Volume 2: Computational Fluid Dynamics最新文献_第5页

Optimal Design for Impeller of a Sludge Pump Using Design of Experiment 用实验设计法对污泥泵叶轮进行优化设计

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5299

Jeong-Min Jin, H. Ji, Youn-J. Kim

引用次数: 0

Computational Studies of Droplet Motion Near a Rough Surface via 3D Spectral Boundary Elements 粗糙表面附近液滴运动的三维光谱边界元计算研究

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5137

Yechun Wang, Xinnan Wang

{"title":"Computational Studies of Droplet Motion Near a Rough Surface via 3D Spectral Boundary Elements","authors":"Yechun Wang, Xinnan Wang","doi":"10.1115/ajkfluids2019-5137","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5137","url":null,"abstract":"\u0000 A plethora of studies have investigated the motion of a liquid droplet in the vicinity of a smooth surface, incurred by shear flow, parabolic flow or gravity. However, there are few studies that consider the roughness of the surface that could affect the droplet motion. In this study, we employ a 3D spectral boundary element method for interfacial dynamics to examine the droplet translation, migration, and deformation in the vicinity of a rough surface due to shear flow. The roughness feature of the surface is comparable to the size of the droplet and is simulated with sinusoidal functions. Topologies of epoxy coating surfaces are also considered in the computations. The roughness and profile of the coating surface is obtained by atomic force microscopy. The computational results show that the surface roughness affects significantly the behavior of a deformable droplet near the surface, including its deformation and migration speed. In return, the dynamics of the droplet also influences the stress distribution on the rough surface. The results of this study could provide theoretical foundation in the prediction of particle induced erosion corrosion of organic coatings.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114673568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Numerical Study of Heat Transfer in a Row of Cylinders by 2D Large Eddy Simulation 二维大涡模拟圆柱排传热的数值研究

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5414

Andreas Stengaard Thorstensen, A. Krogh, B. Dueholm, Sebastian Bækkel Højte, Signe Birkebæk Thomasen, A. Jensen, H. Sørensen, J. Hærvig

{"title":"Numerical Study of Heat Transfer in a Row of Cylinders by 2D Large Eddy Simulation","authors":"Andreas Stengaard Thorstensen, A. Krogh, B. Dueholm, Sebastian Bækkel Højte, Signe Birkebæk Thomasen, A. Jensen, H. Sørensen, J. Hærvig","doi":"10.1115/ajkfluids2019-5414","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5414","url":null,"abstract":"\u0000 Complex flow structures arise as fluids are forced to flow across cylinder rows at moderate Reynolds numbers. In this study a numerical heat transfer analysis of 12 cylinders in an inline configuration is performed using Large Eddy Simulation (LES). The LES is conducted to get a better understanding of changes in the time averaged Nusselt number, 〈Nu〉, and local time averaged Nusselt number, 〈Nuθ〉, for each cylinder in the cylinder row. The simulations are performed at Re = UD/v = 10,000 and Pr = 0.71 with isothermal cylinders and a constant and uniform inflow temperature.\u0000 The results show that the time averaged Nusselt number increases slightly between the first and second cylinder due to increased turbulent velocity fluctuations. Beyond the second cylinder, the time averaged Nusselt number decreases until it reaches a near constant value after the fifth cylinder. For all 12 cylinders the local time averaged Nusselt number around the surface is highest at the stagnation point. The first cylinder in the row has the same distribution as the reference simulation conducted for a single cylinder. From the second cylinder and onwards a larger part of the overall heat transfer is in the spanwise direction compared to the first- and reference cylinder.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131815771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Numerical Simulation and Neural Network Study Using an Upstream Cylinder for Flow Control of an Airfoil 采用上游柱体进行翼型流动控制的数值模拟与神经网络研究

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-4724

Meihua Zhang, Z. Zheng, Yangliu Liu, Xiaoyu Jiang

{"title":"Numerical Simulation and Neural Network Study Using an Upstream Cylinder for Flow Control of an Airfoil","authors":"Meihua Zhang, Z. Zheng, Yangliu Liu, Xiaoyu Jiang","doi":"10.1115/ajkfluids2019-4724","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4724","url":null,"abstract":"\u0000 Flow behaviors of a downstream object can be affected significantly by an upstream object in close proximity. This concept is used for flow control in this study to maximize the lift/drag ratio on a NACA0012 airfoil. A cylinder with cross-flow translational motion is placed upstream of the airfoil. Numerical simulations are carried out with an immersed-boundary method to solve the incompressible, viscous flow at the Reynolds number of 2000. Control parameters that influence the dynamics of flow around the airfoil are systematically investigated, including the oscillating frequency and amplitude of the upstream cylinder, the distances between the cylinder and the airfoil, and the diameter of the cylinder. To obtain sample data properly and efficiently for carrying out the neural network study, the idea of the orthogonal test method is used to set the control parameters in the numerical simulation. The combination of the back-propagation neural network algorithm and the genetic algorithm is applied to find the optimal value of the lift/drag ratio and the corresponding control parameters. The results show that when the cylinder oscillating frequency increases, the ratio increases until negative coefficients occur; when the distance between the cylinder and the airfoil increases or the amplitude of oscillating cylinder increases, the ratio decreases first and then increases; and when the cylinder diameter increases, the ratio increases. Compared to the reference case, the optimized lift/drag ratio increases 178%.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131065846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Numerical Analysis of Steady Blowing Based Active Flow Control for Flow Over Ahmed Body 基于定常吹气的艾哈迈德体流动主动控制数值分析

