Flow, Turbulence and Combustion最新文献

{"title":"Spatial Averaging Effects in Adverse Pressure Gradient Turbulent Boundary Layers","authors":"Fermin Mallor, Ramis Örlü, Philipp Schlatter","doi":"10.1007/s10494-024-00568-w","DOIUrl":"https://doi.org/10.1007/s10494-024-00568-w","url":null,"abstract":"<p>Thermal anemometry sensors for time-resolved velocity measurements average the measured signal over the length of their sensor, thereby attenuating fluctuations stemming from scales smaller than the wire length. Several compensation methods have emerged for wall turbulence, the most prominent ones relying on the small-scale universality in canonical flows or on the reconstruction based on two attenuated variance profiles obtained with sensors of different length. To extend these methods to non-canonical flows, the present work considers various adverse-pressure gradient (APG) turbulent boundary layer (TBL) flows in order to explore how the small-scale energy is affected in the inner and outer layer and how the two prominent correction methods perform as function of wall-distance, wire length and flow condition. Our findings show that the increased levels of small-scale energy in the inner, but also outer layer associated with APG TBLs reduces the applicability of empirical methods based on the universality of small-scale energy. On the other hand, a correction based on the relationship between the spanwise Taylor microscale and the two-point streamwise velocity correlation function, is able to correct the attenuated profiles of non-canonical cases. Combining the strength of both methods, a composite profile for the spanwise Taylor microscale is suggested, which then is used for the correction of probe-length attenuation effects across a multitude of flow conditions.</p>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"45 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141741238","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":"LES of Biomass Syngas Combustion in a Swirl Stabilised Burner: Model Validation and Predictions","authors":"Nikolaos Papafilippou,&nbsp;Francesco Pignatelli,&nbsp;Arman Ahamed Subash,&nbsp;Muhammad Aqib Chishty,&nbsp;Rikard Gebart","doi":"10.1007/s10494-024-00558-y","DOIUrl":"10.1007/s10494-024-00558-y","url":null,"abstract":"<div><p>In this work, numerical investigations were performed using large eddy simulations and validated against detailed measurements in the CeCOST swirl stabilised burner. Both cold and reactive flow have been studied and the model has shown a good agreement with experiments. The verification of the model was done using the LES index of quality and a single grid estimator. The cold flow simulations predicted results closely to experiments setting baseline for the reactive simulations. Coherent structures like the vortex rope above the swirler and a precessing vortex core in the combustion chamber were identified. The reactive conditions were modelled with the Flamelet generated manifold and artificially thickened flame models. Simulations were performed for an experimental syngas composition from black liquor gasification at three different CO₂ dilution levels. Three different Reynolds numbers were investigated with the model matching closely to experimentally detected 2D flow field and OH for the most CO₂ diluted mixture. It was found that the opening angles of the flames differ by a maximum of 13% between experiments and simulations. The most diluted fuel investigated experienced a liftoff distance of 23.5 mm at the Re 25 k. This was also the highest liftoff distance experienced in this cohort of fuels. The same fuel also proved to have the thickest flame annulus at 78.5 mm. Overall, in cases with no experimental data available the predictions made by the model follow the same trends which hints its applicability to higher Re cases.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1189 - 1214"},"PeriodicalIF":2.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00558-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746132","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 Comparison of Evaluation Methodologies of the Fractal Dimension of Premixed Turbulent Flames in 2D and 3D Using Direct Numerical Simulation Data","authors":"Marco Herbert,&nbsp;Nilanjan Chakraborty,&nbsp;Markus Klein","doi":"10.1007/s10494-024-00560-4","DOIUrl":"10.1007/s10494-024-00560-4","url":null,"abstract":"<div><p>A Direct Numerical Simulation (DNS) database of statistically planar flames ranging from the wrinkled flamelets to the thin reaction zones regime and DNS data for a Bunsen premixed flame representing the wrinkled flamelets regime have been utilised to evaluate the fractal dimensions of flame surfaces using the filtering dimension method, the box-counting algorithm and the correlation dimension approach. The fractal dimension evaluated based on the fully resolved three-dimensional data has been found to be reasonably approximated by adding unity to the equivalent fractal dimension evaluated based on two-dimensional projections irrespective of the methodology of extracting fractal dimension. This indicates that the flame surface can be approximated as a self-similar fractal surface for the range of Karlovitz and Damköhler numbers considered here. While all methods, provide results identical to each other for benchmark problems, it has been found that the fractal