RANS edge-based Finite Element (FE) solver modelling high-velocity thermo-chemical non-equilibrium flows, (b) an electromagnetic interactions solver, (c) an ablation module, (d) a Direct Simulation Monte Carlo (DSMC) solver for the rarefied regime, seamlessly linked to the continuum one, and (e) a powerful automatic mesh optimiser finely capturing the many singular hypersonic flow phenomena. Verification and validation simulations for two- and three-dimensional hypersonic flows over a flat plate, a cylinder, a blunt conical body, re-entry capsules, and a waverider geometry demonstrate accurate aerothermodynamic predictions in a wide range of Knudsen numbers, complex geometries and multiphysics.
{"title":"HALO3D: An All-Mach Approach to Hypersonic Flows Simulation","authors":"V. Casseau, Wenbo Zhang, Shrutakeerti Mallikarjun, W. Habashi, Song Gao, A. Karchani","doi":"10.1080/10618562.2022.2094917","DOIUrl":"https://doi.org/10.1080/10618562.2022.2094917","url":null,"abstract":"This paper presents HALO3D, a CFD code simulating the wide range of Mach numbers a hypervelocity vehicle experiences. HALO3D is composed of (a) a RANS edge-based Finite Element (FE) solver modelling high-velocity thermo-chemical non-equilibrium flows, (b) an electromagnetic interactions solver, (c) an ablation module, (d) a Direct Simulation Monte Carlo (DSMC) solver for the rarefied regime, seamlessly linked to the continuum one, and (e) a powerful automatic mesh optimiser finely capturing the many singular hypersonic flow phenomena. Verification and validation simulations for two- and three-dimensional hypersonic flows over a flat plate, a cylinder, a blunt conical body, re-entry capsules, and a waverider geometry demonstrate accurate aerothermodynamic predictions in a wide range of Knudsen numbers, complex geometries and multiphysics.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"112 1","pages":"187 - 206"},"PeriodicalIF":1.3,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77024171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-03-16DOI: 10.1080/10618562.2022.2088739
Walter Arias-Ramírez, J. Larsson
The purpose of this Short Communication is three-fold: to make the case that the question of grid sufficiency in LES should be viewed as a hypothesis test, to demonstrate how this can be done using standard tools from statistics, and to illustrate how this leads to transparent ways to both judge grid sufficiency and to make decisions about how much averaging time is required to make that judgment.
{"title":"Grid Sufficiency in Large Eddy Simulations as a Hypothesis Test","authors":"Walter Arias-Ramírez, J. Larsson","doi":"10.1080/10618562.2022.2088739","DOIUrl":"https://doi.org/10.1080/10618562.2022.2088739","url":null,"abstract":"The purpose of this Short Communication is three-fold: to make the case that the question of grid sufficiency in LES should be viewed as a hypothesis test, to demonstrate how this can be done using standard tools from statistics, and to illustrate how this leads to transparent ways to both judge grid sufficiency and to make decisions about how much averaging time is required to make that judgment.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"178 1","pages":"260 - 264"},"PeriodicalIF":1.3,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76880560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-03-16DOI: 10.1080/10618562.2022.2085255
Yi Wang, G. Vita, Bruño Fraga, Chenghao Lyu, Jianchun Wang, H. Hemida
There are different methods for setting the inlet boundary condition (IBC) in large eddy simulation (LES). However, different methods applied in the same simulation result in different results. In this study, the influence of setting the IBC in the LES with the Lund method, the divergence-free synthetic eddies method (DFSEM), and the digital filter method (DFM) on the simulation of the boundary layer over a flat plate was investigated. For the DFM and the DFSEM, the input parameters such as the turbulent length scales with constant values were tested. The results indicated that simulations based on the DFSEM and the DFM with turbulent length scales equal to the boundary layer thickness by a factor of 0.6 were in good agreement with the direct numerical simulation (DNS) results It can be observed that the simulation results of the DFSEM agree better with the DNS data than the other two methods.
