Flow, Turbulence and Combustion最新文献

{"title":"A Sequential RANS/LES Turbulence Modelling Framework for the Gas-Phase Combustion of Grate-Firing Biomass Furnaces","authors":"A H M Nazmush Sakib,&nbsp;Madjid Birouk","doi":"10.1007/s10494-026-00758-8","DOIUrl":"10.1007/s10494-026-00758-8","url":null,"abstract":"<div><p>Research on converting biomass into heat or power has recently plummeted owing to the importance of renewable energy sources in today’s world. Grate-firing biomass combustion furnace technology has attracted much attention due to its capability of accommodating a wide range of biomass fuels. While this technology has been well established, there is still room for improvement, which can be achieved through optimization studies using numerical simulations. Their success, however, depends on their ability to accurately reproduce the flow field inside these biomass combustion systems. Turbulent flow field inside a grate-firing biomass furnace has traditionally been modelled using RANS-based turbulence models. In this study, a sequential RANS/LES modelling framework is proposed as a practical alternative to the widely adopted RANS-based RNG <i>k</i>−ε model, and is assessed as a computationally feasible coarse scale-resolving approach under practical grid limitations rather than as a fully resolved LES. The results showed improved predictions of temperature profiles, species concentrations, and key combustion parameters, including Damköhler number, scalar dissipation rate, and turbulent flame speed. The improved characterization of the turbulent flow field including residence time within the furnace resulted in enhanced prediction of <span>(N{O_x})</span> emission and related intermediate species.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148060662","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":"A surrogate-based Bayesian framework for parametric calibration of URANS turbulence models informed by anisotropic pressure fluctuations","authors":"Ali Eidi,&nbsp;Richard P. Dwight","doi":"10.1007/s10494-026-00763-x","DOIUrl":"10.1007/s10494-026-00763-x","url":null,"abstract":"<div><p>Flow-induced vibrations in wall-bounded flows remain a major challenge in many engineering applications. While fully predictive turbulence-induced vibration simulations generally require scale-resolving approaches, unsteady Reynolds-averaged Navier–Stokes (URANS) methods are employed in practice due to their favorable computational cost. However, their predictive reliability is limited by uncertainty in turbulence-model parameters, structural model–form error, and deficiencies in representing turbulent fluctuations. This work presents a surrogate-based Bayesian calibration framework for the SST <span>(k)</span>–<span>(omega)</span> model, incorporating anisotropic pressure-fluctuation reconstruction to quantify and reduce model uncertainty. Global Sobol’ sensitivity analysis, surrogate modeling, and Bayesian inference are combined to identify influential parameters and assimilate high-fidelity reference data. The framework is applied to turbulent channel flow, turbulent annular flow, and a blunt-end cantilevered-rod configuration. Across all cases, the specific dissipation-rate coefficient <span>(alpha_{omega1})</span> and the turbulent kinetic-energy dissipation coefficient <span>(beta^*)</span> consistently dominate variability in mean-flow quantities and reconstructed fluctuation statistics. Bayesian calibration constrains these parameters to consistent regions of the admissible space, while less influential coefficients remain weakly informed. Gaussian process regression and polynomial chaos expansion surrogates yield nearly identical posterior and predictive distributions, demonstrating robustness to surrogate choice. Remaining discrepancies with reference data are attributed primarily to structural turbulence model limitations rather than parametric uncertainty.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"117 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00763-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148060663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LES of Multi-Armed Variable Density Jets","authors":"Karol Wawrzak,&nbsp;Artur Tyliszczak","doi":"10.1007/s10494-026-00759-7","DOIUrl":"10.1007/s10494-026-00759-7","url":null,"abstract":"<div><p>Large eddy simulations are performed to investigate the influence of combined axial and helical excitation on the structure and mixing characteristics of variable-density jets. The analysis includes various frequency ratios <span>(mathcal{R})</span>, two Reynolds numbers, and three density ratios between the jet and surrounding flow. Depending on <span>(mathcal{R})</span>, three distinct jet patterns are observed: five-armed, double-spiral and bifurcating. This parameter governs the azimuthal organization of coherent vortical structures, leading to fundamentally different jet shapes and mixing behaviour. The five-armed and double-spiral jets exhibit significantly enhanced entrainment and improved mixing compared to the bifurcating configuration. Entrainment analysis reveals strong suction of ambient fluid in the near field, followed by pronounced radial spreading further downstream. In particular, the double-spiral jet maintains elevated entrainment over a longer streamwise extent and proves especially effective for higher density ratio. A flow uniformity index demonstrates that excitation not only increases the amount of entrained fluid but also promotes its effective mixing into the jet core, leading to rapid homogenization of both mean temperature and its fluctuations. The results highlight the potential of excitation at a tuned <span>(mathcal{R})</span> for controlling jet dynamics and improving mixing.