Flow, Turbulence and Combustion最新文献

{"title":"Liquid Sheet Instability and Breakup in Primary Atomization for a Stirling Engine","authors":"Xinyu Dong,&nbsp;Zhenchang Fang,&nbsp;Feng Zhou,&nbsp;Jiaqi Li,&nbsp;Xincheng Tang,&nbsp;Xinqi Qiao,&nbsp;Chunhua Sun","doi":"10.1007/s10494-022-00371-5","DOIUrl":"10.1007/s10494-022-00371-5","url":null,"abstract":"<div><p>Stirling engines use a pressure swirl nozzle and Combustion Gases Recirculation for fuel atomization and flammable mixture formation. Based on temporal linear stability analysis, an investigation of the liquid sheet instability and breakup in primary atomization is conducted, which reveals the liquid behavior and predicts the Sauter mean diameter (SMD). The effects of ejection ratio, back pressure, load, liquid sheet thickness, and liquid swirl intensity on primary atomization are studied. The results indicate that the ejected gas stabilizes the liquid sheet and holds back primary atomization. Increasing back pressure or load boosts primary atomization. The effect of liquid sheet thickness characterized by the liquid sheet inner radius to outer radius ratio <i>h</i> on instability is nonmonotonic. Above the thickness at <i>h</i> = 0.3, the liquid sheet instability is independent of liquid sheet thickness. Below that, the instability is related to thickness. The disturbance growth first decreases and then increases with decreasing thickness. The liquid swirl intensity has a slight destabilizing effect on the liquid sheet. Without a common rail system, the injection pressure is reduced under a low load, leading to poor atomization. To optimize the atomization under a low load, the common effects of ejection ratio, back pressure, and nozzle exit diameter are analyzed. SMD under the optimal condition decreases greatly. Additionally, the SMD does not decrease monotonically with the nozzle exit diameter.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"351 - 376"},"PeriodicalIF":2.4,"publicationDate":"2022-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4400347","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":"Large–Eddy Simulation of the Flow Inside a Scour Hole Around a Circular Cylinder Using a Cut Cell Immersed Boundary Method","authors":"Lukas Unglehrt,&nbsp;Ulrich Jenssen,&nbsp;Fabian Kurz,&nbsp;Wolfgang Schanderl,&nbsp;Johannes Kreuzinger,&nbsp;Florian Schwertfirm,&nbsp;Michael Manhart","doi":"10.1007/s10494-022-00379-x","DOIUrl":"10.1007/s10494-022-00379-x","url":null,"abstract":"<div><p>We present a novel symmetry-preserving cut cell finite volume method which is a three-dimensional generalisation of the method by Dröge and Verstappen (Int J Numer Method Fluids 47:979–985, 2005). A colour-coding scheme for the three-dimensional cut momentum cell faces reduces the number of possible cut cell configurations. A cell merging strategy is employed to alleviate time step constraints. We demonstrate the energy conservation property of the convective and pressure gradient terms, and the second-order spatial convergence with suitable benchmark cases. We used the scheme to perform highly resolved large–eddy simulations of the flow inside a scour hole around a circular cylinder mounted vertically in a flume. The simulation results are extensively compared to a stereoscopic particle image velocimetry experiment of the same configuration performed by Jenssen and Manhart (Exp Fluids 61:217, 2020). We demonstrate that for the investigated Reynolds numbers (20,000 and 40,000) nearly converged solutions are obtained; however at large computational efforts (up to 2.35 billion cells for the higher Reynolds number). It turns out that the flow topology of the horseshoe vortex system is strongly dependent on the grid resolution. For simulation results obtained on the finest grid, the mean flow and turbulence quantities agree well with the experiment. We investigate the shape and turbulence structure of the horseshoe vortex based on three-dimensional fields, and discuss the distribution of the mean and standard deviation of the wall shear stress in the scour hole and the implications for the physics of the scouring process over a sand bed.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"893 - 929"},"PeriodicalIF":2.4,"publicationDate":"2022-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00379-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4099837","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":"Characterizing the Evolution of Boundary Layers in IC Engines by Combined Direct Numerical and Large-Eddy Simulations","authors":"George K. Giannakopoulos,&nbsp;Karri Keskinen,&nbsp;Jann Koch,&nbsp;Christos E. Frouzakis,&nbsp;Yuri M. Wright,&nbsp;Konstantinos Boulouchos","doi":"10.1007/s10494-022-00383-1","DOIUrl":"10.1007/s10494-022-00383-1","url":null,"abstract":"<div><p>The structure of boundary layers (BLs) and wall heat flux is investigated as they evolve during the compression stroke in an optically accessible, single-cylinder research engine of passenger-car dimensions with a typical four-valve pent-roof design operated at motored and throttled conditions. Three-dimensional direct numerical simulations (DNS) of