Flow, Turbulence and Combustion最新文献

{"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}

{"title":"Identification of Coherent Structures in Hydrogen-Enriched Swirl-Stabilised Flames Using Large-Eddy Simulations with Modal Decomposition Techniques","authors":"Fredherico Rodrigues,&nbsp;José M. Pastor,&nbsp;José M. García-Oliver,&nbsp;Leonardo Pachano,&nbsp;Daniel Mira","doi":"10.1007/s10494-026-00769-5","DOIUrl":"10.1007/s10494-026-00769-5","url":null,"abstract":"<div><p>Large eddy simulations (LES) of an atmospheric swirled burner using a Partially Stirred Reactor (PaSR) closure are performed to investigate the hydrodynamic modes governing flow–flame interactions under hydrogen enrichment. Three technically premixed methane–air flames with increasing level of hydrogen are considered, Flame 1 (0% <span>(text{H}_2)</span>), Flame 2 (40% <span>(text{H}_2)</span>), and Flame 3 (50% <span>(text{H}_2)</span>). Simulations show good agreement with experimental data, particularly in terms of velocity fields and overall flame behaviour. Distinct flame topologies are observed, with Flame 1 exhibiting a lifted M-shaped structure and Flames 2 and 3 forming attached V-shaped flames. Proper Orthogonal Decomposition is applied to identify the dominant coherent structures. Flame 1 is strongly governed by a precessing vortex core (PVC), while Flames 2 and 3 exhibit weaker, more distributed structures. A secondary structure in Flame 1 is identified as a harmonic of the primary PVC, whereas analysis of the respective vortices in hydrogen-enriched Flames 2 and 3 suggests an independent nature. Overall, hydrogen enrichment modifies the strength and coherence of hydrodynamic structures and promotes a partial decoupling between mixing and flow dynamics.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465094","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":"Effects of In-Cylinder Flow and Injection Timing on Multi-Plane Analysis of Fuel-Air Mixture Distribution Under Cold Start Conditions in a Small-Bore Spark-Ignition Engine","authors":"Kartheeswaran Ayyanar,&nbsp;T. N. C. Anand,&nbsp;Mayank Mittal","doi":"10.1007/s10494-026-00772-w","DOIUrl":"10.1007/s10494-026-00772-w","url":null,"abstract":"<div><p>Stringent emission regulations and the demand for improved fuel economy have driven advancements in spark-ignition engines. While direct injection offers better fuel economy and lean-burn combustion, its high cost and packaging complexity limit its adoption in small-bore engines for two- and three-wheelers. Port fuel injection remains preferred for its simpler design and compatibility with modern control strategies. However, during cold start, limited droplet evaporation and persistent wall films hinder combustible mixture formation, leading to misfires and increased unburned hydrocarbon emissions. Additionally, tumble development is restricted by an anticlockwise vortex beneath the intake valve, causing early decay during compression. To examine the influence of in-cylinder flow and injection timing on fuel–air mixture distribution across multiple planes, a computational fluid dynamics framework was developed and validated against experimental data for spray tip penetration (with and without wall impingement) and mixture distribution from planar laser-induced fluorescence. Results show that, in closed-valve injection, vaporized fuel is entrained by intake air and evenly distributed by tumble motion, producing a homogeneous mixture prior to combustion. In contrast, during open-valve injection, the spray enters asymmetrically through the intake valve and interacts with an already developed tumble vortex, confining vapor to one side and sustaining a stratified mixture throughout compression due to weak swirl motion. In addition, a statistical analysis based on the probability density function of the equivalence ratio was evaluated to assess mixture homogeneity across the sectional regions of the in-cylinder domain.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380476","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":"Estimating Hydrogen/Air Flame Acceleration Induced by 3D Flame Instabilities from 2D Simulations","authors":"Cédric C. Mehl","doi":"10.1007/s10494-026-00771-x","DOIUrl":"10.1007/s10494-026-00771-x","url":null,"abstract":"<div><p>The estimation of flame acceleration induced by thermo-diffusive and hydrodynamic instabilities is a key step toward developing accurate models for lean hydrogen combustion. One way to estimate this acceleration is to perform Direct Numerical Simulations (DNS) of laminar unstable flames. However, previous studies have shown that the 3D nature of instabilities significantly enhances the flame propagation speed compared to the 2D predictions. Systematically performing 3D simulations of laminar unstable flames remains out of reach due to prohibitive computational costs. In this work, a series of 2D and 3D DNS under various conditions are performed to establish a link between 2D and 3D flame wrinkling and stretch factors. Models are proposed that accurately estimate the 3D quantities from their 2D counterparts, leading in particular to an improved prediction of the 3D flame consumption speed. The robustness of these models is assessed using simulations performed with another chemical mechanism, and using published data obtained with another CFD solver. The prediction of the wrinkling and stretch factors is found to be highly robust. Overall, the resulting 3D flame consumption speed predictions are very accurate. These findings pave the way for improved subgrid-scale models of flame instabilities in RANS and LES frameworks.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00771-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380478","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}