Flow, Turbulence and Combustion最新文献

{"title":"Relation Between 3 and 2D Wrinkling Factors in Turbulent Premixed Flames","authors":"Markus Klein,&nbsp;Nilanjan Chakraborty","doi":"10.1007/s10494-024-00622-7","DOIUrl":"10.1007/s10494-024-00622-7","url":null,"abstract":"<div><p>The magnitude of the wrinkled flame surface area in turbulent premixed flames divided by its projection in the direction of flame propagation, known as the wrinkling factor, is a fundamental quantity for the purpose of analysis and modelling premixed combustion, for example, in flame surface density based modelling approaches. According to Damköhler’s hypothesis it is closely related to the turbulent burning velocity, an equally important measure of the overall burning rate of a wrinkled flame. Three-dimensional evaluation of the area of highly wrinkled flames remains difficult and experiments are often based on planar measurements. As a result of this, model development and calibration require an extension of 2D measurements to 3D data. Different relations between 2D and 3D wrinkling factors are known in literature and will be discussed in the present work using a variety of direct numerical simulation (DNS) databases combined with theoretical arguments. It is shown, based on an earlier analysis, that the isotropic distribution of the surface area weighted probability density function of the angle between the normal vectors on the measurement plane and the flame surface, provides a very simple relationship, stating that the ratio between 3D and 2D flame surface area is given by <span>(4/pi )</span>, which is found to be in excellent agreement with DNS data of statistically planar turbulent premixed flames.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"519 - 526"},"PeriodicalIF":2.0,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00622-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430878","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 Prediction of the Ignition Probability Map for a Model Aeronautical Spray Burner","authors":"Ernesto Sandoval Garzon,&nbsp;Cédric Mehl,&nbsp;Olivier Colin","doi":"10.1007/s10494-024-00617-4","DOIUrl":"10.1007/s10494-024-00617-4","url":null,"abstract":"<div><p>This study presents the computation of the ignition probability map of a model gas turbine, investigated experimentally at CORIA laboratory, using Large Eddy Simulation (LES). The simulations leverage the recently proposed TFM-AMR-I model, which is based on the Thickened Flame Model (TFM) formalism and enables a full flame resolution (i.e. no thickening) of the flame kernel in the initial instants of ignition. LES simulations of ignition are performed for 14 spatial points distributed in the combustion chamber, with 6 repetitions for each in order to obtain a reasonable estimate of ignition probabilities. Probabilities are adequately predicted for most of the selected points, with a typical error of 30 <span>(%)</span>. Nevertheless, the ignition probability is largely over-estimated at two locations where the mean diameter of liquid droplets is shown to be under-predicted, which may lead to too easy ignitions. Parametric variations show a satisfying robustness of the proposed approach with the two following key highlights: (i) the initial full flame resolution made possible by TFM-AMR-I is necessary, as an abrupt initial thickening leads to an artificial extinction; (ii) a correction of the over-sensitivity of the thickened flame to stretch, recently proposed in the literature, is necessary to predict ignition accurately.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"449 - 467"},"PeriodicalIF":2.0,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430797","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":"Advantages of the Adoption of a Generalized Flame Displacement Velocity as a Central Element of Flamelet Theory","authors":"Hernan Olguin,&nbsp;Pascale Domingo,&nbsp;Luc Vervisch,&nbsp;Christian Hasse,&nbsp;Arne Scholtissek","doi":"10.1007/s10494-024-00618-3","DOIUrl":"10.1007/s10494-024-00618-3","url":null,"abstract":"<div><p>In combustion theory, flames are usually described in terms of the dynamics of iso-surfaces of a specific scalar. The flame displacement speed is then introduced as a local variable quantifying the progression of these iso-surfaces relative to the flow field. While formally defined as a scalar, the physical meaning of this quantity allows relating it with a vector pointing along the normal direction of the scalar iso-surface. In this work, this one-dimensional concept is extended by the introduction of a generalized flame displacement velocity vector, which is associated with the dynamics of iso-surfaces of two generic scalars, <span>(alpha )</span> and <span>(beta )</span>. It is then shown how a new flamelet paradigm can be built around this velocity vector, which leads to (i) an alternative procedure for the derivation of general flamelet equations, which is much simpler and more direct than the ones currently available in the literature, (ii) a very compact set of two-dimensional flamelet equations for the conditioning scalar gradients, <span>(g_{alpha } = |nabla alpha |)</span> and <span>(g_{beta } = |nabla beta |)</span>, which comprise several effects in few terms directly related to the projections of the generalized flame displacement velocity, and (iii) the possibility of characterizing different composition space coordinate systems through the same generalized flame displacement velocity. The proposed framework is discussed in the context of partially premixed combustion, emphasizing how its adoption can contribute to both the further development of 2D flamelet theory and its coupling with CFD codes.