the compression stroke were carried out, which enable full resolution in space and time of all flow and temperature field structures in the entire domain, including the BLs. Since the high computational cost precludes calculation of the scavenging cycle, scale-resolving simulations were employed to provide initial fields for the DNS at intake valve closure. The analysis revealed that BLs deviate from ideal scaling laws commonly adopted in algebraic wall models, and that the non-zero streamwise pressure gradient correlates with changes in the near-wall profiles. Phenomenologically, such deviations are similar to those for developing BLs, and in particular for impinging flows. The momentum BL structure was found to be affected by the large-scale bulk flow motion, in contrast to the thermal BLs which exhibit a more structured behavior following the density increase due to compression. Inspection of the heat flux distribution confirmed the similarity between the flow and heat flux patterns and identified regions of intense heat flux, mainly in locations of strong directed flow towards the wall. The improved characterization of the boundary layer structure and its evolution during the compression stroke not only constitutes an important step towards improved understanding of near-wall phenomena in internal combustion engines, but the vast dataset also serves as a database for development of improved wall models.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 1","pages":"209 - 238"},"PeriodicalIF":2.4,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00383-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5190625","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":"The Influence of Varying Fuel Composition and Flowfield on Turbulent Biogas-Like Flame Characteristics","authors":"Rajesh Sadanandan","doi":"10.1007/s10494-022-00384-0","DOIUrl":"10.1007/s10494-022-00384-0","url":null,"abstract":"<div><p>The flame stability of biogas surrogate flames subjected to variations in fuel composition and flow stabilization mechanisms are experimentally investigated in a non-premixed variable swirl burner (IIST-GVS1) with an axial-plus-tangential swirler. OH* chemiluminesce measurements along with 2D-PIV and probe measurements are performed to get insight into the flame characteristics and the emission levels at different operating conditions of the burner. Fuels with pure CH<span>(_4)</span> and with 20-40 % CO<span>(_2)</span> dilution are tested. 2D-PIV measurements reveal recirculation zones BRZ and ORZ due to the bluff body and combustor walls, respectively, and a central swirl-induced inner recirculation zone (IRZ). The recirculation of hot product gases plays a significant role in flame stabilization. Depending on the global equivalence ratio (<span>(phi _g)</span>), the flame stabilized close to the burner exit, at the boundary of BRZ, or downstream in the swirl-induced region. Though the swirl enhanced the flame stabilization, the region of a stable operating zone (in terms of <span>(phi _g)</span>) reduced with a high amount of swirl. Increasing CO<span>(_2)</span> dilution weakened the flame under all flow conditions with an enlargement of the heat release zone area. For a fixed <span>(phi _g)</span>, changes in fuel type led to local flowfield modification under similar inflow conditions. Also, with increasing CO<span>(_2)</span> dilution, the flame stabilized further downstream in locations with higher turbulence fluctuations and lower axial velocities. The burner, in general, produced deficient levels of NO<span>(_x)</span> emissions. However, higher levels of CO are seen with increasing CO<span>(_2)</span> dilution and at low <span>(phi _g)</span>.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 3","pages":"689 - 705"},"PeriodicalIF":2.4,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00384-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5190650","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":"Schlieren Image Velocimetry of Swirl Sprays","authors":"Danilo Almeida Machado,&nbsp;Fernando de Souza Costa,&nbsp;José Carlos de Andrade,&nbsp;Gabriel Silva Dias,&nbsp;Gustavo Alexandre Achilles Fischer","doi":"10.1007/s10494-022-00385-z","DOIUrl":"10.1007/s10494-022-00385-z","url":null,"abstract":"<div><p>Schlieren image velocimetry (SIV) is based on light deflection through flow heterogeneities and image cross-correlations. This is a low-cost and relatively low complexity technique that allows measurement of the droplet velocity field in a large region of a spray. A Z-type Toepler schlieren system with a high-speed camera was used to determine mean vertical and horizontal droplet velocities, as well as the cone angles of sprays produced by a pressure swirl injector with characteristic geometric constant <i>K</i> = 2. Different LEDs and digital filters were evaluated for edge detection and improvement of image contrast. Open software was adopted for digital image processing and velocimetry. Interrogation windows and overlaps of different sizes were tested to obtain an appropriate correlation for determination of the velocity field. The digital images were