Computers & Fluids最新文献

{"title":"Ablation and molten layer flow simulation for plate model of SiO2f/SiO2 composite material using particle method","authors":"Junjie Gao ,&nbsp;Daiying Deng ,&nbsp;Xiaoguang Luo ,&nbsp;Haitao Han ,&nbsp;Jijun Yu","doi":"10.1016/j.compfluid.2024.106436","DOIUrl":"10.1016/j.compfluid.2024.106436","url":null,"abstract":"<div><div>In this paper, the moving particle semi-implicit method (MPS) is extended from calculating free mobility to simulating the extremely viscous and temperature-dependent molten layer flow of SiO_2f/SiO₂ composite material under aerodynamic heating conditions, which includes strong heating and shear of incoming flow. A method for applying heat flux and airflow shear, based on the conceptual particle approach, has been established. Heat transfer, melting, solidification, and evaporation behaviors are considered, with temperature-dependent viscosity variations also accounted for. The ablative regression of the plate model is verified using experimental results of the SiO_2f/SiO₂ composite material, and results from convergence analysis demonstrate the accuracy of the space step size selection. Surface morphology analysis through three-dimensional computation indicates that the extended particle method also accurately describes the surface morphology of SiO_2f/SiO₂ composite material under aerodynamic heating conditions. Thus, the extended particle method accurately simulates both the ablation process and the surface morphology of the SiO_2f/SiO₂ composite material. The influences of acceleration and surface tension are discussed. Ablative recession, when subject to acceleration, is smaller than that observed in its absence. When exposed to surface tension, the liquid layer tends to form a spherical shape, and the particles behave as a cohesive unit, resulting in smaller ablative recession than in the absence of surface tension.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106436"},"PeriodicalIF":2.5,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314636","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 continuous adjoint to the incompressible (D)DES Spalart-Allmaras turbulence models","authors":"A.-S.I. Margetis ,&nbsp;E.M. Papoutsis-Kiachagias ,&nbsp;K.C. Giannakoglou","doi":"10.1016/j.compfluid.2024.106439","DOIUrl":"10.1016/j.compfluid.2024.106439","url":null,"abstract":"<div><div>This article formulates the continuous adjoint method for the gradient-based shape optimization of fluid flows governed by the incompressible Detached Eddy Simulation (DES) and Delayed-DES (DDES) models, based on the Spalart-Allmaras turbulence model. As both flow models are inherently unsteady, challenges arise regarding the availability of flow fields during the backward in time integration of the unsteady adjoint equations. To minimize both the computational cost and the memory demands, the computed flow fields are compressed using the iPGDZ<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> lossy compression technique, recently developed by the authors. Its application in the context of turbulence-resolving flows, where the compression of flow fields poses an intricate challenge, is a second original contribution of this article. Everything is implemented as an extension to the publicly available <em>adjointOptimisation</em> library of OpenFOAM, which is used to solve the flow and adjoint equations and conduct the optimization. Using two shape optimization problems in external aerodynamics, it is demonstrated that including the adjoint to the turbulence model equation is crucial for the computation of accurate sensitivity derivatives. In contrast to sensitivities computed under the “frozen turbulence” assumption, which neglects variations in turbulent viscosity due to changes in the design variables, the proposed adjoint method yields sensitivities that align with those obtained using Finite Differences. This is due to the Think-Discrete Do-Continuous adjoint method which, inspired by hand-differentiated discrete adjoint, gives rise to consistent discretization schemes of the terms involved in the equations derived by continuous adjoint. Furthermore, it is demonstrated that the proposed adjoint method can significantly benefit from the iPGDZ<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> algorithm, by reducing memory requirements by more than two orders of magnitude, eliminating the need for flow recomputations, while maintaining the accuracy of the computed derivatives. Ways to handle large integration windows of the objective function with this type of flow models are beyond the scope of this article.