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"469 - 486"},"PeriodicalIF":2.0,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430798","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":"Changes in the Transition Process of Roughness-Induced Crossflow Vortices due to Freestream Turbulence","authors":"Kosuke Nakagawa,&nbsp;Takahiro Ishida,&nbsp;Takahiro Tsukahara","doi":"10.1007/s10494-024-00616-5","DOIUrl":"10.1007/s10494-024-00616-5","url":null,"abstract":"<div><p>Laminar-turbulent transitions in boundary layers are one of the major research topics in fluid dynamics. In this study, we focused on a three-dimensional boundary layer formed on a swept flat plate. In this boundary layer, the crossflow instability is dominant, and the instability induces crossflow vortices (CFVs). Many studies have focused on the dependency of the transition process on the intensities of steady or unsteady disturbances, which correspond to a roughness element and freestream turbulence (FST), respectively. On the other hand, the effects of the FST wavelength are still unclear. Moreover, there is a lack of knowledge about the transition processes caused by both steady and unsteady disturbances. We investigated how the transition process of a stationary structure caused by cylindrical roughness changes depending on the FST wavelength using direct numerical simulations. We classified transition processes into two types: processes in which stationary structures grow into CFVs and processes in which hairpin vortices are generated on the stationary structures. The former is further classified into four types depending on the presence or absence of FST and on the FST wavelength. We revealed the contributions of different FST wavelengths to the transition process changes. The short-wavelength FST provides hairpin vortices to the stationary structure at low roughness height conditions because of its high-frequency components. The long-wavelength FST changes the process due to unsteady fluctuations influencing the stationary structure. In summary, the transition processes undergo different mechanisms between short- and long-wavelength FST.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"827 - 855"},"PeriodicalIF":2.0,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00616-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612160","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":"Equivalence Ratio Gradient Effects on Locally Lean, Stoichiometric and Rich Propane/Air and N-Heptane/Air Turbulent Bluff Body Flames","authors":"Evangelos-Panagiotis Mitsopoulos,&nbsp;Stavros-Marios Panou,&nbsp;Michalis Manoudakis,&nbsp;Konstantinos Souflas,&nbsp;Panayiotis Koutmos","doi":"10.1007/s10494-024-00621-8","DOIUrl":"10.1007/s10494-024-00621-8","url":null,"abstract":"<div><p>The effect of inlet mixture stratification was investigated in propane/air and prevaporised n-heptane/air flames stabilized in the near wake region of a bluff-body burner. The employed axisymmetric burner can sustain flame anchoring at global equivalence ratio values in the range of 0.09 ÷ 0.1 independently of fuel type and permits the variation of fuel concentration along the radial direction. Three distinct stratification gradients were studied for the two fuels considered; One burning from rich to lean, one burning from stoichiometric to lean and one burning from stronger lean to weaker lean mixtures. Particle Image Velocimetry, Mie scattering and OH ∗ and CH* Chemiluminescence were used to investigate flame stabilization characteristics of the two fuels and three stratification gradients, while Fourier – Transform Infrared Spectroscopy was performed to assess the equivalence ratio disposition under non-reacting conditions in the near wake region. 2D hydrodynamic strain rates, Damköhler (Da) and Karlovitz (Ka) numbers and flame brush thickness distributions were estimated and analyzed to elucidate the effects of turbulence, mixture composition and fuel type on the investigated flames. Also, the characteristic size of the reacting fluid pockets was assessed using a two-point sample autocorrelation methodology on the OH* chemiluminescence images. Results suggest that supplying the vicinity of the anchoring region with lean peak equivalence ratio mixtures with Lewis numbers greater than unity reduces the flame’s resistance to strain, while supplying it with rich peak equivalence ratio mixtures of Lewis number ≈1, independently of fuel type, favors resistance to strain, suggesting a connection with preferential diffusion effects.