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5239

Bansal Shah, D. Basu

引用次数: 0

Thermo-Fluid Dynamic Design Exploration of a Double Pipe Heat Exchanger 双管换热器热流体动力学设计探索

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-4998

T. Hirano, Mitsuo Yoshimura, K. Shimoyama, A. Komiya

{"title":"Thermo-Fluid Dynamic Design Exploration of a Double Pipe Heat Exchanger","authors":"T. Hirano, Mitsuo Yoshimura, K. Shimoyama, A. Komiya","doi":"10.1115/ajkfluids2019-4998","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4998","url":null,"abstract":"\u0000 Toward a practical application of the additive manufacturing (AM), this study proposes a shape optimization approach for the cross-sectional shape of the inner pipe of a counter-flow double pipe heat exchanger. The cross-sectional shape of the inner pipe is expressed by an algebraic expression with a small number of parameters, and their heat transfer performance is evaluated by a commercial Computational Fluid Dynamics (CFD) solver. The optimization is conducted by the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) assisted by the Kriging surrogate model, and the NSGA-II finds the optimal cross-sectional shape with many protrusions around the perimeter of the inner channel to improve the heat transfer performance. In this study, heat transfer performance is evaluated from the temperature drop at the outlet of the high-temperature fluid. Through the comparison of two cross-sectional shapes with the same heat transfer surface area — average temperature at the outlet of the optimal high-temperature channel is 324.58 K while average temperature at the outlet of a circular high-temperature channel with the same area as the optimal channel is 331.93 K, it is revealed that the number of protrusions plays important roles which contribute not only to increase heat transfer area but also to improve heat transfer performance.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116343634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Turbulent Channel Flow With a Modified k-ω Turbulence Model for High-Order Finite Element Methods 高阶有限元方法中修正k-ω湍流模型的湍流通道流动

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5501

Nojan Bagheri-Sadeghi, B. Helenbrook, K. Visser

{"title":"Turbulent Channel Flow With a Modified k-ω Turbulence Model for High-Order Finite Element Methods","authors":"Nojan Bagheri-Sadeghi, B. Helenbrook, K. Visser","doi":"10.1115/ajkfluids2019-5501","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5501","url":null,"abstract":"\u0000 One-dimensional fully developed channel flow was solved using a modified k–ω turbulence model that was recently proposed for use with high-order finite element schemes. In order to study this new turbulence model’s behavior, determine its dependence on boundary conditions and model constants, and find efficient methods for obtaining solutions, the model was first examined using a linear finite element discretization in 1D. The results showed that an accurate estimate of the parameter εk which is used to define k in terms of the working variable k~ is essential to get an accurate solution. Also, the turbulence model depended sensitively on an accurate estimate of the distance of the first grid point from the wall, which can be difficult to estimate in unstructured grids. This is used for the boundary condition of specific dissipation rate on the wall. This model was then implemented in a high-order finite element code that uses an unstructured mesh of triangles to verify that the 1D results were predictive of the behavior of the full 2D discretization. High-order 2D results were obtained on triangular meshes with element aspect ratios up to 250000.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126901206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Flutter Study on High Speed Train External Windshield by a Tight Coupling Method 高速列车外挡风玻璃颤振的紧密耦合研究

