Pub Date : 2021-03-01DOI: 10.1080/14685248.2021.1898624
S. Horn, J. Aurnou
Coriolis-centrifugal convection ( ) in a cylindrical domain constitutes an idealised model of tornadic storms, where the rotating cylinder represents the mesocyclone of a supercell thunderstorm. We present a suite of direct numerical simulations, analysing the influence of centrifugal buoyancy on the formation of tornado-like vortices (TLVs). TLVs are self-consistently generated provided the flow is within the quasi-cyclostrophic (QC) regime in which the dominant dynamical balance is between pressure gradient and centrifugal buoyancy forces. This requires the Froude number to be greater than the radius-to-height aspect ratio, . We show that the TLVs that develop in our simulations share many similar features with realistic tornadoes, such as azimuthal velocity profiles, intensification of the vortex strength, and helicity characteristics. Further, we analyse the influence of the mechanical bottom boundary conditions on the formation of TLVs, finding that a rotating fluid column above a stationary surface does not generate TLVs if centrifugal buoyancy is absent. In contrast, TLVs are generated in the QC regime with any bottom boundary conditions when centrifugal buoyancy is present. Our simulations bring forth insights into natural supercell thunderstorm systems by identifying properties that determine whether a mesocyclone becomes tornadic or remains non-tornadic. For tornadoes to exist, a vertical temperature difference must be present that is capable of driving strong convection. Additionally, our predictions dimensionally imply a critical mesocyclone angular rotation rate of . Taking a typical mesocyclone height of , this translates to for centrifugal buoyancy-dominated, quasi-cyclostrophic tornadogenesis. The formation of the simulated TLVs happens at all heights on the centrifugal buoyancy time scale . This implies a roughly 1 minute, height-invariant formation for natural tornadoes, consistent with recent observational estimates.
{"title":"Tornado-like vortices in the quasi-cyclostrophic regime of Coriolis-centrifugal convection","authors":"S. Horn, J. Aurnou","doi":"10.1080/14685248.2021.1898624","DOIUrl":"https://doi.org/10.1080/14685248.2021.1898624","url":null,"abstract":"Coriolis-centrifugal convection ( ) in a cylindrical domain constitutes an idealised model of tornadic storms, where the rotating cylinder represents the mesocyclone of a supercell thunderstorm. We present a suite of direct numerical simulations, analysing the influence of centrifugal buoyancy on the formation of tornado-like vortices (TLVs). TLVs are self-consistently generated provided the flow is within the quasi-cyclostrophic (QC) regime in which the dominant dynamical balance is between pressure gradient and centrifugal buoyancy forces. This requires the Froude number to be greater than the radius-to-height aspect ratio, . We show that the TLVs that develop in our simulations share many similar features with realistic tornadoes, such as azimuthal velocity profiles, intensification of the vortex strength, and helicity characteristics. Further, we analyse the influence of the mechanical bottom boundary conditions on the formation of TLVs, finding that a rotating fluid column above a stationary surface does not generate TLVs if centrifugal buoyancy is absent. In contrast, TLVs are generated in the QC regime with any bottom boundary conditions when centrifugal buoyancy is present. Our simulations bring forth insights into natural supercell thunderstorm systems by identifying properties that determine whether a mesocyclone becomes tornadic or remains non-tornadic. For tornadoes to exist, a vertical temperature difference must be present that is capable of driving strong convection. Additionally, our predictions dimensionally imply a critical mesocyclone angular rotation rate of . Taking a typical mesocyclone height of , this translates to for centrifugal buoyancy-dominated, quasi-cyclostrophic tornadogenesis. The formation of the simulated TLVs happens at all heights on the centrifugal buoyancy time scale . This implies a roughly 1 minute, height-invariant formation for natural tornadoes, consistent with recent observational estimates.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"297 - 324"},"PeriodicalIF":1.9,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2021.1898624","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47486937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-16DOI: 10.1080/14685248.2021.1885676
S. Pargal, J. Yuan, G. Brereton
ABSTRACT This paper explores the use of a small-span direct numerical simulation for a transient, smooth-wall turbulent channel flow and then applies the small-span simulation to a transient channel flow with riblets. A flow configuration similar to that of S. He and M. Seddighi (J Fluid Mech. 2013;715:60–102) is used to study the impulse response of a half-height channel flow to an abrupt increase in bulk velocity (with a friction Reynolds number increasing from 180 to 418). A minimal domain span sufficient to include the near-wall quasi-streamwise vortices in the ‘healthy turbulence’ region is used. The turbulent flow undergoes reverse transition toward a quasi-laminar state, followed by a retransition phase to the new equilibrium state. On a smooth wall, detailed comparisons with a full-span case show that the small-span test case captures satisfactorily the essential dynamics during the entire transition process, although it yields a slight delay in recovery to the new equilibrium. This difference is attributed to a slower streak transient growth due to an underestimation of near-wall spanwise fluctuations. This underestimation is associated with the missing large attached eddies that are not contained in the small span of the simulation domain. These comparisons justify the use of small-span simulations for identifying the main flow physics in a non-equilibrium accelerating wall turbulence. The application to the riblet flow shows that riblets do not fundamentally affect the flow dynamics, but delay the retransition as a result of significantly milder streak meandering. The streak-stabilisation effect of riblets is still active in a strongly accelerating turbulence and tends to prolong the flow recovery.