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00759-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172735","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":"EMD Analysis of the Flow Field in an Internal Combustion Engine","authors":"Tim Wegmann,&nbsp;Esther Lagemann,&nbsp;Matthias Meinke,&nbsp;Wolfgang Schröder","doi":"10.1007/s10494-026-00749-9","DOIUrl":"10.1007/s10494-026-00749-9","url":null,"abstract":"<div><p>One of the major problems of the investigation of the flow field in internal combustion engines is the analysis of the impact of cyclic variations on the overall flow structure. Implicit large-eddy simulations (LES) are conducted to quantitatively analyze cold in-cylinder flow with associated cyclic variations in an internal combustion engine. To validate the simulation results, a comparison with stereoscopic PIV measurements in the tumble plane is performed and a grid convergence study is conducted in which five consecutive engine cycles are simulated using meshes ranging from 4.2 to 212 million cells. To quantitatively assess the agreement with the experimental data, weighted relevance and magnitude indices are evaluated for the instantaneous and ensemble averaged velocity vector during the intake and compression strokes. The influence of the number of simulated intake and compression cycles on the results is assessed. The grid convergence study demonstrates that the tumble spin and breakup processes are not accurately resolved by the coarse mesh, although the single-grid estimator suggests sufficient mesh resolution. Overall, satisfactory agreement with experimental data is achieved with sufficient mesh resolution. To analyze cyclic variations, a 2-D noise-assisted multivariate EMD method is applied to the experimental and numerical results. A novel mode separation of the velocity scales, which utilizes the identical decomposition of the ensemble averaged and instantaneous cycle data, is presented. This method simplifies the extraction of the tumble vortex core, enables the estimation of the ensemble mean flow and the analysis of cycle-to-cycle variations despite the limited number of available simulation cycles. The EMD analysis reveals a significant cyclic variance in the position of the tumble vortex core at crank angles between 90 to 120 degrees and 180 to 200 degrees. A correlation between the vortex core position and vortex strength at top dead center is established.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00749-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148173196","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 Relation Between Presumed FDF, Subgrid Variance and Flame Speed in the Wrinkled Flamelet Regime: An A Posteriori Analysis","authors":"Ivan Langella,&nbsp;Nguyen Anh Khoa Doan","doi":"10.1007/s10494-026-00752-0","DOIUrl":"10.1007/s10494-026-00752-0","url":null,"abstract":"<div><p>Presumed PDF/FDF approaches with dependency on second order moments of an appropriately defined progress variable are often used in combustion modelling, but they fail in predicting the limiting behaviour of burning speed when the latter approaches the laminar condition. In this work, we discuss a recently proposed correction for the burning speed in the context of presumed FDF approaches, and test its performance using large eddy simulation (LES). First, the correction model is discussed in relation to the interlink between filtered density function and second order moment (SGS variance in the LES case) from a theoretical point of view, and the further interlink with the LES filter size is discussed. In a second step, a propane flame in the wrinkled flamelet regime of the Borghi diagram is simulated <i>a posteriori</i> using two LES filter size resolutions. We firstly show that the increase of filter size leads to an overestimation of the burning speed. We then show how the incorrect estimation of burning speed with increasing filter size is corrected and how the correction affects the SGS variance. An extended correction model for partially-premixed combustion is also proposed.