Theoretical and Computational Fluid Dynamics最新文献

Nonlinear estimation in turbulent channel flows

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-02-23 DOI: 10.1007/s00162-025-00741-5

Jitong Ding, Simon J. Illingworth

{"title":"Nonlinear estimation in turbulent channel flows","authors":"Jitong Ding, Simon J. Illingworth","doi":"10.1007/s00162-025-00741-5","DOIUrl":"10.1007/s00162-025-00741-5","url":null,"abstract":"<div>We design a nonlinear estimator for channel flows at (Re_{tau }=180) and 590. The nonlinear estimator uses a linear estimator structure based on the linearised Navier–Stokes equations and explicitly calculates the nonlinear forcing from the estimated velocities in physical space. The goal is to use limited velocity measurements to predict the velocity field at other locations. We first use the velocities at one wall-normal height to estimate the velocities at other wall-normal heights. The estimation performance is compared among the nonlinear estimator, the linear estimator and the linear estimator augmented with eddy viscosity. At (Re_{tau }=180), the nonlinear estimator and the linear estimator augmented with eddy viscosity outperform the linear estimator in terms of estimating the velocity magnitudes, structures and energy transfer (production, dissipation and turbulent transport) across the channel height. The limitations of using measurement data at one wall-normal height are discussed. At (Re_{tau }=590), the nonlinear estimator does not work well with only one measurement plane, whereas the linear estimator augmented with eddy viscosity performs well. The performance of the nonlinear estimator and the linear estimator augmented with eddy viscosity at (Re_{tau }=590) is significantly enhanced by providing multiple measurement planes.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00162-025-00741-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143475112","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}

引用次数: 0

Experimentally informed, linear mean-field modelling of circular cylinder aeroacoustics

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-02-19 DOI: 10.1007/s00162-025-00739-z

Robin Prinja, Peter Jordan, Florent Margnat

{"title":"Experimentally informed, linear mean-field modelling of circular cylinder aeroacoustics","authors":"Robin Prinja, Peter Jordan, Florent Margnat","doi":"10.1007/s00162-025-00739-z","DOIUrl":"10.1007/s00162-025-00739-z","url":null,"abstract":"<div>A noise modelling approach is proposed for bluff body wakes such as flow over a cylinder, where the primary noise source comprises large-scale coherent structures such as the vortex shedding flow feature. This phenomenon leads to Aeolian tones in the far-field, and is inherent in wake flows across a range of Reynolds numbers (Re), from low-Re to high-Re turbulent flows. The approach employs linear global stability analysis on the time-averaged mean flow, with amplitude calibration through two-point statistics, and far-field noise calculations from the global mode fluctuations by Curle’s analogy. The overall approach is tested for flow over a cylinder at Reynolds numbers Re = 150 and 13,300. For Re = 150 flow, noise directivity calculations from the present approach agree with direct far-field computations. For Re = 13,300 flow, the mean flow is obtained by particle image velocimetry (PIV). The linear global mode for spanwise-homogeneous-type fluctuations is obtained at the main, lift fluctuation frequency. Calibration of this global mode involves time-resolved PIV data in the streamwise-spanwise plane, which is Fourier transformed in frequency-spanwise wavenumber space. The noise calculations for this global mode are then found to be less than 1 dB off from the microphone measurements.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446515","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}

引用次数: 0

Porous plates at incidence

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-02-12 DOI: 10.1007/s00162-025-00740-6

