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Volume 1: Fluid Mechanics最新文献

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Effect of Active Flow Control Mechanisms on the Turbulent Flow Structures 主动流动控制机制对湍流结构的影响
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-4798
Satoshi Tsubokura, Y. Kawaguchi
{"title":"Effect of Active Flow Control Mechanisms on the Turbulent Flow Structures","authors":"Satoshi Tsubokura, Y. Kawaguchi","doi":"10.1115/ajkfluids2019-4798","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4798","url":null,"abstract":"\u0000 Blowing or suction on the wall is expected to efficiently control the characteristics of wall-bounded turbulent flow such as wall-frictional coefficient. To understand the mechanism of the change of turbulence statistics caused by this method, we experimentally investigated the effect of uniformly blowing and suction flow on a turbulent structure in a relatively simple flow, fully developed turbulent channel flow. For blowing, the friction coefficient and the thickness of the low-speed region increased. These results imply that the boundary layer becomes unstable because the growth of viscous sublayer is rapid and the time-scale of reaching a critical thickness is small due to the blowing from the wall. On the other hand, for suction, the opposite tendency appeared.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129364092","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
Study of a Microfluidic System Based One-Step Blood Cell-Free Region for Biomarker Detection 基于一步无血细胞区微流体系统的生物标志物检测研究
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5301
Anoop Kanjirakat, R. Sadr
{"title":"Study of a Microfluidic System Based One-Step Blood Cell-Free Region for Biomarker Detection","authors":"Anoop Kanjirakat, R. Sadr","doi":"10.1115/ajkfluids2019-5301","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5301","url":null,"abstract":"\u0000 Microfluidic systems are becoming common in the development of point-of-care (PoC) diagnostic systems where various methods are used to efficiently separate blood cells from whole blood. The goal of this research is to develop a passive plasma separator that can easily be integrated into an entire blood-based diagnosis microfluidic platform. In the present work, a one-step process of creating a cell-free region in the flow without the plasma being actively extracted from the whole blood is discussed. Centrifugal force together with a backward facing step is utilized to create a blood cell-free zone. Sensors (typically less than 10 micrometers in size) are proposed to be placed in the cell-free zones for biomarker detection. A detailed numerical study for the design of the microfluidic platform is reported. The two-phase nature of the blood is modeled using a discrete element method (DEM) where blood cells are modeled as spherical constituents with the inclusion of inter-particular interactions. The sizes of the cell-free zones in the microfluidic system are measured for various geometric and flow conditions. An expansion chamber with a larger aspect ratio together with a low Reynold number flow entering it is observed to create a larger cell-free zone.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121269998","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
Direct Numerical Simulation of Supersonic Flow Over a Counter-Rotating Vane-Type Vortex Generator Implemented on Slip Wall 滑移壁上反旋转叶片型涡发生器超音速流动的直接数值模拟
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5312
T. Nagata, T. Daspit, T. Nonomura, E. Loth
{"title":"Direct Numerical Simulation of Supersonic Flow Over a Counter-Rotating Vane-Type Vortex Generator Implemented on Slip Wall","authors":"T. Nagata, T. Daspit, T. Nonomura, E. Loth","doi":"10.1115/ajkfluids2019-5312","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5312","url":null,"abstract":"\u0000 In this study, flow over a pair of vane-type vortex generator is investigated by solving the Navier–Stokes equation. A pair of the vane-type vortex generator implemented on a slip wall in laminar flow is considered so that the problem setting could be simple. The Reynolds number based on freestream quantities and the height of the vanes is set to be 500. The effect of the arrangement and geometry of vanes on the circulation coefficients, induced flow velocities, and aerodynamic force coefficients of VGs are investigated. In addition, a new non-dimensional circulation coefficient, normalized by freestream velocity and the height of the vortex core was introduced and its effectiveness is examined. This new parameter, CΓ’, include the height of the vortex core, so that appears to be a better measure of VG effectiveness on momentum exchange. From the computational results, the wider arrangement can introduce the effective vortices with small drag. Also, the longer vanes can introduce strong and effective vortices with smaller drag coefficient.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116618359","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
Consideration of CFD Analysis Accuracy of Box Fan 箱式风机CFD分析精度的考虑
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-4795
S. Tomimatsu, C. Kato
