Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl最新文献
The current study is focused on the flow through offset, wall confined vertical inserts in a channel. The columns are intended to act as the thermal storage media, which continuously exchange heat with the channel fluid to regulate it thermally. These columns could, for example, be filled with a phase change material (PCM) for passive thermal regulation, or have hot or cold fluid pumped through them for active thermal regulation. The current study has two parts: (1) the flow characterization without heat transfer, and (2) flow characterization during thermal exchange with a PCM used for regulation of bulk fluid temperature. The work presented here is focused only on the first part of the study. The experiments were conducted in a narrow channel, with water as the working fluid. Two geometries of the vertical columns (circular and square) and two offset lengths were considered. For each configuration, experiments were conducted at Reynolds numbers of 20, 50 and 90 (based of the column’s characteristic length). Particle image velocimetry was used to measure the two-dimensional velocity field in a horizontal plane at multiple regions of interest along the length of the channel to characterize the flow passing over columns. The results indicate vortex shedding at the two higher Reynolds numbers. The generation, magnitude and decay rate of turbulent energy is shown to have an offset dependency at Re = 90, but a column shape dependency at Re = 50. The mean flow has a shape dependency due to the difference in separation point over the square and circular columns.
{"title":"Turbulent Flow Characteristics Over Offset Wall Confined Columns in a Channel at Low Reynolds Numbers","authors":"K. Toxopeus, K. Siddiqui","doi":"10.1115/FEDSM2018-83519","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83519","url":null,"abstract":"The current study is focused on the flow through offset, wall confined vertical inserts in a channel. The columns are intended to act as the thermal storage media, which continuously exchange heat with the channel fluid to regulate it thermally. These columns could, for example, be filled with a phase change material (PCM) for passive thermal regulation, or have hot or cold fluid pumped through them for active thermal regulation. The current study has two parts: (1) the flow characterization without heat transfer, and (2) flow characterization during thermal exchange with a PCM used for regulation of bulk fluid temperature. The work presented here is focused only on the first part of the study.\u0000 The experiments were conducted in a narrow channel, with water as the working fluid. Two geometries of the vertical columns (circular and square) and two offset lengths were considered. For each configuration, experiments were conducted at Reynolds numbers of 20, 50 and 90 (based of the column’s characteristic length). Particle image velocimetry was used to measure the two-dimensional velocity field in a horizontal plane at multiple regions of interest along the length of the channel to characterize the flow passing over columns. The results indicate vortex shedding at the two higher Reynolds numbers. The generation, magnitude and decay rate of turbulent energy is shown to have an offset dependency at Re = 90, but a column shape dependency at Re = 50. The mean flow has a shape dependency due to the difference in separation point over the square and circular columns.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74400076","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}
Morteza Kiasadegh, O. Abouali, H. Emdad, G. Ahmadi
In this study, unsteady flow field and fibrous particle deposition in a realistic model of human upper airway system including vestibule to the end of trachea were investigated using the CFD technique. The airway passage model was constructed from the CT image of a 24 year old healthy woman. Unsteady airflow patterns during a full breathing cycle were simulated by solving the Navier-Stokes and continuity equations. For ellipsoidal fiber trajectory analysis under cyclic breathing condition, several user defined functions (UDFs) were coupled to the ANSYS-Fluent discrete phase model (DPM). The presented formulation accounted for solving the coupled translational and rotational equations of motion of ellipsoidal fibers. Total and regional depositions for a range of fiber sizes were evaluated. The transient particle deposition fraction was compared with those obtained from the equivalent steady flow condition. The presented results showed that the steady simulation can predict the total fibrous particle deposition during cyclic breathing with reasonable accuracy but cannot properly predict the regional deposition of particles.
