arXiv: Fluid Dynamics最新文献_第9页

Rico and the jets: Direct numerical simulations of turbulent liquid jets Rico和射流:湍流液体射流的直接数值模拟

arXiv: Fluid Dynamics Pub Date : 2020-07-24 DOI: 10.1103/physrevfluids.5.110501

C. Constante-Amores, L. Kahouadji, A. Batchvarov, S. Shin, J. Chergui, D. Juric, O. Matar

引用次数: 3

Thermodynamically consistent Darcy–Brinkman–Forchheimer framework in matrix acidization 基质酸化中热力学一致的Darcy-Brinkman-Forchheimer框架

arXiv: Fluid Dynamics Pub Date : 2020-07-23 DOI: 10.2516/OGST/2020091

Yuanqing Wu, Jisheng Kou, Shuyu Sun, Yu-Shu Wu

引用次数: 9

Effect of particle inertia on the alignment of small ice crystals in turbulent clouds 粒子惯性对湍流云中小冰晶排列的影响

arXiv: Fluid Dynamics Pub Date : 2020-07-22 DOI: 10.1175/JAS-D-20-0221.1

K. Gustavsson, M. Z. Sheikh, A. Naso, A. Pumir, B. Mehlig

{"title":"Effect of particle inertia on the alignment of small ice crystals in turbulent clouds","authors":"K. Gustavsson, M. Z. Sheikh, A. Naso, A. Pumir, B. Mehlig","doi":"10.1175/JAS-D-20-0221.1","DOIUrl":"https://doi.org/10.1175/JAS-D-20-0221.1","url":null,"abstract":"Small non-spherical particles settling in a quiescent fluid tend to orient so that their broad side faces down, because this is a stable fixed point of their angular dynamics at small particle Reynolds number. Turbulence randomises the orientations to some extent, and this affects the reflection patterns of polarised light from turbulent clouds containing ice crystals. An overdamped theory predicts that turbulence-induced fluctuations of the orientation are very small when the settling number Sv (a dimensionless measure of the settling speed) is large. At small Sv, by contrast, the overdamped theory predicts that turbulence randomises the orientations. This overdamped theory neglects the effect of particle inertia. Therefore we consider here how particle inertia affects the orientation of small crystals settling in turbulent air. We find that it can significantly increase the orientation variance, even when the Stokes number St (a dimensionless measure of particle inertia) is quite small. We identify different asymptotic parameter regimes where the tilt-angle variance is proportional to different inverse powers of Sv. Parameter values for ice crystals in turbulent clouds lie near the boundaries between these regions; ice crystal-alignment in such clouds is thus unlikely to follow a simple power law. The theory predicts how the degree of alignment depends on particle size, shape, and turbulence intensity.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129619767","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

Chaotic measure of the transition between two- and three-dimensional turbulence 二维和三维湍流之间过渡的混沌测量

arXiv: Fluid Dynamics Pub Date : 2020-07-21 DOI: 10.1103/PhysRevFluids.6.054612

D. Clark, Andres Armua, C. Freeman, Daniel Brener, A. Berera

引用次数: 3

Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence 高雷诺数湍流中惯性粒子分布的尺度相关统计

arXiv: Fluid Dynamics Pub Date : 2020-07-18 DOI: 10.1103/PhysRevFluids.6.064304

K. Matsuda, K. Schneider, K. Yoshimatsu

{"title":"Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence","authors":"K. Matsuda, K. Schneider, K. Yoshimatsu","doi":"10.1103/PhysRevFluids.6.064304","DOIUrl":"https://doi.org/10.1103/PhysRevFluids.6.064304","url":null,"abstract":"Multiscale statistical analyses of inertial particle distributions are presented to investigate the statistical signature of clustering and void regions in particle-laden incompressible isotropic turbulence. Three-dimensional direct numerical simulations of homogeneous isotropic turbulence at high Reynolds number ($Re_lambda gtrsim 200$) with up to $10^9$ inertial particles are performed for Stokes numbers ranging from $0.05$ to $5.0$. Orthogonal wavelet analysis is then applied to the computed particle number density fields. Scale-dependent skewness and flatness values of the particle number density distributions are calculated and the influence of Reynolds number $Re_lambda$ and Stokes number $St$ is assessed. For $St sim 1.0$, both the scale-dependent skewness and flatness values become larger as the scale decreases, suggesting intermittent clustering at small scales. For $St le 0.2$, the flatness at intermediate scales, i.e. for scales larger than the Kolmogorov scale and smaller than the integral scale of the flow, increases as $St$ increases, and the skewness exhibits negative values at the intermediate scales. The negative values of the skewness are attributed to void regions. These results indicate that void regions at the intermediate sales are pronounced and intermittently distributed for such small Stokes numbers. As $Re_lambda$ increases, the flatness increases slightly. For $Re_lambda ge 328$, the skewness shows negative values at large scales, suggesting that void regions are pronounced at large scales, while clusters are pronounced at small scales.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125838825","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: 7