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00752-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148173265","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":"Turbulent Flow Characterization of a Fan-Stirred Constant Volume Combustion Chamber Using Large Eddy Simulation","authors":"Paula-Maria Handle-Kesselring,&nbsp;Clemens Gößnitzer,&nbsp;Marc Klawitter,&nbsp;Stefan Posch,&nbsp;Helfried Steiner","doi":"10.1007/s10494-026-00753-z","DOIUrl":"10.1007/s10494-026-00753-z","url":null,"abstract":"<div><p>Understanding turbulent premixed flame propagation under engine-relevant conditions is crucial for advancing efficient combustion technologies. This study applies high-fidelity Large Eddy Simulation (LES) to support the design and optimization of a fan-stirred constant volume combustion chamber intended for future experiments on spherically propagating turbulent premixed flames. The design is representative of large-bore engine conditions: moderate to high turbulence intensities with integral length scales significantly larger than the characteristic flame thickness. The numerical analysis focuses on this flow regime by accurately resolving the incompressible, isothermal, transient flow field generated by six rotating fans operating at two different rotation speeds of 2000 and 10,000 rpm, aiming to achieve high turbulence intensities with minimal mean flow in the optical measurement region. The evaluation of the LES-predicted turbulence intensities and the mean velocities indicates that the flow field generated in the targeted central region is statistically stationary and spatially homogeneous. The analysis of the Reynolds stress tensor invariants in the Lumley triangle proves a nearly isotropic turbulence. Moreover, the computed turbulence intensities and integral length scales evaluated with velocity autocorrelation functions are in close agreement with target values representative of large-bore internal combustion engines. These findings confirm the viability of the proposed design for future experimental investigations of flame–turbulence interactions of different fuels like ammonia and ammonia-hydrogen mixtures under engine-like operating conditions.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00753-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148173268","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 Induced Mixing-Chemistry Interaction within Ultra-Lean (textrm{H}_2) Flame Structures","authors":"Yuvraj,&nbsp;Swetaprovo Chaudhuri","doi":"10.1007/s10494-026-00755-x","DOIUrl":"10.1007/s10494-026-00755-x","url":null,"abstract":"<div><p>This study investigates the Conditionally Averaged Structure (CAS) of reactive scalars using 3D Direct Numerical Simulation (DNS) datasets of ultra-lean and near-stoichiometric premixed <span>(textrm{H}_2)</span>-air turbulent flames, with effective Lewis numbers <span>(Leapprox 0.5)</span> and <span>(0.8)</span>, and Karlovitz numbers <span>(Kasimmathcal{O}(100))</span> and <span>(Kasimmathcal{O}(1000))</span>, respectively. The CAS unravels how turbulent mixing progressively layers surfaces with curvatures from negative to positive in the neighborhood of the zero curvature location of the reference scalar isosurface, triggering differential and preferential diffusion, amplifying specific chemical pathways. These effects enhance density-weighted local displacement speed, <span>(widetilde{S_d})</span>, even at zero curvature for ultra-lean, high <span>(Ka)</span>, <span>(textrm{H}_2)</span> flames. Irrespective of the reactant equivalence ratio and the chosen isoscalar surface, <span>(widetilde{S_d})</span> is enhanced at large negative curvatures from localized flame-flame interactions and is explained by the existing interaction model. CAS at zero-curvature captures the reactant side negatively curved self-interactions and product side positively curved structures. The positive curvature generates enhanced heat release driven by differential diffusion. Investigation of species concentration, their production rates, and detailed chemical pathways within the CAS thus reveals the mechanism underpinning the enhancement of heat release rate at zero curvature locations. The curvature organization within the ultra-lean flame CAS promotes enhanced <span>(textrm{H}_2)</span> diffusion from the negatively curved regions to the positively curved ones downstream. This enhances reactive radical (H, O, OH) production, and their back diffusion to increase <span>(textrm{H}_2)</span> consumption rates, heat release rate and consequently <span>(widetilde{S_d})</span>, compared to laminar flames, all at zero-curvature locations of these intensely turbulent flames.