dimension evaluation based on box-counting method provides almost identical results as that obtained using the filtering dimension method for both three and two dimensions, while the fractal dimensions based on the correlation dimension tend to be slightly smaller. The findings of the current analysis have the potential to be used to reliably estimate the actual fractal dimension in 3D based on experimentally obtained 2D binarised reaction progress variable field. The inner cut-off scales estimated based on all three methodologies yield comparable results in terms of order of magnitude with the box-counting method predicting a smaller value of inner cut-off scale in comparison to other methods. The execution times for fractal dimension extraction based on filtering dimension and box-counting methodologies are found to be comparable but the correlation dimension method is found to be considerably faster than the two alternative approaches and provides results consistent with theoretical bounds in all cases.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1145 - 1160"},"PeriodicalIF":2.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00560-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141721988","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":"Instability Modes and Scaling Analysis During Electro-Hydro-Dynamic-Atomization: Theoretical and Experimental Study","authors":"Alok Kumar Ray","doi":"10.1007/s10494-024-00567-x","DOIUrl":"10.1007/s10494-024-00567-x","url":null,"abstract":"<div><p>The electro-hydro-dynamic-atomization (EHDA) is a well-established technology with numerous micro/nanoparticle fabrication applications. However, a consistent method for explaining the physics behind the process has yet to be established. The present study aims to report a comprehensive non-dimensional analysis to develop a correlation between different process parameters. The dimensionless numbers derived from Buckingham’s pi theorem match well with those derived from the Navier–Stokes equation, establishing the forces involved in EHDA. Flow instability modes during the EHDA process are experimentally visualized using the flow visualization technique and characterized using a microscope. The instability modes are described using derived non-dimension numbers, and results closely align with Ganan-Calvo’s findings. Derived scaling for the current is in good agreement with Ganan-Calvo (1997), which complies with the condition if δ_μ × (Q/Qo)^1/3 &gt;  &gt; 1, then I/Io = 11 × (Q/Qo)^1/4 -5. Moreover, the ratio of ln (Ehd)/ ln (Md) in cone jet mode is found to be ≈2, irrespective of fluids.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"947 - 974"},"PeriodicalIF":2.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141647399","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 Wall Modeling With Adverse Pressure Gradient for High Reynolds Number Separated Flows","authors":"Sajad Mozaffari,&nbsp;Jérôme Jacob,&nbsp;Pierre Sagaut","doi":"10.1007/s10494-024-00562-2","DOIUrl":"10.1007/s10494-024-00562-2","url":null,"abstract":"<div><p>This paper applies a recently developed approach for modeling turbulence near wall regions within a lattice Boltzmann solver, in combination with a Hybrid RANS/LES turbulence model, to study turbulent separated flows at high Reynolds numbers. To simulate unsteady detached flows on a non-body-fitted Cartesian grid, wall models are employed to estimate the effects of unresolved near-wall turbulence on the overall flow. The article presents the extension of an equilibrium power law wall model to handle adverse pressure gradients and its application in simulating external aerodynamic flows. Hybrid RANS/LES simulations are conducted for two challenging test cases: a 3D NACA-4412 airfoil near stall and a complex Ahmed body configuration. Comparison with a reference simulation involving resolved boundary layers and experimental data demonstrates the strong performance of the wall model, when considering adverse pressure gradients, in simulating turbulent boundary layers under various conditions, ranging from fully attached to mild to high adverse pressure gradients.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"923 - 945"},"PeriodicalIF":2.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141648305","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":"LES of Premixed Turbulent Combustion Using Filtered Tabulated Chemistry","authors":"Maximilian Bambauer,&nbsp;Michael Pfitzner,&nbsp;Markus Klein","doi":"10.1007/s10494-024-00563-1","DOIUrl":"10.1007/s10494-024-00563-1","url":null,"abstract":"<div><p>The filtered tabulated chemistry (FTACLES) approach utilizes data from pre-tabulated explicitly filtered 1D flame profiles for closure of the LES-filtered transport terms. Different methodologies are discussed to obtain a suitable progress variable <i>c</i> from detailed chemistry calculations of a methane/air flame. In this context, special focus is placed on the analytical modeling of the reaction source term using series of parameterized Gaussians. For increasing effective filter sizes in LES (i.e. including the flame thickening) the precise shape of the reaction rate profile becomes less and less relevant. In particular, it is shown that for one-step chemistry, a single Gaussian is sufficient to derive an explicitly expressible 1D flame profile with a prescribed laminar flame speed