{"title":"Influence of Turbulent Inlet Boundary Condition on Large Eddy Simulation Over a Flat Plate Boundary Layer","authors":"Yi Wang, G. Vita, Bruño Fraga, Chenghao Lyu, Jianchun Wang, H. Hemida","doi":"10.1080/10618562.2022.2085255","DOIUrl":"https://doi.org/10.1080/10618562.2022.2085255","url":null,"abstract":"There are different methods for setting the inlet boundary condition (IBC) in large eddy simulation (LES). However, different methods applied in the same simulation result in different results. In this study, the influence of setting the IBC in the LES with the Lund method, the divergence-free synthetic eddies method (DFSEM), and the digital filter method (DFM) on the simulation of the boundary layer over a flat plate was investigated. For the DFM and the DFSEM, the input parameters such as the turbulent length scales with constant values were tested. The results indicated that simulations based on the DFSEM and the DFM with turbulent length scales equal to the boundary layer thickness by a factor of 0.6 were in good agreement with the direct numerical simulation (DNS) results It can be observed that the simulation results of the DFSEM agree better with the DNS data than the other two methods.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"113 1","pages":"232 - 259"},"PeriodicalIF":1.3,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82470302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2074001
T. Misaka, T. Nakazawa, S. Obayashi, Seiji Kubo, Norio Asaumi, T. Ideta
In this study, Reynolds-averaged Navier-Stokes (RANS) simulations were carried out to predict the film cooling effectiveness of an inclined round jet in crossflow using turbulence model parameters optimised based on measurement data. The posterior distributions of the generalised (GEKO) turbulence model parameters were estimated using a computationally efficient surrogate model with the Markov chain Monte Carlo method, which provides a framework for probabilistic parameter estimation based on measurement data. The results show that using the maximum a posterior parameters for a blowing ratio of 0.5 gives better predictions than using the default parameters of the GEKO model. The estimated parameters were then applied to flows with a higher blowing ratio and different hole geometry to evaluate the generalisation performance. In both cases, the results were improved by properly predicting the spread of the cooling flow.
{"title":"Bayesian Uncertainty Reduction of Generalised k-ω Turbulence Model for Prediction of Film-Cooling Effectiveness","authors":"T. Misaka, T. Nakazawa, S. Obayashi, Seiji Kubo, Norio Asaumi, T. Ideta","doi":"10.1080/10618562.2022.2074001","DOIUrl":"https://doi.org/10.1080/10618562.2022.2074001","url":null,"abstract":"In this study, Reynolds-averaged Navier-Stokes (RANS) simulations were carried out to predict the film cooling effectiveness of an inclined round jet in crossflow using turbulence model parameters optimised based on measurement data. The posterior distributions of the generalised (GEKO) turbulence model parameters were estimated using a computationally efficient surrogate model with the Markov chain Monte Carlo method, which provides a framework for probabilistic parameter estimation based on measurement data. The results show that using the maximum a posterior parameters for a blowing ratio of 0.5 gives better predictions than using the default parameters of the GEKO model. The estimated parameters were then applied to flows with a higher blowing ratio and different hole geometry to evaluate the generalisation performance. In both cases, the results were improved by properly predicting the spread of the cooling flow.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"25 1","pages":"152 - 166"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81772391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2052282
E. Katamine, Ryuga Kawai, Yasushi Yoshida
This paper presents a numerical solution to a shape optimisation of stationary fluid-structure-interactive (FSI) fields. The minimisation problem for total dissipation energy in the viscous flow field and the mean compliance minimisation problem in order to achieve stiffness maximisation in the structural field are considered for the shape optimisation. In the FSI analysis, a weak coupled analysis is used to alternately analyse the governing equations of the flow field and the structural field considering geometrically nonlinear. Shape derivative function of the shape optimisation problem is derived theoretically using the adjoint variable method and the formulae of the shape derivative with respect to domain variation of the distribution function. Reshaping is carried out by the gradient method proposed as an approach to solving shape optimisation. Numerical analysis program for the shape optimisation problem is developed by using FreeFEM, and the validity of the proposed method is confirmed by the results of 2D problems.
