arXiv: Fluid Dynamics最新文献_第8页

Recirculation regions in wakes with base bleed 有底出血的尾迹中的再循环区域

arXiv: Fluid Dynamics Pub Date : 2020-08-19 DOI: 10.1103/PHYSREVFLUIDS.6.034608

K. Steiros, Nikolaos Bempedelis, Liuyang Ding

引用次数: 4

Nonaxisymmetric flow characteristics in head-on collision of spinning droplets 旋转液滴正面碰撞的非轴对称流动特性

arXiv: Fluid Dynamics Pub Date : 2020-08-19 DOI: 10.1103/physrevfluids.5.113601

Chengming He, Peng Zhang

{"title":"Nonaxisymmetric flow characteristics in head-on collision of spinning droplets","authors":"Chengming He, Peng Zhang","doi":"10.1103/physrevfluids.5.113601","DOIUrl":"https://doi.org/10.1103/physrevfluids.5.113601","url":null,"abstract":"Effects of spinning motion on the bouncing and coalescence between a spinning droplet and a non-spinning droplet undergoing the head-on collision were numerically studied by using a Volume-of-Fluid method. A prominent discovery is that the spinning droplet can induce significant non-axisymmetric flow features for the head-on collision of equal-size droplets composed of the same liquid. Specifically, a non-axisymmetric bouncing was observed, and it is caused by the conversion of the spinning angular momentum into the orbital angular momentum. This process is accompanied by the rotational kinetic energy loss due to the interaction between the rotational and radial flows of the droplets. A non-axisymmetric internal flow and a delayed separation after temporary coalescence were also observed, and they are caused by the enhanced interface oscillation and internal-flow-induced viscous dissipation. The spinning motion can also promote the mass interminglement of droplets because the locally non-uniform mass exchange occurs at the early collision stage by non-axisymmetric flow and is further stretched along the filament at later collision stages. In addition, it is found that the non-axisymmetric flow features increase with increasing the orthogonality of the initial translational motion and the spinning motion of droplets.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133276273","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: 5

The role of the “monopole” instability in the evolution of two-dimensional turbulent free shear layers “单极子”不稳定性在二维湍流自由剪切层演化中的作用

arXiv: Fluid Dynamics Pub Date : 2020-08-15 DOI: 10.1063/5.0025838

S. Suryanarayanan, G. Brown, R. Narasimha

{"title":"The role of the “monopole” instability in the evolution of two-dimensional turbulent free shear layers","authors":"S. Suryanarayanan, G. Brown, R. Narasimha","doi":"10.1063/5.0025838","DOIUrl":"https://doi.org/10.1063/5.0025838","url":null,"abstract":"The role of instability in the growth of a 2D, temporally evolving, `turbulent' free shear layer is analyzed using vortex-gas simulations that condense all dynamics into the kinematics of the Biot-Savart relation. The initial evolution of perturbations in a constant-vorticity layer is found to be in accurate agreement with the linear stability theory of Rayleigh. There is then a stage of non-universal evolution of coherent structures that is closely approximated not by Rayleigh stability theory, but by the Karman-Rubach-Lamb linear instability of monopoles, until the neighboring coherent structures merge. After several mergers, the layer evolves eventually to a self-preserving reverse cascade, characterized by a universal spread rate found by Suryanarayanan et al. (Phys.Rev.E 89, 013009, 2014) and a universal value of the ratio of dominant spacing of structures ($Lambda_f$) to the layer thickness ($delta_omega$). In this universal, self-preserving state, the local amplification of perturbation amplitudes is accurately predicted by Rayleigh theory for the locally existing `base' flow. The model of Morris et al. (Proc.Roy.Soc. A 431, 219-243, 1990.), which computes the growth of the layer by balancing the energy lost by the mean flow with the energy gain of the perturbation modes (computed from an application of Rayleigh theory), is shown, however, to provide a non-universal asymptotic state with initial condition dependent spread-rate and spectra. The reason is that the predictions of the Rayleigh instability, for a flow regime with coherent structures, are valid only at the special value of $Lambda_f/delta_omega$ achieved in the universal self-preserving state.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129207910","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