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106439"},"PeriodicalIF":2.5,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322292","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":"MH-DCNet: An improved flow field prediction framework coupling neural network with physics solver","authors":"Qisong Xiao ,&nbsp;Xinhai Chen ,&nbsp;Jie Liu ,&nbsp;Chunye Gong ,&nbsp;Yufei Sun","doi":"10.1016/j.compfluid.2024.106440","DOIUrl":"10.1016/j.compfluid.2024.106440","url":null,"abstract":"<div><div>With the development of intelligent computing technology, deep learning methods have provided an efficient solution for rapid flow field prediction in computational fluid dynamics (CFD) problems. However, existing methods have limitations in handling interference among physical variables due to different data distributions, leading to a decline in prediction performance. In this paper, we propose MH-DCNet, an improved flow field prediction framework that couples a neural network with a physics solver. Specifically, to address the data distribution problem, we design a multi-head deep convolutional neural network that decouples the prediction of physical variables through multiple encoders and decoders. We also develop a hybrid loss function by introducing the mean structural similarity to better capture the complex spatial structures and distribution features of flow fields. We evaluate MH-DCNet with unseen geometries and various flow conditions. Experimental results show that MH-DCNet outperforms other advanced models in efficiency and generalization capability. It accelerates the prediction process by 2.35 times compared to the CFD method while meeting the convergence constraints.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106440"},"PeriodicalIF":2.5,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314637","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":"Application of the iteratively regularized Gauss–Newton method to parameter identification problems in Computational Fluid Dynamics","authors":"Stefan Langer","doi":"10.1016/j.compfluid.2024.106438","DOIUrl":"10.1016/j.compfluid.2024.106438","url":null,"abstract":"<div><div>Field Inversion and Machine Learning is an active field of research in <strong>C</strong>omputational <strong>F</strong>luid <strong>D</strong>ynamics (CFD). This approach can be leveraged to obtain a closed-form correction for a given turbulence model to improve the predictions. The fundamental approach is to insert a parameter into the system of RANS equations and determine it in a way such that, for example, a given pressure distribution is better approximated compared to the one obtained with the original set of equations. The goal of this article is twofold. Numerical arguments are presented that these kinds of problems can be severely ill-posed. In the second part, an approach is presented to directly reconstruct the turbulent viscosity field along with an example. The <strong>I</strong>teratively <strong>R</strong>egularized <strong>G</strong>auss-<strong>N</strong>ewton <strong>M</strong>ethod (IRGNM) is used for a realization. The construction of a problem-adapted norm for a finite volume method is presented. Finally, an outlook is presented on how this approach can be used to possibly modify or improve turbulence models such that not only one, but a larger number of test cases are considered.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106438"},"PeriodicalIF":2.5,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322291","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":"Space–time adaptive ADER-DG finite element method with LST-DG predictor and a posteriori sub-cell ADER-WENO finite-volume limiting for multidimensional detonation waves simulation","authors":"I.S. Popov","doi":"10.1016/j.compfluid.2024.106425","DOIUrl":"10.1016/j.compfluid.2024.106425","url":null,"abstract":"<div><div>The space–time adaptive ADER–DG finite element method with LST–DG predictor and a posteriori sub–cell ADER–WENO finite–volume limiting was used for simulation of multidimensional reacting flows with detonation waves. The presented numerical method does not use any ideas of splitting or fractional time steps methods. The modification of the LST–DG predictor has been developed, based on a local partition of the time step in cells in which strong reactivity of the medium is observed. This approach made it possible to obtain solutions to classical problems of flows with detonation waves and strong stiffness, without significantly decreasing the time step. The results obtained show the very high applicability and efficiency of using the ADER–DG–<span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>N</mi></mrow></msub></math></span> method with a posteriori sub–cell limiting for simulating reactive flows with detonation waves. The numerical solution shows the correct formation and propagation of ZND detonation waves. The structure of detonation waves is resolved by this numerical method with subcell resolution even on coarse spatial meshes. The smooth components of the numerical solution are correctly and very accurately reproduced by the numerical method. Non–physical artifacts of the numerical solution, typical for problems with detonation waves, such as the propagation of non–physical shock waves and weak detonation fronts ahead of the main detonation front, did not arise in the results obtained. The results of simulating rather complex problems associated with the propagation of detonation waves in significantly inhomogeneous domains are presented, which show that all the main features of detonation flows are correctly reproduced by this numerical method. It can be concluded that the space–time adaptive ADER–DG–<span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>N</mi></mrow></msub></math></span> method with LST–DG predictor and a posteriori sub–cell ADER–WENO finite–volume limiting is perfectly applicable to simulating fairly complex reacting flows with detonation waves.