Flow, Turbulence and Combustion最新文献

{"title":"Installation Effects on Jet Aeroacoustics","authors":"Peter Jordan, Ulf Michel","doi":"10.1007/s10494-024-00574-y","DOIUrl":"10.1007/s10494-024-00574-y","url":null,"abstract":"","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 3","pages":"537 - 538"},"PeriodicalIF":2.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142409662","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":"Computational Study of Laser-Induced Modes of Ignition in a Coflow Combustor","authors":"Donatella Passiatore,&nbsp;Jonathan M. Wang,&nbsp;Diego Rossinelli,&nbsp;Mario Di Renzo,&nbsp;Gianluca Iaccarino","doi":"10.1007/s10494-024-00575-x","DOIUrl":"10.1007/s10494-024-00575-x","url":null,"abstract":"<div><p>This study investigates laser-induced ignition in a model-rocket combustor through computational simulations. The primary focus is on characterizing successful and unsuccessful ignition scenarios and elucidating the underlying physical mechanisms. Large Eddy simulations (LESs) are utilized to explore laser-based forced ignition in a methane–oxygen combustor, with attention given to the intricate interplay of factors such as initial condition variability and turbulent flow field. Perturbations in laser parameters and initial flow conditions introduce stochastic behavior, revealing critical insights into ignition location relative to the fuel-oxidizer mixture. A significant methodological innovation lies in the adaptation of established image analysis techniques to track and monitor the transport of hot packets within the flow field. By extending these tools, the study provides insights into the interaction between ignition kernels and flammable gases, offering a more comprehensive understanding of the phenomenon. Results highlight the interplay between hydrodynamic ejections from the laser spark and turbulent fluctuations in the background flow. Indeed, the hydrodynamic ejection emanating from the laser spark, which typically plays a central role for isolated kernels in quiescent flows, competes with the entrainment velocity if its values are within the same order of magnitude and if the laser focal location is particularly close to the shear layer’s edge.\u0000</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1055 - 1079"},"PeriodicalIF":2.0,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178594","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":"Gradient Information and Regularization for Gene Expression Programming to Develop Data-Driven Physics Closure Models","authors":"Fabian Waschkowski,&nbsp;Haochen Li,&nbsp;Abhishek Deshmukh,&nbsp;Temistocle Grenga,&nbsp;Yaomin Zhao,&nbsp;Heinz Pitsch,&nbsp;Joseph Klewicki,&nbsp;Richard D. Sandberg","doi":"10.1007/s10494-024-00579-7","DOIUrl":"10.1007/s10494-024-00579-7","url":null,"abstract":"<div><p>Learning accurate numerical constants when developing algebraic models is a known challenge for evolutionary algorithms, such as Gene Expression Programming (GEP). This paper introduces the concept of adaptive symbols to the GEP framework by Weatheritt and Sandberg (J Comput Phys 325:22–37, 2016a) to develop advanced physics closure models. Adaptive symbols utilize gradient information to learn locally optimal numerical constants during model training, for which we investigate two types of nonlinear optimization algorithms. The second contribution of this work is implementing two regularization techniques to incentivize the development of implementable and interpretable closure models. We apply <span>(L_2)</span> regularization to ensure small magnitude numerical constants and devise a novel complexity metric that supports the development of low complexity models via custom symbol complexities and multi-objective optimization. This extended framework is employed to four use cases, namely rediscovering Sutherland’s viscosity law, developing laminar flame speed combustion models and training two types of fluid dynamics turbulence models. The model prediction accuracy and the convergence speed of training are improved significantly across all of the more and less complex use cases, respectively. The two regularization methods are essential for developing implementable closure models and we demonstrate that the developed turbulence models substantially improve simulations over state-of-the-art models.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"145 - 175"},"PeriodicalIF":2.0,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00579-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178760","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 Comprehensive Study About Implicit/Explicit Large-Eddy Simulations with Implicit/Explicit Filtering","authors":"Pedro Stefanin Volpiani","doi":"10.1007/s10494-024-00577-9","DOIUrl":"10.1007/s10494-024-00577-9","url":null,"abstract":"<div><p>A high-order computational fluid dynamics code was developed to simulate the compressible Taylor–Green vortex problem by means of large-eddy (LES) and direct numerical simulations. The code, BASIC, uses explicit central-differencing to compute the spatial derivatives and explicit low storage Runge–Kutta methods for the temporal discretization. Central-differencing schemes were combined with relaxation filtering or with splitting formulas to discretize convective derivative operators. The application of split forms to convective derivatives generally guarantees good stability properties with marginal dissipation. However, these types of schemes were found to be unsuited to perform implicit large-eddy simulations (ILES). The minimally dissipative schemes showed acceptance performance, only when combined with a sub-grid scale model. The relaxation-filtering strategy, on the other hand, although more dissipative, was proven to be more adequate to perform ILES. We showed that reducing the filter dissipation, by optimizing its damping function, has a positive impact in the flow solution. When performing ILES, the utilization of split formulas in conjunction with relaxation filtering has equally yielded promising results. This combined approach enhances numerical stability while preserving low levels of numerical dissipation.