arXiv: Fluid Dynamics最新文献_第10页

Scale-dependent Rayleigh–Taylor dynamics with variable acceleration by group theory approach 基于群论方法的变加速度瑞利-泰勒动力学

arXiv: Fluid Dynamics Pub Date : 2020-07-01 DOI: 10.1063/5.0012035

S. Abarzhi, K. Williams

{"title":"Scale-dependent Rayleigh–Taylor dynamics with variable acceleration by group theory approach","authors":"S. Abarzhi, K. Williams","doi":"10.1063/5.0012035","DOIUrl":"https://doi.org/10.1063/5.0012035","url":null,"abstract":"This work focuses on Rayleigh-Taylor instability (RTI)driven by acceleration with power-law time-dependence. We review the existing theoretical approaches, apply the group theory approach to solve this long-standing problem, and yield the unified framework for the scale-dependent dynamics of Rayleigh-Taylor (RT) bubbles and RT spikes. For the early-time linear dynamics we provide the dependence of RTI evolution on the acceleration parameters and the initial conditions. For the late-time nonlinear dynamics, we find a continuous family of asymptotic solutions, directly link the interface velocity to the interface morphology and the interfacial shear, derive solutions for the regular bubbles and for the singular spikes, and study stability of these solutions. The properties of special nonlinear solutions in the RT family are scrupulously described, including the critical, the Taylor, the Layzer-drag, and the Atwood solutions. It is shown that the fastest Atwood bubble is regular and stable, and the fastest Atwood spike is singular and unstable. The essentially multi-scale and interfacial character of RT dynamics is demonstrated. The former can be understood by viewing RT coherent structure of bubbles and spikes as a standing wave with the growing amplitude. The latter implies that RT flow has effectively no motion of the fluids away from the interface and has intense motion of the fluids near the interface, with shear-driven vortical structures appearing at the interface. Our theory agrees with available observations, and elaborates extensive benchmarks for future research and for better understanding of RT driven phenomena in plasmas.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126044624","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: 13

Asymmetric Stokes Flow Induced by a Transverse Point Force Acting Near a Finite-Sized Elastic Membrane 有限尺寸弹性膜附近横向点力诱导的不对称斯托克斯流

arXiv: Fluid Dynamics Pub Date : 2020-06-24 DOI: 10.7566/jpsj.89.124401

Abdallah Daddi-Moussa-Ider

{"title":"Asymmetric Stokes Flow Induced by a Transverse Point Force Acting Near a Finite-Sized Elastic Membrane","authors":"Abdallah Daddi-Moussa-Ider","doi":"10.7566/jpsj.89.124401","DOIUrl":"https://doi.org/10.7566/jpsj.89.124401","url":null,"abstract":"A deep understanding of the physical interactions between nanoparticles and target cell membranes is important in designing efficient nanocarrier systems for drug delivery applications. Here, we present a theoretical framework to describe the hydrodynamic flow field induced by a point-force singularity (Stokeslet) directed parallel to a finite-sized elastic membrane endowed with shear and bending rigidities. We formulate the elastohydrodynamic problem as a mixed-boundary-value problem, which we then reduce into a well-behaved system of integro-differential equations. It follows that shear and bending linearly decouple so that the solution of the overall flow problem can be obtained by linear superposition of the contributions arising from these modes of deformation. Additionally, we probe the effect of the membrane on the hydrodynamic drag acting on a nearby particle, finding that, in a certain range of parameters, translational motion near an elastic membrane with only energetic resistance toward shear can, surprisingly, be sped up compared to bulk fluid. Our results may find applications in microrheological characterizations of colloidal systems near elastic confinements.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127437007","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

Coupled population balance and large eddy simulation model for polydisperse droplet evolution in a turbulent round jet 湍流圆形射流中多分散液滴演化的耦合种群平衡和大涡模拟模型