{"title":"Impulse response of turbulent flow in smooth and riblet-walled channels to a sudden velocity increase","authors":"S. Pargal, J. Yuan, G. Brereton","doi":"10.1080/14685248.2021.1885676","DOIUrl":"https://doi.org/10.1080/14685248.2021.1885676","url":null,"abstract":"ABSTRACT This paper explores the use of a small-span direct numerical simulation for a transient, smooth-wall turbulent channel flow and then applies the small-span simulation to a transient channel flow with riblets. A flow configuration similar to that of S. He and M. Seddighi (J Fluid Mech. 2013;715:60–102) is used to study the impulse response of a half-height channel flow to an abrupt increase in bulk velocity (with a friction Reynolds number increasing from 180 to 418). A minimal domain span sufficient to include the near-wall quasi-streamwise vortices in the ‘healthy turbulence’ region is used. The turbulent flow undergoes reverse transition toward a quasi-laminar state, followed by a retransition phase to the new equilibrium state. On a smooth wall, detailed comparisons with a full-span case show that the small-span test case captures satisfactorily the essential dynamics during the entire transition process, although it yields a slight delay in recovery to the new equilibrium. This difference is attributed to a slower streak transient growth due to an underestimation of near-wall spanwise fluctuations. This underestimation is associated with the missing large attached eddies that are not contained in the small span of the simulation domain. These comparisons justify the use of small-span simulations for identifying the main flow physics in a non-equilibrium accelerating wall turbulence. The application to the riblet flow shows that riblets do not fundamentally affect the flow dynamics, but delay the retransition as a result of significantly milder streak meandering. The streak-stabilisation effect of riblets is still active in a strongly accelerating turbulence and tends to prolong the flow recovery.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"353 - 379"},"PeriodicalIF":1.9,"publicationDate":"2021-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2021.1885676","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48306553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-01DOI: 10.1080/14685248.2020.1849712
Xiaole Wang, B. Cui, Zuoli Xiao
ABSTRACT The performance of ultra-high-lift (UHL) low-pressure turbine (LPT) is subject to complex flow phenomena (e.g. separation, transition and reattachment) which require advanced modelling for accurate numerical predictions. The feasibility and fidelity of three widely used transition-based turbulence models are evaluated in the Reynolds-Averaged Navier-Stokes (RANS) prediction of low-Reynolds number flows in linear UHL LPT cascade (T106C). All three transition models prove to capture the tendency that the size of separation bubble decreases with the increase of Reynolds number or inlet turbulence intensity. It turns out that intermittency factor-transition momentum thickness Reynolds number based shear stress transport turbulence model is the most accurate among the three models, expect for the clean inlet case at an isentropic outlet Reynolds number of . It is suggested that different viscosity ratios should be prescribed at the inlet for various models to mimic the effect of turbulence intensities precisely. In order to take into account the periodic wakes in computation, a moving cylindrical bar is added to the cascade inlet. The assessment of the capability of three models in predicting unsteady wake induced transition is carried out for selected Reynolds numbers. Some practical suggestions are given for the use of transition models based on RANS equations in simulation of the ultra-high-lift LPT cascade flows at low Reynolds numbers.