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5422

Q. Jiang, Guannan Zheng, Guilin Zhao

{"title":"Flutter Study on High Speed Train External Windshield by a Tight Coupling Method","authors":"Q. Jiang, Guannan Zheng, Guilin Zhao","doi":"10.1115/ajkfluids2019-5422","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5422","url":null,"abstract":"\u0000 Flutter is a complex problem caused by the interaction between the elastic structure and the flow field around that. In this paper a study of flutter on high speed train external windshield is presented.\u0000 Here, a coupling scheme of computational fluid dynamics (CFD) and computational structure dynamics (CSD) is applied to simulate the flutter problems. Specifically, some key technologies like tight coupling method, information transfer and mesh deformation strategy are involved. Repeatedly exchanging information in the sub-iteration of physical time step is basically typical of tight coupling method, which is a second-order accuracy method. This flutter methodology has been applied for standard model AGARD 445.6 wing and other engineering examples, with lots of excellent results obtained.\u0000 In this high speed train external windshield flutter research, eight train speed conditions are chosen to simulate the flutter issue, including 250km/h, 300km/h, 350km/h, 400 km/h, 450 km/h, 500 km/h, 550 km/h and 600 km/h. As for structural model, the first 30 order modes of elastic windshield are taken into consideration for CFD/CSD coupling simulation. In addition, it is defined to be the flutter boundary once the generalized displacement curve performing as persistent oscillation, which is the critical stable state for the vibration of external windshield. According to the research, under a specific train speed condition, adjustment of modal eigenfrequency can lead to the change of vibration stability. Furthermore, it is found that there is a positive correlation between train speed and modal eigenfrequency. So the optimal windshield scheme under different operating speeds is proposed that in order for the convergent vibration, a measure of changing eigenfrequency can be taken to ensure the vibration convergent and flutter cannot occur.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115125290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Uncertainty Quantification of Molten Hafnium Infusion Into a B4C Packed-Bed 熔融铪注入B4C填充床的不确定度定量

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5281

A. Schiaffino, V. Kotteda, Vinod Kumar, A. Bronson, Sanjay Shantha-Kumar

{"title":"Uncertainty Quantification of Molten Hafnium Infusion Into a B4C Packed-Bed","authors":"A. Schiaffino, V. Kotteda, Vinod Kumar, A. Bronson, Sanjay Shantha-Kumar","doi":"10.1115/ajkfluids2019-5281","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5281","url":null,"abstract":"\u0000 In the manufacturing of metal matrix composites (MMC), liquid-metal reactive infusion with a solid mesh or particles composed of ceramic or metal may be used. The objective of this study is to determine the uncertainty quantification of the modeling of liquid hafnium infusion to expedite the processing and improve properties of MMCs ultimately. Uncertainty quantification (UQ) characterized the uncertainty scientifically especially for high-performance computing with observed physics and/or chemistry of the phenomena and predicted from estimated parameters. In this work, molten hafnium infusing through a boron carbide packed bed is modeled to optimize the manufacturing of components used for a hypersonic vehicle. The creation of molten matrix composites by the infiltration of molten metal represents a formidable challenge to be accurately modeled. First, the structural randomness associated with porous mediums complicates the prediction of the flow passing through it. Secondly, the properties of the molten metal could vary inside our control volume, since the temperature inside the control volume is not constant. Also, there are several chemical reactions and solidification rates occurring in during the impregnation. Given the recent advances in high-performance computing, an in-house pore network simulator are implemented along with Dakota, an open-source, exascale software, to determine the optimal parameters (e.g., porosity and temperature) and uncertainty quantification for the modeling.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124871635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Comprehensive Study of Asymmetric Micro-Droplet Splitting in T-Junction t型结中微液滴不对称分裂的综合研究

Volume 2: Computational Fluid Dynamics Pub Date : 2019-07-28 DOI: 10.1115/ajkfluids2019-5284

W. Cheng, R. Sadr, Arum Han

{"title":"A Comprehensive Study of Asymmetric Micro-Droplet Splitting in T-Junction","authors":"W. Cheng, R. Sadr, Arum Han","doi":"10.1115/ajkfluids2019-5284","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5284","url":null,"abstract":"\u0000 Splitting a single droplet into two unequal portions using a microfluidic T-junction has been an important functional feature of many modern lab-on-a-chip devices. A recent study introduced a general criterion for asymmetric droplet break-up in the range of intermediate Capillary numbers. The current work attempts to analyze, in more details, the different underlying mechanisms governing the asymmetric break-up process. In particular, this work focuses on the relationship between the break-up mechanism versus the splitting ratio of the daughter droplets. CFD simulation is used to closely monitor the effect of different fluid properties on the evolution of droplet break-up process. The splitting ratio under different flow conditions is characterized. Four mechanisms for primary droplet break-up are defined as follows: break-up with permanent obstruction, unstable break-up, breakup with tunnels and non-breakup. In particular, the main focus of this study is on the unstable break-up mechanisms where is very likely results to a much-deviated splitting ratio. Typically, yet unexpectedly, the resulting splitting ratio is often larger than the pressure gradient ratio in the T-junction. However, the two ratios are approximately equals to each other under a limited set of flow conditions. It has been observed that the splitting ratio could be more than double the pressure gradient ratio of the T-junction. The break-up is observed to be in the permanent obstruction mode if the splitting ratio is about the same magnitude as the pressure gradient ratio. The effects of the T-junction geometry on the break-up will also be examined.","PeriodicalId":346736,"journal":{"name":"Volume 2: Computational Fluid Dynamics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129651397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0