arXiv: Fluid Dynamics Pub Date : 2020-06-24 DOI: 10.1103/physrevfluids.5.114305

A. Aiyer, C. Meneveau

{"title":"Coupled population balance and large eddy simulation model for polydisperse droplet evolution in a turbulent round jet","authors":"A. Aiyer, C. Meneveau","doi":"10.1103/physrevfluids.5.114305","DOIUrl":"https://doi.org/10.1103/physrevfluids.5.114305","url":null,"abstract":"A population balance model coupled with large eddy simulations (LES) is adapted and applied to study the evolution of oil droplets in a turbulent jet including the effects of droplet breakup. A key unknown in simulating secondary breakup in turbulent multiphase jets is the inflow size distribution generated within the primary breakup zone near the nozzle exit. A mono-disperse injection inflow condition is commonly used for simplicity, but this choice is often unrealistic. In order to provide more realistic inlet conditions for LES, we develop a one dimensional (1D) parcel model to predict the evolution of the dispersed phase along the jet centerline due to the combined effects of advection, radial turbulent transport and droplet breakup due to turbulence in the regions closer to the jet nozzle that cannot be resolved using coarse LES. The model is validated with experimental data measured far from the nozzle. The 1D model is also used to generate an initial size distribution for use in a coarse-resolution LES of a turbulent jet. Number density fields for each bin of the discretized droplet size distribution are modeled using an Eulerian LES approach and scalar transport equations are solved for each bin. LES results are compared to published experimental data, with good agreement and we examine the statistics of the velocity field and the concentration of the polydisperse oil droplet plumes for two droplet Weber numbers. We find that the centerline decay rate of the concentration for different droplet sizes is modified in the breakup dominated zone. Unlike Reynolds averaged approaches, LES also allows us to quantify size distribution variability due to turbulence. We quantify the radial and axial distributions and the variability of key quantities such as the Sauter mean diameter, total surface area and droplet breakup time-scale and explore their sensitivity to the Weber number.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127655568","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: 10

Flame- and flow-conditioned vorticity transport in premixed swirl combustion 预混合涡流燃烧中火焰和流动条件下的涡量输运

arXiv: Fluid Dynamics Pub Date : 2020-06-17 DOI: 10.1016/j.proci.2020.06.211

A. Kazbekov, A. Steinberg

引用次数: 13

Mixed modeling for large-eddy simulation: The single-layer and two-layer minimum-dissipation-Bardina models 大涡模拟的混合模式:单层和双层最小耗散- bardina模式

arXiv: Fluid Dynamics Pub Date : 2020-06-15 DOI: 10.1063/5.0015293

L. B. Streher, M. H. Silvis, P. Cifani, R. Verstappen

{"title":"Mixed modeling for large-eddy simulation: The single-layer and two-layer minimum-dissipation-Bardina models","authors":"L. B. Streher, M. H. Silvis, P. Cifani, R. Verstappen","doi":"10.1063/5.0015293","DOIUrl":"https://doi.org/10.1063/5.0015293","url":null,"abstract":"Predicting the behavior of turbulent flows using large-eddy simulation requires modeling of the subgrid-scale stress tensor. This tensor can be approximated using mixed models, which combine the dissipative nature of functional models with the capability of structural models to approximate out-of-equilibrium effects. The currently existing mixed models, however, are based on ad hoc linear combinations of models and lack mathematical motivation. We, therefore, propose a mathematical basis to mix (functional) eddy-viscosity models with the (structural) Bardina model. With this methodology we obtain the mixed anisotropic minimum-dissipation (AMD) -Bardina model. In order to also obtain a physics-conforming model for wall-bounded flows, we further develop this mixed model into a two-layer approach: the near-wall region is parameterized with the AMD-Bardina model, whereas the outer region is computed with the Bardina model. The original and two-layer AMD-Bardina models are tested in turbulent channel flows at various Reynolds numbers, and improved predictions are obtained when the mixed models are applied in comparison to the computations with the AMD and Bardina models alone. The results obtained with the two-layer AMD-Bardina model are particularly remarkable: both first- and second-order statistics are extremely well predicted and even the inflection of the mean velocity in the channel center is captured. Hence, a very promising model is obtained for large-eddy simulations of turbulent channel flows at moderate and high Reynolds numbers.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122366889","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

Effective boundary conditions for magnetohydrodynamic flows with thin Hartmann layers 薄哈特曼层磁流体动力学流动的有效边界条件

arXiv: Fluid Dynamics Pub Date : 2020-06-12 DOI: 10.1063/1.1423287

A. Pothérat, J. Sommeria, R. Moreau

引用次数: 7

Effects of tilt on the orientation dynamics of the large-scale circulation in turbulent Rayleigh–Bénard convection 倾斜对湍流rayleigh - bsamadard对流大尺度环流方向动力学的影响

