arXiv: Fluid Dynamics最新文献_第7页

Rigid body motion in viscous flows using the finite element method 粘性流动中刚体运动的有限元分析

arXiv: Fluid Dynamics Pub Date : 2020-09-07 DOI: 10.1063/5.0029242

M. Herreros, S. Ligüérzana

{"title":"Rigid body motion in viscous flows using the finite element method","authors":"M. Herreros, S. Ligüérzana","doi":"10.1063/5.0029242","DOIUrl":"https://doi.org/10.1063/5.0029242","url":null,"abstract":"A new model for the numerical simulation of a rigid body moving in a viscous fluid flow using FEM is presented. One of the most interesting features of this approach is the small computational effort required to solve the motion of the rigid body compared to a pure fluid solver. The model is based on the idea of extending the fluid velocity inside the rigid body and solving the flow equations with a penalization term to enforce rigid motion inside the solid. In order to get the velocity field in the fluid domain the Navier-Stokes equations for an incompressible viscous flow are solved using a fractional-step procedure combined with the two-step Taylor-Galerkin for the fractional linear momentum. Once the velocity field in the fluid domain is computed, calculation of the rigid motion is obtained by averaging translation and angular velocities over the solid. One of the main challenges when dealing with the fluid-solid interaction is the proper modelling of the interface which separates the solid moving mass from the viscous fluid. In this work the combination of the level set technique and the two-step Taylor-Galerkin algorithm for tracking the fluid-solid interface is proposed. The good properties exhibited by the two-step Taylor-Galerkin, minimizing oscillations and numerical diffusion, make this method suitable to accurately advect the solid domain avoiding distortions at its boundaries, and thus preserving the initial size and shape of the rigid body. The proposed model has been validated against empirical solutions, experimental data and numerical simulations found in the literature. In all tested cases, the numerical results have shown to be accurate, proving the potential of the proposed model as a valuable tool for the numerical analysis of the fluid-solid interaction.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130309917","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: 2

Inertial migration of oblate spheroids in a plane channel 平面通道中椭球体的惯性迁移

arXiv: Fluid Dynamics Pub Date : 2020-09-04 DOI: 10.1063/5.0028353

Tatiana V. Nizkaya, Anna S. Gekova, J. Harting, E. S. Asmolov, O. Vinogradova

引用次数: 13

Assessment of unsteady flow predictions using hybrid deep learning based reduced-order models 基于混合深度学习的降阶模型的非定常流预测评估

arXiv: Fluid Dynamics Pub Date : 2020-09-03 DOI: 10.1063/5.0030137

S. R. Bukka, R. Gupta, A. Magee, R. Jaiman

{"title":"Assessment of unsteady flow predictions using hybrid deep learning based reduced-order models","authors":"S. R. Bukka, R. Gupta, A. Magee, R. Jaiman","doi":"10.1063/5.0030137","DOIUrl":"https://doi.org/10.1063/5.0030137","url":null,"abstract":"In this paper, we present two deep learning-based hybrid data-driven reduced order models for the prediction of unsteady fluid flows. The first model projects the high-fidelity time series data from a finite element Navier-Stokes solver to a low-dimensional subspace via proper orthogonal decomposition (POD). The time-dependent coefficients in the POD subspace are propagated by the recurrent net (closed-loop encoder-decoder updates) and mapped to a high-dimensional state via the mean flow field and POD basis vectors. This model is referred as POD-RNN. The second model, referred to as convolution recurrent autoencoder network (CRAN), employs convolutional neural networks (CNN) as layers of linear kernels with nonlinear activations, to extract low-dimensional features from flow field snapshots. The flattened features are advanced using a recurrent (closed-loop manner) net and up-sampled (transpose convoluted) gradually to high-dimensional snapshots. Two benchmark problems of the flow past a cylinder and flow past a side-by-side cylinder are selected as the test problems to assess the efficacy of these models. For the problem of flow past a single cylinder, the performance of both the models is satisfactory, with CRAN being a bit overkill. However, it completely outperforms the POD-RNN model for a more complicated problem of flow past side-by-side cylinders. Owing to the scalability of CRAN, we briefly introduce an observer-corrector method for the calculation of integrated pressure force coefficients on the fluid-solid boundary on a reference grid. This reference grid, typically a structured and uniform grid, is used to interpolate scattered high-dimensional field data as snapshot images. These input images are convenient in training CRAN. This motivates us to further explore the application of CRAN models for the prediction of fluid flows.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114657320","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: 56

