Pub Date : 2019-11-24DOI: 10.1103/physrevfluids.5.110518
Colm‐cille P. Caulfield
Understanding how turbulence leads to the enhanced irreversible transport of heat and other scalars in density-stratified fluids is a fundamental research challenge in geophysical and environmental fluid dynamics, although there are still leading-order open questions. One useful approach to addressing these questions is to consider carefully chosen idealized flow geometries. It is then possible to analyze in detail the energetic pathways and the subtle interplay between various characteristic time and length scales. Such analyses can lead to insight into at least some of the apparently mysterious emergent properties of turbulent stratified mixing.
{"title":"Open questions in turbulent stratified mixing: Do we even know what we do not know?","authors":"Colm‐cille P. Caulfield","doi":"10.1103/physrevfluids.5.110518","DOIUrl":"https://doi.org/10.1103/physrevfluids.5.110518","url":null,"abstract":"Understanding how turbulence leads to the enhanced irreversible transport of heat and other scalars in density-stratified fluids is a fundamental research challenge in geophysical and environmental fluid dynamics, although there are still leading-order open questions. One useful approach to addressing these questions is to consider carefully chosen idealized flow geometries. It is then possible to analyze in detail the energetic pathways and the subtle interplay between various characteristic time and length scales. Such analyses can lead to insight into at least some of the apparently mysterious emergent properties of turbulent stratified mixing.","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82613906","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 coalescence dynamics of an ethanol droplet freely falling on a sessile ethanol droplet is investigated experimentally using a high-speed imaging system. The regime maps showing the partial coalescence and spreading behaviors in the plane of the Weber number (We) and the volume of the sessile droplet (Vp) normalized with the volume of the impacting droplet (Vi) have been presented. The partial coalescence phenomenon is observed when the ratio of the volume of the sessile droplet to that of the impacting droplet (Vp/Vi) is greater than two. For Vp/Vi = 2, the size of the daughter droplet is found to be about 0.1 times as that of the impacting droplet, which increases with the increase in the We and normalized volume of the sessile droplet. In the present study, the negative curvature of the droplet coupled with the presence of the substrate leads to a different coalescence dynamics.
{"title":"Coalescence dynamics of a droplet on a sessile droplet","authors":"Manish Kumar, R. Bhardwaj, K. Sahu","doi":"10.1063/1.5129901","DOIUrl":"https://doi.org/10.1063/1.5129901","url":null,"abstract":"The coalescence dynamics of an ethanol droplet freely falling on a sessile ethanol droplet is investigated experimentally using a high-speed imaging system. The regime maps showing the partial coalescence and spreading behaviors in the plane of the Weber number (We) and the volume of the sessile droplet (Vp) normalized with the volume of the impacting droplet (Vi) have been presented. The partial coalescence phenomenon is observed when the ratio of the volume of the sessile droplet to that of the impacting droplet (Vp/Vi) is greater than two. For Vp/Vi = 2, the size of the daughter droplet is found to be about 0.1 times as that of the impacting droplet, which increases with the increase in the We and normalized volume of the sessile droplet. In the present study, the negative curvature of the droplet coupled with the presence of the substrate leads to a different coalescence dynamics.","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86316328","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}
Pub Date : 2019-11-23DOI: 10.1103/physrevfluids.5.013601
Sivanandan Kavuri, Mounika Balla, M. Tripathi, K. Sahu, R. Govindarajan
In most of the industrial processes today we might have to deal with bubbly flows. The starting point to this problem is to find the interactions between a pair of bubbles. In this thesis the effect of viscosity and density ratios on a pair of rising bubbles is examined. The ranges of the viscosity and the density ratios are chosen such that they represent pairs of fluids which are commonly used in industries and households. To understand the dynamics of pair of bubbles rising inside quiescent liquid we compared them with the dynamics of a of single bubble rising in a liquid. Tripathi et al. [20] identified five different regimes which describe the dynamics of a rising bubble in a quiescent liquid. The region I corresponds to low inertial regime where an air bubble rises maintaining its azimuthal symmetry and the region III corresponds to high inertial regime where the motion of a rising air bubble is chaotic. In this thesis the effect of the viscosity ratio and the density ratios on two bubbles rising side by side are found in region I and region III corresponding to the rise dynamics of a single bubble. Further to completely analyze the dynamics of pair of bubbles we plotted shapes, trajectories, aspect ratios, velocity contours and voricity of the two-bubbles over a wide range of the viscosity and density ratios(ranging from gas-liquid to liquid-liquid systems).