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00755-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148173269","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":"Interaction of Two Streamwise-Separated Miniature Helmholtz Resonators with a Grazing Turbulent Boundary Layer","authors":"Abdelrahman Hassanein,&nbsp;Davide Modesti,&nbsp;Woutijn J. Baars","doi":"10.1007/s10494-026-00746-y","DOIUrl":"10.1007/s10494-026-00746-y","url":null,"abstract":"<div><p>We investigate the interaction between two miniature Helmholtz resonators (HRs), separated in the streamwise direction, and a grazing turbulent boundary layer (TBL). This study aims to understand how the resonators modify the velocity fluctuations in the grazing flow, with the goal of informing the design of surface features capable of deterministically influencing turbulence dynamics. By building on the study of Hassanein et al. (Phys Rev Fluids 9(11):114610, 2024), the model for the resonator-turbulence interaction, for a single HR, will be explored for multiple resonators. The grazing turbulent flow is studied experimentally using time-resolved planar particle image velocimetry; the resonators themselves are embedded in the wall beneath a TBL at a friction Reynolds number of <span>(Re_tau approx 2000)</span> and are tuned so that their resonance frequency coincides with the peak of the wall-pressure spectrum. Three streamwise separation distances are considered. At resonance, the streamwise-separated HRs exhibit minimal interaction, producing an amplification pattern resembling independent HR units. At sub-resonant frequencies, the energy of streamwise velocity fluctuations is reduced downstream of the second orifice, with attenuation increasing as the separation distance decreases. We hypothesise that this attenuation arises from an increase in the phase velocity of pressure fluctuations above the resonators, which dephases the resonator-induced velocity (driven by pressure exciting the resonator) and the velocity fluctuation in the incoming flow. These findings, combined with a fundamental understanding of passive resonator-induced modifications to wall impedance, provide guidance for designing arrays of resonators to manipulate turbulence.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00746-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Thickened Flame Model Adapted to Auto-Ignition/Propagation Regimes for the Large-Eddy Simulation of Dual-Fuel Combustion","authors":"Sarah Fehér,&nbsp;Olivier Colin,&nbsp;Stéphane Jay","doi":"10.1007/s10494-026-00754-y","DOIUrl":"10.1007/s10494-026-00754-y","url":null,"abstract":"<div><p>Dual-fuel combustion (DFC) is a promising concept for low-emission, highly efficient internal combustion engines. Large-Eddy Simulation (LES) enables detailed analysis for engine design, but the complex combustion process in DFC, involving the transition from pilot-fuel auto-ignition to premixed flame propagation challenges existing turbulent combustion models. This study presents a new combustion model for DFC based on the Thickened Flame Model (TFM). TFM is well validated for premixed combustion but results in delayed ignition predictions. This work introduces a transported ignition sensor to relax the thickening factor, thereby modulating thickening to the combustion regime. Thickening during auto-ignition is avoided while seamlessly reverting to a classical TFM approach during flame propagation. A burnt gas criterion is also proposed to reliably detect the transition. Results obtained in one-dimensional dual-fuel cases demonstrate that the proposed approach successfully captures auto-ignition delays and flame propagation. An academic dodecane/methane jet case is proposed to validate the model under 3D turbulent conditions against fully flame resolved simulations. The model successfully predicted the heat-release rate and temperature evolution. The model underpredicted heat-release rate for cases with small pilot quantity due to thickening reducing the flame surface, highlighting the importance of efficiency models used in conjunction with TFM.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00754-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148008966","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":"Ensemble-Based Data Assimilation Without CFD-Generated Ensembles: A Scaling Approach for RANS Simulations Under ABL Inflow","authors":"Nikolaos Petros Pallas,&nbsp;Demetri Bouris","doi":"10.1007/s10494-026-00761-z","DOIUrl":"10.1007/s10494-026-00761-z","url":null,"abstract":"<div><p>Creating ensembles for ensemble-based data assimilation (DA) in numerical simulations is often the greatest computational burden when applied to complex flow problems. In the present short communication, an ensemble-based DA method is presented, with the main novelty being the creation of the CFD ensemble by means of a simple scaling procedure and not additional CFD runs. This approach is in line with the common assumptions that the CFD uncertainty mainly originates from uncertain inlet conditions and that Reynolds number independence is observed for the examined flow. The developed method is applied to the case of a surface-mounted cube, immersed in the turbulent flow of an atmospheric boundary layer (ABL). Particle Image Velocimetry (PIV) measurements are assimilated into a RANS simulation. Both the mean velocities and the turbulence kinetic energy exhibit significant correction even when only 2% of the full PIV dataset is assimilated, while the computational cost remains comparable to that of a single CFD run.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"116 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-026-00761-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148008967","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}