obtained with 5 × 10³ fps and a resolution of 2.77 pixels/mm. Since the swirl sprays analysed presented instabilities, a number of 100 cross-correlations of images was required to reduce mean velocity fluctuations. Injection pressures varied from 0.05 to 7 bar and mass flow rates varied from 1.389 to 13.89 g/s, using water as test fluid. The wideband warm white LED with Laplacian or high-pass filters provided velocity data for a larger range of injection pressures. Mean axial velocities varied from 3.3 to 11.3 m/s, approximately, with mean horizontal velocities varying from around 0.17 to 3.3 m/s for pressures from 0.05 to 3.22 bar. The velocity data were compared to microscopic shadowgraphy results, showing a good agreement. Spray cone angles ranged from about 32.5^o to 69.5°, for injection pressures from 0.05 to 7 bar, and results of triangulation with a blue LED were closer to semi-empirical data.</p><h3>Graphic Abstract</h3>\u0000 <figure><div><div><div><picture><source><img></source></picture></div></div></div></figure>\u0000 </div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"489 - 513"},"PeriodicalIF":2.4,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00385-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5167238","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":"Experimental Characterization of Upper Trailing Edge Flaps for Transonic Buffet Control","authors":"Alessandro D’Aguanno,&nbsp;Ferdinand F. J. Schrijer,&nbsp;Bas W. van Oudheusden","doi":"10.1007/s10494-022-00381-3","DOIUrl":"10.1007/s10494-022-00381-3","url":null,"abstract":"<div><p>This experimental study investigates the possibility of controlling transonic buffet by means of a trailing edge flap with an upward deflection (referred to as “upper trailing edge flap”, or: UTEF). Different geometries (straight and serrated) and dimensions of UTEFs (with heights ranging between 1 and 2% of the chord) have been studied with respect to their impact on the buffet behavior. The effectiveness of the UTEFs has been investigated with schlieren and particle image velocimetry (PIV) in the transonic-supersonic wind tunnel of TU Delft at Ma = 0<i>.</i>70, <i>α</i> = 3<i>.</i>5°. The schlieren results demonstrated the efficacy of the use of UTEFs for reducing the range of the buffet oscillations when the height of the UTEF was equal to at least 1.5%c. This result was corroborated by a flow characterization with PIV data and which highlighted that, in presence of a control system, not only the shock oscillation range is reduced but also the intensity of the separated area pulsation. The use of serrated UTEFs, despite having an effect on the local flow field, was found to be ineffective in alleviating buffet oscillations. The adoption of the best behaving UTEF configuration (straight 2%c UTEF) proved to only slightly alter the circulation value compared to the clean configuration, while it also proved to be effective in an off-buffet condition (Ma = 0<i>.</i>74 and <i>α</i> = 2<i>.</i>5°).</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"325 - 350"},"PeriodicalIF":2.4,"publicationDate":"2022-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00381-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5132803","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":"Laser Spark Evolution in an Ethylene Jet in Supersonic Crossflow Configuration","authors":"Dan Fries,&nbsp;Devesh Ranjan,&nbsp;Suresh Menon","doi":"10.1007/s10494-022-00382-2","DOIUrl":"10.1007/s10494-022-00382-2","url":null,"abstract":"<div><p>Ignition and relighting in supersonic flows is an important challenge for the design of hypersonic propulsion systems. Supersonic compressible flows of interest exhibit much larger local variations in velocity, shear, and thermodynamic state than their incompressible counterparts. Thus, it is of interest to study the relationship between ignition kernel evolution, the initial spark location, and the kernel’s subsequent flow state history. We leverage the flexibility of a laser plasma ignition system to systematically explore a large set of spark locations on the symmetry plane of an ethylene jet in supersonic crossflow setup. CH* measurements are used to visualize chemically active regions and results are correlated with flow field properties derived from Mie-scattering data of the non-reacting flow field. Our study describes the laser plasma properties in detail and scrutinizes the effect of turbulent mixing and flow dilatation on ignition kernels. Finally, the results yield general guidelines for favorable ignition locations in the engineering design of chemically reactive compressible flows.