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106425"},"PeriodicalIF":2.5,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310974","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":"Three-dimensional mesoscopic investigation of directional coalescence of two droplets impacting on a wall with wettability difference","authors":"Pengcheng Zhu,&nbsp;Xiaolong He,&nbsp;Jianmin Zhang,&nbsp;Haonan Peng","doi":"10.1016/j.compfluid.2024.106423","DOIUrl":"10.1016/j.compfluid.2024.106423","url":null,"abstract":"<div><p>In this work, a three-dimensional (3D) nonorthogonal pseudopotential lattice Boltzmann method (LBM) was proposed to investigate the coalescence dynamics of two droplets impacting on a wall with wettability difference. The influences of the wettability difference, Weber number, offset distance on the low-wettability side on the coalescence dynamics and the contact-line evolution processes were systematically examined. Both symmetric and asymmetric distributions of the droplet-coalescence behaviors were considered. Our findings reveal that the wettability difference has a significant influence on the asymmetric-retracting and wetting-equilibrium stages, identifying three modes: pin-slip, slip and no-rebound, and slip and rebound. The rebound time is dominated by the high-wettability wall. At a larger Weber number, droplets exhibit a large retracting velocity, which results in increased pumping velocity and earlier rebound time. In addition, a dramatic retraction of the three-phase contact line (TPCL) on the low-wettability wall is observed, leading to the detachment of the liquid bridge from the low-wettability wall, and the formation of a cavity. With increasing offset distance on the low-wettability wall, three different evolution modes are found: coalescence-rebound, coalescence-separation, and non-coalescence. A power function relationship is reported between the Weber number <span><math><mtext>We</mtext></math></span> and the offset distance <span><math><msup><mrow><mi>L</mi></mrow><mo>*</mo></msup></math></span> both on the high-wettability wall and low-wettability wall for three modes of coalescence behavior with <span><math><mrow><mtext>We</mtext><mo>∼</mo><msup><mrow><mi>L</mi></mrow><mrow><mo>*</mo><mi>α</mi></mrow></msup></mrow></math></span>. The value of the exponent <span><math><mi>α</mi></math></span> ranges from 4.6 to 7.4. This study showcases the effectiveness of the 3D nonorthogonal pseudopotential LBM in predicting the complex interface phenomena and characteristics of the multiphase flow structures under investigation.</p></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106423"},"PeriodicalIF":2.5,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142233733","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":"Inductive plasma excitation forcing configuration on reduction of tip distorted inflow effect on the aerodynamic stability of axial compressor rotor","authors":"Ali Khoshnejad ,&nbsp;Reza Ebrahimi ,&nbsp;Sohrab Gholamhosein Pouryoussefi","doi":"10.1016/j.compfluid.2024.106433","DOIUrl":"10.1016/j.compfluid.2024.106433","url":null,"abstract":"<div><p>This research delves into the mitigating impacts of dielectric barrier discharge (DBD) plasma excitation induced forcing orientation against the detrimental consequences of distinct radial tip distortions which in turn affect the axial compressor rotor performance and alters the flow structure at the tip region. Full annulus transient CFD simulation was utilized to evaluate the consequences of plasma actuation at distorted conditions with different blockage percentages. Beyond flow field and frequency analysis, the study further characterized rotor performance under different conditions by evaluating key performance metrics, including total pressure rise coefficient, stall margin variation, and span-wise rotor inlet velocity distribution. The injection of momentum caused by plasma actuators to the low-energy region behind the distortion screens proved to be effective on rotor aerodynamic stability facing radial tip distortion. In the case where 15 % of the inlet area was blocked, the stall margin varied from -8 % to -3.5 % with axial plasma actuators in action. However, the best configuration of plasma actuators for the enhancement of the stall margin and flow characteristics was identified to have opposite forcing direction with respect to the rotor rotational velocity. Additionally, these actuators suppressed frequencies caused by fluctuations in the rotor blade row tip leakage vortex, suggesting an improvement in the flow pattern within the rotor tip area.