{"title":"Numerical Simulation of Airflow and Ellipsoidal Particle Deposition in Human Upper Respiratory Tract","authors":"Morteza Kiasadegh, O. Abouali, H. Emdad, G. Ahmadi","doi":"10.1115/FEDSM2018-83380","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83380","url":null,"abstract":"In this study, unsteady flow field and fibrous particle deposition in a realistic model of human upper airway system including vestibule to the end of trachea were investigated using the CFD technique. The airway passage model was constructed from the CT image of a 24 year old healthy woman.\u0000 Unsteady airflow patterns during a full breathing cycle were simulated by solving the Navier-Stokes and continuity equations. For ellipsoidal fiber trajectory analysis under cyclic breathing condition, several user defined functions (UDFs) were coupled to the ANSYS-Fluent discrete phase model (DPM). The presented formulation accounted for solving the coupled translational and rotational equations of motion of ellipsoidal fibers.\u0000 Total and regional depositions for a range of fiber sizes were evaluated. The transient particle deposition fraction was compared with those obtained from the equivalent steady flow condition. The presented results showed that the steady simulation can predict the total fibrous particle deposition during cyclic breathing with reasonable accuracy but cannot properly predict the regional deposition of particles.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"107 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91174253","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}
Hariprasad Chakkalaparambil Many, V. Srinivasan, A. Raghavan
In this paper, flow structures around a corner modified square cylinder (side dimension, Bo) are presented and discussed. Cylinders with various corner arcs (circular) were considered (arc radius ‘r’). For various Corner Ratios (CR = r/Bo), values ranging from 0 to 0.5, flow visualization experiments were conducted in a water channel and the results are reported at Re = 2100 (based on Bo). Results presented are for two cases (a) stationary cylinders reporting the values of CD (coefficient of drag), St (Strouhal no.), and D (vortex size) and (b) oscillating cylinders at fe/fs = 1 (fe is the cylinder excitation frequency and fs is the vortex shedding frequency) and a/Bo = 0.8 (a is the cylinder oscillation amplitude). The work is aimed to explore the most effective configuration for drag reduction. Cylinder with corner ratio of 0.2 is proved to be the most effective one among the cases considered in this study with 19.3% drag reduction. As a major highlight, in contrast to the results of the previous studies, current study do not reveal a monotonous decrease of drag with increasing corner modification. Instead, it is shown here that, there is a specific value of CR ratio where the drag is the minimum most. A peculiar type of vortex structure was observed in the cases of stationary cylinders with CR > 0.2, contributing to the increase in drag. In the case of oscillating cylinders, description of one complete cycle for all CR ratios at various time instances are presented. The near-wake structures were observed to be dependent on the CR ratio. Counter intuitively, cylinder oscillation does not bring major difference in vortex size compared to the stationary case.
{"title":"Effect of Corner-Arc on the Flow Structures Around a Square Cylinder","authors":"Hariprasad Chakkalaparambil Many, V. Srinivasan, A. Raghavan","doi":"10.1115/FEDSM2018-83367","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83367","url":null,"abstract":"In this paper, flow structures around a corner modified square cylinder (side dimension, Bo) are presented and discussed. Cylinders with various corner arcs (circular) were considered (arc radius ‘r’). For various Corner Ratios (CR = r/Bo), values ranging from 0 to 0.5, flow visualization experiments were conducted in a water channel and the results are reported at Re = 2100 (based on Bo). Results presented are for two cases (a) stationary cylinders reporting the values of CD (coefficient of drag), St (Strouhal no.), and D (vortex size) and (b) oscillating cylinders at fe/fs = 1 (fe is the cylinder excitation frequency and fs is the vortex shedding frequency) and a/Bo = 0.8 (a is the cylinder oscillation amplitude). The work is aimed to explore the most effective configuration for drag reduction. Cylinder with corner ratio of 0.2 is proved to be the most effective one among the cases considered in this study with 19.3% drag reduction. As a major highlight, in contrast to the results of the previous studies, current study do not reveal a monotonous decrease of drag with increasing corner modification. Instead, it is shown here that, there is a specific value of CR ratio where the drag is the minimum most. A peculiar type of vortex structure was observed in the cases of stationary cylinders with CR > 0.2, contributing to the increase in drag. In the case of oscillating cylinders, description of one complete cycle for all CR ratios at various time instances are presented. The near-wake structures were observed to be dependent on the CR ratio. Counter intuitively, cylinder oscillation does not bring major difference in vortex size compared to the stationary case.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81153863","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}
The classical grid turbulence is revisited in an effort to better understand the role of the finite-thickness flow passage of the turbulence generator. The virtually zero-thickness orificed perforated plate (OPP) is contrasted with its reversed counterpart, the converging-nozzled perforated plate (CNPP). The respective turbulent flows are detailed via a triple-wire of a constant-temperature hot wire anemometer. The two flows are compared in terms of the spatial evolution of the essential turbulence characteristics, including the various turbulence intensities and length scales. As expected, a higher level of turbulence resulted from the sharp edges of the OPP. Surprisingly, the finite-thickness converging passages of the CNPP caused the other turbulence parameters to behave rather perplexingly.