Temperature profiles, plumes, and spectra in the surface layer of convective boundary layers 对流边界层表层的温度分布、羽流和光谱

arXiv: Fluid Dynamics Pub Date : 2020-07-16 DOI: 10.1063/5.0023429

K. Mcnaughton, S. Chowdhuri

{"title":"Temperature profiles, plumes, and spectra in the surface layer of convective boundary layers","authors":"K. Mcnaughton, S. Chowdhuri","doi":"10.1063/5.0023429","DOIUrl":"https://doi.org/10.1063/5.0023429","url":null,"abstract":"We survey temperature patterns and heat transport in convective boundary layers (CBLs) from the perspective that these are emergent properties of far-from-equilibrium, complex dynamical systems. We introduce a two-temperature (2T) toy model to define the cross-sectional areas of plumes, and connect the scaling properties of temperature gradients, temperature variance and heat transport to this area. We examine temperature ($T$) probability density functions and $w$-$T$ joint probability density functions, $T$ spectra and $wT$ cospectra observed both within and above the surface friction layer. Here $w$ is vertical velocity. In our discussion of $T$ spectra and $wT$ cospectra we focus on the self-similarity property of the plumes and flux events above the SFL. We interpret the $z^{1/2}$ dependence of the mixed length scale for wavenumbers in the $T$ spectra as reflecting the cross-sectional areas of the plumes, and so with the $z^{-1/2}$ form of the temperature profile, where $z$ is observation height. We introduce new scaling results for $T$ spectra and $wT$ cospectra from within the surface friction layer (SFL), based on a data from the SLTEST experiment. We confirm earlier results showing that the scaling behaviours of $T$ spectra and $wT$ cospectra change for heights below $z/z_s<0.1$, where $z_s$ the height of the SFL, and come to display properties associated with random diffusion. We conclude by contrasting our interpretation of the role of buoyancy as a system-wide action in CBL flows with that of Richardson, whose ideas inform the current interpretation of the statistical fluid mechanics model of boundary-layer flows.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116306076","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

Scaling behavior of density gradient accelerated mixing rate in shock bubble interaction 密度梯度的标度行为加速了激波气泡相互作用中的混合速率

arXiv: Fluid Dynamics Pub Date : 2020-07-11 DOI: 10.1103/PhysRevFluids.6.064502

B. Yu, Haoyang Liu, Hong Liu

{"title":"Scaling behavior of density gradient accelerated mixing rate in shock bubble interaction","authors":"B. Yu, Haoyang Liu, Hong Liu","doi":"10.1103/PhysRevFluids.6.064502","DOIUrl":"https://doi.org/10.1103/PhysRevFluids.6.064502","url":null,"abstract":"Variable-density mixing in shock bubble interaction, a canonical flow of so-called RichtermyerMeshkov instability, is studied by the high-resolution simulation. While the dissipation mainly controls the passive scalar mixing rate, an objective definition of variable-density mixing rate characterizing the macroscopic mixing formation is still lacking, and the fundamental behavior of mixing rate evolution is not yet well understood. Here, we first show that the variable-density mixing of shock bubble interaction is distinctly different from the previous observations in the passive scalar mixing. The widely-accepted hyperbolic conservation of the first moment of concentration in the scalar mixing, i.e., the conservation of the mean concentration, is violated in shock bubble interaction. We further combine the compositional transport equation and the divergence relation for the miscible flows to provide the evidence that the existence of density gradient accelerated mixing rate, decomposed by the accelerated dissipation term and redistributed diffusion term, contributes to the anomalous decrease of the mean concentration of species. Further analyzing a number of simulations for a broad range of shock Mach numbers, Reynolds numbers, and Peclet numbers, the density gradient accelerated mixing rate exhibits nearly independent of the dimensionless numbers, which paves a new way to understand the variable-density effect on the connection between global and local mixing behavior.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122202723","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