Chandan Bose, Callum Bruce, Ignazio Maria Viola

{"title":"Porous plates at incidence","authors":"Chandan Bose, Callum Bruce, Ignazio Maria Viola","doi":"10.1007/s00162-025-00740-6","DOIUrl":"10.1007/s00162-025-00740-6","url":null,"abstract":"<div>This paper investigates the effect of permeability on two-dimensional rectangular plates at incidences. The flow topology is investigated for Reynolds number (Re) values between 30 and 90, and the forces on the plate are discussed for (Re=30), where the wake is found to be steady for any value of the Darcy number (Da) and the flow incidence ((alpha )). At (Re=30), for a plate normal to the stream and vanishing Da, the wake shows a vortex dipole with a stagnation point on the plate surface. With increasing Da, the separation between the vortex dipole and the plate increases; the vortex dipole shortens and is eventually annihilated at a critical Da. For any value of Da below the critical one, the vortex dipole disappears with decreasing (alpha ). However, at low Da, the two saddle-node pairs merge at the same (alpha ), annihilating the dipole; while at high Da, they merge at different (alpha ), resulting in a single recirculating region for intermediate incidences. The magnitudes of lift, drag, and torque decrease with Da. Nevertheless, there exists a range of Da and (alpha ), where the magnitude of the plate-wise force component increases with Da, driven by the shear on the plate’s pressure side. Finally, the analysis of the fluid impulse suggests that the lift and drag reduction with Da are associated with the weakening of the leading and trailing edge shear layer, respectively. The present findings will be directly beneficial in understanding the role of permeability on small permeable bodies.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00162-025-00740-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143388771","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}

引用次数: 0

Performance investigations of the two-phase mixer for liquid metal magnetohydrodynamic generator

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-02-08 DOI: 10.1007/s00162-025-00738-0

Shaozheng Wang, Zhongtian Liu, Hulin Huang, Peng Lu

{"title":"Performance investigations of the two-phase mixer for liquid metal magnetohydrodynamic generator","authors":"Shaozheng Wang, Zhongtian Liu, Hulin Huang, Peng Lu","doi":"10.1007/s00162-025-00738-0","DOIUrl":"10.1007/s00162-025-00738-0","url":null,"abstract":"To efficiently utilize gas driving liquid metal for two-phase magnetohydrodynamic power generatior, a double-nozzle venturi mixer was proposed and the impact of mixer key dimensions, applied magnetic field and load factor on the mixing characteristics and power generation performance were investigated by adopting the VOF (volume of fluid) method in this paper. The results show that the velocity of liquid metal is greatly increased by the high-pressure gas in the mixer and the two-phase churn flow regime with lower two-phase slip ratio and higher uniformity, which represents a better mixing effect, can be found in the mixer with the smaller ratio of nozzle area to gas inlet area ((S_{textrm{n}}/S_{textrm{g}})) and the larger ratio of mixing chamber area to total inlet area ((S_{textrm{m}}/S_{textrm{i}})). In the range of this study, the output current, output power, and power generation efficiency of the LMMHD generator reach the maximum as (S_{textrm{n}}/S_{textrm{g}}=0.040) and (S_{textrm{m}}/S_{textrm{i}}=0.144). When the magnetic field is small, appropriately increasing it not only enhances the volume fraction of liquid metal in the power generation channel, but also upgrades the two-phase uniformity, which are beneficial to improve the output power (P_{textrm{wo}}) and power generation efficiency (eta ). However, the bigger magnetic field also leads to the uprising of two-phase slip ratio that makes the power generation performance be deteriorated.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143361672","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}

引用次数: 0

Active learning of data-assimilation closures using graph neural networks 基于图神经网络的数据同化闭包主动学习

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-01-14 DOI: 10.1007/s00162-025-00737-1

Michele Quattromini, Michele Alessandro Bucci, Stefania Cherubini, Onofrio Semeraro

{"title":"Active learning of data-assimilation closures using graph neural networks","authors":"Michele Quattromini, Michele Alessandro Bucci, Stefania Cherubini, Onofrio Semeraro","doi":"10.1007/s00162-025-00737-1","DOIUrl":"10.1007/s00162-025-00737-1","url":null,"abstract":"<div>The spread of machine learning techniques coupled with the availability of high-quality experimental and numerical data has significantly advanced numerous applications in fluid mechanics. Notable among these are the development of data assimilation and closure models for unsteady and turbulent flows employing neural networks (NN). Despite their widespread use, these methods often suffer from overfitting and typically require extensive datasets, particularly when not incorporating physical constraints. This becomes compelling in the context of numerical simulations, where, given the high computational costs, it is crucial to establish learning procedures that are effective even with a limited dataset. Here, we tackle those limitations by developing NN models capable of generalizing over unseen data in low-data limit by: (i) incorporating invariances into the NN model using a Graph Neural Networks (GNNs) architecture; and (ii) devising an adaptive strategy for the selection of the data utilized in the learning process. GNNs are particularly well-suited for numerical simulations involving unstructured domain discretization and we demonstrate their use by interfacing them with a Finite Elements (FEM) solver for the supervised learning of Reynolds-averaged Navier–Stokes equations. We consider as a test-case the data-assimilation of meanflows past generic bluff bodies, at different Reynolds numbers (50 le Re le 150), characterized by an unsteady dynamics. We show that the GNN models successfully predict the closure term; remarkably, these performances are achieved using a very limited dataset selected through an active learning process ensuring the generalization properties of the RANS closure term. The results suggest that GNN models trained through active learning procedures are a valid alternative to less flexible techniques such as convolutional NN. \u0000</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976430","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}