{"title":"Effect of viscosity and density ratios on two drops rising side by side","authors":"Sivanandan Kavuri, Mounika Balla, M. Tripathi, K. Sahu, R. Govindarajan","doi":"10.1103/physrevfluids.5.013601","DOIUrl":"https://doi.org/10.1103/physrevfluids.5.013601","url":null,"abstract":"In most of the industrial processes today we might have to deal with bubbly flows. The starting point to this problem is to find the interactions between a pair of bubbles. In this thesis the effect of viscosity and density ratios on a pair of rising bubbles is examined. The ranges of the viscosity and the density ratios are chosen such that they represent pairs of fluids which are commonly used in industries and households. To understand the dynamics of pair of bubbles rising inside quiescent liquid we compared them with the dynamics of a of single bubble rising in a liquid. Tripathi et al. [20] identified five different regimes which describe the dynamics of a rising bubble in a quiescent liquid. The region I corresponds to low inertial regime where an air bubble rises maintaining its azimuthal symmetry and the region III corresponds to high inertial regime where the motion of a rising air bubble is chaotic. In this thesis the effect of the viscosity ratio and the density ratios on two bubbles rising side by side are found in region I and region III corresponding to the rise dynamics of a single bubble. Further to completely analyze the dynamics of pair of bubbles we plotted shapes, trajectories, aspect ratios, velocity contours and voricity of the two-bubbles over a wide range of the viscosity and density ratios(ranging from gas-liquid to liquid-liquid systems).","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86594020","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}
Elastic instabilities are identified as flow instabilities occurring in the presence of low inertial effects, induced by the combination of strong elastic forces with nonlinearities of the flow. In continuous flow laminar mixing applications, the onset of these instabilities is likely to occur in the window of applied flow rates; therefore, it is important to understand the effects of their onset on the process efficiency. In this work, we investigated experimentally the onset of elastic instabilities in two tubular static mixers with different geometric features, i.e., the Kenics helical mixer and the SMB-R mixer, the latter characterized by a double X-shaped bar geometry. We obtained concentration maps at various mixer lengths by means of planar laser induced fluorescence techniques. To deduce a generalized effect of the fluid elasticity on the mixing patterns, we tested three fluids with different rheological behavior—a Boger fluid and two shear-thinning fluids. For all cases, we observed deviations from the Newtonian benchmark as soon as the Deborah number exceeded unity, even though different transitions occurred as the mean flow rate increased. The effect of the instability on the mixing patterns strongly depended on the different kinematics induced by the two geometries: for the helical mixer, the typical lamellar structure is not recovered and the two liquid streams remain unmixed, while for the SMB-R, the concentration maps are strongly unsteady, showing temporally and spatially chaotic fluctuations of the mass fraction. In both cases, the instabilities worsen the mixing efficiency compared to the Newtonian case.
{"title":"Viscoelastic flow instabilities in static mixers: Onset and effect on the mixing efficiency","authors":"S. Migliozzi, L. Mazzei, P. Angeli","doi":"10.1063/5.0038602","DOIUrl":"https://doi.org/10.1063/5.0038602","url":null,"abstract":"Elastic instabilities are identified as flow instabilities occurring in the presence of low inertial effects, induced by the combination of strong elastic forces with nonlinearities of the flow. In continuous flow laminar mixing applications, the onset of these instabilities is likely to occur in the window of applied flow rates; therefore, it is important to understand the effects of their onset on the process efficiency. In this work, we investigated experimentally the onset of elastic instabilities in two tubular static mixers with different geometric features, i.e., the Kenics helical mixer and the SMB-R mixer, the latter characterized by a double X-shaped bar geometry. We obtained concentration maps at various mixer lengths by means of planar laser induced fluorescence techniques. To deduce a generalized effect of the fluid elasticity on the mixing patterns, we tested three fluids with different rheological behavior—a Boger fluid and two shear-thinning fluids. For all cases, we observed deviations from the Newtonian benchmark as soon as the Deborah number exceeded unity, even though different transitions occurred as the mean flow rate increased. The effect of the instability on the mixing patterns strongly depended on the different kinematics induced by the two geometries: for the helical mixer, the typical lamellar structure is not recovered and the two liquid streams remain unmixed, while for the SMB-R, the concentration maps are strongly unsteady, showing temporally and spatially chaotic fluctuations of the mass fraction. In both cases, the instabilities worsen the mixing efficiency compared to the Newtonian case.","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91127054","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}
Felix Schindler, Till Zuerner, T. Vogt, Sven Eckertz, J. Schumacher
{"title":"Rayleigh-B'{e}nard Convection in Liquid Metal under Influence of Vertical Magnetic Fields","authors":"Felix Schindler, Till Zuerner, T. Vogt, Sven Eckertz, J. Schumacher","doi":"10.14278/RODARE.232","DOIUrl":"https://doi.org/10.14278/RODARE.232","url":null,"abstract":"","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78268779","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}
Bryson T. Sullivan, T. Whalen, S. Laurence, D. Bodony
Sustained flight at hypersonic speeds presents an enduring challenge to vehicle design and control. An extreme aerothermal environment acting on geometrically thin, multifunctional structures can r...
