Flow, Turbulence and Combustion最新文献

{"title":"Evaluation of Non-ideal Fluid Modeling for Droplet Evaporation in Jet-Engine-Like Conditions","authors":"Davide Cavalieri,&nbsp;Jacopo Liberatori,&nbsp;Matteo Blandino,&nbsp;Pasquale Eduardo Lapenna,&nbsp;Mauro Valorani,&nbsp;Pietro Paolo Ciottoli","doi":"10.1007/s10494-024-00610-x","DOIUrl":"10.1007/s10494-024-00610-x","url":null,"abstract":"<div><p>Mid-century climate neutrality targets for the aviation industry foster the development of ultra-high overall pressure ratio jet engines. Consequently, comprehensive numerical models driving the design process must tackle the severe thermodynamic conditions expected to occur during the various flight operational phases. In the current study, we present a cost-effective framework for addressing droplet vaporization phenomena in jet-engine-relevant conditions, leveraging real-fluid thermophysical modeling and high-pressure vapor-liquid equilibrium interfacial thermodynamics. We evaluate the impact of a non-ideal fluid approach on predicting the evaporation process of a single n-dodecane droplet in air, mimicking operating conditions relevant to aero-engines. For the conditions examined, the numerical results indicate that adopting a real-fluid thermodynamic treatment results in a deviation of the droplet vaporization rate from an ideal-fluid approach, for which we have outlined the thermodynamic states that lead to mixture non-ideality. Notably, we envisage the most impactful model discrepancies in transport property estimation, thus affecting the heat and mass transfer rates. Lastly, we analyze and quantify the role of the detailed phase equilibrium model in the droplet evaporation process, assessing its actual impact for the conditions of interest, and discussing the cost-effectiveness in commonly computational fluid dynamics tools.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"857 - 885"},"PeriodicalIF":2.0,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612218","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":"Performance Analysis of Two-Dimensional Plane Diffusers at a Moderate Reynolds Number by Means of Unsteady RANS","authors":"Alex Ravaioli,&nbsp;Rithvik Magal,&nbsp;Alessandro Talamelli,&nbsp;Gabriele Bellani","doi":"10.1007/s10494-024-00599-3","DOIUrl":"10.1007/s10494-024-00599-3","url":null,"abstract":"<div><p>Diffusers are devices found in several engineering applications and their performance and design are object of numerous investigations. However, relatively few investigations have been dedicated to diffusers operating at low and moderate Reynolds numbers. In this regime, the flow could be laminar, turbulent or transitional, and the aerodynamic performance of the diffuser becomes highly dependent on the specific value of the Reynolds number and inlet conditions. In particular, the present study focuses on evaluating the role of inlet conditions on the performance and flow behaviour of two-dimensional diffusers on this specific Reynolds number regime (<span>(Re approx 8000)</span>). Furthermore, the diffuser discharges in a stationary chamber and it does not present a tail-pipe configuration, a condition that has not found a clear presence in the existing literature so far. A numerical investigation of two-dimensional plane diffusers was performed at <span>(Re = 8163)</span> for 9 different cases, combined varying the inlet turbulence intensity (0.05, 3, and 10 percent), and the velocity profile, characterised by different blockage factors (0, 0.05 and 0.33). For each case, the divergence angle ranged from 0 to 30 degrees, and several URANS simulations were performed using the <span>(k-omega)</span> <i>Transitional SST</i> model that accounts for the possible transition of the boundary layer. The results show that the design recommendations valid for high Reynolds number diffusers with a thin boundary layer are not always applicable, and extreme caution must be exercised when dealing with operating conditions that do not ensure a sufficiently high turbulence level at the inlet. The divergence angles of the stall regimes are shown, and performance indicators (e.g. pressure-recovery coefficients) are reported. These reveal a strong decrement (up to 60 percent) of the pressure recovery on reducing turbulence intensity from 10 percent to 0.05 percent. The blockage factor of the velocity profile has an important effect on performance as well. In order to simplify the comparison between the different blockage factors, a modified effectiveness was employed to account for the distortion introduced by a non-uniform inlet velocity profile.