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"417 - 440"},"PeriodicalIF":2.4,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4990131","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":"Hybrid RANS/LES Simulations and Aeroacoustic Analysis of Jet Flows using an hp-Adaptive Discontinuous Galerkin Method","authors":"Francesca Basile,&nbsp;Jean-Baptiste Chapelier,&nbsp;Romain Laraufie,&nbsp;Pascal Frey","doi":"10.1007/s10494-022-00376-0","DOIUrl":"10.1007/s10494-022-00376-0","url":null,"abstract":"<div><p>In this paper, an <i>hp</i>-adaptation strategy designed for discontinuous Galerkin methods is extended and applied to hybrid RANS/LES simulations. The 3D <i>hp-</i>adaptive strategy is suited for tetrahedral and hybrid prismatic/tetrahedral meshes, and relies on a metric-based remeshing approach. The metric field and the polynomial map of the adapted meshes are built from an <i>a posteriori</i> error estimator which couples the measure of the energy associated with the highest-order modes and the inter-element jumps of the solution, combined with a smoothness sensor which guides the choice between <i>h-</i> and <i>p-</i>adaptation. The turbulence modeling relies on a Zonal Detached Eddy Simulation approach. The developed <i>hp</i>-adaptation algorithm is assessed in the context of hybrid RANS/LES simulations of the PPRIME nozzle configuration at diameter-based Reynolds number equal to <span>(10^6)</span>, starting the adaptive process from previously RANS-adapted meshes. Far-field acoustic analysis are performed using a Ffowcs Williams−Hawkings method.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"239 - 273"},"PeriodicalIF":2.4,"publicationDate":"2022-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4948729","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":"Multiple Mapping Conditioning Mixing Time Scales for Turbulent Premixed Flames","authors":"Nadezhda Iaroslavtceva,&nbsp;Andreas Kronenburg,&nbsp;Oliver T. Stein","doi":"10.1007/s10494-022-00375-1","DOIUrl":"10.1007/s10494-022-00375-1","url":null,"abstract":"<div><p>A novel multiple mapping conditioning (MMC) mixing time scale model for turbulent premixed combustion has been developed. It combines time scales for the flamelet and distributed flame regimes with the aid of a blending function. The blending function serves two purposes. Firstly, it helps to identify zones where the premixed flame resides and where the time scale associated with the premixed flame shall be used. Secondly, it uses the Karlovitz number to identify the turbulent premixed combustion regime and to reduce the weighting of the premixed flame time scale if Karlovitz numbers are high and deviations from the flamelet regime are expected. A series of three-dimensional direct numerical simulations (DNS) of statistically one dimensional, freely propagating turbulent methane-air flames provides a wide range of turbulent combustion regimes for the mixing model validation. The new mixing time scale provides correct predictions of the flame speed of freely propagating turbulent flames which could not be matched by most recognized mixing models. The turbulent flame structure predicted by the new model is in good agreement with DNS for all combustion regimes from flamelet to the thickened reaction zone.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"110 2","pages":"395 - 415"},"PeriodicalIF":2.4,"publicationDate":"2022-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00375-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4839654","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":"Implementation and Validation of an Algebraic Wall Model for LES in Nek5000","authors":"Emmanuel Gillyns,&nbsp;Sophia Buckingham,&nbsp;Grégoire Winckelmans","doi":"10.1007/s10494-022-00378-y","DOIUrl":"10.1007/s10494-022-00378-y","url":null,"abstract":"<div><p>Turbulent flows are most often wall-bounded, rendering the treatment of the wall essential. In this work, the near-wall layer is modelled in large eddy simulations which enables simulating high Reynolds number flows. An algebraic wall model has been implemented in the spectral element code Nek5000. It consists of an approximate boundary condition that relates the wall shear stress to the velocity measured close to the wall, on the upper edge of the first spectral element. The wall shear stress model approximates the law of the wall for hydraulically smooth cases. The model is applied to channel flow cases at <span>(Re_{tau }=1000)</span> and at <span>(Re_{tau }=5200)</span>. The wmLES results obtained with the present implementation are seen to compare very well with those of reference direct numerical simulations in the resolved region. They also remain remarkably close to the reference results for a large part of the under-resolved region; which is not necessarily the case when using low order implementations and even other types of high order discretizations, as found in the literature. Various parameters are studied such as the time averaging, the height of the near wall under-resolved element, and the mesh requirements. The obtained results indicate that accurate results can be obtained with Nek5000 at a reduced cost thanks to this newly implemented wmLES model. This work provides the necessary guidelines for simple flows, and it will serve as a first basis for simulating more complex flows at high Reynolds numbers.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"109 4","pages":"1111 - 1131"},"PeriodicalIF":2.4,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-022-00378-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4771449","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}