Flow, Turbulence and Combustion最新文献

{"title":"Impact of Flame-Generated Turbulent Intensity and Flame Speed on the Low-Order Modelling of Light-Round","authors":"Léo C. C. Mesquita,&nbsp;Roberto Ciardiello,&nbsp;Epaminondas Mastorakos","doi":"10.1007/s10494-022-00357-3","DOIUrl":"10.1007/s10494-022-00357-3","url":null,"abstract":"<div><p>A previously-developed low-order Lagrangian stochastic model for ignition of premixed and non-premixed flames is modified in this paper to improve the numerical prediction of the light-round process in premixed annular combustors. The model refinements take into account Flame-Generated Turbulent Intensity (FGTI) and impose a turbulent flame speed correlation to the flame particles using expressions from the literature. For this, using RANS CFD results as an input, the model was applied to simulate the ignition transient in a premixed, swirled bluff body stabilised annular combustor to characterise the light-round time, both in stable conditions and close to the stability limits. Several cases were analysed, where flame speed and fuel were varied and light-round times were compared to experimental results. The proposed modifications improved the accuracy of the light-round time predictions, suggesting that FGTI may be an important phenomenon to be modelled. This modified model coupled with dilatation and the Peter’s assumption for the turbulent flame speed resulted in considerable improvement for the light-round time calculation for the explored range of parameters. This is an attractive feature considering the low computational cost of these simulations, which can be run in a single core of a local workstation. The improved model can help gas turbine engineers assess the ignition behaviour of annular combustors early in the design process.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"1039 - 1058"},"PeriodicalIF":2.4,"publicationDate":"2022-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00357-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4780781","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":"CFD Simulation of Particle-Laden Flow in a 3D Differentially Heated Cavity Using Coarse Large Eddy Simulation","authors":"M. A. Sayed,&nbsp;A. Dehbi,&nbsp;M. Hadžiabić,&nbsp;B. Ničeno,&nbsp;K. Mikityuk","doi":"10.1007/s10494-022-00356-4","DOIUrl":"10.1007/s10494-022-00356-4","url":null,"abstract":"<div><p>Particulate flow in closed space is involved in many engineering applications. In this paper, the prediction of particle removal is investigated in a thermally driven 3D cavity at turbulent Rayleigh number Ra = 10⁹ using Coarse Large Eddy Simulation (CLES). The depletion dynamics of SiO₂ aerosol with aerodynamic diameters between 1.4 and 14 µm is reported in an Euler/Lagrange framework. The main focus of this work is therefore to assess the effect of the subgrid-scale motions on the prediction of the particulate flow in a buoyancy driven 3D cavity flow when the mesh resolution is coarse and below optimal LES standards. The research is motivated by the feasibility of modeling more complex particulate flows with reduced CPU cost.</p><p>The cubical cavity of 0.7 m side-length is set to have a temperature difference of 39 K between the two facing cold and hot vertical walls. As a first step, the carrier fluid flow was validated by comparing the first and second-moment statistics against both previous well-resolved LES and experimental databases [Kalilainen (J. Aero Sci. 100:73–87, 2016); Dehbi (J. Aero. Sci. 103:67–82, 2017)]. First moment Eulerian statistics show a very good match with the reference data both qualitatively and quantitatively, whereas higher moments show underprediction due to the lesser spatial resolution. In a second step, six particle swarms spanning a wide range of particle Stokes numbers were computed to predict particle depletion. In particular, predictions of 1.4 and 3.5 µm particles were compared to LES and available experimental data. Particles of low inertia i.e. dp &lt; 3.5 µm are more affected by the SGS effects, while bigger ones i.e. dp = 3.5–14 µm exhibit much less grid-dependency. Lagrangian statistics reported in both qualitative and quantitative fashions show globally a very good agreement with reference LES and experimental databases at a fraction of the CPU power needed for optimal LES.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"961 - 990"},"PeriodicalIF":2.4,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00356-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4641121","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":"Dissipation Rate Estimation in a Highly Turbulent Isotropic Flow Using 2D-PIV","authors":"Cameron Verwey,&nbsp;Madjid Birouk","doi":"10.1007/s10494-022-00343-9","DOIUrl":"10.1007/s10494-022-00343-9","url":null,"abstract":"<div><p>In experimental turbulent flows, the estimation of the dissipation rate of turbulent kinetic energy, <span>(varepsilon)</span>, is a challenge. The dimensional analysis approach is the simplest of the many available strategies, where <span>(varepsilon = C_{varepsilon} k^{3/2}/L)</span>. Although the proportionality