{"title":"Numerical investigation on ultra-high-lift low-pressure turbine cascade aerodynamics at low Reynolds numbers using transition-based turbulence models","authors":"Xiaole Wang, B. Cui, Zuoli Xiao","doi":"10.1080/14685248.2020.1849712","DOIUrl":"https://doi.org/10.1080/14685248.2020.1849712","url":null,"abstract":"ABSTRACT The performance of ultra-high-lift (UHL) low-pressure turbine (LPT) is subject to complex flow phenomena (e.g. separation, transition and reattachment) which require advanced modelling for accurate numerical predictions. The feasibility and fidelity of three widely used transition-based turbulence models are evaluated in the Reynolds-Averaged Navier-Stokes (RANS) prediction of low-Reynolds number flows in linear UHL LPT cascade (T106C). All three transition models prove to capture the tendency that the size of separation bubble decreases with the increase of Reynolds number or inlet turbulence intensity. It turns out that intermittency factor-transition momentum thickness Reynolds number based shear stress transport turbulence model is the most accurate among the three models, expect for the clean inlet case at an isentropic outlet Reynolds number of . It is suggested that different viscosity ratios should be prescribed at the inlet for various models to mimic the effect of turbulence intensities precisely. In order to take into account the periodic wakes in computation, a moving cylindrical bar is added to the cascade inlet. The assessment of the capability of three models in predicting unsteady wake induced transition is carried out for selected Reynolds numbers. Some practical suggestions are given for the use of transition models based on RANS equations in simulation of the ultra-high-lift LPT cascade flows at low Reynolds numbers.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"114 - 139"},"PeriodicalIF":1.9,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1849712","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44071133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-26DOI: 10.1080/14685248.2021.1876877
R. Kunnen
Rotating Rayleigh–Bénard convection is a simple model system used to study the interplay of buoyant forcing and rotation. Many recent studies have focused on the geostrophic regime of turbulent rotating convection where the principal balance of forces is between the Coriolis force and the pressure gradient. This regime is believed to be representative of conditions in geophysical and astrophysical flows. We hope to be able to extrapolate findings from laboratory experiments and numerical simulations towards these large-scale natural flows. In this paper I sketch the phase diagram of the geostrophic regime of rotating convection, put experimental and numerical studies in their place in these diagrams and discuss the partitioning into subranges characterised by different flow structures and heat transfer scaling. I also discuss some complications faced by experimentalists, such as constraints on the dimensions of the convection cell, wall modes near the sidewall and centrifugal buoyancy.
{"title":"The geostrophic regime of rapidly rotating turbulent convection","authors":"R. Kunnen","doi":"10.1080/14685248.2021.1876877","DOIUrl":"https://doi.org/10.1080/14685248.2021.1876877","url":null,"abstract":"Rotating Rayleigh–Bénard convection is a simple model system used to study the interplay of buoyant forcing and rotation. Many recent studies have focused on the geostrophic regime of turbulent rotating convection where the principal balance of forces is between the Coriolis force and the pressure gradient. This regime is believed to be representative of conditions in geophysical and astrophysical flows. We hope to be able to extrapolate findings from laboratory experiments and numerical simulations towards these large-scale natural flows. In this paper I sketch the phase diagram of the geostrophic regime of rotating convection, put experimental and numerical studies in their place in these diagrams and discuss the partitioning into subranges characterised by different flow structures and heat transfer scaling. I also discuss some complications faced by experimentalists, such as constraints on the dimensions of the convection cell, wall modes near the sidewall and centrifugal buoyancy.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"267 - 296"},"PeriodicalIF":1.9,"publicationDate":"2021-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2021.1876877","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47009077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-29DOI: 10.1080/14685248.2020.1863416
M. Ajmi, N. Hnaien, Saloua Marzouk, Lioua Kolsi, Kaouther Ghachem, H. B. Aissia
ABSTRACT The present numerical study aims to numerically investigate the dynamic and turbulent characteristics of a two-dimensional and turbulent offset jet. Three different parameters were investigated: The Reynolds numbers (Re) which was varied from 10000 to 30000, wall inclination angle (α) that was from −20° to +20° and finally the offset ratio (OR) which extends from 3.25–13. Ansys Fluent was numerical CFD solver used in this present investigation. The simultaneous effects of the OR, Re and α were investigated in details. The velocity and pressure contours showed that these three parameters do not contribute equally in the development of such a flow. Also, the turbulent characteristics, such as the turbulence intensities and energies depicted how each parameter influences, separately, the turbulent flow production. Furthermore, different of tripled parameters correlations were developed. These correlations may be of help to more understand certain offset jet flow features more accurately and to predict their exact values.
