Theoretical and Computational Fluid Dynamics最新文献_第7页

Aerodynamic and aeroacoustic performance of a pitching foil with trailing edge serrations at a high Reynolds number 带后缘锯齿的俯仰箔在高雷诺数下的气动和气声性能

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-10-09 DOI: 10.1007/s00162-023-00677-8

Xueyu Ji, Li Wang, Sridhar Ravi, John Young, Joseph C. S. Lai, Fang-Bao Tian

{"title":"Aerodynamic and aeroacoustic performance of a pitching foil with trailing edge serrations at a high Reynolds number","authors":"Xueyu Ji, Li Wang, Sridhar Ravi, John Young, Joseph C. S. Lai, Fang-Bao Tian","doi":"10.1007/s00162-023-00677-8","DOIUrl":"10.1007/s00162-023-00677-8","url":null,"abstract":"The aerodynamic and aeroacoustic performance of a low-aspect-ratio ((hbox {AR}=0.2)) pitching foil during dynamic stall are investigated numerically with focus on the effects of trailing edge serrations. A hybrid method coupling an immersed boundary method for incompressible flows with the Ffowcs Williams–Hawkings acoustic analogy is employed. Large eddy simulation and turbulent boundary layer equation wall model are also employed to capture the turbulent effects. A modified NACA0012 foil with a rectangular trailing edge flap attached to the trailing edge (baseline case) undergoing pitching motion is considered. Trailing edge serrations are applied to the trailing edge flap and their effects on the aerodynamic and aeroacoustic performance of the oscillating airfoil are considered by varying the wave amplitude ((2h^*= 0.05, 0.1), and 0.2) at a Reynolds number of 100,000 and a Mach number of 0.05. It is found that the reduction of the sound pressure level at the dimensionless frequency band (St_{b}in [1.25,4]) can be over 4 dB with the presence of the trailing edge serrations ((2h^*=0.1)), while the aerodynamic performance and its fluctuations are not significantly altered except a reduction around 10% in the negative moment coefficient and it fluctuations. This is due to the reduction of the average spanwise coherence function and the average surface pressure with respect to that of the baseline case, suggesting the reduction of the spanwise coherence and the noise source may result in the noise reduction. Analysis of the topology of the near wake coherent structure for (2h^*=0.1) reveals that the alignment of the streamwise-oriented vortex with the serration edge may reduce the surface pressure fluctuation.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"38 6","pages":"825 - 844"},"PeriodicalIF":2.2,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00162-023-00677-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135093791","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

Galerkin spectral estimation of vortex-dominated wake flows 旋涡主导尾流的伽辽金谱估计

IF 2.2 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-08-07 DOI: 10.1007/s00162-023-00670-1

Katherine J. Asztalos, Abdulrahman Almashjary, Scott T. M. Dawson

{"title":"Galerkin spectral estimation of vortex-dominated wake flows","authors":"Katherine J. Asztalos, Abdulrahman Almashjary, Scott T. M. Dawson","doi":"10.1007/s00162-023-00670-1","DOIUrl":"10.1007/s00162-023-00670-1","url":null,"abstract":"We propose a technique for performing spectral (in time) analysis of spatially-resolved flowfield data, without needing any temporal resolution or information. This is achieved by combining projection-based reduced-order modeling with spectral proper orthogonal decomposition. In this method, space-only proper orthogonal decomposition is first performed on velocity data to identify a subspace onto which the known equations of motion are projected, following standard Galerkin projection techniques. The resulting reduced-order model is then utilized to generate time-resolved trajectories of data. Spectral proper orthogonal decomposition (SPOD) is then applied to this model-generated data to obtain a prediction of the spectral content of the system, while predicted SPOD modes can be obtained by lifting back to the original velocity field domain. This method is first demonstrated on a forced, randomly generated linear system, before being applied to study and reconstruct the spectral content of two-dimensional flow over two collinear flat plates perpendicular to an oncoming flow. At the range of Reynolds numbers considered, this configuration features an unsteady wake characterized by the formation and interaction of vortical structures in the wake. Depending on the Reynolds number, the wake can be periodic or feature broadband behavior, making it an insightful test case to assess the performance of the proposed method. In particular, we show that this method can accurately recover the spectral content of periodic, quasi-periodic, and broadband flows without utilizing any temporal information in the original data. To emphasize that temporal resolution is not required, we show that the predictive accuracy of the proposed method is robust to using temporally-subsampled data.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"38 6","pages":"801 - 823"},"PeriodicalIF":2.2,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44195277","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