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"891 - 922"},"PeriodicalIF":2.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937208","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":"Statistical Inference of Upstream Turbulence Intensity for the Flow Around a Bluff Body with Massive Separation","authors":"Tom Moussie,&nbsp;Paolo Errante,&nbsp;Marcello Meldi","doi":"10.1007/s10494-024-00573-z","DOIUrl":"10.1007/s10494-024-00573-z","url":null,"abstract":"<div><p>The Benchmarck on the Aerodynamics of a Rectangular 5:1 Cylinder is studied using a data-driven technique which bridges numerical simulation and available experimental results. Because of intrinsic features of the tools used for investigation, in particular in terms of set-up and boundary conditions, significant discrepancies have been observed in the literature when comparing experimental and numerical results. An approach based on the Ensemble Kalman Filter is here used to optimize a synthetic turbulent inlet used as boundary condition in the numerical calculation, in order to reduce the discrepancy with the available experiments. The data-driven method successfully optimizes the boundary condition features, which produce a significant improvement of the accuracy in the prediction of the flow. These findings open perspectives of application towards the analysis of realistic cases, where boundary conditions are complex and usually unknown.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"853 - 889"},"PeriodicalIF":2.0,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00573-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937213","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":"Correction to: Aero-structural Analysis of a Scramjet Technology Demonstrator Designed to Operate at an Altitude of 23 km at Mach 5.8","authors":"Paulo César de Oliveira Júnior,&nbsp;João Carlos Arantes Costa Júnior,&nbsp;Paulo Gilberto de Paula Toro","doi":"10.1007/s10494-024-00569-9","DOIUrl":"10.1007/s10494-024-00569-9","url":null,"abstract":"","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1053 - 1053"},"PeriodicalIF":2.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141926849","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":"Multi-cycle Direct Numerical Simulations of a Laboratory Scale Engine: Evolution of Boundary Layers and Wall Heat Flux","authors":"Bogdan A. Danciu, George K. Giannakopoulos, Mathis Bode, Christos E. Frouzakis","doi":"10.1007/s10494-024-00576-w","DOIUrl":"https://doi.org/10.1007/s10494-024-00576-w","url":null,"abstract":"<p>Multi-cycle direct numerical simulations (DNS) of a laboratory-scale engine at technically relevant engine speeds (1500 and 2500 rpm) are performed to investigate the transient velocity and thermal boundary layers (BL) as well as the wall heat flux during the compression stroke under motored operation. The time-varying wall-bounded flow is characterized by a large-scale tumble vortex, which generates vortical structures as the flow rolls off the cylinder wall. The bulk flow is found to strongly affect the development of the BL profiles, especially at higher engine speeds. As a result, the large-scale flow structures lead to alternating pressure gradients near the wall, invalidating the flow equilibrium assumptions used in typical wall modeling approaches. The thickness of the velocity BL and of the viscous sublayer was found to scale inversely with engine speed and crank angle. The thermal BL thickness also scales inversely with engine speed but increases with in-cylinder temperature. In contrast, thermal displacement thickness, which is sometimes used as a proxy for thermal BL thickness, was found to decrease with increasing temperature in the bulk. Examination of the heat flux distribution revealed areas of increased heat flux, particularly at places characterized by strong flow directed towards the wall. In addition, significant cyclic variations in the surface-averaged wall heat flux were observed for both engine speeds. An analysis of the cyclic tumble ratio revealed that the cycles with lower tumble ratio values near top dead center (TDC), indicative of an earlier tumble breakdown, also exhibit higher surface averaged wall heat fluxes. These findings extend previous numerical and experimental results for the evolution of BL structure during the compression stroke and serve as an important step for future engine simulations under realistic operating conditions.