arXiv - PHYS - Fluid Dynamics最新文献_第9页

A generalized adaptive central-upwind scheme for compressible flow simulations and preventing spurious vortices 用于可压缩流动模拟和防止虚假涡流的广义自适应中央上风方案

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-04 DOI: arxiv-2409.02340

Amareshwara Sainadh Chamarthi

{"title":"A generalized adaptive central-upwind scheme for compressible flow simulations and preventing spurious vortices","authors":"Amareshwara Sainadh Chamarthi","doi":"arxiv-2409.02340","DOIUrl":"https://doi.org/arxiv-2409.02340","url":null,"abstract":"This work introduces a novel adaptive central-upwind scheme designed for\u0000simulating compressible flows with discontinuities in the flow field. The\u0000proposed approach offers significant improvements in computational efficiency\u0000over the central gradient-based reconstruction approach presented in [1]\u0000(Hoffmann, Chamarthi and Frankel, JCP 2024). By leveraging a combination of\u0000conservative and characteristic variable reconstruction, the proposed approach\u0000demonstrates oscillation-free results while effectively reducing computational\u0000costs and improving the results. Furthermore, the adaptive central-upwind\u0000algorithm is generalized to be compatible not only with the gradient-based\u0000reconstruction as in [1] but with other existing methods. In this regard, with\u0000the proposed algorithm, the standard fifth/sixth-order reconstruction scheme\u0000has also been shown to outperform existing schemes with a 20-30% reduction in\u0000computational expense with improved results. Notably, the proposed approach has\u0000successfully prevented the generation of spurious vortices in the double shear\u0000layer test cases, even with linear schemes, showcasing its robustness and\u0000effectiveness.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212750","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

Thermoelectricity at a gallium-mercury liquid metal interface 镓汞液态金属界面的热电效应

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-04 DOI: arxiv-2409.02507

Marlone Vernet, Stephan Fauve, Christophe Gissinger

引用次数: 0

Adaptive mesh refinement algorithm for CESE schemes on quadrilateral meshes 四边形网格上 CESE 方案的自适应网格细化算法

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-03 DOI: arxiv-2409.01562

Lisong Shi, Chaoxiong Zhang, Chih-Yung Wen

引用次数: 0

Capillary-driven migration of droplets on conical fibers 锥形纤维上液滴的毛细管驱动迁移

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-03 DOI: arxiv-2409.01822

Yixiao Mao, Chengxi Zhao, Kai Mu, Kai Li, Ting Si

{"title":"Capillary-driven migration of droplets on conical fibers","authors":"Yixiao Mao, Chengxi Zhao, Kai Mu, Kai Li, Ting Si","doi":"arxiv-2409.01822","DOIUrl":"https://doi.org/arxiv-2409.01822","url":null,"abstract":"A droplet placed on a hydrophilic conical fiber tends to move toward the end\u0000of larger radii due to capillary action. Experimental investigations are\u0000performed to explore the dynamics of droplets with varying viscosities and\u0000volumes on different fibers at the microscale. Droplets are found to accelerate\u0000initially and subsequently decelerate during migration. A dynamic model is\u0000developed to capture dynamics of the droplet migration, addressing the\u0000limitations of previous equilibrium-based scaling laws. Both experimental\u0000results and theoretical predictions indicate that droplets on more divergent\u0000fibers experience a longer acceleration phase. Additionally, gravitational\u0000effects are pronounced on fibers with small cone angles, exerting a substantial\u0000influence on droplet migration even below the capillary scale. Moreover,\u0000droplets move more slowly on dry fibers compared to those prewetted with the\u0000same liquid, primarily attributed to the increased friction. The experiments\u0000reveal the formation of a residual liquid film after droplet migration on dry\u0000fibers, leading to considerable volume loss in the droplets. To encompass the\u0000intricacies of migration on dry fibers, the model is refined to incorporate a\u0000higher friction coefficient and variable droplet volumes, providing a more\u0000comprehensive depiction of the underlying physics.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212751","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

Effects of fetch length on turbulent boundary layer recovery past a step-change in surface roughness 阶梯长度对表面粗糙度阶跃变化后湍流边界层恢复的影响

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-03 DOI: arxiv-2409.02082

Martina Formichetti, Dea D. Wangsawijaya, Sean Symon, Bharathram Ganapathisubramani