</p></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106433"},"PeriodicalIF":2.5,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142239768","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":"High-order finite volume method for solving compressible multicomponent flows with Mie–Grüneisen equation of state","authors":"Feng Zheng ,&nbsp;Jianxian Qiu","doi":"10.1016/j.compfluid.2024.106424","DOIUrl":"10.1016/j.compfluid.2024.106424","url":null,"abstract":"<div><p>In this paper, we propose a new high-order finite volume method for solving the multicomponent fluids problem with Mie–Grüneisen EOS. Firstly, based on the cell averages of conservative variables, we develop a procedure to reconstruct the cell averages of the primitive variables in a high-order manner. Secondly, the high-order reconstructions employed in computing numerical fluxes are implemented in a characteristic-wise manner to reduce numerical oscillations as much as possible and obtain high-resolution results. Thirdly, advection equation within the governing system is rewritten in a conservative form with a source term to enhance the scheme’s performance. We utilize integration by parts and high-order numerical integration techniques to handle the source terms. Finally, all variables are evolved by using Runge–Kutta time discretization. All steps are carefully designed to maintain the equilibrium of pressure and velocity for the interface-only problem, which is crucial in designing a high-resolution scheme and adapting to more complex multicomponent problems. We have performed extensive numerical tests for both one- and two-dimensional problems to verify our scheme’s high resolution and accuracy.</p></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106424"},"PeriodicalIF":2.5,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142168149","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 coupled block implicit solver for the incompressible Navier–Stokes equations on collocated grids","authors":"Mark A. George,&nbsp;Nicholas Williamson,&nbsp;Steven W. Armfield","doi":"10.1016/j.compfluid.2024.106426","DOIUrl":"10.1016/j.compfluid.2024.106426","url":null,"abstract":"<div><p>A fully coupled matrix-free method is developed for solving the incompressible steady-state Navier–Stokes equations on a collocated finite volume grid. This is achieved by offsetting the momentum equations relative to the continuity equation they are implicitly coupled to at each cell and updating the solution by sweeping planes in 3D and lines in 2D. The effect of sweeping direction on convergence rate is investigated for the 3D laminar lid driven cavity at Reynolds number 200 and 1000 and 3D laminar backwards facing step at Reynolds number 100 and 200. For these flow cases, a speed-up of up to an order of magnitude compared to SIMPLE schemes of OpenFOAM and ANSYS Fluent and the coupled solver of ANSYS Fluent was observed.</p></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106426"},"PeriodicalIF":2.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162977","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 implicit Large Eddy Simulation of turbomachinery flows using the Flux Reconstruction method","authors":"Feng Wang","doi":"10.1016/j.compfluid.2024.106422","DOIUrl":"10.1016/j.compfluid.2024.106422","url":null,"abstract":"<div><p>A high-order flux reconstruction solver has been developed and validated to perform implicit large-eddy simulations of industrially representative turbomachinery flows. The T106c low-pressure turbine and VKI LS89 high-pressure turbine cases are studied. The solver uses the Rusanov Riemann solver to compute the inviscid fluxes on the wall boundaries, and HLLC or Roe to evaluate inviscid fluxes for internal faces. The impact of Riemann solvers is demonstrated in terms of accuracy and non-linear stability for turbomachinery flows. It is found that HLLC is more robust than Roe, but both Riemann solvers produce very similar results if stable solutions can be obtained. For non-linear stabilization, a local modal filter, which combines a smooth indicator and a modal filter, is used to stabilize the solution. This approach requires a tuning parameter for the smoothness criterion. Detailed analysis has been provided to guide the selection of a suitable value for different spatial orders of accuracy. This local modal filter is also compared with the recent positivity-preserving entropy filter in terms of accuracy and stability for the LS89 turbine case. The entropy filter could stabilize the computation but is more dissipative than the local modal filter. Regarding the spanwise spacing of the grid, the case of the LS89 turbine shows that a <span><math><msup><mrow><mi>z</mi></mrow><mrow><mo>+</mo></mrow></msup></math></span> of approximately <span><math><mrow><mn>45</mn><mo>−</mo><mn>60</mn></mrow></math></span> is suitable for obtaining a satisfactory prediction of the heat transfer coefficient of the mean flow. This would allow for a coarse grid spacing in the spanwise direction and a cost-effective ILES aerothermal simulation for turbomachinery flows.</p></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"284 ","pages":"Article 106422"},"PeriodicalIF":2.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162979","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}