</p>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"58 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937209","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":"Experimental and Full-Annulus Simulation Analysis of the Rotating Stall in a Centrifugal Compressor Stage with a Vaned Diffuser","authors":"Yufang Zhang,&nbsp;Shuai Li,&nbsp;Hechun Yu,&nbsp;Linlin Cui","doi":"10.1007/s10494-024-00578-8","DOIUrl":"10.1007/s10494-024-00578-8","url":null,"abstract":"<div><p>Flow instability such as rotating stall and even surge occurs when the centrifugal compressor stage operates under low flow conditions. This phenomenon is an extremely complex dynamic process, and it is closely related to the aerodynamic performance and internal flow of the stage. Therefore, it is necessary to study the flow development characteristics in the stage. This paper employs experimental measurement and full-annulus numerical simulation to investigate the effects of diffuser stall on the aerodynamic performance of the compressor and the internal flow of the impeller. The propagation direction, speed, evolution characteristics, and the number of the stall cell were obtained by experimental measurement, and the numerical simulation method was verified. The numerical results that there is a stall limit cycle with counter-clockwise rotation between the flow rate and total pressure ratio of the compressor when the diffuser stalls. Meanwhile, it is found that the stall limit cycle is closely related to the separation strength of the internal flow in the compressor. Finally, the coherent flow structure near the vane shroud side is identified by the modal decomposition methods when the diffuser stalls. The research results in this paper promote an in-depth understanding of the stall mechanism of centrifugal compressors.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"199 - 219"},"PeriodicalIF":2.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937212","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 Surface Temperature Measurements Resolving Flame-Wall Interactions of Lean H2-Air and CH4-Air Flames Using Phosphor Thermometry","authors":"Anthony O. Ojo,&nbsp;Abhijit Padhiary,&nbsp;Brian Peterson","doi":"10.1007/s10494-024-00571-1","DOIUrl":"10.1007/s10494-024-00571-1","url":null,"abstract":"<div><p>Spatiotemporal wall temperature (T_wall) distributions resulting from flame-wall interactions of lean H₂-air and CH₄-air flames are measured using phosphor thermometry. Such measurements are important to understand transient heat transfer and wall heat flux associated with various flame features. This is particularly true for hydrogen, which can exhibit a range of unique flame features associated with combustion instabilities. Experiments are performed within a two-wall passage, in an optically accessible chamber. The phosphor ScVO₄:Bi³⁺ is used to measure T_wall in a 22 × 22 mm² region with 180 µm/pixel resolution and repetition rate of 1 kHz. Chemiluminescence imaging is combined with phosphor thermometry to correlate the spatiotemporal dynamics of the flame with the heat signatures imposed on the wall. Measurements are performed for lean H₂-air flames with equivalence ratio Φ = 0.56 and compared to CH₄-air flames with Φ = 1. T_wall signatures for H₂-air Φ = 0.56 exhibit alternating high and low-temperature vertical streaks associated with finger-like flame structures, while CH₄-air flames exhibit larger scale wrinkling with identifiable crest/cusp regions that exhibit higher/lower wall temperatures, respectively. The underlying differences in flame morphology and T_wall distributions observed between the CH₄-air and lean H₂-air mixtures are attributed to the differences in their Lewis number (CH₄-air Φ = 1: Le = 0.94; H₂-air Φ = 0.56: Le = 0.39). Findings are presented at two different passage spacings to study the increased wall heat loss with larger surface-area-to-volume ratios. Additional experiments are conducted for H₂-air mixtures with Φ = 0.45, where flame propagation was slower and was more suitable to resolve the wall heat signatures associated with thermodiffusive instabilities. These unstable flame features impose similar wall heat fluxes as flames with 2–3 times greater flame power. In this study, these flame instabilities occur within a small space/time domain, but demonstrate the capability to impose appreciable heat fluxes on surfaces.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1161 - 1188"},"PeriodicalIF":2.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00571-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937210","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":"Towards Direct Numerical Simulations of Reactivity-Controlled Compression Ignition Engine Using n-Octanol/Ethanol Fuel Blends","authors":"Antony Premkumar, Francesca Loffredo, Heinz Pitsch, Markus Klein","doi":"10.1007/s10494-024-00570-2","DOIUrl":"https://doi.org/10.1007/s10494-024-00570-2","url":null,"abstract":"<p>The results of a two-dimensional direct numerical simulation of a lean n-octanol-ethanol fuel blend under Reactivity Controlled Compression Ignition (RCCI) conditions are presented in this paper. Stratified temperature and high reactivity fuel fields of Gaussian, bi-modal, and log-normal distributions are studied for uncorrelated and correlated scenarios. The pimple loop is made to run twice to achieve compression heating. A chemical mechanism with 171 species and 734 reactions was developed to capture autoignition characteristics and flame propagation reasonably well. Diagnosing techniques published in the literature are used to determine whether the flame fronts are spontaneously propagating or not. As reported previously for other fuel blends under RCCI conditions, both deflagration and spontaneous ignition flame fronts are observed to co-exist. Gaussian, bi-modal, and log-normal fields respectively move towards a spontaneously igniting mode. Correlating temperature and high reactivity fuel fields not only makes combustion more spontaneously igniting but also more premixed. The analysis reveals the sensitivity of the DNS results with respect to the initial conditions which accordingly should be chosen with care.</p>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"3 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869098","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}