arXiv: Fluid Dynamics Pub Date : 2020-06-11 DOI: 10.1063/5.0018051

Dandan Ji, Kunlun Bai, E. Brown

{"title":"Effects of tilt on the orientation dynamics of the large-scale circulation in turbulent Rayleigh–Bénard convection","authors":"Dandan Ji, Kunlun Bai, E. Brown","doi":"10.1063/5.0018051","DOIUrl":"https://doi.org/10.1063/5.0018051","url":null,"abstract":"We experimentally test the effects of tilting a turbulent Rayleigh-B{e}nard convection cell on the dynamics of the large-scale circulation (LSC) orientation $theta_0$. The probability distribution of $theta_0$ is measured, and used to obtain a tilt-induced potential acting on $theta_0$, which is used in a low-dimensional model of diffusion of $theta_0$ in a potential. The form of the potential is sinusoidal in $theta_0$, and linear in tilt angle for small tilt angles, which is explained by a simple geometric model of the vector direction of the mean buoyancy force acting on the LSC. However, the magnitude of the tilt-induced forcing is found to be two orders of magnitude larger than previously predicted. When this parameter is adjusted to match values obtained from the probability distribution of $theta_0$, the diffusive model can quantitatively predict effects of tilt on $theta_0$. In particular, tilt causes a change in potential barrier height between neighboring corners of a cubic cell, and changes in the barrier-crossing rate for $theta_0$ to escape a corner are predicted with an accuracy of $pm30%$. As a cylindrical cell is tilted, the tilt-induced potential provides a restoring force which induces oscillations when it exceeds the strength of damping; this critical tilt angle is predicted within 20%, and the prediction is consistent with measured oscillation frequencies. These observations show that a self-consistent low-dimensional model can be extended to include the dynamics of $theta_0$ due to tilt. However, the underprediction of the effect of tilt on $theta_0$ warrants revisiting the predicted magnitude.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116352704","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

A Comparison of Turbulence Generated by 3DS Sparse Grids with Different Blockage Ratios and Different Co-frame Arrangements 不同阻塞比和不同共框排列的3DS稀疏网格产生湍流的比较

arXiv: Fluid Dynamics Pub Date : 2020-06-08 DOI: 10.1007/978-3-030-63591-6_30

M. Usama, N. Malik

引用次数: 0

Start-up and cessation of steady shear and extensional flows: Exact analytical solutions for the affine linear Phan-Thien–Tanner fluid model 稳定剪切和拉伸流动的启动和停止:仿射线性Phan-Thien-Tanner流体模型的精确解析解

arXiv: Fluid Dynamics Pub Date : 2020-06-07 DOI: 10.1063/5.0017326

D. Shogin

{"title":"Start-up and cessation of steady shear and extensional flows: Exact analytical solutions for the affine linear Phan-Thien–Tanner fluid model","authors":"D. Shogin","doi":"10.1063/5.0017326","DOIUrl":"https://doi.org/10.1063/5.0017326","url":null,"abstract":"Exact analytical solutions for start-up and cessation flows are obtained for the affine linear Phan-Thien--Tanner fluid model. They include the results for start-up and cessation of steady shear flows, of steady uniaxial and biaxial extensional flows, and of steady planar extensional flows. The solutions obtained show that at start-up of steady shear flows, the stresses go through quasi-periodic exponentially damped oscillations while approaching their steady-flow values (so that stress overshoots are present); at start-up of steady extensional flows, the stresses grow monotonically, while at cessation of steady shear and extensional flows, the stresses decay quickly and non-exponentially. The steady-flow rheology of the fluid is also reviewed, the exact analytical solutions obtained in this work for steady shear and extensional flows being simpler than the alternative formulas found in the literature. The properties of steady and transient solutions, including their asymptotic behavior at low and high Weissenberg numbers, are investigated in detail. Generalization to the multimode version of the Phan-Thien--Tanner model is also discussed. Thus, this work provides a complete analytical description of the rheology of the affine linear Phan-Thien--Tanner fluid in start-up, cessation, and steady regimes of shear and extensional flows.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131397298","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

A shallow water model for magnetohydrodynamic flows with turbulent Hartmann layers 具有湍流哈特曼层的浅水磁流体动力学流动模型

arXiv: Fluid Dynamics Pub Date : 2020-06-06 DOI: 10.1063/1.3592326

A. Pothérat, J. Schweitzer

{"title":"A shallow water model for magnetohydrodynamic flows with turbulent Hartmann layers","authors":"A. Pothérat, J. Schweitzer","doi":"10.1063/1.3592326","DOIUrl":"https://doi.org/10.1063/1.3592326","url":null,"abstract":"We establish a shallow water model for flows of electrically conducting fluids in homogeneous static magnetic fields that are confined between two parallel planes where turbulent Hartmann layers are present. This is achieved by modelling the wall shear stress in these layers using the Prandtl's mixing length model, as did the authors of Albousssiere & Lingwood (Phys. Fluids, 2000). The idea for this new model arose from the failure of previous shallow water models that assumed a laminar Hartmann layer to recover the correct amount of dissipation found in some regimes of the MATUR experiment. This experiment, conducted by the authors of Messadek & Moreau (J. Fluid Mech. 2002), consisted of a thin layer of mercury electrically driven in differential rotation in a transverse magnetic field. Numerical Simulations of our new model in the configuration of this experiment allowed us to recover experimental values of both the global angular momentum and the local velocity up to a few percent when the Hartmann layer was in a sufficiently well developed turbulent state. We thus provide an evidence that the unexplained level of dissipation observed in MATUR in these specific regimes was caused by turbulence in the Hartmann layers. A parametric analysis of the flow, made possible by the simplicity of our model, also revealed that turbulent friction in the Hartmann layer prevented quasi-2D turbulence from becoming more intense and limited the size of the large scales.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128181622","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