引用次数: 0

Simple shape model for normal shock trains in straight channels 直道中正常激波列的简单形状模型

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2025-01-13 DOI: 10.1007/s00162-025-00736-2

Fangyou Yu, Tinglong Huang, Hao Chen, Qifan Zhang, Lianjie Yue

{"title":"Simple shape model for normal shock trains in straight channels","authors":"Fangyou Yu, Tinglong Huang, Hao Chen, Qifan Zhang, Lianjie Yue","doi":"10.1007/s00162-025-00736-2","DOIUrl":"10.1007/s00162-025-00736-2","url":null,"abstract":"<div>Normal shock trains are a flow phenomenon of significance to ramjet engines, but it remains unclear what its structure is decided by and how it evolves with the incoming Mach number. To seek a theoretical explanation, the minimum entropy production principle is generalized to the quasi-steady behavior of normal shock trains in two-dimensional straight channels with uniform incoming flow. Numerical simulations are also performed to validate the model together with the data collected from public literature. The analysis suggests that the flow parameters of a normal shock train depend on the inviscid shock-shock interactions rather than the local boundary-layer separations, though the angles of two incident shocks should still be equal as similar to the case that complies with the free-interaction theory. The shock feet’s positions, meanwhile, are allowed to be coincident or not, free from the entropy restriction. This freedom of position explains why both symmetric and partially asymmetric normal shock trains could be found previously. Further theoretical calculations reveal the inclinations of two incident shocks increase first and then decrease with the incoming Mach number, peaking at 48.570 degrees when the Mach number reaches 1.753. It is also indicated that the Mach number range allowing for a normal shock train is 1.652 to 2.254, giving evidence for past observations.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976349","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}

引用次数: 0

A numerical procedure to study the stability of helical vortices 研究螺旋涡稳定性的数值方法

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2024-12-27 DOI: 10.1007/s00162-024-00734-w

Yonghui Xu, Ivan Delbende, Yuji Hattori, Maurice Rossi

{"title":"A numerical procedure to study the stability of helical vortices","authors":"Yonghui Xu, Ivan Delbende, Yuji Hattori, Maurice Rossi","doi":"10.1007/s00162-024-00734-w","DOIUrl":"10.1007/s00162-024-00734-w","url":null,"abstract":"<div>A numerical approach is proposed for the study of instabilities in helical vortex systems as found in the near-wake of turbines or propellers. The methodology has a high degree of generality, yet the present paper focusses on the case of one unique helical vortex. First, a method based on helical symmetry aimed at computing a three-dimensional base flow with prescribed parameters—helical pitch, helical radius, vortex circulation, core size and inner jet component—is presented. Second, the linear instability of this base flow is examined by reducing the three-dimensional instability problem to two-dimensional simulations with wavenumbers prescribed along the helix axis. Each simulation converges towards an exponentially growing or decaying complex state from which eigenfunctions, growth rate and frequency are extracted. This procedure is validated against a standard method based on direct three-dimensional numerical simulations of the Navier–Stokes equations linearized in the vicinity of the same helical base flows. Three illustrative base flows are presented with or without inner jet component, the instability of which is dominated, at the prescribed axial wavenumber, by unstable modes of three different types: long-wave instability, short-wave elliptic and curvature instabilities. Results from the new procedure and from the fully three-dimensional one are found in excellent agreement, which validates the new methodology. The gain in computational time is typically the one that is achieved while going from three-dimensional to two-dimensional simulations.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890413","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}

引用次数: 0

Analytical solutions for particle dispersion in Taylor–Green vortex flows Taylor-Green涡旋流动中粒子弥散的解析解