{"title":"Consideration of CFD Analysis Accuracy of Box Fan","authors":"S. Tomimatsu, C. Kato","doi":"10.1115/ajkfluids2019-4795","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4795","url":null,"abstract":"This CFD benchmark activity for a box fan has been conducted through the Industrial Committee for Supercomputing Promotion (ICSCP) and the Fan Noise Prediction Working Group from the “Promotion of Practical Use of HPC in Turbomachinery” Subcommittee established in the Turbomachinery Society of Japan. In this benchmark activity, various CFD software has been used.\u0000 In this study, ANSYS CFX 18.2 is used and the difference in results are investigated by changing the turbulence model and the mesh model. The results between the k-epsilon model and the Shear Stress Transport (SST) model show a reverse trend. That is to say, the k-epsilon model overestimates the pressure difference at the high flow range and the SST model underestimates it at the low flow range compared with the experimental result. In order to improve these numerical results, CFD analysis is conducted by changing mesh models. The number of the blade surface mesh, and the initial height, height ratio, and number of prism layers are changed, but there is no improvement through these approaches. In this paper, CFD verification and validation are conducted for the box fan.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"159 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116156543","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
Control of Particle Distribution at the Outlet of a Double Y-Microchannel Using Pulsatile Flow 用脉动流控制双y型微通道出口颗粒分布
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5219
M. Nguyen, H. Peerhossaini, M. M. Salek, M. Jarrahi
{"title":"Control of Particle Distribution at the Outlet of a Double Y-Microchannel Using Pulsatile Flow","authors":"M. Nguyen, H. Peerhossaini, M. M. Salek, M. Jarrahi","doi":"10.1115/ajkfluids2019-5219","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5219","url":null,"abstract":"\u0000 While a variety of active and passive techniques have been proposed for steady flows, pulsatile flow has received much less attention. Pulsation makes more control parameters available for passive methods and enables them to separate particles. The purpose of this work is to determine the effects of phase shift between two entering flows (only one includes the particles) on particle separation inside a double Y-microchannel. Numerical simulations were carried out for both steady and pulsating flow conditions. The results showed that when the velocity amplitude ratio (β) is less than 2, the separation index increases with the phase shift (φ) and the highest efficiency occurs at φ = 180°. A similar trend can be observed for higher values of β only if the pulsation period is short enough. A series of experiments qualitatively validated the numerical results.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128759256","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
Robustness of Turbulent Stripes in Particle-Laden Channel Flows 含颗粒通道流中湍流条纹的鲁棒性
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5149
M. Hanabusa, T. Tsukahara
{"title":"Robustness of Turbulent Stripes in Particle-Laden Channel Flows","authors":"M. Hanabusa, T. Tsukahara","doi":"10.1115/ajkfluids2019-5149","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5149","url":null,"abstract":"\u0000 It is known that intermittent localized turbulence, so-called turbulent stripes, sustains in the form of oblique bands in subcritical transitional regime of channel flows. The pattern is formed and accompanied by secondary flows along the localized turbulence. In particle-laden turbulent flows, turbulent intensity can be enhanced or suppressed by particles. However, the effect of the particles on the turbulent stripes in subcritical transitional regime is still unknown. In this paper, we investigated the particle distributions with respect to the turbulent stripes in one-way coupling simulations and studied the effect of particle-fluid interactions on the robustness of the stripes in two-way coupling simulations. In one-way coupling, the turbulent stripe provides a cluster of heavier, or large-Stokes-number, particles in a form of oblique band similar to the stripe, in the wall-parallel direction. Furthermore, heavier particles accumulate near the wall even without gravity. In two-way coupling, the stripes tend to be broken for heavier particles. The stability of the pattern also depends on the particle volume fraction. For higher volume fraction of particle, particles have a significant effect on the sustenance of the stripes. In such a case, the particle-fluid interactions exhibit the force that accelerates the fluid near the wall. The turbulent kinetic energies of large-scale flow and fine-scale eddies are attenuated by heavier particles. Different wave-number scaled structures were generated and disappeared as a laminarization process.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126162155","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
LDV Measurement of Turbulent Pipe Flow With Traveling Wavy Elastic Wall for Drag Reduction 行波弹性壁减阻紊流的LDV测量
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5691
S. Nakazawa, Takaaki Shimura, A. Mitsuishi, K. Iwamoto, A. Murata
{"title":"LDV Measurement of Turbulent Pipe Flow With Traveling Wavy Elastic Wall for Drag Reduction","authors":"S. Nakazawa, Takaaki Shimura, A. Mitsuishi, K. Iwamoto, A. Murata","doi":"10.1115/ajkfluids2019-5691","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5691","url":null,"abstract":"\u0000 Drag reduction effect by traveling wavy wall deformation control in turbulent pipe flow was experimentally investigated. From the visualization, we confirmed the downstream traveling wave although it was not uniform in the circumferential direction. When the frequency is 110 Hz, the wall deformation amplitude and the wavelength indicated that the effective values for drag reduction. The wavespeed is approximately effective values for drag reduction. As a result, the maximum drag reduction rate of 6.8 % is obtained. The result of a LDV measurement shows that the mean streamwise velocity gradient decreased near the wall by the control, which leads to drag reduction.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131600039","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