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"617 - 642"},"PeriodicalIF":2.0,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430937","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":"The Impact of Real Roughness Features on Boundary Layer Transition","authors":"Sivaramakrishnan Malathi Ananth,&nbsp;Subhathra Sabapathy,&nbsp;Nagabhushana Rao Vadlamani,&nbsp;John Coull","doi":"10.1007/s10494-024-00605-8","DOIUrl":"10.1007/s10494-024-00605-8","url":null,"abstract":"<div><p>In this work, the effects of realistic roughness scales on boundary layer transition are investigated using high-resolution scale-resolving simulations. This is in contrast to most of the roughness-induced transition studies reported in the literature based on ordered and well-defined surface roughness elements. Two highly irregular surface roughness patterns are generated from a given roughness patch by selectively filtering out the higher frequencies. The transitional behavior of a laminar boundary layer developing over these roughness scales is examined at <span>(text {Re}_{delta _{in}^{*}}=360)</span> and 540, defined in terms of the inflow velocity and inlet displacement thickness. The impact on transition is explored by examining the instantaneous and time-averaged flow fields. The results show that the transition onset is sensitive to the roughness scales: the inclusion of finer scales reduces the spacing between roughness features thereby constraining the lateral development of the flow. The streaks are weaker due to the mutual sheltering effect and the finer scales are shown to promote spanwise inhomogeneity of flow in the transition region. This effect is found to be much more prominent at low Reynolds numbers. In contrast, filtering out the finer roughness scales results in an earlier transition onset, caused by strong streaks developing from the horseshoe vortices wrapping around sparsely packed roughness features. Further cases are studied to investigate the spatial features of roughness that are important for transition. A series of high-fidelity simulations using selective retention of roughness features are performed at <span>(text {Re}_{delta _{in}^{*}}=360)</span>. The transition onset can be predicted satisfactorily by retaining the dominant scales (20 tallest peaks in this study) from the original rough surface while the valleys and fine-scale features are shown to have minimal effect. In addition, we demonstrate that modifying the roughness patch or Reynolds number during the simulation alters the transition onset, which gets quickly established within <span>(approx 1725k_{rms}/U_{in})</span>. These findings have the potential to reduce the computational cost and further aid in improving the transition correlations employed in low-fidelity simulations.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 Heat and Mass Transfer","pages":"737 - 763"},"PeriodicalIF":2.0,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612063","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":"Near-Field Mixing in a Coaxial Dual Swirled Injector","authors":"Sylvain Marragou,&nbsp;Thibault Frédéric Guiberti,&nbsp;Thierry Poinsot,&nbsp;Thierry Schuller","doi":"10.1007/s10494-024-00596-6","DOIUrl":"10.1007/s10494-024-00596-6","url":null,"abstract":"<div><p>Improving mixing between two coaxial swirled jets is a subject of interest for the development of next generations of fuel injectors. This is particularly crucial for hydrogen injectors, where the separate introduction of fuel and oxidizer is preferred to mitigate the risk of flashback. Raman scattering is used to measure the mean compositions and to examine how mixing between fuel and air streams evolves along the axial direction in the near-field of the injector outlet. The parameters kept constant include the swirl level <span>(S_e = 0.67)</span> in the annular channel, the injector dimensions, and the composition of the oxidizer stream, which is air. Experiments are carried out in cold flow conditions for different compositions of the central stream, including hydrogen and methane but also helium and argon. Three dimensionless mixing parameters are identified, the velocity ratio <span>(u_e/u_i)</span> between the external stream and internal stream, the density ratio <span>(rho _e/rho _i)</span> between the two fluids, and the inner swirl level <span>(S_i)</span> in the central channel. Adding swirl to the central jet significantly enhances mixing between the two streams very close to the injector outlet. Mixing also increases with higher velocity ratios <span>(u_e/u_i)</span>, independently of the inner swirl. Additionally, higher density ratios <span>(rho _e/rho _i)</span> enhance mixing between the two streams only in the case without swirl conferred to the central flow. A model is proposed for coaxial swirled jets, yielding a dimensionless mixing progress parameter that only depends on the velocity ratio <span>(u_e/u_i)</span> and geometrical features of the swirling flow that can be determined by examining the structure of the velocity field. Comparing the model with experiments, it is shown to perform effectively across the entire range of velocity ratios <span>(0.6 le u_e/u_i le 3.8)</span>, density ratios <span>(0.7 le rho _e/rho _i le 14.4)</span>, and inner swirl levels <span>(0.0 le S_i le 0.9)</span>. This law may be used to facilitate the design of coaxial swirled injectors.