Flow, Turbulence and Combustion最新文献

{"title":"A Combustion Model Validation Framework for Turbulent Premixed Hydrogen-Air Flames Utilizing OpenFOAM","authors":"Svenja Nerzak,&nbsp;Ludovico Nista,&nbsp;Marco Vivenzo,&nbsp;Michael Gauding,&nbsp;Heinz Pitsch","doi":"10.1007/s10494-026-00745-z","DOIUrl":"10.1007/s10494-026-00745-z","url":null,"abstract":"<div><p>Developing accurate and robust combustion models is challenging, and their validation can be equally demanding. Even when suitable experimental or numerical datasets are available, setting up and performing validation simulations often requires substantial resources. As a result, most validation studies focus on a single dataset from experiments or numerical simulations, which is generally insufficient for a comprehensive model assessment. Systematic model evaluation, therefore, benefits from a comprehensive, standardized, and easy-to-use validation framework containing multiple validation datasets. This paper introduces a validation framework for combustion models and demonstrates its application to a state-of-the-art flamelet model for large-eddy simulations. The framework deploys the open-source <i>OpenFOAM</i> toolbox to provide an openly accessible simulation standard allowing straightforward integration of newly developed models and facilitating the adoption by the research community. It includes eight validation cases based on both experimental data and direct numerical simulations, and is designed to be readily expandable by the community to accommodate an arbitrarily large number of additional cases. For all cases, the reference data, together with the required configurations and mesh files, are provided. The framework facilitates the systematic assessment of combustion models by automatically performing simulations for all cases and providing comparisons between model predictions and reference data. As a demonstration, a flamelet-based model for lean premixed hydrogen combustion is implemented in <i>OpenFOAM</i> and evaluated within the proposed framework, providing insights into the model’s capabilities and limitations across different flow and combustion conditions.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00745-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614066","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":"Turbulence Modification Under the Influence of Pressure Gradients","authors":"Ali Uzun,&nbsp;Mujeeb R. Malik","doi":"10.1007/s10494-026-00781-9","DOIUrl":"10.1007/s10494-026-00781-9","url":null,"abstract":"<div><p>Reynolds stress budgets computed from a direct numerical simulation of the spanwise-periodic flow over a Gaussian bump are analyzed to gain insight into turbulence modification under different pressure-gradient regimes in three subregions. The four nonzero Reynolds stress components are defined in the local orthogonal coordinate system at a given location on the bump surface. The first subregion starts upstream of the bump under a mild adverse pressure gradient (APG) that becomes progressively stronger toward the bump. The second subregion succeeds the first subregion near the bump foot and contains a strong favorable pressure gradient (FPG) until very near the bump apex. The third subregion is the strong APG section that begins near the apex and lasts until the flow separation point. The mild/strong APG reduces the mean shear rate near the wall, which has a dampening effect on turbulence production while the strong FPG leads to an order of magnitude increase in near-wall turbulence production as a result of the much-enhanced mean shear rate. The mean shear rate of the buffer zone between inner and outer parts of the decelerated flow past the apex also gives way to enhanced production. The turbulent kinetic energy (TKE) gets redistributed internally among the normal stress components via the pressure-strain correlation. For the shear stress, pressure strain is generally a consuming term. The reduction in near-wall TKE production in the APG sections leads to decreases in pressure-strain amplitudes for all normal stresses. For the shear stress, a similar correlation between production and pressure strain also exists in the mild APG section, but a more intricate behavior is found in the strong APG section. In the strong FPG region, the much-amplified near-wall production of turbulence leads to substantial enhancements of the pressure-strain correlation for all components. As the flow goes through different pressure-gradient regimes, the decreasing/increasing deficits or surpluses between energizing (production and/or pressure strain) and consuming (dissipation and/or pressure strain) terms near the wall are balanced by the relevant spatially-redistributive terms that proportionally either diminish or amplify in magnitude. The budget surpluses resulting from the much-amplified near-wall turbulence production in the strong FPG section lead to the formation of an internal layer beneath the accelerated boundary layer, where new near-wall peaks emerge for the wall-normal and shear stresses as the original peaks of the other components strengthen substantially. The paper describes the rather complex flow dynamics that eventually leads to boundary-layer separation.