Shock stand-off distances over sharp wedges for thermally non-equilibrium dissociating nitrogen flows 热非平衡解离氮流的尖锐楔形激波隔离距离

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-07-29 DOI: 10.1007/s00162-023-00669-8

U. Yildiz, D. Vatansever, B. Celik

{"title":"Shock stand-off distances over sharp wedges for thermally non-equilibrium dissociating nitrogen flows","authors":"U. Yildiz, D. Vatansever, B. Celik","doi":"10.1007/s00162-023-00669-8","DOIUrl":"10.1007/s00162-023-00669-8","url":null,"abstract":"In this study, shock stand-off distances for thermally and chemically non-equilibrium flows of nitrogen over wedges are computationally investigated via a hypersonic computational fluid dynamics solver, hyperReactingFoam by spanning a parameter space that consists of ranges of Mach number, 4–10, specific heat ratio, 1.40–1.61 and wedge angles, 60(^circ )–90(^circ ). Then, the space is reduced into the parameters of inverse density ratio across the shock and dimensionless wedge angle which will be used as variables for quadratic functions that represent shock stand-off distances. Besides the functions of shock stand-off distances, detached shock profiles of computationally modeled flows are represented by parabolic equations. The flows are observed to be chemically frozen for Mach number ranges of 4–5 regardless of the specific heat ratio value of the nitrogen mixture. Our results show that the shock stand-off distance decreases as Mach number is increased from 4 to 7, if the wedge angle and free-stream specific heat ratio are kept the same. On the other hand, if Mach number is increased beyond 7, the shock stand-off distance starts to extend due to the dissociation of nitrogen molecules behind the shock wave. At Mach 10, nitrogen completely dissociates over 90(^circ ) wedge for all specific heat ratios considered in the present study. Increased leading edge angle of the wedge or specific heat ratio of free-stream yields longer shock stand-off distance.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 6","pages":"799 - 821"},"PeriodicalIF":3.4,"publicationDate":"2023-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44093250","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

Interaction between depth variation and turbulent diffusion in depth-averaged vorticity equations 深度平均涡度方程中深度变化与湍流扩散的相互作用

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-07-21 DOI: 10.1007/s00162-023-00665-y

Balázs Sándor, Péter Torma, K. Gábor Szabó, Tamás Kalmár-Nagy

引用次数: 0

Faster flicker of buoyant diffusion flames by weakly rotatory flows 弱旋转流引起的浮力扩散火焰的更快闪烁

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-07-18 DOI: 10.1007/s00162-023-00671-0

Tao Yang, Peng Zhang

{"title":"Faster flicker of buoyant diffusion flames by weakly rotatory flows","authors":"Tao Yang, Peng Zhang","doi":"10.1007/s00162-023-00671-0","DOIUrl":"10.1007/s00162-023-00671-0","url":null,"abstract":"Flickering buoyant diffusion methane flames in weakly rotatory flows were computationally and theoretically investigated. The prominent computational finding is that the flicker frequency nonlinearly increases with the nondimensional rotational intensity R (up to 0.24), which is proportional to the nondimensional circumferential circulation. This finding is consistent with the previous experimental observations that rotatory flows enhance flame flicker to a certain extent. Based on the vortex-dynamical understanding of flickering flames that the flame flicker is caused by the periodic shedding of buoyancy-induced toroidal vortices, a scaling theory is formulated for flickering buoyant diffusion flames in weakly rotatory flows. The theory predicts that the increase of flicker frequency f obeys the scaling relation (left( f-f_{0} right) propto R^{2}), which agrees very well with the present computational results. In physics, the external rotatory flow enhances the radial pressure gradient around the flame, and the significant baroclinic effect (mathrm {nabla }ptimes mathrm {nabla }rho ) contributes an additional source for the growth of toroidal vortices so that their periodic shedding is faster.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 6","pages":"781 - 798"},"PeriodicalIF":3.4,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45671843","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: 3