\u0000</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"221 - 242"},"PeriodicalIF":2.0,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00596-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994571","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":"Performance Analysis of Heat Transfer and User Thermal Comfort on Latent Heat Treatment of Scald Wound Based on Spray Cooling","authors":"Xinglong Zhang,&nbsp;Yu Wang,&nbsp;Risto Kosonen","doi":"10.1007/s10494-024-00601-y","DOIUrl":"10.1007/s10494-024-00601-y","url":null,"abstract":"<div><p>Spray cooling has been proved to be an effective method for treating scald. However, enhancing its cooling effectiveness and improving user’s thermal comfort are the key factors for its practical implementation. In this study, numerical simulation with computational fluid dynamics software and experimental testing, and subjective questionnaire surveys. Factors influencing the heat removal efficiency of spray cooling for scald treatment and the user’s perception under spray cooling conditions were studied. The results showed that spray temperature had a significant impact on cooling efficiency. The distance between the spray and skin, mass flow rate, and spray medium also had noticeable effects. Additionally, the influence of spray cooling on thermal sensation and thermal comfort under different spray temperatures was investigated. By introducing a “temperature correction coefficient”, thermal sensation data closer to scald conditions were obtained. Experimental results demonstrated that compared to splashing, spray cooling exhibited better cooling effectiveness and comfort feelings. Using the Predicted Mean Vote and Thermal Comfortable Vote as indicators and considering both cooling effectiveness and human thermal comfort, the optimal cooling temperature for females was determined to be 13.1 °C and for males 13.5 °C under scald conditions.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 2","pages":"677 - 710"},"PeriodicalIF":2.0,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of Thermal Boundary Models for Large Eddy Simulations of Natural Convection","authors":"Lise Ceresiat,&nbsp;Miltiadis V. Papalexandris","doi":"10.1007/s10494-024-00594-8","DOIUrl":"10.1007/s10494-024-00594-8","url":null,"abstract":"<div><p>In this paper, we report on the efficacy of four different thermal boundary models for Wall-Modelled Large Eddy Simulations (WMLES) of turbulent natural convection. Our test cases consist of Rayleigh-Bénard convection of liquid water at two Rayleigh numbers, <span>(Ra =1.35{times }10^8)</span> and <span>(Ra =10^9)</span>, respectively. Two configurations are examined, namely, convection in a box and in a cavity; the latter one involving a free-slip top boundary. For these test cases, the numerical results obtained via WMLES with the thermal boundary models are compared with those of Wall-Resolved Large-Eddy Simulations. According to our comparative studies, a particular version of the so-called Kays &amp; Crawford model provides the most accurate predictions, at least for the test cases considered herein. Additionally, in this paper, we report on WMLES of turbulent convection at a higher Rayleigh number, <span>(Ra =5{times }10^9)</span>, with the aforementioned model. For this case, we analyse herein the flow structure and present results for first and second-order statistics of the flow.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"117 - 144"},"PeriodicalIF":2.0,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995745","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":"Analysis of Droplet Evaporation Dynamics Using Computational Singular Perturbation and Tangential Stretching Rate","authors":"Lorenzo Angelilli,&nbsp;Riccardo Malpica Galassi,&nbsp;Pietro Paolo Ciottoli,&nbsp;Francisco E. Hernandez-Perez,&nbsp;Mauro Valorani,&nbsp;Hong G. Im","doi":"10.1007/s10494-024-00592-w","DOIUrl":"10.1007/s10494-024-00592-w","url":null,"abstract":"<div><p>Computational singular perturbation (CSP) has been successfully used in the analysis of complex chemically reacting flows by systematically identifying the intrinsic timescales and slow invariant manifolds that capture the essential subprocesses driving the dynamics of the system. In this article, the analytical and computational framework is applied for the first time to analyze the Lagrangian droplets undergoing evaporation and dispersion in the surrounding gases. First, a rigorous mathematical formulation is derived to adapt the CSP tools into the droplet dynamics equations, including the formal definition of the tangential stretching rate (TSR) that represents the explosive/dissipative nature of the system. A steady ammonia and a falling water droplet studies are then conducted to demonstrate the utility of the CSP methodology in identifying various physical mechanisms driving the evolution of the system, such as the distinction of thermal-driven and mass-driven regimes. Various definitions of the importance indices are also examined to provide in-depth analysis of different subprocesses and their interactions in modifying the droplet dynamics.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"275 - 298"},"PeriodicalIF":2.