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613687","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":"Data-Driven Calibration of Transition Models for Natural Convection Flows","authors":"Ioannis Kyritsopoulos,&nbsp;Saleh Rezaeiravesh,&nbsp;Vladimir Duffal,&nbsp;Sofiane Benhamadouche,&nbsp;Alistair Revell","doi":"10.1007/s10494-026-00770-y","DOIUrl":"10.1007/s10494-026-00770-y","url":null,"abstract":"<div><p>This study investigates the physical mechanism of laminar-to-turbulent transition in natural convection by developing algebraic Local-Correlation-based Transition Models (LCTMs) through a physics-based, data-driven framework combining Bayesian optimisation and Symbolic Regression. Accurate transition prediction is critical for high-Rayleigh-number natural convection applications, where standard RANS models and existing transition correlations, calibrated for flows without buoyancy effects, fail to capture the transition onset and boundary layer development. We employ DNS data from differentially heated rectangular cavities (Rayleigh number (Ra) = <span>(10^{10})</span> to <span>(10^{11})</span>) to calibrate model parameters by Bayesian optimisation, then use Symbolic Regression with buoyancy and transition-specific invariants to discover explicit algebraic expressions that generalise across flow conditions. Two models are developed: ML-1, optimised for high Rayleigh-number accuracy, and ML-2, designed for broader generalisation across laminar and turbulent regimes. Validation against a natural convection vertical boundary layer, tall rectangular cavities, and a square cavity demonstrates substantial improvements over baseline RANS models, with the data-driven LCTMs accurately predicting transition location, Nusselt number, and velocity and temperature profiles, showing promising capability for enhancing natural convection predictions while maintaining RANS efficiency.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00770-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614062","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":"On the Relationship Between Flow Field and Emissions in a MILD Combustor","authors":"Paolo Candeloro,&nbsp;Antonio Pugliese,&nbsp;Stefano Meloni,&nbsp;Donato Cecere,&nbsp;Guido Troiani,&nbsp;Eugenio Giacomazzi,&nbsp;Tiziano Pagliaroli,&nbsp;Roberto Camussi","doi":"10.1007/s10494-026-00776-6","DOIUrl":"10.1007/s10494-026-00776-6","url":null,"abstract":"<div><p>The present manuscript investigates the influence of velocity, vorticity and temperature in a hydrogen combustor operating under Moderate or Low Intense oxygen Dilution conditions, focusing on the <span>(NO)</span> formation. The study was conducted on a database obtained from Large Eddy Simulations and an approach based on Proper Orthogonal Decomposition was used to study the most relevant coherent structures. It was shown that the dominant structures are primarily associated with air (oxidizer) and hydrogen (fuel) inlet jets and the vortex region that forms at the outlet. Modal decomposition of these specific areas identifies vortex wandering and pulsation modes. Whereas, the two jets exhibit a bending motion, tending to interact and coalesce within the vortex. Moreover, the temporal analysis of the POD coefficients shows a strong mutual connection between velocity, temperature and <span>(NO)</span> formation. It is also shown that vortex dynamics is closely related to jet modes and, consequently, strongly affects both heat transfer processes and <span>(NO)</span> formation.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613793","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":"Flame-Resolved and Filtered Tabulated-Chemistry Simulations of a Turbulent Bluff-Body Stabilized Premixed Hydrogen-Air Flame","authors":"Chiara Matteucci,&nbsp;Davide Cavalieri,&nbsp;Davide Schintu,&nbsp;Pasquale Eduardo Lapenna,&nbsp;Francesco Creta","doi":"10.1007/s10494-026-00778-4","DOIUrl":"10.1007/s10494-026-00778-4","url":null,"abstract":"<div><p>This work presents a flame resolved direct numerical simulation (DNS) and three Large Eddy Simulations (LES) of the bluff-body stabilized turbulent premixed <span>(textrm{H}_{2})</span>-air flame experimentally studied at NTNU. The DNS are compared to experimental data, and the velocity fields, heat release rate, and OH distributions, show good overall agreement. An Optimal Estimator analysis is conducted in order to identify the set of progress variables most suited to represent the thermochemical states present in the DNS on a tabulated manifold. The resulting progress variable set is used to construct a tabulated manifold through 1D unstretched laminar flamelets, which is combined with a consistent FTACLES formulation to conduct three Large Eddy Simulations (LES) of the same burner. The three LES, differing in the subgrid wrinkling model considered, show a good agreement with the DNS velocity fields, but fail in reproducing correctly the heat release rate and the <span>( Y_{textrm{OH}})</span> distribution, while consistently overpredicting the temperature values. These findings, combined with the analysis of the joint Probability Density Functions of the LES, suggest that the inclusion of a wrinkling factor is not enough for the correct reproduction of the flame with the adopted formulation, and strained flamelets should be included in the generated manifold.