{"title":"Shape Optimisation of Fluid-Structure Interactive Field Considering Geometrically Nonlinear Structure","authors":"E. Katamine, Ryuga Kawai, Yasushi Yoshida","doi":"10.1080/10618562.2022.2052282","DOIUrl":"https://doi.org/10.1080/10618562.2022.2052282","url":null,"abstract":"This paper presents a numerical solution to a shape optimisation of stationary fluid-structure-interactive (FSI) fields. The minimisation problem for total dissipation energy in the viscous flow field and the mean compliance minimisation problem in order to achieve stiffness maximisation in the structural field are considered for the shape optimisation. In the FSI analysis, a weak coupled analysis is used to alternately analyse the governing equations of the flow field and the structural field considering geometrically nonlinear. Shape derivative function of the shape optimisation problem is derived theoretically using the adjoint variable method and the formulae of the shape derivative with respect to domain variation of the distribution function. Reshaping is carried out by the gradient method proposed as an approach to solving shape optimisation. Numerical analysis program for the shape optimisation problem is developed by using FreeFEM, and the validity of the proposed method is confirmed by the results of 2D problems.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"38 1","pages":"138 - 151"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85872882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2070954
T. Kurahashi
Digitization has progressed in recent years in response to Covid-19 with considerable advances in the field of CFD. The term ‘digital twin’ is gaining attention as a technology for collecting information in physical space via the ‘Internet of Things (IoT)’, etc., and reproducing physical space in virtual space based on transmitted data. With the advance in IoT technology, numerical information such as measurement and observation data has become readily available. The Kalman filter and the particle filter are well-known methods by which observation data can be included in numerical simulations, modifying the simulated data to approach the observation data. Due in part to the fact that information has become freely available via the Internet, several reference documents on data assimilation methods such as the Kalman filter and the particle filter have been published in Japan over the last decade. With data assimilation, the accuracy of the system equation, i.e. the discretized governing equation that adds the system noise term, depends on the optimal estimated value. It is therefore important to select a high discretization method to obtain highly accurate estimation solution that includes the effects of observed data. At the same time, with the progress of digitization, technology related to resin and metal 3D printers continue to develop. It is now much easier to make objects using a 3D printer, even shapes that are otherwise difficult to manufacture. Many researchers have therefore been directing their attention to techniques of shape optimization and topology optimization with new developments and techniques widely discussed at domestic and international conferences on computational mechanics. Given the above, we have planned a special issue on data assimilation and optimal design in the field of CFD, in which we focus principally on Japanese technologies. We feature here papers submitted by researchers involved in data assimilation and mathematical design based on numerical simulations in the field of CFD. We would like to express our appreciation to all the researchers in this field, and especially thank those who have contributed to this publication by submitting their papers.