Transport and deposition of dilute microparticles in turbulent thermal convection 湍流热对流中稀微粒子的输运和沉积

arXiv: Fluid Dynamics Pub Date : 2020-07-11 DOI: 10.1063/5.0018804

A. Xu, Shi Tao, Leping Shi, H. Xi

{"title":"Transport and deposition of dilute microparticles in turbulent thermal convection","authors":"A. Xu, Shi Tao, Leping Shi, H. Xi","doi":"10.1063/5.0018804","DOIUrl":"https://doi.org/10.1063/5.0018804","url":null,"abstract":"We analyze the transport and deposition behavior of dilute microparticles in turbulent Rayleigh-Benard convection. Two-dimensional direct numerical simulations were carried out for the Rayleigh number ($Ra$) of $10^{8}$ and the Prandtl number ($Pr$) of 0.71 (corresponding to the working fluids of air). The Lagrangian point particle model was used to describe the motion of microparticles in the turbulence. Our results show that the suspended particles are homogeneously distributed in the turbulence for the Stokes number ($St$) less than $10^{-3}$, and they tend to cluster into bands for $10^{-3} lesssim St lesssim 10^{-2}$. At even larger $St$, the microparticles will quickly sediment in the convection. We also calculate the mean-square displacement (MSD) of the particle's trajectories. At short time intervals, the MSD exhibits a ballistic regime, and it is isotropic in vertical and lateral directions; at longer time intervals, the MSD reflects a confined motion for the particles, and it is anisotropic in different directions. We further obtained a phase diagram of the particle deposition positions on the wall, and we identified three deposition states depending on the particle's density and diameter. An interesting finding is that the dispersed particles preferred to deposit on the vertical wall where the hot plumes arise, which is verified by tilting the cell and altering the rotation direction of the large-scale circulation.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128620706","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

Suppression of electroconvective and morphological instabilities by an imposed cross flow of the electrolyte 通过施加电解质的横流抑制电对流和形态不稳定性

arXiv: Fluid Dynamics Pub Date : 2020-07-09 DOI: 10.1103/PHYSREVFLUIDS.6.033701

Gaojin Li, Alex Townsend, L. Archer, D. Koch

{"title":"Suppression of electroconvective and morphological instabilities by an imposed cross flow of the electrolyte","authors":"Gaojin Li, Alex Townsend, L. Archer, D. Koch","doi":"10.1103/PHYSREVFLUIDS.6.033701","DOIUrl":"https://doi.org/10.1103/PHYSREVFLUIDS.6.033701","url":null,"abstract":"Electroconvection and its coupling with a morphological instability are important in many applications, including electrodialysis, batteries and fuel cells. In this work, we study the effects of a two-dimensional channel flow on the electroconvective and morphological instabilities using two approaches. In the bulk analysis, we consider the instability of the electroneutral bulk region driven by a second kind electroosmosis slip velocity boundary condition and derive the asymptotic solutions for small and large wavenumbers. In the full analysis, we consider the entire region of the liquid electrolyte and use the ultraspherical spectral method to numerically solve the eigenvalue problems. Both studies show that the imposed flow significantly affects the electroconvective instability. The imposed flow generates a shielding effect by deforming the perturbed ion concentration field and hinders the ion transfer from low- to high- concentration regions which causes the instability. It fully suppresses the electroconvective instability at small wavenumbers and reduces the growth rate of the perturbations at large wavenumbers. The direct effect of the flow on the morphological instability is minor, while the suppression of the electroconvective instability may change the wavenumber of the most unstable mode of the coupled instabilities. For the electroconvective instability, the bulk analysis is qualitatively different from the full analysis at high wavenumbers. For the morphological instability, good agreement is found between the two studies at both small and large wavenumbers.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"924 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116419010","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

Discrete self-similarity in the formation of satellites for viscous cavity break up 粘性空腔破裂时卫星形成的离散自相似性

arXiv: Fluid Dynamics Pub Date : 2020-07-06 DOI: 10.1103/PHYSREVFLUIDS.6.013201

M. Fontelos, Qiming Wang

引用次数: 1