{"title":"Perforated-Plate Turbulence: Orifice Versus Converging Nozzle","authors":"Yang Yang, D. Ting, S. Ray","doi":"10.1115/FEDSM2018-83038","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83038","url":null,"abstract":"The classical grid turbulence is revisited in an effort to better understand the role of the finite-thickness flow passage of the turbulence generator. The virtually zero-thickness orificed perforated plate (OPP) is contrasted with its reversed counterpart, the converging-nozzled perforated plate (CNPP). The respective turbulent flows are detailed via a triple-wire of a constant-temperature hot wire anemometer. The two flows are compared in terms of the spatial evolution of the essential turbulence characteristics, including the various turbulence intensities and length scales. As expected, a higher level of turbulence resulted from the sharp edges of the OPP. Surprisingly, the finite-thickness converging passages of the CNPP caused the other turbulence parameters to behave rather perplexingly.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"345 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77792242","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}
The problem of three-dimensional steady shock wave interaction is a key issue for supersonic and hypersonic corner flow. Due to the complexity of shock configurations, there is no analytical theory to such problem and the mechanism of three-dimensional shock waves and boundary layer interaction has not been clearly known. In this paper, an analytical approach to the problem of three-dimensional steady shock wave interaction was exhibited to analytically interpret the mechanism of three-dimensional interaction of two oblique planar shock waves. The results showed that the problem of three-dimensional steady shock wave interaction could be transformed to that of two moving shock wave interaction in two-dimensional plane, and there are various interaction configurations such as regular interaction, Mach interaction and weak interaction. The mechanism of three-dimensional shock wave interaction is helpful to understand the complex flow mechanism induced by three-dimensional shock wave and boundary layer in hypersonic flow. The interaction of three-dimensional shock waves and boundary layer plays important role in the complex flow feature in hypersonic rudder region. The contact surface induced by three-dimensional shock waves represents a local jet. When the flow jet impinges on the boundary layer of wall surface, the jet makes the boundary layer thinner and will inevitably cause local heat flux peak. The interaction configurations of three-dimensional shock wave play important role in the gasdynamic heating mechanisms of hypersonic complex flow.
{"title":"The Mechanism of Three-Dimension Steady Shock Wave Interaction","authors":"Chun Wang, Ruixin Yang, Zonglin Jiang","doi":"10.1115/FEDSM2018-83023","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83023","url":null,"abstract":"The problem of three-dimensional steady shock wave interaction is a key issue for supersonic and hypersonic corner flow. Due to the complexity of shock configurations, there is no analytical theory to such problem and the mechanism of three-dimensional shock waves and boundary layer interaction has not been clearly known. In this paper, an analytical approach to the problem of three-dimensional steady shock wave interaction was exhibited to analytically interpret the mechanism of three-dimensional interaction of two oblique planar shock waves. The results showed that the problem of three-dimensional steady shock wave interaction could be transformed to that of two moving shock wave interaction in two-dimensional plane, and there are various interaction configurations such as regular interaction, Mach interaction and weak interaction. The mechanism of three-dimensional shock wave interaction is helpful to understand the complex flow mechanism induced by three-dimensional shock wave and boundary layer in hypersonic flow. The interaction of three-dimensional shock waves and boundary layer plays important role in the complex flow feature in hypersonic rudder region. The contact surface induced by three-dimensional shock waves represents a local jet. When the flow jet impinges on the boundary layer of wall surface, the jet makes the boundary layer thinner and will inevitably cause local heat flux peak. The interaction configurations of three-dimensional shock wave play important role in the gasdynamic heating mechanisms of hypersonic complex flow.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86302050","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}
Turbulent free jets attracted the focus of many scientists within the past century regarding the understanding of mass- and momentum transport in the turbulent shear field, especially in the near-field and the self-similar region. Recent investigations attempt to understand the intermediate fields, called the mixing transition or ‘the route to self-similarity’. An apparent gap is recognized in light of this mixing transition, with two main conjectures being put forth. Firstly the flow will always asymptotically reach a fully self-similar state if boundary conditions permit. The second proposes partial and local self-similarity within the mixing transition. We address the later with an experimental investigation of the intermediate field turbulence dynamics in a non-confined free jet with a nozzle diameter of 12.7 mm and an outer scale Reynolds number of 15,000. High speed Particle Image Velocimetry (PIV) is used to record the velocity fields with a final spatial resolution of 194 × 194 μm2. The analysis focuses on higher order moments and two-point correlations of velocity variances in space and time. We observed local self-similarity in the measured correlation fields. Coherent structures are present within the near-field where the turbulent energy spectrum cascades along a dissipative slope. Towards the transition region, the spectrum smoothly transforms to a viscous cascade, as it is commonly observed in the self-similar region.