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"487 - 518"},"PeriodicalIF":2.0,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430933","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":"Binary Droplet Collisions in Bioprinting: Influence of Material Properties on Mixing and Repeatability","authors":"Élfego Ruiz-Gutiérrez,&nbsp;Josef Hasslberger,&nbsp;Markus Klein,&nbsp;Kenny Dalgarno,&nbsp;Nilanjan Chakraborty","doi":"10.1007/s10494-024-00606-7","DOIUrl":"10.1007/s10494-024-00606-7","url":null,"abstract":"<div><p>The study of suspended binary droplet collisions is an active research topic that has gathered interest due to its complexity and its industrial applications such as bioprinting. For many techniques that rely on the collision of two droplets, the quality of the outcome depends on the mixing process that begins when the droplets come in contact with each other. In this work, we study how the difference in material properties of colliding droplets, such as viscosity and surface tension, affect the mixing process. Employing multiphase direct numerical simulations, the distribution of the impinging liquids and the structure of the flow field have been analysed to find ways of mixing and process repeatability optimisation. To analyse the effects that differences in viscosity and surface tension have in the mixing process, the flows emerging from the collision are analysed. The differences in kinematic viscosity, in the range of <span>(1 times 10^{-7})</span> to <span>(1 times 10^{-5},text {m}^{2}text {s}^{-1})</span> and surface tension, in the range of 36 to <span>({82.7,mathrm{text {m}text {N} , text {m}^{-1}}})</span>, have also been demonstrated to affect the trajectory of the centre of mass and morphology of the droplets upon collision and thus could have implications from the point of view of process repeatability. In the parameter space considered here, it was found that differences in viscosity and surface tension enhance the mixing due to the departure from the symmetry in the collision.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"913 - 939"},"PeriodicalIF":2.0,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00606-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612060","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":"Numerical Prediction of Cavitation for a Horizontal Axis Tidal Turbine","authors":"Adriano Evangelisti,&nbsp;Giuliano Agati,&nbsp;Domenico Borello,&nbsp;Luca Mazzotta,&nbsp;Paolo Capobianchi,&nbsp;Paolo Venturini","doi":"10.1007/s10494-024-00615-6","DOIUrl":"10.1007/s10494-024-00615-6","url":null,"abstract":"<div><p>This paper aims at assessing cavitation in a scaled tidal turbine geometry through numerical simulations. Cavitation occurrence is predicted by using the Singhal cavitation model, based on the Rayleigh-Plesset equation, for treating bubble dynamics. Turbulence is modelled adopting a Reynolds Averaged Navier Stokes (RANS) approach, specifically employing the Shear Stress Transport (SST) <i>k-</i>ω model to simulate the fluid flow. The Reboud density function is applied to adjust the eddy viscosity computation in the cavitation region. Initially, cavitation and turbulence models are validated using a NACA 66 (mod) hydrofoil profile as a test case. Numerical and experimental pressure coefficients are compared on the hydrofoil suction side for a selected cavitation condition. A Mesh Sensitivity Analysis (MSA) is performed to ensure simulation accuracy, comparing numerical results with experimental data on the Horizontal Axis Tidal Turbine (HATT) scaled domain. Based on this analysis, the optimal computational grid is selected. Experimental and numerical power and thrust coefficients are then compared across different tip speed ratios. Finally, cavitation occurrence is evaluated for four different regimes, namely the cut-in, the peak-power, the curve highest velocity and the off-set tip speed ratios. Computational Fluid Dynamics (CFD) solutions reveal vapor formation around turbine components, highlighting regions most exposed to cavitation onset.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"887 - 912"},"PeriodicalIF":2.0,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612041","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":"Assessing the Multi-Regime Capability of the Super-Grid Linear Eddy Model (SG-LEM) Using the Darmstadt Multi-Regime Burner","authors":"Abhilash Menon,&nbsp;Alan Kerstein,&nbsp;Michael Oevermann","doi":"10.1007/s10494-024-00602-x","DOIUrl":"10.1007/s10494-024-00602-x","url":null,"abstract":"<div><p>Recent advances in combustion modelling for Large Eddy Simulation (LES) have increasingly utilised lower-dimensional manifolds, such as Flamelet Generated Manifolds and Flamelet/Progress Variable methods, due to their computational efficiency. These methods typically rely on one-dimensional representations of flame structures, often assuming premixed or non-premixed configurations. However, practical combustion devices frequently operate under partially-premixed conditions and present challenges due to mixture inhomogeneities and complex flow features. The Linear Eddy Model (LEM) offers an alternative by directly simulating turbulence-chemistry interactions without presuming specific flame structures. However, traditional LES-LEM approaches are computationally quite expensive due to the need for resolved LEM domains to be embedded in every LES cell.The authors developed the Super-Grid LEM (SG-LEM) method (Comb. Theor. Model.  