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00778-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613794","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":"Threshold-Controlled Restructuring of Ultra-Lean Combustion Dynamics in a Hydrogen-Assisted Spark-Ignition Engine","authors":"Michal Puškár,&nbsp;Melichar Kopas","doi":"10.1007/s10494-026-00779-3","DOIUrl":"10.1007/s10494-026-00779-3","url":null,"abstract":"<div><p>Hydrogen-assisted combustion has emerged as a promising pathway for extending ultra-lean operating limits in spark-ignition engines; however, the physical mechanisms governing combustion stabilization under extreme dilution remain insufficiently understood. In particular, the existence of critical hydrogen concentrations separating partial combustion enhancement from fundamentally reorganized ultra-lean combustion behavior has not been systematically investigated. The present study experimentally examines hydrogen-assisted ultra-lean combustion in a dual-fuel spark-ignition engine over a wide range of air excess ratios (λ = 1.0–2.2) and hydrogen energy shares (0–40%HES). Combustion behavior was analyzed using a multi-level combustion-dynamics framework including cyclic variability, combustion phasing, pressure-rise evolution, heat-release topology, and thermodynamic response. The results reveal a pronounced threshold-type stabilization behavior rather than gradual linear improvement with increasing hydrogen fraction. A distinct transition region was identified between approximately 20% and 30%HES, separating dilution-sensitive combustion from a globally coherent ultra-lean combustion regime. Below the threshold, hydrogen enrichment primarily delayed instability onset but failed to suppress progressive deterioration of heat-release organization under increasing dilution. Above the threshold, however, the combustion process fundamentally reorganized into a dynamically coherent distributed combustion regime characterized by stabilized flame propagation, controlled instability growth, smooth heat-release evolution, and sustained thermodynamic effectiveness even at air excess ratios exceeding λ = 2.0. The findings demonstrate that stable ultra-lean combustion is governed more strongly by preservation of coherent heat-release organization than by maintenance of compact combustion duration alone. The identified threshold-controlled combustion transition therefore represents a physically meaningful restructuring of ultra-lean combustion dynamics rather than merely an extension of conventional lean-burn operation.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00779-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614026","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":"Assimilating Rough Features: A Data-Driven Framework to Infer Rough Wall Properties from Sparse Experimental Data","authors":"Martina Formichetti,&nbsp;Uttam Cadambi Padmanaban,&nbsp;Ping He,&nbsp;Sean Symon,&nbsp;Bharathram Ganapathisubramani","doi":"10.1007/s10494-026-00777-5","DOIUrl":"10.1007/s10494-026-00777-5","url":null,"abstract":"<div><p>Surface roughness influences turbulent boundary layers (TBLs) primarily through the roughness function <span>(Delta U^+)</span> and the equivalent sand-grain roughness height <span>(k_s)</span>. Direct determination of <span>(k_s)</span> typically requires detailed velocity and wall-shear stress measurements, which are often impractical. As an alternative, this study presents a data assimilation framework that modifies a smooth-wall Reynolds-Averaged Navier–Stokes (RANS) baseline to match sparse rough-wall particle image velocimetry (PIV) data in the fully rough regime. Through this approach, secondary variables such as the friction velocity, <span>(u_tau)</span>, and <span>(k_s)</span> can be inferred from the assimilated flow fields. The assimilated TBL reproduces experimental velocity profiles within 1% and predicts friction velocity within 1–6% of the experimental measurements. Furthermore, the <span>(k_s)</span> values inferred from the assimilation also match the experimental data up to 1%. These results demonstrate the potential of data assimilation as a cost-effective alternative to high-fidelity methods and support the generalisation of the framework to model streamwise-varying roughness by treating <span>(k_s)</span> as a function of fetch length.