constant, <span>(C_{varepsilon})</span>, is commonly stated to be on the order of unity, there is little experimental evidence to verify this claim for zero-mean stirred-chamber configurations in general, nor is there detailed information on how <span>(C_{varepsilon})</span> might systematically vary with flow conditions. Given the importance of zero-mean chambers for both practical and fundamental studies on turbulent flows, reliable data on the magnitude of <span>(C_{varepsilon})</span> would be an asset. The goal of the present investigation is to rigorously determine <span>(varepsilon)</span> in turbulent helium gas using medium-resolution particle image velocimetry (PIV) combined with the corrected spatial gradient method—these results lead directly to <span>(C_{varepsilon})</span>. Helium maintains relatively large Kolmogorov length scales, <span>(eta)</span>, due to its high kinematic viscosity, making it possible to resolve spatial velocity gradients in strongly turbulent fields (<span>(k le {17.6},hbox {m}^{2},hbox{s}^{-2})</span>) with only modest magnification while avoiding many of the difficulties associated with micro-PIV. The results confirm that the vector spacing, <span>(varDelta x)</span>, must be less than <span>(eta)</span> to properly calculate the spatial velocity gradients—a recommendation that has not been universally agreed upon. We provide comprehensive <span>(C_{varepsilon})</span> results up to <span>(Re_lambda = 220)</span> by varying the fan speed, fan count, and chamber pressure. <span>(C_{varepsilon})</span> eventually falls to a value of <span>({sim }0.5)</span>, although the true asymptotic value of <span>(C_{varepsilon})</span>—if it exists—remains elusive.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 3","pages":"647 - 665"},"PeriodicalIF":2.4,"publicationDate":"2022-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00343-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4523217","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 Combined Numerical and Experimental Investigation of Cycle-to-Cycle Variations in an Optically Accessible Spark-Ignition Engine","authors":"Hongchao Chu,&nbsp;Cooper Welch,&nbsp;Hani Elmestikawy,&nbsp;Shangyi Cao,&nbsp;Marco Davidovic,&nbsp;Benjamin Böhm,&nbsp;Andreas Dreizler,&nbsp;Heinz Pitsch","doi":"10.1007/s10494-022-00353-7","DOIUrl":"10.1007/s10494-022-00353-7","url":null,"abstract":"<div><p>A combined numerical and experimental investigation is carried out to analyze the cycle-to-cycle variations (CCV) in an optically accessible spark-ignition engine with port fuel injection. A stable and an unstable operating condition is considered. Well-established turbulence, combustion, and ignition models are employed in the large-eddy simulations (LES). High-speed measurements of the velocity field via particle image velocimetry and flame imaging in the tumble plane are conducted in the experiments. A detailed comparison between LES and experiments is carried out, including the in-cylinder pressure, the flow fields, the spatial flame distribution, and the fields conditioned on fast and slow cycles. Good agreement is achieved for the variables considering all cycles; yet, some discrepancies are observed for the conditionally averaged quantities. A systematic quantitative correlation analysis between the selected influencing variables and the CCV is presented, in which the influencing variables are extracted from different length scales (r = 3 mm, 12 mm, and 43 mm) and the CCV are distinguished between the early flame kernel development and later flame propagation. Even though the most relevant influencing parameters are different for the two operating conditions, the location of the coherent vortex structure is found to be important for the CCV of both cases.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 1","pages":"3 - 29"},"PeriodicalIF":2.4,"publicationDate":"2022-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00353-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4482844","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":"ZDES Simulation and Spectral Analysis of a High-Reynolds-Number Out-of-Equilibrium Turbulent Boundary Layer","authors":"Jaime Vaquero,&nbsp;Nicolas Renard,&nbsp;Sébastien Deck","doi":"10.1007/s10494-022-00361-7","DOIUrl":"10.1007/s10494-022-00361-7","url":null,"abstract":"<div><p>A test-case for the assessment of Zonal Detached Eddy Simulation (ZDES) mode 3 [which corresponds to a Wall-Modelled Large Eddy Simulation approach (WMLES)] for turbulent boundary layers in pressure gradient conditions is presented. The demanding test-case corresponds to an experiment at high Reynolds number, reaching up to <span>(Re_theta approx 13000)</span>, probably too expensive for Direct Numerical Simulation or Wall-Resolved Large Eddy Simulation, but still affordable using ZDES mode 3 (WMLES). At the considered station, the boundary layer is in out-of-equilibrium conditions. The presented results prove the advantage of the scale-resolving approach, the ZDES mode 3, with respect to the RANS approach, as evidenced by the better representation observed for the mean velocity and Reynolds stress profiles, in particular in the outer layer where non-canonical effects are more evident. Thanks to the resolved turbulence, a more physically realistic flow is predicted by ZDES mode 3 and more in depth analysis of turbulence is accessible. In particular, spectral analysis of turbulence is performed in this study, and a scale-dependent convection velocity is also assessed for the first time with a hybrid RANS/LES approach in out-of-equilibrium conditions. Such analysis allow to identify some features of the turbulent scales distribution within the boundary layer, which seem responsible for some uncommon features observed in the present mean flow.