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2024-12-24 DOI: 10.1007/s00162-024-00731-z

Yuval Dagan

引用次数: 0

Input–output study of mode-frequency characteristics in a low-speed axial compressor 低速轴流压气机模态-频率特性的输入输出研究

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2024-12-16 DOI: 10.1007/s00162-024-00733-x

Jiahao Hu, Ruize Xu, Dengke Xu, Xu Dong, Dakun Sun, Xiaofeng Sun

{"title":"Input–output study of mode-frequency characteristics in a low-speed axial compressor","authors":"Jiahao Hu, Ruize Xu, Dengke Xu, Xu Dong, Dakun Sun, Xiaofeng Sun","doi":"10.1007/s00162-024-00733-x","DOIUrl":"10.1007/s00162-024-00733-x","url":null,"abstract":"The dynamic characteristics of mode behavior in a low-speed, single-stage axial compressor are crucial for studying linear stall inception. An input–output analysis framework has been established, enabling the introduction of forcing into the compressor system and identifying the most energetic mode. Both standard and compressed input–output analysis are conducted to explore sensitive forcing positions and flow variables, with opposition control employed to suppress energy gain. As throttling progresses, a shift in high energy gain distribution from high-order to first-order circumferential modes is observed, with two distinct branches emerging across the domain of circumferential mode numbers and forcing frequencies. Compressed input–output analysis shows that limiting the forcing range to the shroud, from the inlet to the rotor blade section, is sufficient to excite the energetic mode in the current cases. Subsequently, opposition control is applied at the shroud to suppress energy amplification and modulate stall propensity within these two distinct branches. The results reveal that axial velocity control reduces energy amplification and suppresses perturbation modes related to stall inception. A comprehensive assessment of componentwise energy amplification is conducted, considering various variable forcing. The predicted results indicate that velocity perturbations are the predominant factors influencing the resolvent mode distribution pattern. Moreover, opposition control significantly impacts the critical branch associated with stall inception.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142826153","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}

引用次数: 0

Fully convolutional networks for velocity-field predictions based on the wall heat flux in turbulent boundary layers 基于紊流边界层壁面热流的速度场预测的全卷积网络

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2024-12-16 DOI: 10.1007/s00162-024-00732-y

Luca Guastoni, Arivazhagan G. Balasubramanian, Firoozeh Foroozan, Alejandro Güemes, Andrea Ianiro, Stefano Discetti, Philipp Schlatter, Hossein Azizpour, Ricardo Vinuesa

{"title":"Fully convolutional networks for velocity-field predictions based on the wall heat flux in turbulent boundary layers","authors":"Luca Guastoni, Arivazhagan G. Balasubramanian, Firoozeh Foroozan, Alejandro Güemes, Andrea Ianiro, Stefano Discetti, Philipp Schlatter, Hossein Azizpour, Ricardo Vinuesa","doi":"10.1007/s00162-024-00732-y","DOIUrl":"10.1007/s00162-024-00732-y","url":null,"abstract":"<div>Fully-convolutional neural networks (FCN) were proven to be effective for predicting the instantaneous state of a fully-developed turbulent flow at different wall-normal locations using quantities measured at the wall. In Guastoni et al. (J Fluid Mech 928:A27, 2021. https://doi.org/10.1017/jfm.2021.812), we focused on wall-shear-stress distributions as input, which are difficult to measure in experiments. In order to overcome this limitation, we introduce a model that can take as input the heat-flux field at the wall from a passive scalar. Four different Prandtl numbers (Pr = nu /alpha = (1,2,4,6)) are considered (where (nu ) is the kinematic viscosity and (alpha ) is the thermal diffusivity of the scalar quantity). A turbulent boundary layer is simulated since accurate heat-flux measurements can be performed in experimental settings: first we train the network on aptly-modified DNS data and then we fine-tune it on the experimental data. Finally, we test our network on experimental data sampled in a water tunnel. These predictions represent the first application of transfer learning on experimental data of neural networks trained on simulations. This paves the way for the implementation of a non-intrusive sensing approach for the flow in practical applications.</div>","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"39 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00162-024-00732-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845070","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}

引用次数: 0