Fingering instability in Marangoni spreading on a deep layer of polymer solution 马兰戈尼在深层聚合物溶液中扩散的指指不稳定性

arXiv: Fluid Dynamics Pub Date : 2020-08-13 DOI: 10.1063/5.0028882

Xue Ma, Menglin Zhong, Yifeng He, Zhanwei Liu, Zhenzhen Li

引用次数: 13

Electro-osmotic instability of concentration enrichment in curved geometries for an aqueous electrolyte 水溶液电解质在弯曲几何中浓度富集的电渗透不稳定性

arXiv: Fluid Dynamics Pub Date : 2020-08-03 DOI: 10.1103/physrevfluids.5.091701

Bingrui Xu, Zhibo Gu, Wei Liu, P. Huo, Yueting Zhou, S. Rubinstein, M. Bazant, B. Zaltzman, I. Rubinstein, D. Deng

引用次数: 2

Crystallization and jamming in narrow fluidized beds 窄流化床中的结晶和堵塞

arXiv: Fluid Dynamics Pub Date : 2020-07-30 DOI: 10.1063/5.0015410

F. Cúñez, E. Franklin

{"title":"Crystallization and jamming in narrow fluidized beds","authors":"F. Cúñez, E. Franklin","doi":"10.1063/5.0015410","DOIUrl":"https://doi.org/10.1063/5.0015410","url":null,"abstract":"A fluidized bed is basically a suspension of granular material by an ascending fluid in a tube, and it has a rich dynamics that includes clustering and pattern formation. When the ratio between the tube and grain diameters is small, different behaviors can be induced by high confinement effects. Some unexpected and curious behaviors, that we investigate in this paper, are the crystallization and jamming of grains in liquids with velocities higher than that for incipient fluidization, supposed to maintain the grains fluidized. In our experiments, performed in a vertical tube of transparent material, different grains, water velocities, resting times, and velocity decelerations were used. An analysis of the bed evolution based on image processing shows that, after a decreasing flow that reaches a velocity still higher than that for incipient fluidization, grains become organized in lattice structures of high compactness, where they are trapped though with small fluctuations. These structures are initially localized and grow along time, in a similar manner as happens in phase transitions and glass formation. After a certain time, if the liquid velocity is slightly increased, jamming occurs, with grains being completely blocked and their fluctuation disappearing. We show that different lattice structures appear depending on the grain type. Our results provide new insights into fluidization conditions, glass-like formation and jamming.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121660129","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: 15

Mixing in a rotating soft microchannel under electrical double layer effect: A variational calculus approach 电双层效应下旋转软微通道的混合:变分演算方法

arXiv: Fluid Dynamics Pub Date : 2020-07-29 DOI: 10.1063/5.0051990

H. Gaikwad, P. Mondal

{"title":"Mixing in a rotating soft microchannel under electrical double layer effect: A variational calculus approach","authors":"H. Gaikwad, P. Mondal","doi":"10.1063/5.0051990","DOIUrl":"https://doi.org/10.1063/5.0051990","url":null,"abstract":"We study the effect of the grafted polyelectrolyte layer on the flow dynamics, and its consequences on underlying mixing in the rotating microfluidic channel. For this analysis, the method used by Sadeghi et al. (J. Fluid Mech., vol. 887, 2020, pp. A13; Phys. Rev. Fluids., vol. 4 (6), 2019, 063701-23), is modified by incorporating the non-linear effect stemming from the polyelectrolyte layer induced electrostatics to solve the coupled system of equations, integrated with the non-homogeneous boundary conditions. This method is used to obtain the velocity distribution in the asymptotic limit of geostrophic plug flow under the framework of variational calculus approach. We analyze the mixing dynamics from the perspective of both qualitative assessment and quantitative evaluation. For the qualitative estimation, we focus on the Poincar'e map analysis, while the entropy of mixing approach is used for the mixing quantification. Results show that the grafted polyelectrolyte layer in contact with the ionic solution leads to the development of an electrical double layer, which upon interacting with the external electric field, strengthens the electroosmotic pumping in the fluidic channel. Such polyelectrolyte layer modulated strong electroosmotic pumping together with its intrinsic feature of offering a frictional drag to the underlying transport helps to modulate the primary as well as the secondary flows in the channel under the influence of rotational forces. With an alteration in the electroosmotic pumping and frictional drag force, tuneable through the thickness of the grafted polyelectrolyte layer, we obtain different types of secondary flow vortex configurations viz., a standard double-vortex, dumbbell-shaped vortex and the transition state between the formers. A significant change in the structure and strengths of these vortices modulates the chaotic mixing in the present configuration","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126822284","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: 8