{"title":"Numerical investigation and triple-parameters correlations development on the dynamic characteristics of a turbulent offset jet","authors":"M. Ajmi, N. Hnaien, Saloua Marzouk, Lioua Kolsi, Kaouther Ghachem, H. B. Aissia","doi":"10.1080/14685248.2020.1863416","DOIUrl":"https://doi.org/10.1080/14685248.2020.1863416","url":null,"abstract":"ABSTRACT The present numerical study aims to numerically investigate the dynamic and turbulent characteristics of a two-dimensional and turbulent offset jet. Three different parameters were investigated: The Reynolds numbers (Re) which was varied from 10000 to 30000, wall inclination angle (α) that was from −20° to +20° and finally the offset ratio (OR) which extends from 3.25–13. Ansys Fluent was numerical CFD solver used in this present investigation. The simultaneous effects of the OR, Re and α were investigated in details. The velocity and pressure contours showed that these three parameters do not contribute equally in the development of such a flow. Also, the turbulent characteristics, such as the turbulence intensities and energies depicted how each parameter influences, separately, the turbulent flow production. Furthermore, different of tripled parameters correlations were developed. These correlations may be of help to more understand certain offset jet flow features more accurately and to predict their exact values.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"325 - 352"},"PeriodicalIF":1.9,"publicationDate":"2020-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1863416","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41424438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-29DOI: 10.1080/14685248.2020.1846050
Rodrigo Petrone dos Anjos, Ricardo de Andrade Medronho, Tânia Suaiden Klein
ABSTRACT Hydrocyclones are widely used in industry and CFD has been used to compute them. Reynolds stress turbulence models (RSM), which are computationally costly and oftentimes hard to converge, are often recommended in these computations. The present work has selected a liquid-liquid separation hydrocyclone for which single-phase experimental tangential and axial velocity profiles are available. CFD has been employed to test simpler turbulence models than the RSM and results have been compared with experimental data. The turbulence models assessed in the present work were: standard k-ε, standard k-ε with a curvature correction term, RNG k-ε, realizable k-ε, k-ω, SST, a two-time-scale linear eddy viscosity model, nonlinear quadratic and cubic k-ε eddy viscosity models and the Gibson and Launder and LRR Reynolds stress models. Computations have been carried out with OpenFOAM 2.2.2. Results using the Gibson and Launder turbulence model have been compared to some obtained with Ansys Fluent and these were in agreement. Results have shown that all turbulence models, apart from the RSM, returned basically the same tangential velocity profiles as the standard model. All turbulence models have failed in predicting axial velocity. Assessment of the Reynolds stresses has indicated that the internal flow field in hydrocyclones might be shear dominant and that the Reynolds shear stress component is the most relevant to correctly predict tangential velocity. Geometric proportions of hydrocyclones may affect significantly the intensity of rotational and streamline curvature effects. Two-equation eddy-viscosity models are likely to be able to attend such condition, since appropriate levels of eddy viscosity are predicted at free and forced vortexes regions, however further investigation is still needed.