{"title":"Recent Japanese Progress on Data Assimilation and Optimal Design by CFD","authors":"T. Kurahashi","doi":"10.1080/10618562.2022.2070954","DOIUrl":"https://doi.org/10.1080/10618562.2022.2070954","url":null,"abstract":"Digitization has progressed in recent years in response to Covid-19 with considerable advances in the field of CFD. The term ‘digital twin’ is gaining attention as a technology for collecting information in physical space via the ‘Internet of Things (IoT)’, etc., and reproducing physical space in virtual space based on transmitted data. With the advance in IoT technology, numerical information such as measurement and observation data has become readily available. The Kalman filter and the particle filter are well-known methods by which observation data can be included in numerical simulations, modifying the simulated data to approach the observation data. Due in part to the fact that information has become freely available via the Internet, several reference documents on data assimilation methods such as the Kalman filter and the particle filter have been published in Japan over the last decade. With data assimilation, the accuracy of the system equation, i.e. the discretized governing equation that adds the system noise term, depends on the optimal estimated value. It is therefore important to select a high discretization method to obtain highly accurate estimation solution that includes the effects of observed data. At the same time, with the progress of digitization, technology related to resin and metal 3D printers continue to develop. It is now much easier to make objects using a 3D printer, even shapes that are otherwise difficult to manufacture. Many researchers have therefore been directing their attention to techniques of shape optimization and topology optimization with new developments and techniques widely discussed at domestic and international conferences on computational mechanics. Given the above, we have planned a special issue on data assimilation and optimal design in the field of CFD, in which we focus principally on Japanese technologies. We feature here papers submitted by researchers involved in data assimilation and mathematical design based on numerical simulations in the field of CFD. We would like to express our appreciation to all the researchers in this field, and especially thank those who have contributed to this publication by submitting their papers.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"76 1","pages":"91 - 91"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77707773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2051496
Takashi Nakazawa, T. Misaka, Y. Hasegawa
This paper proposes a shape optimisation method for suppressing a time fluctuation part of the two-dimensional jet-in-cross flow. Previously, the author has formulated a shape optimisation problem for suppressing transient fluids using Snapshot proper orthogonal decomposition (POD). This study extends it to a two-dimensional jet-in-cross flow. For this purpose, the eigenvalues of Snapshot POD are integrated to a cost function, where the constraint functions are the nonstationary Navier–Stokes equation and the eigenvalue equation of Snapshot POD. An objective functional is described using Lagrange multipliers and the finite element method as the sum of the cost and constraint functions. To verify the proposed optimisation strategy, using the gradient method for domain deformation, all triangles over a mesh are deformed, which causes the cost function to decrease. Finally, the eigenvalues of Snapshot POD in the initial and optimal domains are compared.
{"title":"Optimal Design for Suppressing Time Fluctuation Part of Two-Dimensional Jet in Crossflow","authors":"Takashi Nakazawa, T. Misaka, Y. Hasegawa","doi":"10.1080/10618562.2022.2051496","DOIUrl":"https://doi.org/10.1080/10618562.2022.2051496","url":null,"abstract":"This paper proposes a shape optimisation method for suppressing a time fluctuation part of the two-dimensional jet-in-cross flow. Previously, the author has formulated a shape optimisation problem for suppressing transient fluids using Snapshot proper orthogonal decomposition (POD). This study extends it to a two-dimensional jet-in-cross flow. For this purpose, the eigenvalues of Snapshot POD are integrated to a cost function, where the constraint functions are the nonstationary Navier–Stokes equation and the eigenvalue equation of Snapshot POD. An objective functional is described using Lagrange multipliers and the finite element method as the sum of the cost and constraint functions. To verify the proposed optimisation strategy, using the gradient method for domain deformation, all triangles over a mesh are deformed, which causes the cost function to decrease. Finally, the eigenvalues of Snapshot POD in the initial and optimal domains are compared.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"8 1","pages":"112 - 124"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82869659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2085257
Masamichi Nakamura, Y. Ozawa, T. Nonomura
ABSTRACT The objective of this study is to obtain accurate flow field analysis results in a short computational time by using data assimilation, which increases the accuracy of Reynolds averaged Navier-Stokes (RANS) simulations with low grid resolution. The large-eddy simulation (LES) results are assimilated into RANS simulations. In those simulations, the turbulence-model parameters are optimised by an ensemble Kalman filter with a proposed method for adaptive hyperparameter optimisation. The target of calculations is the flow field around a square cylinder of the Reynolds number of approximately . Only the surface pressure of the square cylinder is used as an observation variable. For this shape, the assimilated RANS flow field is similar to that given by the LES analysis, and the drag coefficient reproducibility is improved by . The turbulence-model parameters are also used in the analyses of different cross-sectional shape and are found to improve the reproducibility of the flow field.