and thermal flame thickness. The resulting artificial flame profile is shown to have similarities with profiles based on carbon chemistry and detailed reaction mechanisms. Next, the behavior of the filtered <i>c</i>-transport equation is analyzed and several possible closure methods are compared for a wide range of filter widths. It is shown that the unclosed contribution of the filtered diffusion term can be combined with the subgrid convection term, thus simplifying the FTACLES formulation. The model is implemented in OpenFOAM and validated in 1D for a variety of LES filter sizes in combination with artificial flame thickening. A power-law-based wrinkling model is modified for use with artificial flame thickening and combined with the FTACLES model to enable 3D simulations of a premixed turbulent Bunsen burner. The comparison of 3D Large Eddy Bunsen flame simulations at increasing levels of turbulence intensity shows a good match to experimental results for most investigated cases. In addition, the results are mostly insensitive to the variation of the mesh size.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1111 - 1143"},"PeriodicalIF":2.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00563-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570184","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":"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/s10494-024-00564-0","DOIUrl":"10.1007/s10494-024-00564-0","url":null,"abstract":"<div><p>Aerodynamic and structural analysis was conducted for a generic supersonic combustion demonstrator designed to operate under flight conditions at an altitude of 23 km and a speed corresponding to Mach number 5.8. Optimization methodologies were applied to the compression section of the model to ensure the required temperature and Mach number conditions at the combustion chamber entrance for the spontaneous combustion of hydrogen fuel, as well as to the expansion section to meet the Brayton thermodynamic cycle. In the aerodynamic analysis, both analytical and numerical approaches were considered for cases without fuel injection and with fuel burning, treating air as a calorically perfect gas without viscous effects. In the structural analysis, only the case with fuel burning was evaluated due to its higher structural demands. Additionally, cases with different plate thicknesses (6 mm, 4 mm, 3 mm, and 2.5 mm) were considered, and the components of the scramjet consisted of Stainless Steel 304 (beams and ribs), Aluminum 7075 (side panels and ramps), Inconel 718, or Tungsten (leading edges and combustion chamber entrance). The results of the aerodynamic numerical simulation demonstrated that the designed scramjet was capable of meeting both on-lip and on-corner shock conditions, ensuring maximum atmospheric air capture. In the structural numerical simulation, for sheets thicker than 2.5 mm, the maximum equivalent von Mises stress in the structure was lower than the yield stress of the materials used, indicating that the deformations were within the elastic regime and thus reversible.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"1025 - 1052"},"PeriodicalIF":2.0,"publicationDate":"2024-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570239","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":"On the Flow Past a Three-Element Wing: Mean Flow and Turbulent Statistics","authors":"Ricard Montalà, Oriol Lehmkuhl, Ivette Rodriguez","doi":"10.1007/s10494-024-00566-y","DOIUrl":"https://doi.org/10.1007/s10494-024-00566-y","url":null,"abstract":"<p>Large eddy simulations (LES) on the flow past the 30P30N three-element high-lift wing at a moderate Reynolds number <span>(Re_c=750,000)</span> and three different angles of attack <span>(alpha =5)</span>, 9 and <span>(23^circ )</span> are conducted. The main focus is on the time-averaged statistics of the turbulent flow. The form drag noticeably increases with the angle of attack, while viscous drag remains roughly constant and contributes minimally to the total drag. This is associated with the significant pressure peaks found in the main element with increasing angles of attack and hence, the development of stronger adverse pressure gradients. At <span>(alpha =23^circ )</span>, this leads to the development of a prominent wake downstream this element that eventually evolves into a visible recirculation region above the flap, indicating the onset of stall conditions. In the flap, strong adverse pressure gradients are observed at small angles of attack instead, i.e., <span>(alpha =5)</span> and <span>(9^circ )</span>. This is attributed to the flap’s deflection angle with respect to the main wing, which causes a small separation of the boundary layer as the flow approaches the trailing edge. At the stall angle of attack, i.e., <span>(alpha =23^circ )</span>, the spread of the main element wake maintains attached the flow near the flap wall, thus mitigating the pressure gradient there and preventing the flow to undergo separation. The shear layers developed on the slat and main coves are also analysed, with the slat shear layer showing more prominence. In the slat, its size and intensity noticeably decrease with the angle of attack as the stagnation point moves towards the slat cusp. Conversely, the size of the shear layer developed in the main element cavity remains approximately constant regardless of the angle of attack. At the lower angles of attack, i.e., <span>(alpha =5)</span> and <span>(9^circ )</span>, the development of the shear layer is anticipated by the turbulent separation of the flow along the pressure side of the main wing, leading to increased levels of turbulence downstream. At the higher angle of attack, i.e., <span>(alpha =23^circ )</span>, the shear layer is originated by the cavity separation and transition to turbulence occurs within the cavity.