Experimental Investigation for the Better Control of Flows Over a Simplified Vehicle Configuration With Dielectric Barrier Discharge Plasma Actuator 介质阻挡放电等离子体作动器在简化车辆配置下更好地控制流动的实验研究
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5121
S. Sekimoto, Keigo Shimizu, T. Nakashima, K. Fujii, Takenori Hiraoka, T. Nouzawa
{"title":"Experimental Investigation for the Better Control of Flows Over a Simplified Vehicle Configuration With Dielectric Barrier Discharge Plasma Actuator","authors":"S. Sekimoto, Keigo Shimizu, T. Nakashima, K. Fujii, Takenori Hiraoka, T. Nouzawa","doi":"10.1115/ajkfluids2019-5121","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5121","url":null,"abstract":"\u0000 Reduction of aerodynamic drag is a big subject for vehicle development from the point of view of the global environment conservation. On the other hand, the optimization of vehicle body for less aerodynamic drag strictly defines the body shape and limits the freedom of design. Therefore, novel flow control technology is desired to enable small aerodynamic drag with excellent design. In the present study, a dielectric barrier discharge plasma actuator is installed on a simplified vehicle model with the round-shaped rear end to control the flow around the rear end for drag reduction. Experiments are conducted with the model (L840mm × H300mm × W300mm) in a Gottingen type wind tunnel with a ground plate. Reynolds number is fixed at 1,200,000, corresponding to a freestream velocity of approximately 20 m/s. Aerodynamic force, surface pressure near the rear edge, and total pressure and velocity field are measured. In the result of aerodynamic force measurement, driving plasma actuator successfully achieves 3% drag reduction at the most. Flow field measurement of total pressure and two-component velocity shows the difference of vortex structure near the rear end between off and on. Plasma actuation in this study can move the vortex structure away from the body surface rather than suppress the vortex or circulation.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129543308","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
Open-Source Computational Fluid Dynamics in Engineering Education 工程教育中的开源计算流体动力学
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-5475
I. Nedyalkov
{"title":"Open-Source Computational Fluid Dynamics in Engineering Education","authors":"I. Nedyalkov","doi":"10.1115/ajkfluids2019-5475","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5475","url":null,"abstract":"\u0000 Computational Fluid Dynamics (CFD) is widely used in industry but is not discussed sufficiently in undergraduate engineering education. In some cases, CFD is studied only from a mathematical perspective, focusing on computational partial differential equations, and in some cases it is introduced as a black-box tool. A hybrid CFD class was developed for undergraduate and graduate students at the University of New Hampshire, which combines the two approaches. The students are exposed to the mathematics and physics behind CFD, and they also utilize OpenFOAM — an open source CFD package — to work on practical problems. Since the code is open-source, the students are able to see and modify it. Although OpenFOAM is challenging due to the minimum graphical user interface, the code-base environment forces the students to learn what the code is doing. Sample assignments and project submissions from the students are presented in the paper.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128584382","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
Experimental Analysis of Turbulent Wake Development Behind a Permeable Cylinder 透水圆柱后湍流尾迹发展的实验分析
Volume 1: Fluid Mechanics Pub Date : 2019-11-20 DOI: 10.1115/ajkfluids2019-4790
Yasufumi Horimoto, Yusuke Suzuki, K. Hagiwara, Y. Kawaguchi
{"title":"Experimental Analysis of Turbulent Wake Development Behind a Permeable Cylinder","authors":"Yasufumi Horimoto, Yusuke Suzuki, K. Hagiwara, Y. Kawaguchi","doi":"10.1115/ajkfluids2019-4790","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4790","url":null,"abstract":"\u0000 To investigate the effect of permeability on turbulent wake behind a cylinder in uniform flow, we conduct particle image velocimetry on turbulent wake behind permeable cylinders, which are made of mesh sheets, of different permeabilities and compare the results with those for a solid cylinder. For relatively lower permeability, turbulent wake is quite similar to the case for a solid cylinder except for a slight shift in the streamwise direction of the reversed flow region implying turbulent Kármán vortex shedding. On the other hand, for higher permeability, the structure of turbulence is qualitatively different. More concretely, turbulent Kármán vortices disappear. Interestingly, however, the momentum deficit for such flow is comparable with that of a solid cylinder. This considerable momentum deficit can be understood with isotropic turbulence caused by the flow penetrating through the mesh constructing the cylinders. These results imply that turbulent wake behind a permeable cylinder involves dynamics both of wake and grid turbulence and the latter one dominates when permeability is sufficiently high.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131025879","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
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