{"title":"Effects of fetch length on turbulent boundary layer recovery past a step-change in surface roughness","authors":"Martina Formichetti, Dea D. Wangsawijaya, Sean Symon, Bharathram Ganapathisubramani","doi":"arxiv-2409.02082","DOIUrl":"https://doi.org/arxiv-2409.02082","url":null,"abstract":"Recent studies focusing on the response of turbulent boundary layers (TBL) to\u0000a step-change in roughness have provided insight into the scaling and\u0000characterisation of TBLs and the development of the internal layer. Although\u0000various step-change combinations have been investigated, ranging from\u0000smooth-to-rough to rough-to-smooth, the \"minimum\" required roughness fetch\u0000length over which the TBL returns to its homogeneously rough behaviour remains\u0000unclear. Moreover, the relationship between a finite- and infinite-fetch\u0000roughness function (and the equivalent sandgrain roughness) is also unknown. In\u0000this study, we determine the minimum \"equilibrium fetch length\" for TBL\u0000developing over a smooth-to-rough step-change as well as the expected error in\u0000local skin friction if the fetch length is under this minimum threshold. An\u0000experimental study is carried out where the flow is initially developed over a\u0000smooth wall, and then a step-change is introduced using patches of P24\u0000sandpaper. 12 roughness fetch lengths are tested in this study, systematically\u0000increasing from $L = 1delta_2$ up to $L = 39delta_2$ (where textit{L} is the\u0000roughness fetch length and $delta_2$ is the TBL thickness of the longest fetch\u0000case), measured over a range of Reynolds numbers ($4cdot10^2 leq Re_tau leq\u00002cdot10^5$). Results show that the minimum fetch length needed to achieve full\u0000equilibrium recovery is around $20delta_2$. Furthermore, we observe that $C_f$\u0000recovers to within 10% of its recovered value for fetch lengths $geq\u00005delta_2$. This information allows us to incorporate the effects of roughness\u0000fetch length on the skin friction and roughness function.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212753","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

Dynamic Wall Shear Stress Measurement using Event-based 3D Particle Tracking 利用基于事件的三维粒子跟踪进行动态墙壁剪切应力测量

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-03 DOI: arxiv-2409.01757

Christian E. Willert, Joachim Klinner

{"title":"Dynamic Wall Shear Stress Measurement using Event-based 3D Particle Tracking","authors":"Christian E. Willert, Joachim Klinner","doi":"arxiv-2409.01757","DOIUrl":"https://doi.org/arxiv-2409.01757","url":null,"abstract":"We describe the implementation of a 3d Lagrangian particle tracking (LPT)\u0000system based on event-based vision (EBV) and demonstrate its application for\u0000the near-wall characterization of a turbulent boundary layer (TBL) in air. The\u0000viscous sublayer of the TBL is illuminated by a thin light sheet that grazes\u0000the surface of a thin glass window inserted into the wind tunnel wall. The data\u0000simultaneously captured by three synchronized event-cameras is used to\u0000reconstruct the 3d particle tracks within 400 $mu$m of the wall on a field of\u0000view of 12.0 mm x 7.5 mm. The velocity and position of particles within the\u0000viscous sublayer permit the estimation of the local vector of the unsteady wall\u0000shear stress (WSS) under the assumption of linearity between particle velocity\u0000and WSS. Thereby, time-evolving maps of the unsteady WSS and higher order\u0000statistics are obtained that are in agreement with DNS data at matching\u0000Reynolds number. Near-wall particle acceleration provide the rate of change of\u0000the WSS which exhibits fully symmetric log-normal superstatistics. Two-point\u0000correlations of the randomly spaced WSS data are obtained by a bin-averaging\u0000approach and reveal information on the spacing of near-wall streaks. The\u0000employed compact EBV hardware coupled with suited LPT tracking algorithms\u0000provide data quality on par with currently used, considerably more expensive,\u0000high-speed framing cameras.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212755","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

A wall model for separated flows: embedded learning to improve a posteriori performance 分离流的墙模型：嵌入式学习提高后验性能

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-02 DOI: arxiv-2409.00984

Zhideng Zhou, Xin-lei Zhang, Guo-wei He, Xiaolei Yang

{"title":"A wall model for separated flows: embedded learning to improve a posteriori performance","authors":"Zhideng Zhou, Xin-lei Zhang, Guo-wei He, Xiaolei Yang","doi":"arxiv-2409.00984","DOIUrl":"https://doi.org/arxiv-2409.00984","url":null,"abstract":"The development of a wall model using machine learning methods for the\u0000large-eddy simulation (LES) of separated flows is still an unsolved problem.\u0000Our approach is to leverage the significance of separated flow data, for which\u0000existing theories are not applicable, and the existing knowledge of\u0000wall-bounded flows (such as the law of the wall) along with embedded learning\u0000to address this issue. The proposed so-called features-embedded-learning (FEL)\u0000wall model comprises two submodels: one for predicting the wall shear stress\u0000and another for calculating the eddy viscosity at the first off-wall grid\u0000nodes. We train the former using the wall-resolved LES data of the periodic\u0000hill flow and the law of the wall. For the latter, we propose a modified mixing\u0000length model, with the model coefficient trained using the ensemble Kalman\u0000method. The proposed FEL model is assessed using the separated flows with\u0000different flow configurations, grid resolutions, and Reynolds numbers. Overall\u0000good a posteriori performance is observed for predicting the statistics of the\u0000recirculation bubble, wall stresses, and turbulence characteristics. The\u0000statistics of the modelled subgrid-scale (SGS) stresses at the first off-wall\u0000grids are compared with those calculated using the wall-resolved LES data. The\u0000comparison shows that the amplitude and distribution of the SGS stresses\u0000obtained using the proposed model agree better with the reference data when\u0000compared with the conventional wall model.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227824","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 laws for the sound generation of bio-inspired flapping wings 生物启发式拍翼发声的缩放定律