Film coating by directional droplet spreading on fibers 用定向液滴在纤维上扩散的方法涂膜

arXiv: Fluid Dynamics Pub Date : 2020-09-02 DOI: 10.1103/PHYSREVFLUIDS.6.014004

T. Chan, Carmen L. Lee, C. Pedersen, K. Dalnoki-Veress, A. Carlson

引用次数: 6

Immiscible Rayleigh-Taylor turbulence using mesoscopic lattice Boltzmann algorithms 使用介观晶格玻尔兹曼算法的非混相瑞利-泰勒湍流

arXiv: Fluid Dynamics Pub Date : 2020-08-31 DOI: 10.1103/PhysRevFluids.6.054606

Hugo S. Tavares, Luca Biferale, M. Sbragaglia, A. Mailybaev

{"title":"Immiscible Rayleigh-Taylor turbulence using mesoscopic lattice Boltzmann algorithms","authors":"Hugo S. Tavares, Luca Biferale, M. Sbragaglia, A. Mailybaev","doi":"10.1103/PhysRevFluids.6.054606","DOIUrl":"https://doi.org/10.1103/PhysRevFluids.6.054606","url":null,"abstract":"We studied turbulence induced by the Rayleigh-Taylor (RT) instability for 2D immiscible two-component flows by using a multicomponent lattice Boltzmann method with a Shan-Chen pseudopotential implemented on GPUs. We compare our results with the extension to the 2D case of the phenomenological theory for immiscible 3D RT studied by Chertkov and collaborators ({it Physical Review E 71, 055301, 2005}). Furthermore, we compared the growth of the mixing layer, typical velocity, average density profiles and enstrophy with the equivalent case but for miscible two-component fluid. Both in the miscible and immiscible cases, the expected quadratic growth of the mixing layer and the linear growth of the typical velocity are observed with close long-time asymptotic prefactors but different initial transients. In the immiscible case, the enstrophy shows a tendency to grow like $propto t^{3/2}$, with the highest values of vorticity concentrated close to the interface. In addition, we investigate the evolution of the typical drop size and the behavior of the total length of the interface in the emulsion-like state, showing the existence of a power law behavior compatible with our phenomenological predictions. Our results can also be considered as a first validation step to extend the application of lattice Boltzmann tool to study the 3D immiscible case.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128710773","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: 6

Theoretical analysis for dynamic contact angle hysteresis on chemically patterned surfaces 化学图案表面动态接触角滞后的理论分析

arXiv: Fluid Dynamics Pub Date : 2020-08-28 DOI: 10.1063/5.0027747

Xianmin Xu, Xiaoping Wang

引用次数: 10

Leidenfrost drop impact on inclined superheated substrates 莱顿弗罗斯特水滴对倾斜过热基材的影响

arXiv: Fluid Dynamics Pub Date : 2020-08-26 DOI: 10.1063/5.0027115

Yujie Wang, Ayoub El Bouhali, Sijia Lyu, Lu Yu, Y. Hao, Z. Zuo, Shuhong Liu, Chao Sun

{"title":"Leidenfrost drop impact on inclined superheated substrates","authors":"Yujie Wang, Ayoub El Bouhali, Sijia Lyu, Lu Yu, Y. Hao, Z. Zuo, Shuhong Liu, Chao Sun","doi":"10.1063/5.0027115","DOIUrl":"https://doi.org/10.1063/5.0027115","url":null,"abstract":"In real applications, drops always impact on solid walls with various inclinations. For the oblique impact of a Leidenfrost drop, which has a vapor layer under its bottom surface to prevent its direct contact with the superheated substrate, the drop can nearly frictionlessly slide along the substrate accompanied by the spreading and the retracting. To individually study these processes, we experimentally observe ethanol drops impact on superheated inclined substrates using high-speed imaging from two different views synchronously. We first study the dynamic Leidenfrost temperature, which mainly depends on the normal Weber number ${We}_perp $. Then the substrate temperature is set to be high enough to study the Leidenfrost drop behaviors. During the spreading process, drops always keep uniform. And the maximum spreading factor $D_m/D_0$ follows a power-law dependence on the large normal Weber number ${We}_perp $ as $D_m/D_0 = sqrt{We_perp /12+2}$ for $We_perp geq 30$. During the retracting process, drops with low impact velocities become non-uniform due to the gravity effect. For the sliding process, the residence time of all studied drops is nearly a constant, which is not affected by the inclination and $We$ number. The frictionless vapor layer results in the dimensionless sliding distance $L/D_0$ follows a power-law dependence on the parallel Weber number $We_parallel$ as $L/D_0 propto We_parallel^{1/2}$. Without direct contact with the substrate, the behaviors of drops can be separately determined by ${We}_perp $ and $We_parallel$. When the impact velocity is too high, the drop fragments into many tiny droplets, which is called the splashing phenomenon. The critical splashing criterion is found to be $We_perp ^*simeq$ 120 or $K_perp = We_perp Re_perp^{1/2} simeq$ 5300 in the current parameter regime.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133970434","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: 11