28, 2024) to address these computational challenges by coarse-graining the LES mesh and embedding individual LEM domains within <i>clusters</i> of LES cells. This study evaluates SG-LEM in the context of the Multi-Regime Burner (MRB) introduced by Butz et al. (Combust. Flame, 210, 2019), which features both premixed and non-premixed flame characteristics. SG-LEM simulations of the MRB case demonstrate the method’s sensitivity to clustering parameters, with flow-aligned clusters significantly improving flame stability. LEM domains on the super-grid were able to represent the MRB flame topology while LES radial profiles including velocity, mixture fraction, temperature, and <span>({textrm{CO}})</span> mass fraction, were validated against experimental data and also reference simulations using standard combustion closures. The work also investigates discrepancies in CO profiles using conditional statistics and stand-alone LEM simulations. Finally, the work identifies areas of improvement for the SG-LEM framework, in particular relating to cluster generation, and (advective and diffusive) mass exchange between neighbouring LEM domains, as well as possible solutions for future SG-LEM implementations which could improve the model’s predictive capability.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"395 - 420"},"PeriodicalIF":2.0,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00602-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430845","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 Feasibility of a Self-adaptive Strategy for Hybrid RANS/LES Based on Physical Criteria and its Initial Testing on Low Reynolds Number Backward-Facing Step Flow","authors":"Martin David,&nbsp;Mahitosh Mehta,&nbsp;Rémi Manceau","doi":"10.1007/s10494-024-00583-x","DOIUrl":"10.1007/s10494-024-00583-x","url":null,"abstract":"<div><p>Hybrid RANS/LES methods can produce more reliable results than RANS with a reasonable computational cost. Thus, they have the potential to become the next workhorse in the industry. However, in continuous approaches, whether or not they depend on the grid step explicitly, the ability of the model to switch to a well-resolved LES depends on the mesh generated by the user, such that the results are user-dependent. The present paper proposes a self-adaptive strategy, in which the RANS and LES zones are determined using physical criteria, in order to mitigate the user influence. Starting from an initial RANS computation, successive HTLES are carried out and the mesh is refined according to the criteria. To demonstrate the feasibility of this strategy, the method is applied to the backward-facing step case with the Hybrid Temporal Large Eddy Simulation (HTLES) approach, but is suitable for any other hybrid approach. The results obtained show that the method reaches a fixed point after only a few simulations and significantly improves the predictions when compared to RANS, with no intervention from the user. Even though the process is still a long way from being applicable to a wide range of turbulent flows, this paper is a demonstrator of the applicability of this self-adaptive strategy.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"49 - 79"},"PeriodicalIF":2.0,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995780","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":"Spatiotemporal Characteristics of Turbulent Flows Around Partially Submerged Circular Cylinders","authors":"Mark K. Israel,&nbsp;Karen Dow,&nbsp;Shawn P. Clark,&nbsp;Mark F. Tachie","doi":"10.1007/s10494-024-00598-4","DOIUrl":"10.1007/s10494-024-00598-4","url":null,"abstract":"<div><p>This paper presents a time-resolved particle image velocimetry investigation of the spatiotemporal characteristics of the wake flow around a partially submerged horizontal circular cylinder with and without upstream ice cover. This study is applicable to offshore structures such as ice booms. In the experiments, the cylinder was submerged with 50% of its surface below the free surface and the Reynolds number was 10,000. A reference experiment was performed with the cylinder fully immersed in the uniform flow for comparison. Due to the absence of an upper shear layer, the recirculation length of the submerged cylinder is longer, but the turbulence levels are lower compared to the uniform case, and an upstream ice cover reduces the recirculation length and turbulence levels around the submerged cylinder compared to the open water case. The wake of the cylinders is highly anisotropic, regardless of boundary condition, with vertical fluctuating velocities being dominant over streamwise fluctuating velocities in the uniform case and vice versa in the submerged cases. In the uniform case, the turbulence production is maximum on the wake centerline, but in the submerged cases, the maximum turbulence production occurs within the shear layer. The frequency spectra of fluctuating velocities also showed that the wake of a submerged cylinder is characterized by multiple low, distinct frequencies indicative of a wide range of vortical structures, regardless of the upstream flow condition.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"995 - 1015"},"PeriodicalIF":2.0,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612102","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}