arXiv: Fluid Dynamics最新文献_第5页

On the unsteady throttling dynamics and scaling analysis in a typical hypersonic inlet–isolator flow 典型高超声速进气道隔离流非定常节流动力学及标度分析

arXiv: Fluid Dynamics Pub Date : 2020-10-10 DOI: 10.1063/5.0032740

K. Sekar, S. K. Karthick, S. Jegadheeswaran, R. Kannan

{"title":"On the unsteady throttling dynamics and scaling analysis in a typical hypersonic inlet–isolator flow","authors":"K. Sekar, S. K. Karthick, S. Jegadheeswaran, R. Kannan","doi":"10.1063/5.0032740","DOIUrl":"https://doi.org/10.1063/5.0032740","url":null,"abstract":"The flow field in a two-dimensional three-ramp hypersonic mixed-compression inlet in a freestream Mach number of $M_infty=5$ is numerically solved to understand the unsteady throttling dynamics. Throttling conditions are simulated by varying the exit area of the isolator in the form of plug insets. Different throttling ratios between $0leq zeta leq 0.7$ in steps of 0.1 are considered. No unsteadiness is observed for $zetaleq 0.2$ and severe unsteadiness is found for $0.3 leq zeta leq 0.7$. The frequency of unsteadiness ($f$) increases rapidly with $zeta$. As $zeta$ increases, the amount of reversed mass inside the isolator scales with the frequency and the exit mass flow rate. A general framework is attempted to scale the unsteady events based on the gathered knowledge from the numerical study. The inlet-isolator flow is modeled as an oscillating flow through a duct with known upstream design conditions like the freestream Mach number ($M_infty$) and the isolator inlet Mach number ($M_i$). Factors like the mass occupied by the duct volume, the characteristic unsteady frequency, throttling ratio, and the exit mass flow rate through the duct are used to form a non-dimensional parameter $beta$, which scales with the upstream design parameter $xi=M_i/M_infty$. The scaling parameters are further exploited to formulate a semi-empirical relation using the existing experimental results at different throttling ratios from the open literature. The unsteady frequencies from the present two-dimensional numerical exercise are also shown to agree with the proposed scaling and the resulting semi-empirical relation.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128000244","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: 37

Eigenmode analysis of membrane stability in inviscid flow 无粘流动中膜稳定性的特征模态分析

arXiv: Fluid Dynamics Pub Date : 2020-10-08 DOI: 10.1103/PHYSREVFLUIDS.6.043901

C. Mavroyiakoumou, S. Alben

引用次数: 11

Forced Imbibition in Stratified Porous Media 层状多孔介质中的强制渗吸

arXiv: Fluid Dynamics Pub Date : 2020-10-05 DOI: 10.1103/physrevapplied.14.054009

Nancy B. Lu, A. Pahlavan, Christopher A. Browne, D. Amchin, H. Stone, S. Datta

引用次数: 5

Numerical Simulation of Iced Wing Using Separating Shear Layer Fixed Turbulence Models 冰翼分离剪切层固定湍流模型的数值模拟

arXiv: Fluid Dynamics Pub Date : 2020-10-05 DOI: 10.2514/1.J060143

Haoran Li, Yufei Zhang, Haixin Chen

引用次数: 6

Nemchinov-Dyson Solutions of the Two-Dimensional Axisymmetric Inviscid Compressible Flow Equations 二维轴对称无粘可压缩流动方程的Nemchinov-Dyson解

arXiv: Fluid Dynamics Pub Date : 2020-10-02 DOI: 10.2172/1671066

Jesse F. Giron, S. Ramsey, R. Baty

引用次数: 0

The area localized coupled model for analytical mean flow prediction in arbitrary wind farm geometries 任意风电场几何形状分析平均流量预测的区域局部耦合模型

arXiv: Fluid Dynamics Pub Date : 2020-09-28 DOI: 10.1063/5.0042573

Genevieve M. Starke, C. Meneveau, J. King, D. Gayme

{"title":"The area localized coupled model for analytical mean flow prediction in arbitrary wind farm geometries","authors":"Genevieve M. Starke, C. Meneveau, J. King, D. Gayme","doi":"10.1063/5.0042573","DOIUrl":"https://doi.org/10.1063/5.0042573","url":null,"abstract":"This work introduces the Area Localized Coupled (ALC) model, which extends earlier approaches to coupling classical wake superposition and atmospheric boundary layer models in order to enable applicability to arbitrary wind-farm layouts. Coupling wake and top-down boundary layer models is particularly challenging since the latter requires averaging over planform areas associated with certain turbine-specific regions of the flow. The ALC model uses Voronoi tesselation to define a local area around each turbine. A top-down description of a developing internal boundary layers is then applied over Voronoi cells upstream of each turbine to estimate the local mean velocity profile. Coupling between the velocity at hub-height based on this localized top-down model and a wake model is achieved by enforcing a minimum least-square-error in mean velocity in each cell. The ALC model is implemented using a wake model with a profile that transitions from a top-hat to Gaussian function and accounts for wake interactions through linear superposition. Detailed comparisons to large-eddy simulation (LES) data demonstrate the efficacy of the model in accurate predictions of both power and hub height velocity for complex wind farm geometries. Further validation with LES for a hybrid array-random farm that has half of the turbines arranged in an array and the other half randomly distributed indicates the model's versatility with respect to capturing results from different wind farm configurations. In both cases, the ALC model is shown to produce improved power predictions for both the farm and individual turbines over prevailing approaches for a range of wind inflow directions.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123992084","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: 9