{"title":"Coherent Structures and Correlation Fields in the Mixing Transition of a Turbulent Round Free Jet","authors":"B. Krohn, Sunming Qin, V. Petrov, A. Manera","doi":"10.1115/FEDSM2018-83280","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83280","url":null,"abstract":"Turbulent free jets attracted the focus of many scientists within the past century regarding the understanding of mass- and momentum transport in the turbulent shear field, especially in the near-field and the self-similar region. Recent investigations attempt to understand the intermediate fields, called the mixing transition or ‘the route to self-similarity’. An apparent gap is recognized in light of this mixing transition, with two main conjectures being put forth. Firstly the flow will always asymptotically reach a fully self-similar state if boundary conditions permit. The second proposes partial and local self-similarity within the mixing transition. We address the later with an experimental investigation of the intermediate field turbulence dynamics in a non-confined free jet with a nozzle diameter of 12.7 mm and an outer scale Reynolds number of 15,000. High speed Particle Image Velocimetry (PIV) is used to record the velocity fields with a final spatial resolution of 194 × 194 μm2. The analysis focuses on higher order moments and two-point correlations of velocity variances in space and time. We observed local self-similarity in the measured correlation fields. Coherent structures are present within the near-field where the turbulent energy spectrum cascades along a dissipative slope. Towards the transition region, the spectrum smoothly transforms to a viscous cascade, as it is commonly observed in the self-similar region.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79519280","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}
The continuous development of wind turbine technology gradually leads to larger, more flexible blades with increasing aspect ratios and high tip speeds, while in everyday operation or extreme cases the blades experience stalled flow conditions. These aforementioned facts create the need for further study and physical understanding of stall induced vibrations – stall flutter. In this context an aeroelastic setup was constructed at the NTUA subsonic wind tunnel with a rigid rectangular wing (500 mm × 1400 mm) of a NACA 64-418 airfoil supported by a spring system that enables pitching and plunging motions. The elastic axis of the wing is located 35% of the chord far from the leading edge while its center of mass at 46%. Increasing the free stream velocity (up to Re = 670 000) under various initial static angles of attack, the wing was set at fluid induced oscillations (pitching and plunging). The response of the wing under these conditions was recorded employing two accelerometers and two wire sensors for both the rotational and linear wing displacements. At the same time, in the middle of the wing span thirty (30) fast responsive pressure transducers measured the pressure distribution along the chord, while strain gauges attached to the wing rotating shaft measured the applied unsteady aerodynamic loading. Based on the above simultaneously measured quantities various aspects of the aeroelastic instability of the examined wing were revealed.