{"title":"Assessment of turbulence models for single phase CFD computations of a liquid-liquid hydrocyclone using OpenFOAM","authors":"Rodrigo Petrone dos Anjos, Ricardo de Andrade Medronho, Tânia Suaiden Klein","doi":"10.1080/14685248.2020.1846050","DOIUrl":"https://doi.org/10.1080/14685248.2020.1846050","url":null,"abstract":"ABSTRACT Hydrocyclones are widely used in industry and CFD has been used to compute them. Reynolds stress turbulence models (RSM), which are computationally costly and oftentimes hard to converge, are often recommended in these computations. The present work has selected a liquid-liquid separation hydrocyclone for which single-phase experimental tangential and axial velocity profiles are available. CFD has been employed to test simpler turbulence models than the RSM and results have been compared with experimental data. The turbulence models assessed in the present work were: standard k-ε, standard k-ε with a curvature correction term, RNG k-ε, realizable k-ε, k-ω, SST, a two-time-scale linear eddy viscosity model, nonlinear quadratic and cubic k-ε eddy viscosity models and the Gibson and Launder and LRR Reynolds stress models. Computations have been carried out with OpenFOAM 2.2.2. Results using the Gibson and Launder turbulence model have been compared to some obtained with Ansys Fluent and these were in agreement. Results have shown that all turbulence models, apart from the RSM, returned basically the same tangential velocity profiles as the standard model. All turbulence models have failed in predicting axial velocity. Assessment of the Reynolds stresses has indicated that the internal flow field in hydrocyclones might be shear dominant and that the Reynolds shear stress component is the most relevant to correctly predict tangential velocity. Geometric proportions of hydrocyclones may affect significantly the intensity of rotational and streamline curvature effects. Two-equation eddy-viscosity models are likely to be able to attend such condition, since appropriate levels of eddy viscosity are predicted at free and forced vortexes regions, however further investigation is still needed.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"79 - 113"},"PeriodicalIF":1.9,"publicationDate":"2020-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1846050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46351276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-09DOI: 10.1080/14685248.2020.1856859
Yuhan Huang, Zhenhua Xia, Shiyi Chen
Hysteresis behaviour was reported in spanwise rotating plane Couette flow (RPCF) at Reynolds number with varying rotation number in a recent work (Huang et al. Phys. Rev. Fluids 2019;4:052401(R)). Here, is half of the velocity difference between two walls, h is half of the channel width, ν is the kinematic viscosity and is the constant angular velocity in the spanwise direction. In this paper, we perform two groups of direct numerical simulations at where Ro varies in steps along two opposite directions to investigate the hysteresis behaviour in RPCF at a relatively higher Reynolds number. It is found that when Reynolds number increases to 2600, the hysteresis of flow structures still exists in RPCF, but the span of the hysteresis loop shrinks from to . Turbulent statistics, such as the friction Reynolds number, turbulent kinetic energy and mean velocity gradient at the centreline, all exhibit similar hysteresis behaviours.
{"title":"Hysteresis behaviour in spanwise rotating plane Couette flow at Re w = 2600","authors":"Yuhan Huang, Zhenhua Xia, Shiyi Chen","doi":"10.1080/14685248.2020.1856859","DOIUrl":"https://doi.org/10.1080/14685248.2020.1856859","url":null,"abstract":"Hysteresis behaviour was reported in spanwise rotating plane Couette flow (RPCF) at Reynolds number with varying rotation number in a recent work (Huang et al. Phys. Rev. Fluids 2019;4:052401(R)). Here, is half of the velocity difference between two walls, h is half of the channel width, ν is the kinematic viscosity and is the constant angular velocity in the spanwise direction. In this paper, we perform two groups of direct numerical simulations at where Ro varies in steps along two opposite directions to investigate the hysteresis behaviour in RPCF at a relatively higher Reynolds number. It is found that when Reynolds number increases to 2600, the hysteresis of flow structures still exists in RPCF, but the span of the hysteresis loop shrinks from to . Turbulent statistics, such as the friction Reynolds number, turbulent kinetic energy and mean velocity gradient at the centreline, all exhibit similar hysteresis behaviours.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"254 - 266"},"PeriodicalIF":1.9,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1856859","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49026410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-02DOI: 10.1080/14685248.2020.1860214
Gao Yang, H. Iacovides, T. Craft, D. Apsley
In this study, a RANS model of turbulent conjugate heat transfer has been developed, which is applicable across a range of different combination of fluid and solid thermal properties. This is achieved by focusing on the transport equations for the temperature variance and its dissipation rate across the solid walls which bound the flow region. In this investigation we make use of a wider range of DNS data reported by other researchers, to advance our understanding of the processes involved and to revise and extend the capabilities of the model of Craft et al [12] including a more physical fluid-solid interface condition on the dissipation of thermal fluctuations and a dependence of model coefficients on Prandtl number. The resulting model is shown to successfully reproduce the penetration of thermal fluctuations into solid regions, and their subsequent decay across the solid, for a wide range of fluid to solid thermal property ratios, and Prandtl numbers, thereby bringing a step change to RANS capabilities in turbulent conjugate heat transfer analysis.