Deconvolutional artificial neural network models for large eddy simulation of turbulence 用于湍流大涡模拟的去卷积人工神经网络模型

arXiv: Fluid Dynamics Pub Date : 2020-07-28 DOI: 10.1063/5.0027146

Zelong Yuan, C. Xie, Jianchun Wang

{"title":"Deconvolutional artificial neural network models for large eddy simulation of turbulence","authors":"Zelong Yuan, C. Xie, Jianchun Wang","doi":"10.1063/5.0027146","DOIUrl":"https://doi.org/10.1063/5.0027146","url":null,"abstract":"Deconvolutional artificial neural network (DANN) models are developed for subgrid-scale (SGS) stress in large eddy simulation (LES) of turbulence. The filtered velocities at different spatial points are used as input features of the DANN models to reconstruct the unfiltered velocity. The grid width of the DANN models is chosen to be smaller than the filter width, in order to accurately model the effects of SGS dynamics. The DANN models can predict the SGS stress more accurately than the conventional approximate deconvolution method (ADM) and velocity gradient model (VGM) in a prior study: the correlation coefficients can be made larger than 99% and the relative errors can be made less than 15% for the DANN model. In an a posteriori study, a comprehensive comparison of the DANN model, the implicit large eddy simulation (ILES), the dynamic Smagorinsky model (DSM), and the dynamic mixed model (DMM) shows that: the DANN model is superior to the ILES, DSM, and DMM models in the prediction of the velocity spectrum, various statistics of velocity and the instantaneous coherent structures without increasing the considerable computational cost. Besides, the trained DANN models without any fine-tuning can predict the velocity statistics well for different filter widths. These results indicate that the DANN framework with consideration of SGS spatial features is a promising approach to develop advanced SGS models in the LES of turbulence.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128486996","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: 52

Intermittent dynamic bursting in vertically vibrated liquid drops 垂直振动液滴的间歇动态爆裂

arXiv: Fluid Dynamics Pub Date : 2020-07-27 DOI: 10.1063/5.0031593

A. Pototsky, I. Maksymov, S. Suslov, J. Leontini

引用次数: 5

Fluctuations and correlations of reactive scalars near chemical equilibrium in incompressible turbulence 不可压缩湍流中化学平衡附近反应量的波动和相关性

arXiv: Fluid Dynamics Pub Date : 2020-07-27 DOI: 10.1103/PhysRevFluids.5.084608

Wenwei Wu, E. Calzavarini, F. G. Schmitt, Lipo Wang

{"title":"Fluctuations and correlations of reactive scalars near chemical equilibrium in incompressible turbulence","authors":"Wenwei Wu, E. Calzavarini, F. G. Schmitt, Lipo Wang","doi":"10.1103/PhysRevFluids.5.084608","DOIUrl":"https://doi.org/10.1103/PhysRevFluids.5.084608","url":null,"abstract":"The statistical properties of species undergoing chemical reactions in a turbulent environment are studied. We focus on the case of reversible multi-component reactions of second and higher orders, in a condition close to chemical equilibrium sustained by random large-scale reactant sources, while the turbulent flow is highly developed. In such a state a competition exists between the chemical reaction that tends to dump reactant concentration fluctuations and enhance their correlation intensity and the turbulent mixing that on the contrary increases fluctuations and remove relative correlations. We show that a unique control parameter, the Damkh\"{o}ler number ($Da_theta$) that can be constructed from the scalar Taylor micro-scale, the reactant diffusivity and the reaction rate characterises the functional dependence of fluctuations and correlations in a variety of conditions, i.e., at changing the reaction order, the Reynolds and the Schmidt numbers. The larger is such a Damkh\"{o}ler number the more depleted are the scalar fluctuations as compared to the fluctuations of a passive scalar field in the same conditions, and vice-versa the more intense are the correlations. A saturation in this behaviour is observed beyond $Da_theta simeq mathcal{O}(10)$. We provide an analytical prediction for this phenomenon which is in excellent agreement with direct numerical simulation results.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131446928","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