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"1059 - 1079"},"PeriodicalIF":2.4,"publicationDate":"2022-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00361-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4411128","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":"Classifying Regions of High Model Error Within a Data-Driven RANS Closure: Application to Wind Turbine Wakes","authors":"Julia Steiner,&nbsp;Axelle Viré,&nbsp;Richard P. Dwight","doi":"10.1007/s10494-022-00346-6","DOIUrl":"10.1007/s10494-022-00346-6","url":null,"abstract":"<div><p>Data-driven Reynolds-averaged Navier–Stokes (RANS) turbulence closures are increasing seen as a viable alternative to general-purpose RANS closures, when LES reference data is available—also in wind-energy. Parsimonious closures with few, simple terms have advantages in terms of stability, interpret-ability, and execution speed. However experience suggests that closure model corrections need be made only in limited regions—e.g. in the near-wake of wind turbines and not in the majority of the flow. A parsimonious model therefore must find a middle ground between precise corrections in the wake, and zero corrections elsewhere. We attempt to resolve this impasse by introducing a classifier to identify regions needing correction, and only fit and apply our model correction there. We observe that such classifier-based models are significantly simpler (with fewer terms) than models without a classifier, and have similar accuracy, but are more prone to instability. We apply our framework to three flows consisting of multiple wind-turbines in neutral conditions with interacting wakes.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 3","pages":"545 - 570"},"PeriodicalIF":2.4,"publicationDate":"2022-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00346-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4372959","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":"Direct numerical simulations of turbulent channel flow over ratchet roughness","authors":"Angela Busse,&nbsp;Oleksandr Zhdanov","doi":"10.1007/s10494-022-00352-8","DOIUrl":"10.1007/s10494-022-00352-8","url":null,"abstract":"<div><p>The influence of the orientation of ratchet-type rough surfaces on their fluid dynamic roughness effect is investigated using direct numerical simulations of turbulent channel flow at <span>(Re_{tau }=395)</span>. The ratchet length-to-height ratio is varied from <span>(ell /k=2)</span> to 16 for a fixed ratchet height of <span>(k/delta =0.1)</span> where <span>(delta)</span> is the mean channel half-height. The results show that both roughness function and mean flow and turbulence statistics strongly depend on the ratchet orientation. Existing empirical formulae, which estimate the roughness function <span>(Delta U^+)</span> or the equivalent sand-grain roughness <span>(k_s)</span> based on surface-slope related parameters such as the effective slope or the Sigal-Danberg parameter, fail to accurately predict the differences between ratchet surfaces with high windward slopes and ratchet surfaces with high leeward slopes.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"1195 - 1213"},"PeriodicalIF":2.4,"publicationDate":"2022-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00352-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4375263","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":"Effect of Streamline Curvature on Three-Dimensionality of Transitional Near-Wall Flow in a Linear Hydrofoil Cascade: A DNS Investigation","authors":"Wei Zhang","doi":"10.1007/s10494-022-00359-1","DOIUrl":"10.1007/s10494-022-00359-1","url":null,"abstract":"<div><p>The laminar flow on a curved surface transits to turbulent induced by streamline curvature which generates pressure gradient field and separated shear layer flow. We performed a direct numerical simulation investigation on transitional flow through a linear cascade consist of S-shaped S3525 hydrofoil which has different curvature variations on the two surfaces, i.e., concave-to-convex and convex- to-concave in the streamwise direction. The objectives are to quantitatively assess the effects of streamline curvature of the hydrofoil surface on the three-dimensionality of the separated and transitional flow, including the patterns of separation and reattachment, formation and development of three-dimensional boundary layer flow, and statistics on non-homogeneous turbulent near-wall flow. Comparisons between the near-wall flows of the two surfaces demonstrate the effect of streamline curvature and its associated influential mechanisms such as pressure gradient field. Numerical data reveal that transition and occurrence of three-dimensional flow are observed earlier for the concave-to-convex surface; intermittent flow is generated in the concave section near the leading edge and convex section near the trailing edge where three-dimensionality of flow and turbulent fluctuations are the most pronounced. However, the boundary layer and near-wall flow for the convex-to-concave surface is quite stable until the concave section, thus three-dimensionality of separation and reattachment, boundary layer flow and turbulent behaviors are only notable near the trailing edge.