随着风力机技术的不断发展，叶片逐渐变得更大、更灵活，展弦比越来越大，叶尖速度也越来越高，但在日常运行或极端情况下，叶片会出现停滞状态。上述事实表明，需要对失速引起的振动-失速颤振进行进一步的研究和物理理解。在这种情况下，在NTUA亚音速风洞中建立了一个气动弹性装置，该装置采用刚性矩形机翼(500 mm × 1400 mm)的NACA 64-418翼型，由弹簧系统支撑，可以实现俯仰和俯冲运动。机翼弹性轴距弦前缘35%，质心距弦前缘46%。在不同初始静态迎角下，增加自由流速度(Re = 67万)，将机翼设置为流体诱导振荡(俯仰和俯冲)。使用两个加速度计和两个线传感器记录了机翼在这些条件下的响应，用于旋转和线性机翼位移。同时，在翼跨中间的30个快速响应压力传感器测量了沿弦的压力分布，而连接在机翼旋转轴上的应变片测量了所施加的非定常气动载荷。基于上述同时测量的量，揭示了被测机翼气动弹性失稳的各个方面。
{"title":"Stall Flutter Measurements on a Rectangular Wing","authors":"D. Gkiolas, F. Mouzakis, D. Mathioulakis","doi":"10.1115/FEDSM2018-83162","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83162","url":null,"abstract":"The continuous development of wind turbine technology gradually leads to larger, more flexible blades with increasing aspect ratios and high tip speeds, while in everyday operation or extreme cases the blades experience stalled flow conditions. These aforementioned facts create the need for further study and physical understanding of stall induced vibrations – stall flutter. In this context an aeroelastic setup was constructed at the NTUA subsonic wind tunnel with a rigid rectangular wing (500 mm × 1400 mm) of a NACA 64-418 airfoil supported by a spring system that enables pitching and plunging motions. The elastic axis of the wing is located 35% of the chord far from the leading edge while its center of mass at 46%. Increasing the free stream velocity (up to Re = 670 000) under various initial static angles of attack, the wing was set at fluid induced oscillations (pitching and plunging). The response of the wing under these conditions was recorded employing two accelerometers and two wire sensors for both the rotational and linear wing displacements. At the same time, in the middle of the wing span thirty (30) fast responsive pressure transducers measured the pressure distribution along the chord, while strain gauges attached to the wing rotating shaft measured the applied unsteady aerodynamic loading. Based on the above simultaneously measured quantities various aspects of the aeroelastic instability of the examined wing were revealed.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80912187","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}
Twin round and elliptic jets with nozzle spacing of S/d = 2.8 are investigated and the results are compared with those obtained from single jets. The measurements were performed at Re = 10000 using particle image velocimetry. The results show that the twin elliptic jets merge and combine faster than the round jets. However, the twin elliptic jets have lower spreading than their corresponding single jet but in the round jets it is opposite. The vortical structures obtained using swirling strength analysis are more intense in the elliptic jets compared with the round jets; consistent with their higher spreading. In the shear layers, the velocity skewness is considerably positive due to the diffusion of high-speed jet fluid towards the ambient. On the other hand, the streamwise skewness on the centerline is negative because of the entrainment of low-speed ambient fluid; resulting in centerline velocity decay. In addition, the joint and weighted joint probability density functions are used to understand the dominant events which contribute into the mixing of the jets with their surrounding fluid.
{"title":"Comparative Evaluation of Single/Twin Round and Elliptic Jets Using Particle Image Velocimetry","authors":"Seyed Sobhan Aleyasin, M. Tachie","doi":"10.1115/FEDSM2018-83495","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83495","url":null,"abstract":"Twin round and elliptic jets with nozzle spacing of S/d = 2.8 are investigated and the results are compared with those obtained from single jets. The measurements were performed at Re = 10000 using particle image velocimetry. The results show that the twin elliptic jets merge and combine faster than the round jets. However, the twin elliptic jets have lower spreading than their corresponding single jet but in the round jets it is opposite. The vortical structures obtained using swirling strength analysis are more intense in the elliptic jets compared with the round jets; consistent with their higher spreading. In the shear layers, the velocity skewness is considerably positive due to the diffusion of high-speed jet fluid towards the ambient. On the other hand, the streamwise skewness on the centerline is negative because of the entrainment of low-speed ambient fluid; resulting in centerline velocity decay. In addition, the joint and weighted joint probability density functions are used to understand the dominant events which contribute into the mixing of the jets with their surrounding fluid.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81348303","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}
Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl
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