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-02 DOI: arxiv-2409.00900

Li Wang, Xueyue Ji, John Young, Fang-Bao Tian

引用次数: 0

Flux scaling in Rayleigh Bénard convection: a local boundary layer analysis 瑞利贝纳德对流中的通量缩放：局部边界层分析

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-02 DOI: arxiv-2409.00930

Prafulla P. Shevkar, Baburaj A. Puthenveettil

{"title":"Flux scaling in Rayleigh Bénard convection: a local boundary layer analysis","authors":"Prafulla P. Shevkar, Baburaj A. Puthenveettil","doi":"arxiv-2409.00930","DOIUrl":"https://doi.org/arxiv-2409.00930","url":null,"abstract":"We study the effect of shear due to the large scale flow (LSF) on the heat\u0000flux in Rayleigh B'enard convection for a range of near-plate Rayleigh numbers\u0000$8times 10^7 leq Ra_w leq 5times 10^{14}$, by studying its effect on the\u0000local boundary layers (BLs) on either sides of the plumes, which are much\u0000thinner than the global shear BL created by the LSF velocity $V_F$. Considering\u0000these local BLs forced externally by the LSF, we obtain a fifth order algebraic\u0000equation for the local boundary layer thicknesses. Solving these equations\u0000numerically using $Re$ relations for aspect ratios $Gamma=1$ and 0.5, we\u0000obtain the variation of the local BL thicknesses with the longitudinal distance\u0000for various $Ra_w$. We find that the average shear acting on the edges of these\u0000local BLs ($overline{u|}_{z=delta}$) increases as $overline{u|}_{z=delta}\u0000sim Ra_w^{1/3}$ for $8times 10^7leq Ra_w leq 10^{12}$ at $Gamma=1$, and as\u0000$overline{u|}_{z=delta} sim Ra_w^{0.38}$ for $1times 10^{11}leq Ra_w leq\u00005times 10^{14}$ at $Gamma=0.5$. We then estimate the average local thermal BL\u0000thickness to find the global Nusselt number $Nu$.We find that $Nusim Ra_w^m$,\u0000where $mapprox 0.327$ for $8times 10^7 leq Ra_w leq 1times 10^{12}$ at\u0000$Gamma=1$, and $m=0.33$ for $1times10^{11}leq Ra_w leq 5times10^{14}$ at\u0000$Gamma=0.5$. Inspite of the increasing shear on these BLs with increasing\u0000$Ra_w$, we then surprisingly obtain the classical 1/3 scaling of flux since the\u0000shear forcing acting on those BLs remains sub-dominant compared to the NCBL\u0000velocities ($V_{bl}$) within these BLs, upto $Ra_wleq 5times10^{14}$.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"200 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212756","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

Continuous generation of confined bubbles: viscous effect on the gravito-capillary pinch off 密闭气泡的连续生成：粘性对重力-毛细管挤压的影响

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-01 DOI: arxiv-2409.00637

Haruka Hitomi, Ko Okumura

{"title":"Continuous generation of confined bubbles: viscous effect on the gravito-capillary pinch off","authors":"Haruka Hitomi, Ko Okumura","doi":"arxiv-2409.00637","DOIUrl":"https://doi.org/arxiv-2409.00637","url":null,"abstract":"We investigate continuous generation of bubbles from a bath of air in viscous\u0000liquid in a confined geometry. In our original setup, bubbles are spontaneously\u0000generated by virtue of buoyancy and a gate placed in the cell: the gate acts\u0000like an inverted funnel trapping air beneath it before continuously generating\u0000bubbles at the tip. The dynamics is characterized by the period of the bubble\u0000formation and the size of bubbles as a function of the amount of air under the\u0000gate. By analyzing the data obtained for various parameters, we successfully\u0000identified in a clear manner that the dynamics of the bubble formation is\u0000governed by dissipation in thin films whose thickness is determined by\u0000Derjaguin's law balanced by a gravitational energy change due to buoyancy,\u0000after examining numerous possibilities of dissipation, demonstrating the\u0000potential of scaling analysis even in extremely complex cases. Furthermore, we\u0000uncover a novel type of pinch-off condition, which convincingly explains the\u0000size of the bubble created: in the present case viscosity plays a vital role\u0000beyond the conventional mechanism of Tate in which gravity competes with\u0000capillarity, revealing a general mechanism of pinching-off at low Reynolds\u0000number. Accordingly, the present study significantly and fundamentally advance\u0000our knowledge of bubble generation and bubble pinch-off in a clear manner with\u0000the results relevant for a wide variety of applications in many fields. In\u0000particular, the present study demonstrates a new avenue in microfluidics for\u0000understanding physical principles by scaling up the system, without losing the\u0000characters of the flow at low Reynolds numbers.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142212759","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