Wind tunnel effects on gust-interaction simulations 风-相互作用模拟中的风洞效应

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-07-16 DOI: 10.1007/s00162-023-00668-9

Diederik Beckers, Jeff D. Eldredge

{"title":"Wind tunnel effects on gust-interaction simulations","authors":"Diederik Beckers, Jeff D. Eldredge","doi":"10.1007/s00162-023-00668-9","DOIUrl":"10.1007/s00162-023-00668-9","url":null,"abstract":"Large-amplitude flow disturbances, or gusts, can drastically alter the aerodynamic forces on an airfoil and are regularly investigated through wind tunnel (or water tunnel) experiments. The gusts generated in those experiments are often further analyzed using numerical simulations, but usually without fully accounting for the wind tunnel walls or gust generator. The current work investigates the wind tunnel effects on the predicted lift response and flow field using a computational framework that models the viscous flow around the airfoil but treats the tunnel walls and gust generation as inviscid boundary conditions. We apply this model to three examples and compare the predicted gust response with the responses predicted by a free-space viscous model and a classical unsteady aerodynamics model to highlight the wind tunnel effects. We find that the wind tunnel modeling introduces non-negligible effects depending on the airfoil and gust configurations. These effects include the confinement effect of the wind tunnel walls and the triggering of flow separation when it does not occur in the corresponding free-space model. In the last example, we also note that this virtual counterpart of an actual wind tunnel can be paired with experiments through data assimilation to increase the accuracy of the gust response or perform parameter estimation.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 4","pages":"533 - 548"},"PeriodicalIF":3.4,"publicationDate":"2023-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4651002","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 framework for linear stability analysis of two-phase stratified pipe flows 两相分层管流线性稳定性分析的数值框架

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-07-13 DOI: 10.1007/s00162-023-00667-w

Ilya Barmak, Alexander Gelfgat, Neima Brauner

{"title":"A numerical framework for linear stability analysis of two-phase stratified pipe flows","authors":"Ilya Barmak, Alexander Gelfgat, Neima Brauner","doi":"10.1007/s00162-023-00667-w","DOIUrl":"10.1007/s00162-023-00667-w","url":null,"abstract":"A numerical framework for rigorous linear stability analysis of two-phase stratified flows of two immiscible fluids in horizontal circular pipes is presented. For the first time, three-dimensional disturbances, including those at the interface between two fluids, are considered. The proposed numerical framework is based on a finite volume method and allows solving the problem numerically in bipolar cylindrical coordinates. In these coordinates, both the pipe wall and the unperturbed interface (of a constant curvature, e.g., plane interface, as considered in this work) coincide with the coordinate surfaces. Thereby, the no-slip as well as the interfacial boundary conditions can be imposed easily. It also enables investigation of the local behavior of the flow field and shear stresses in the vicinity of the triple points, where the interface contacts the pipe wall. The results obtained in the bipolar coordinates are verified by an independent numerical solution based on the problem formulation in Cartesian coordinates, where the pipe wall is treated by the immersed boundary method. Two representative examples of gas–liquid and liquid–liquid flows are included to demonstrate the applicability of the proposed numerical technique for analyzing the flow stability.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 5","pages":"559 - 587"},"PeriodicalIF":3.4,"publicationDate":"2023-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42608436","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

Vortex interactions of two burst-and-coast swimmers in a side-by-side arrangement 两个冲岸游泳者并排排列的涡旋相互作用

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-06-24 DOI: 10.1007/s00162-023-00664-z

Li-Ming Chao, Amneet Pal Singh Bhalla, Liang Li

引用次数: 0

Effects of wavelength on vortex structure and turbulence kinetic energy transfer of flow over undulated cylinders 波长对波动圆柱上流动涡流结构和湍流动能传递的影响

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-06-18 DOI: 10.1007/s00162-023-00661-2