{"title":"Direct Simulation of Fluid–Structure Interaction in a Hypersonic Compression-Ramp Flow","authors":"Bryson T. Sullivan, T. Whalen, S. Laurence, D. Bodony","doi":"10.2514/1.J059072","DOIUrl":"https://doi.org/10.2514/1.J059072","url":null,"abstract":"Sustained flight at hypersonic speeds presents an enduring challenge to vehicle design and control. An extreme aerothermal environment acting on geometrically thin, multifunctional structures can r...","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86112760","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}
Mohammad Ahmed, C. Howell, D. Rotsch, J. Nolen, F. Krishichayan, Noiki Fumnilola Risalah
Radioisotopes play important roles in numerous areas ranging from medical treatments to national security and basic re-search. Some examples include investigations of structures and reactions involving atomic nuclei, Mossbauer spectroscopy, radio- thermoelectric generation, nuclear device detection, and the mitigation of nuclear proliferation. The high speci(cid:12)c activity beta emitters such as 47 Sc, 67 Cu, 77 As, and 186 Re are of extreme interest to the community as they have ideal nuclear properties for medical applications. The present ongoing work is dedicated to develop methodologies for the determination of photonuclear cross sections over multiple energies in a single irradiation and simultaneously determine the feasibility of production of these in-demand radioisotopes using electron linear accelerator. By using activation techniques, cross sectional data is being obtained for these radioisotopes. The present talk will be focused on the technology development for medical radioisotope production using monoenergetic photon beams provided by the HIGS facility at TUNL. Work supported in part by the U.S. DOE Isotope Program
{"title":"Measurements of Photonuclear Reaction Pathways towards Promising Medical Radioisotopes","authors":"Mohammad Ahmed, C. Howell, D. Rotsch, J. Nolen, F. Krishichayan, Noiki Fumnilola Risalah","doi":"10.2172/1830308","DOIUrl":"https://doi.org/10.2172/1830308","url":null,"abstract":"Radioisotopes play important roles in numerous areas ranging from medical treatments to national security and basic re-search. Some examples include investigations of structures and reactions involving atomic nuclei, Mossbauer spectroscopy, radio- thermoelectric generation, nuclear device detection, and the mitigation of nuclear proliferation. The high speci(cid:12)c activity beta emitters such as 47 Sc, 67 Cu, 77 As, and 186 Re are of extreme interest to the community as they have ideal nuclear properties for medical applications. The present ongoing work is dedicated to develop methodologies for the determination of photonuclear cross sections over multiple energies in a single irradiation and simultaneously determine the feasibility of production of these in-demand radioisotopes using electron linear accelerator. By using activation techniques, cross sectional data is being obtained for these radioisotopes. The present talk will be focused on the technology development for medical radioisotope production using monoenergetic photon beams provided by the HIGS facility at TUNL. Work supported in part by the U.S. DOE Isotope Program","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"190 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90122230","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}
Kristofer Meehan, A. Starikovskiy, A. Dogariu, R. Miles
{"title":"Two Component Electric Field Dynamics of a ns-SDBD Plasma with Sub-Nanosecond Resolution by Femtosecond EFISH","authors":"Kristofer Meehan, A. Starikovskiy, A. Dogariu, R. Miles","doi":"10.2514/6.2020-1747","DOIUrl":"https://doi.org/10.2514/6.2020-1747","url":null,"abstract":"","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90830144","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}
{"title":"Modeling of streamer interaction with dense and rarefied flat gaseous layers","authors":"A. Starikovskiy, N. Aleksandrov","doi":"10.2514/6.2020-1663","DOIUrl":"https://doi.org/10.2514/6.2020-1663","url":null,"abstract":"","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90912615","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}
Pub Date : 2019-10-29DOI: 10.3126/jnphyssoc.v5i1.26935
Sushil Kc, D. Subedi, R. Shrestha
In this work, a plasma jet has been generated with capillary tube having external diameter 4.0 mm and thickness 1.0 mm. An Argon has been used as a working gas. The electrical characteristics of this device like instantaneous power, and discharge current have been measured. The effects of applied voltage on the dissipated power of the device have been investigated. The current is measured with the current probe whereas the voltage is measured from the locally fabricated voltage divider having ratio 1201:1. The electron density has been found out using power balance method. In addition, the power consumption during the discharge has also been studied with the help of Lissajous Figures. The calculated power consumption has been compared with other manual as well as I-V plots.
{"title":"Electrical Characterization of an Atmospheric Pressure Plasma Jet","authors":"Sushil Kc, D. Subedi, R. Shrestha","doi":"10.3126/jnphyssoc.v5i1.26935","DOIUrl":"https://doi.org/10.3126/jnphyssoc.v5i1.26935","url":null,"abstract":"In this work, a plasma jet has been generated with capillary tube having external diameter 4.0 mm and thickness 1.0 mm. An Argon has been used as a working gas. The electrical characteristics of this device like instantaneous power, and discharge current have been measured. The effects of applied voltage on the dissipated power of the device have been investigated. The current is measured with the current probe whereas the voltage is measured from the locally fabricated voltage divider having ratio 1201:1. The electron density has been found out using power balance method. In addition, the power consumption during the discharge has also been studied with the help of Lissajous Figures. The calculated power consumption has been compared with other manual as well as I-V plots.","PeriodicalId":9375,"journal":{"name":"Bulletin of the American Physical Society","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76922095","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}
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