{"title":"Low-Grid-Resolution-RANS-Based Data Assimilation of Time-Averaged Separated Flow Obtained by LES","authors":"Masamichi Nakamura, Y. Ozawa, T. Nonomura","doi":"10.1080/10618562.2022.2085257","DOIUrl":"https://doi.org/10.1080/10618562.2022.2085257","url":null,"abstract":"ABSTRACT The objective of this study is to obtain accurate flow field analysis results in a short computational time by using data assimilation, which increases the accuracy of Reynolds averaged Navier-Stokes (RANS) simulations with low grid resolution. The large-eddy simulation (LES) results are assimilated into RANS simulations. In those simulations, the turbulence-model parameters are optimised by an ensemble Kalman filter with a proposed method for adaptive hyperparameter optimisation. The target of calculations is the flow field around a square cylinder of the Reynolds number of approximately . Only the surface pressure of the square cylinder is used as an observation variable. For this shape, the assimilated RANS flow field is similar to that given by the LES analysis, and the drag coefficient reproducibility is improved by . The turbulence-model parameters are also used in the analyses of different cross-sectional shape and are found to improve the reproducibility of the flow field.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"47 1","pages":"167 - 185"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79202654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-02-07DOI: 10.1080/10618562.2022.2052281
Shun Takahashi, T. Misaka, Shotaro Nara, Naoki Sugiyama, Tetsuo Nohara, Yuiki Kuramoto, Y. Kawamoto, Akira Obara, Rina Osada, Asuka Kikuchi, M. Ochiai, Kazuo Osumi, N. Ishikawa
Spray flows containing droplets and particles are used in various industrial fields. In this study, we investigate an efficient and reliable way to predict the spray flow of droplets by combining the discrete droplet model (DDM) with ensemble data assimilation for application to such industrial problems. The aim is to augment cross-sectional measurements such as particle image velocimetry (PIV) with fast DDM simulations of droplets. In this paper, we focus on the numerical experiment of data assimilation, which is also known as twin experiments, and discuss how such cross-sectional measurements and DDM can be integrated by the ensemble Kalman filter. The results showed that the position and velocity of the droplet and the spray nozzle's state were estimated by assimilating the time-averaged velocity measurements on the cross-section using a carefully prepared ensemble of droplets. Furthermore, the droplet size distribution was estimated indirectly through DDM.
{"title":"Augmentation of Cross-Sectional Spray Measurements with Discrete Droplet Model Using Ensemble Kalman Filter","authors":"Shun Takahashi, T. Misaka, Shotaro Nara, Naoki Sugiyama, Tetsuo Nohara, Yuiki Kuramoto, Y. Kawamoto, Akira Obara, Rina Osada, Asuka Kikuchi, M. Ochiai, Kazuo Osumi, N. Ishikawa","doi":"10.1080/10618562.2022.2052281","DOIUrl":"https://doi.org/10.1080/10618562.2022.2052281","url":null,"abstract":"Spray flows containing droplets and particles are used in various industrial fields. In this study, we investigate an efficient and reliable way to predict the spray flow of droplets by combining the discrete droplet model (DDM) with ensemble data assimilation for application to such industrial problems. The aim is to augment cross-sectional measurements such as particle image velocimetry (PIV) with fast DDM simulations of droplets. In this paper, we focus on the numerical experiment of data assimilation, which is also known as twin experiments, and discuss how such cross-sectional measurements and DDM can be integrated by the ensemble Kalman filter. The results showed that the position and velocity of the droplet and the spray nozzle's state were estimated by assimilating the time-averaged velocity measurements on the cross-section using a carefully prepared ensemble of droplets. Furthermore, the droplet size distribution was estimated indirectly through DDM.","PeriodicalId":56288,"journal":{"name":"International Journal of Computational Fluid Dynamics","volume":"1 1","pages":"125 - 137"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79257221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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