</p>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"1 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141550469","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":"Jet Installation Noise Modelling for Round and Chevron Jets","authors":"Hussain A. Abid,&nbsp;Annabel P. Markesteijn,&nbsp;Sergey A. Karabasov,&nbsp;Hasan Kamliya Jawahar,&nbsp;Mahdi Azarpeyvand","doi":"10.1007/s10494-024-00559-x","DOIUrl":"10.1007/s10494-024-00559-x","url":null,"abstract":"<div><p>Wall-Modelled Large Eddy Simulations (LES) are conducted using a high-resolution CABARET method, accelerated on Graphics Processing Units (GPUs), for a canonical configuration that includes a flat plate within the linear hydrodynamic region of a single-stream jet. This configuration was previously investigated through experiments at the University of Bristol. The simulations investigate jets at acoustic Mach numbers of 0.5 and 0.9, focusing on two types of nozzle geometries: round and chevron nozzles. These nozzles are scaled-down versions (3:1 scale) of NASA’s SMC000 and SMC006 nozzles. The parameters from the LES, including flow and noise solutions, are validated by comparison with experimental data. Notably, the mean flow velocity and turbulence distribution are compared with NASA’s PIV measurements. Additionally, the near-field and far-field pressure spectra are evaluated in comparison with data from the Bristol experiments. For far-field noise predictions, a range of techniques are employed, ranging from the Ffowcs Williams–Hawkings (FW–H) method in both permeable and impermeable control surface formulations, to the trailing edge scattering model by Lyu and Dowling, which is based on the Amiet trailing edge noise theory. The permeable control surface FW–H solution, incorporating all jet mixing and installation noise sources, is within 2 dB of the experimental data across most frequencies and observer angles for all considered jet cases. Moreover, the impermeable control surface FW–H solution, accounting for some quadrupole noise contributions, proves adequate for accurate noise spectra predictions across all frequencies at larger observer angles. The implemented edge-scattering model successfully captures the mechanism of low-frequency sound amplification, dominant at low frequencies and high observer angles. Furthermore, this mechanism is shown to be effectively consistent for both <span>(M=0.5)</span> and <span>(M=0.9)</span>, and for jets from both round and chevron nozzles.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 3","pages":"827 - 852"},"PeriodicalIF":2.0,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00559-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528549","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":"Air-Film Coupling in Prefilming Airblast Atomisers and the Implications for Subsequent Atomisation","authors":"Jack R. J. Wetherell,&nbsp;Andrew Garmory","doi":"10.1007/s10494-024-00565-z","DOIUrl":"10.1007/s10494-024-00565-z","url":null,"abstract":"<div><p>Prefilming airblast atomisers are commonly used in gas turbine combustion system fuel injectors. As the film propagates across the prefilmer it interacts with the high velocity gas stream above it. In this paper a numerical investigation into this interaction is presented. A Coupled Level Set &amp; Volume of Fluid method is used to simulate the development of the film along the KIT-ITS planar prefilmer (Gepperth et al., in: 23rd European conference on liquid atomization and spray systems (ILASS-Europe 2010), Brno, Czech Republic, September, 2010). Initial results showed the importance of correctly specifying the contact angle as too high a value leads to the formation of rivulets instead of a continuous film. An analysis of the film and air showed two-way coupling. The presence of the film increases the growth rate of the gas phase boundary layer, and the strength and size of the turbulent structures within it. Surface waves form in the film, initially driven by the turbulent fluctuations, but developing into transverse waves. These waves are shown to be independent, stochastic events instead of a periodic wave system. At the trailing edge of the prefilmer the increased turbulence level in the air, the variations in the film thickness and the associated change in fuel mass flow and momentum will have large implications for the atomisation process and subsequent fuel spray. These will also impact simulation of the atomisation, as the boundary condition complexity is much greater than commonly used, and the variations will require larger domains and longer simulation times to obtain fully converged atomisation statistics.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"113 4","pages":"975 - 1002"},"PeriodicalIF":2.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-024-00565-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141530109","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}