Stability of slowly evaporating thin liquid films of binary mixtures 二元混合物缓慢蒸发薄液膜的稳定性

arXiv: Fluid Dynamics Pub Date : 2020-08-24 DOI: 10.1103/physrevfluids.5.104007

R. Nazareth, G. Karapetsas, K. Sefiane, O. Matar, P. Valluri

{"title":"Stability of slowly evaporating thin liquid films of binary mixtures","authors":"R. Nazareth, G. Karapetsas, K. Sefiane, O. Matar, P. Valluri","doi":"10.1103/physrevfluids.5.104007","DOIUrl":"https://doi.org/10.1103/physrevfluids.5.104007","url":null,"abstract":"We consider the evaporation of a thin liquid layer which consists of a binary mixture of volatile liquids. The mixture is on top of a heated substrate and in contact with the gas phase that consists of the same vapour as the binary mixture. The effect of thermocapillarity, solutocapillarity and the van der Waals interactions are considered. We derive the long-wave evolution equations for the free interface and the volume fraction that govern the two-dimensional stability of the layer subject to the above coupled mechanisms and perform a linear stability analysis. Our results demonstrate two modes of instabilities, a monotonic instability mode and an oscillatory instability mode. We supplement our results from stability analysis with transient simulations to examine the dynamics in the nonlinear regime and analyse how these instabilities evolve with time. More precisely we discuss how the effect of relative volatility along with the competition between thermal and solutal Marangoni effect defines the mode of instability that develops during the evaporation of the liquid layer due to preferential evaporation of one of the components.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"180 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127587738","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: 2

Dissipative instability of converging cylindrical shock wave 会聚圆柱激波的耗散不稳定性

arXiv: Fluid Dynamics Pub Date : 2020-08-23 DOI: 10.1063/5.0027109

S. Chefranov

引用次数: 6

Pairs of surface wave packets with zero-sum energy in the Hawking radiation analog 在霍金辐射模拟中具有零和能量的表面波包对

arXiv: Fluid Dynamics Pub Date : 2020-08-21 DOI: 10.1103/physrevd.102.104061

A. Guha, E. Heifetz, Akanksha Gupta

{"title":"Pairs of surface wave packets with zero-sum energy in the Hawking radiation analog","authors":"A. Guha, E. Heifetz, Akanksha Gupta","doi":"10.1103/physrevd.102.104061","DOIUrl":"https://doi.org/10.1103/physrevd.102.104061","url":null,"abstract":"Here we propose a minimal analog gravity setup and suggest how to select two surface gravity wave packets in order to mimic some key aspects of Hawking radiation from the horizon of non-rotating black holes. Our proposed setup, unlike the scattering problem conventionally studied, constitutes of a constant mean flow over a flat bathymetry, in which the two wave packets possess the same amount of wave action but equal and opposite (sign) amount of energy, thereby mimicking virtual particles created out of near horizon vacuum fluctuations. Attention is given to the physical mechanism relating to the signs of the wave action and energy norm with the wave's intrinsic and total phase speeds. We construct narrow wave packets of equal wave action, the one with positive energy and group speed propagates against the mean flow and escapes from the black hole as Hawking radiation, while the other with negative energy and group speed is drifted by the mean flow and falls into it. Hawking's prediction of low frequency mode amplification is satisfied in our minimal model by construction. We find that the centroid wavenumbers and surface elevation amplitudes of the wave packets are related by simple analytical expressions.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129055202","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: 2