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the Partially Stirred Reactor Model for LES in a Swirl-Stabilized Turbulent Premixed Flame","authors":"Fredherico Rodrigues,&nbsp;José M. García-Oliver,&nbsp;José M. Pastor,&nbsp;Daniel Mira","doi":"10.1007/s10494-024-00589-5","DOIUrl":"10.1007/s10494-024-00589-5","url":null,"abstract":"<div><p>This study presents an assessment of the Partially Stirred Reactor (PaSR) as a subgrid model for large eddy simulations (LES) of turbulent premixed combustion. The PaSR-LES approach uses a skeletal mechanism for methane/air combustion, and requires the transport of all the species, with a closure for the filtered source terms. The rate of progress for each reaction is given by the mixing and chemical time scales, which are computed from global flame parameters and a turbulent time scale respectively. This model is applied to a swirled combustor exhibiting a V-flame shape attached to the nozzle, subjected to heat loss. LES are carried out for two distinct equivalence ratios at atmospheric pressure. The flow fields and the thermochemical states from PaSR-LES are compared with the experimental data and solutions based on Flamelet Generated Manifolds (FGM). The results show good correlation with the experiments and FGM-LES, though also some sensitivity to the resolution. The approach also reproduces well the effect of heat loss, which is determined by the use of a chemical time scale given by a progress variable. Dedicated analysis of the swirl-stabilized flame on different regions is conducted evaluating the capabilities of the model to reproduce the burning velocity, flame shape and flame structure.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"359 - 386"},"PeriodicalIF":2.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994330","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 Reformulation of the Laminar Kinetic Energy Model to Enable Multi-mode Transition Predictions","authors":"Roberto Pacciani,&nbsp;Yuan Fang,&nbsp;Leonardo Metti,&nbsp;Michele Marconcini,&nbsp;Richard Sandberg","doi":"10.1007/s10494-024-00590-y","DOIUrl":"10.1007/s10494-024-00590-y","url":null,"abstract":"<div><p>The paper describes the development of a novel transition/turbulence model based on the laminar kinetic energy concept. The model is intended as a base framework for data-driven improvements. Starting from a previously developed framework, mainly aimed at separated-flow transition predictions, suitable terms for model generalization are identified and reformulated for handling different transition modes, namely bypass and separated-flow modes. The ideology for the definition of new terms has its roots in mixing phenomenological and correlation-based arguments, ensuring generality and flexibility and allowing a variety of lines of action for improving model components via machine-learning approaches. The model calibration, carried out with reference to flat plate test cases subjected to different pressure gradients and freestream turbulence levels, is discussed in detail. Although the constructed model is calibrated on a group of classic flat plat cases, the validation campaign, mostly carried out on gas turbine cascades, demonstrates its ability to predict transitional flows with engineering accuracy. Finally, while the model is not specifically developed for natural transition predictions, satisfactory predictions are obtained in scenarios with low freestream turbulence for flat plate and airfoil flows.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"114 1","pages":"81 - 116"},"PeriodicalIF":2.0,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00590-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994695","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":"Variable Resolution in Scale-Resolved Simulations of Turbulence","authors":"Magnus Carlsson,&nbsp;Stefan Wallin,&nbsp;Sharath Girimaji","doi":"10.1007/s10494-024-00591-x","DOIUrl":"10.1007/s10494-024-00591-x","url":null,"abstract":"<div><p>A new formulation for scale-resolved simulations of turbulence with variable resolution (VR) is proposed. A delayed detached-eddy simulation (DDES) model based on the <span>(k-omega)</span> framework is extended with VR-terms representing the commutation terms arising from variable resolution defined in terms of the DDES length scale. The VR-terms are responsible for the exchange of turbulence kinetic energy between the resolved and unresolved partitioning of the computational representation of turbulent flow. The new formulation is implemented in a general-purpose CFD code and applied on two cases, namely, a mixing shear layer and a wall-mounted hump and have been compared with and combined with the baseline model and two additional grey-area mitigation (GAM) formulations. The proposed method is shown to provide the mechanism for the exchange of energy between unresolved and resolved representation of the flow and to enhance the transition from modelled to resolved turbulence and thus improve the prediction of the resolved Reynolds stresses, development of the vorticity thickness for the shear layer flow and the skin friction recovery length for the hump flow.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"115 Simulation and Measurements","pages":"105 - 125"},"PeriodicalIF":2.0,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100168","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}