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00777-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148459060","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":"Characterization of Active Flow Control for a Generic Vehicle Model","authors":"Mohammed Khalid Hossen,&nbsp;Mohammad Saeedi","doi":"10.1007/s10494-026-00774-8","DOIUrl":"10.1007/s10494-026-00774-8","url":null,"abstract":"<div><p>This study performed a high-fidelity wall-resolved large-eddy simulations to investigate the impact of active flow control using an unsteady suction on an Ahmed body model with a <span>(25^circ )</span> slant angle. A key goal of this work is the validation of the baseline flow, which yields a drag coefficient in close agreement with the ERCOFTAC benchmark experimental results. A comprehensive analysis is conducted to characterize the influence of the suction on flow topology and turbulence dynamics across the separation, reverse-flow, reattachment, and wake-recovery regions. Flow modifications are examined using qualitative visualizations of mean velocity and pressure coefficient, together with quantitative analyses of first- and higher-order turbulence statistics, including resolved Reynolds stresses. The results reveal that suction control re-energizes the boundary layer near the slant leading edge, modifies the so-called large-scale C-pillar vortices and substantially reduces the recirculation zone. Furthermore, deeper insight is obtained through single probability density functions of resolved velocity fluctuation at multiple downstream locations. In controlled case, the analysis reveals a marked reduction in flow intermittency over the slant surface and in the near-wake.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148459169","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":"Special Issue “Recent Advances in Jets Wakes and Separated Flows”","authors":"Antonio Andreini,&nbsp;Marc Bellenoue,&nbsp;Simone Camarri,&nbsp;Kilian Oberleithner,&nbsp;Toshihiko Shakouchi","doi":"10.1007/s10494-026-00775-7","DOIUrl":"10.1007/s10494-026-00775-7","url":null,"abstract":"","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465846","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":"Assessment of ({v^2} - f - k - omega ) model in predicting turbulent channel flow with rough walls","authors":"A. Sojoudi,&nbsp;D. J. Bergstrom","doi":"10.1007/s10494-026-00773-9","DOIUrl":"10.1007/s10494-026-00773-9","url":null,"abstract":"<div><p>Modeling turbulent flow over rough surfaces remains a fundamental challenge in Reynolds-Averaged Navier–Stokes (RANS) simulations. Traditional approaches rely on equivalent sand grain roughness, <span>(k_s^ + )</span>, to represent roughness effects, but this hydrodynamic scaling often fails to capture the influence of complex surface geometries, particularly in the transitionally rough regime. This study presents a novel extension of the <span>({v^2} - f - k - omega )</span> turbulence model for rough-wall duct flows. The test case adopted is turbulent channel flow with <span>(R{e_tau } = 1000)</span> to <span>(2000)</span> and <span>(0 le k_s^ + le {rm{ 100}})</span>. The study investigates, for the first time within a RANS <span>({v^2} - f - k - omega )</span> framework, the use of a roughness-sensitive boundary condition (BC) for the wall-normal Reynolds stress <span>(langle {v^2}rangle )</span>. The primary objective is to examine whether roughness effects on <span>(langle {v^2}rangle _w^ + )</span> can be represented using equivalent sand-grain roughness scaling. The calibration based on Nikuradse data indicates that <span>(k_s^ + )</span> alone is insufficient to characterize the near-wall behavior of <span>({v^2}_w^ + )</span>, and that the near-wall behavior of <span>(langle {v^2}rangle _w^ + )</span> also depends on the global flow state through <span>(R{e_tau })</span> within the fully developed channel-flow configuration considered here. When coupled with standard treatments for <span>(k)</span> and <span>(omega )</span> based on <span>(k_s^ + )</span> the BC is shown to improve predictions of the roughness function and friction factor across both transitional and fully rough regimes. Next, the model is further extended by introducing a scaling framework that relates <span>({v^2})</span> at the wall to the geometric roughness metrics: effective slope, skewness, and root mean square height of roughness based on the analysis of experimental results from the literature. This metric-based formulation introduces roughness geometry directly into the wall-normal Reynolds stress BC, while retaining conventional <span>(k_s^ + )</span>-based wall treatments for the remaining turbulence variables, and demonstrates agreement with DNS data for the roughness function and to a lesser degree friction factor, especially in the transitionally rough regime where geometry exerts a strong influence. The results highlight both the strengths and limitations of current RANS approaches: while global quantities such as roughness function and friction factor can be reproduced, the near-wall physics is approximated through an elevated eddy viscosity rather than explicit resolution of the pressure drag.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465376","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}