Kathleen Lyons, Raúl Bayoán Cal, Jennifer A. Franck

{"title":"Effects of wavelength on vortex structure and turbulence kinetic energy transfer of flow over undulated cylinders","authors":"Kathleen Lyons, Raúl Bayoán Cal, Jennifer A. Franck","doi":"10.1007/s00162-023-00661-2","DOIUrl":"10.1007/s00162-023-00661-2","url":null,"abstract":"Passive flow control is commonly used on bluff bodies for drag and oscillating lift reduction across a range of engineering applications. This research explores a spanwise undulated cylinder inspired by seal whiskers that is shown to reduce hydrodynamic forces when compared to smooth cylinders. Although the fluid flow over this complex geometry has been documented experimentally and computationally, investigations surrounding geometric modifications to the undulation topography have been limited, and fluid mechanisms by which force reduction is induced have not been fully examined. Five variations of undulation wavelength are simulated at Reynolds number (text {Re}=250) and compared with results from a smooth elliptical cylinder. Vortex structures and turbulence kinetic energy (TKE) transfer in the wake are analyzed to explain how undulation wavelength affects force reduction. Modifications to the undulation wavelength generate a variety of flow patterns including alternating vortex rollers and hairpin vortices. Maximum force reduction is observed at wavelengths that are large enough to allow hairpin vortices to develop without intersecting each other and small enough to prevent the generation of additional alternating flow structures. The differences in flow structures modify the magnitude and location of TKE production and dissipation due to changes in mean and fluctuating strain. Decreased TKE production and increased dissipation in the near wake result in overall lower TKE and force reduction. Understanding the flow physics linking geometry to force reduction will guide appropriate parameter selection in bio-inspired design applications.\u0000","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 4","pages":"485 - 504"},"PeriodicalIF":3.4,"publicationDate":"2023-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4725044","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: 2

Design of optimal wing maneuvers in a transverse gust encounter through iterated simulation or experiment 通过反复模拟或实验设计横向阵风遭遇时的最佳机翼机动

IF 3.4 3区工程技术

Theoretical and Computational Fluid Dynamics Pub Date : 2023-06-15 DOI: 10.1007/s00162-023-00659-w

Xianzhang Xu, Antonios Gementzopoulos, Girguis Sedky, Anya R. Jones, Francis D. Lagor

{"title":"Design of optimal wing maneuvers in a transverse gust encounter through iterated simulation or experiment","authors":"Xianzhang Xu, Antonios Gementzopoulos, Girguis Sedky, Anya R. Jones, Francis D. Lagor","doi":"10.1007/s00162-023-00659-w","DOIUrl":"10.1007/s00162-023-00659-w","url":null,"abstract":"Wing–gust encounters cause harmful lift transients that can be mitigated through maneuvering of the wing. This paper presents a method to generate an open-loop (i.e., prescribed) maneuver that optimally regulates the lift on the wing during a transverse gust encounter. Obtaining an optimal maneuver is important for laboratory experiments on the physics of wing–gust interactions and may be useful for the future design of feedback controllers. Prior work of the authors has shown that an Iterative Maneuver Optimization (IMO) framework can generate an optimal maneuver by using a surrogate model to propose a control signal that is then tested in experiment or high-fidelity simulation. The input to the surrogate model is updated to account for differences between the test data and the expected output. The optimal maneuver is obtained through iteration of this process. This paper simplifies the IMO method by replacing the surrogate model with the classical lift model of Theodorsen, removing the process of optimization over the surrogate model, and removing the requirement to know the time-averaged profile of the gust. The proposed method, referred to as Simplified IMO (SIMO), only requires input and output data collected from simulations or experiments that interact with the gust. Numerical simulations using a Leading Edge Suction Parameter modulated Discrete Vortex Model are presented to generate the input and output data of the wing–gust encounters for this paper. Experiments in a towing tank also validated the SIMO method. The results show an optimal pitch maneuver and an optimal plunge maneuver that can each regulate lift during a transverse gust encounter.","PeriodicalId":795,"journal":{"name":"Theoretical and Computational Fluid Dynamics","volume":"37 4","pages":"465 - 484"},"PeriodicalIF":3.4,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00162-023-00659-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4903585","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