Size-dependent particle migration and trapping in three-dimensional microbubble streaming flows 三维微泡流流中大小相关的粒子迁移和捕获

arXiv: Fluid Dynamics Pub Date : 2020-09-27 DOI: 10.1103/physrevfluids.5.114201

Andreas Volk, M. Rossi, Bhargav Rallabandi, C. Kaehler, S. Hilgenfeldt, A. Marin

引用次数: 4

Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants 弱拉伸预混球形火焰在局部均相和非均相反应物中的传播

arXiv: Fluid Dynamics Pub Date : 2020-09-27 DOI: 10.1063/5.0031638

Qiang Li, Huangwei Zhang, C. Shu

{"title":"Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants","authors":"Qiang Li, Huangwei Zhang, C. Shu","doi":"10.1063/5.0031638","DOIUrl":"https://doi.org/10.1063/5.0031638","url":null,"abstract":"Propagation of weakly stretched spherical flames in partially pre-vaporized fuel sprays is theoretically investigated in this work. A general theory is developed to describe flame propagation speed, flame temperature, droplet evaporation onset and completion locations. The influences of liquid fuel and gas mixture properties on spherical spray flame propagation are studied. The results indicate that the spray flame propagation speed is enhanced with increased droplet mass loading and/or evaporation heat exchange coefficient (or evaporation rate). Opposite trends are found when the latent heat is high, due to strong evaporation heat absorption. Fuel vapor and temperature gradients are observed in the post-flame evaporation zone of heterogeneous flames. Evaporation completion front location considerably changes with flame radius, but the evaporation onset location varies little relative to the flame front when the flame propagates. For larger droplet loading and smaller evaporation rate, the fuel droplet tends to complete evaporation behind the flame front. Flame bifurcation occurs with high droplet mass loading under large latent heat, leading to multiplicity of flame propagation speed, droplet evaporation onset and completion fronts. The flame enhancement or weakening effects by the fuel droplet sprays are revealed by enhanced or suppressed heat and mass diffusion process in the pre-flame zone. Besides, for heterogeneous flames, heat and mass diffusion in the post-flame zone also exists. The mass diffusion for both homogeneous and heterogeneous flames is enhanced with decreased Lewis number. The magnitude of Markstein length is considerably reduced with increased droplet loading. Moreover, post-flame droplet burning behind heterogeneous flame influences the flame propagation speed and Markstein length when the liquid fuel loading is relatively low.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134179782","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

Effects of surface topography on low Reynolds number droplet/bubble flow through a constricted passage 表面形貌对低雷诺数液滴/气泡在狭窄通道中流动的影响

arXiv: Fluid Dynamics Pub Date : 2020-09-24 DOI: 10.1063/5.0031255

Aditya Singla, Bahni Ray

{"title":"Effects of surface topography on low Reynolds number droplet/bubble flow through a constricted passage","authors":"Aditya Singla, Bahni Ray","doi":"10.1063/5.0031255","DOIUrl":"https://doi.org/10.1063/5.0031255","url":null,"abstract":"This paper is an attempt to study the effects of surface topography on the flow of a droplet (or a bubble) in a low Reynolds number flow regime. Multiphase flows through a constricted passage find many interesting applications in chemistry and biology. The main parameters which determine the flow properties such as flow rate and pressure drop, and govern the complex multiphase phenomena such as drop coalescence, break-up and snap-off in a straight channel flow are the viscosity ratio, droplet size and ratio of the viscous forces to the surface tension forces (denoted by Capillary number). But in flow through a constricted passage, in addition to the above-mentioned parameters, various other geometric parameters such as constriction ratio, length and shape of the constriction, phase angle, and spacing between the constrictions also start playing an important role. Most of the studies done on the problem of drop flow through a constricted passage have aimed to understand the role of physical parameters, with some studies extending their analysis to understand the variation of one or two geometric parameters. But no study could be found which explicitly evaluates the role of surface topography. An attempt has been made to unify the current literature as well as analyze the effect of the geometric parameters by understanding the physics and mechanisms involved. The non-dimensional numbers which govern this problem are then identified using the scaling analysis.","PeriodicalId":328276,"journal":{"name":"arXiv: Fluid Dynamics","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126692172","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

Aspect ratio affects iceberg melting 宽高比影响冰山融化

arXiv: Fluid Dynamics Pub Date : 2020-09-22 DOI: 10.1103/PHYSREVFLUIDS.6.023802

Eric W. Hester, C. McConnochie, C. Cenedese, L. Couston, G. Vasil

引用次数: 11