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 3","pages":"603 - 625"},"PeriodicalIF":2.4,"publicationDate":"2022-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00359-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4375703","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":"Investigation of Engine Combustion and Auto-ignition of a Multicomponent Surrogate Fuel with NTC Behavior Under Knocking Conditions","authors":"Magnus Kircher,&nbsp;Sebastian Popp,&nbsp;Sandro Gierth,&nbsp;Andrea Pati,&nbsp;Jonathan Schneider,&nbsp;Marco Günther,&nbsp;Christian Hasse","doi":"10.1007/s10494-022-00351-9","DOIUrl":"10.1007/s10494-022-00351-9","url":null,"abstract":"<div><p>The occurrence of knocking combustion is limiting the efficiency of modern spark ignition engine operation. Thus, an understanding of the processes at the knock limit is required for further optimization of the combustion process. In this work, the combustion of a multicomponent Toluene Reference Fuel (TRF) in a single-cylinder research engine is investigated under knocking conditions. The fuel exhibits a negative temperature coefficient (NTC) regime for thermodynamic conditions relevant to the engine operation. A precursor model is used to capture the auto-ignition process. Under homogeneous conditions, a two-stage auto-ignition is observed. Inside the NTC regime, the temperature affects both first-stage and second-stage auto-ignition delay times. With a subsequently conducted multi-cycle engine LES, the effects of temperature stratification and turbulent flame propagation on the local auto-ignition process are investigated. It is observed, that the NTC behavior leads to a widespread two-stage auto-ignition. The knock intensity observed in the experiments is directly related to the mass consumed by auto-ignition. This is due to the fast consumption of the auto-ignited mass by the flame front. With that, the NTC behavior affects the local auto-ignition process in the unburned mixture while the flame propagation determines the knock intensity for the operating conditions at the knock limit.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 1","pages":"149 - 169"},"PeriodicalIF":2.4,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00351-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4328168","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":"Particle Image Velocimetry Measurements in Accelerated, Transonic Wake Flows","authors":"Judith Richter,&nbsp;Charalampos Alexopoulos,&nbsp;Bernhard Weigand","doi":"10.1007/s10494-022-00339-5","DOIUrl":"10.1007/s10494-022-00339-5","url":null,"abstract":"<div><p>This paper reports on particle image velocimetry (PIV) measurements in compressible accelerated wake flows generated by two different central injector types, which are mounted in a convergent-divergent nozzle. The injectors differ by the extent of their trailing edge located either in the subsonic (injector A) or supersonic flow region (injector B). In addition, the undisturbed nozzle flow without injector is studied as a reference case. The PIV results reveal typical wake flow structures expected in subsonic (injector A) and supersonic (injector B) wake flows. They further show that the Reynolds stresses <span>(mathrm {Re_{xx}})</span> and <span>(mathrm {Re_{yy}})</span> significantly decay in all three cases due to the strong acceleration throughout the nozzle. Interestingly, in the case of injector A, the flow stays non-isotropic with <span>(mathrm {Re_{yy}}&gt;mathrm {Re_{xx}})</span> also far downstream in the supersonic flow region. These measurements were motivated by the lack of velocity data needed to validate numerical simulations. That is why this paper additionally contains results from (unsteady) Reynolds-averaged Navier-Stokes ((U)RANS) simulations of the two wake flows investigated experimentally. The URANS simulation of the injector A case is able to accurately predict the entire flow field and periodic fluctuations at the wake centerline. However, in the case of injector B, the RANS simulation underestimates the far wake centerline velocity by about <span>(4%)</span>.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 3","pages":"667 - 696"},"PeriodicalIF":2.4,"publicationDate":"2022-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00339-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4198510","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}