{"title":"RANS Model development on temperature variance in conjugate heat transfer","authors":"Gao Yang, H. Iacovides, T. Craft, D. Apsley","doi":"10.1080/14685248.2020.1860214","DOIUrl":"https://doi.org/10.1080/14685248.2020.1860214","url":null,"abstract":"In this study, a RANS model of turbulent conjugate heat transfer has been developed, which is applicable across a range of different combination of fluid and solid thermal properties. This is achieved by focusing on the transport equations for the temperature variance and its dissipation rate across the solid walls which bound the flow region. In this investigation we make use of a wider range of DNS data reported by other researchers, to advance our understanding of the processes involved and to revise and extend the capabilities of the model of Craft et al [12] including a more physical fluid-solid interface condition on the dissipation of thermal fluctuations and a dependence of model coefficients on Prandtl number. The resulting model is shown to successfully reproduce the penetration of thermal fluctuations into solid regions, and their subsequent decay across the solid, for a wide range of fluid to solid thermal property ratios, and Prandtl numbers, thereby bringing a step change to RANS capabilities in turbulent conjugate heat transfer analysis.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"180 - 207"},"PeriodicalIF":1.9,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1860214","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46700234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-02DOI: 10.1080/14685248.2020.1855352
G. Boffetta, Francesco Toselli, M. Manfrin, S. Musacchio
We report of a series of laboratory experiments and numerical simulations of freely decaying rotating turbulent flows confined in domains with variable height. We show that the vertical confinement has important effects on the formation of large-scale columnar vortices, the hallmark of rotating turbulence, and in particular delays the development of the cyclone–anticyclone asymmetry. We compare the experimental and numerical results face-to-face, showing the robustness of the results.
{"title":"Cyclone–anticyclone asymmetry in rotating thin fluid layers","authors":"G. Boffetta, Francesco Toselli, M. Manfrin, S. Musacchio","doi":"10.1080/14685248.2020.1855352","DOIUrl":"https://doi.org/10.1080/14685248.2020.1855352","url":null,"abstract":"We report of a series of laboratory experiments and numerical simulations of freely decaying rotating turbulent flows confined in domains with variable height. We show that the vertical confinement has important effects on the formation of large-scale columnar vortices, the hallmark of rotating turbulence, and in particular delays the development of the cyclone–anticyclone asymmetry. We compare the experimental and numerical results face-to-face, showing the robustness of the results.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"242 - 253"},"PeriodicalIF":1.9,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1855352","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42368404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-02DOI: 10.1080/14685248.2020.1849710
P. Suresh, T. Sundararajan, K. Srinivasan, Sarit K. Das
Heated horizontal plane jets find wide applications in engineering appliances such as air curtains and discharge of industrial effluents. In the present study, experimental investigations are conducted on a heated horizontal plane jet with the Reynolds numbers in the transitional regime, using a hotwire anemometer. In the far to very far-field (20 < x/d < 100) centreline velocity decay and jet spread increases faster with the decrease of Reynolds number. This is because, with the increase of Reynolds number, the turbulent kinetic energy is distributed on a broadband of scales. As a result, larger scales, which are responsible for increased entrainment, get weaker. The shifting of the centre plane generally occurs in the far region for low Reynolds number jets. A comparison with the result of an isothermal jet at similar Reynolds numbers from the literature at identical conditions shows that the turbulence intensity is decreased due to heating. Centreline velocity decays slowly and half-width increases marginally for a heated jet when compared with an isothermal jet. The effect of heating is prominent for low Re jets. Spectral development shows a delayed transition due to heating. Probability density function plots reveal lack of equilibrium and presence of large-scale eddies in the flow field.
{"title":"Experimental investigation of the influence of Reynolds number and buoyancy on the flow development of a plane jet in the transitional regime","authors":"P. Suresh, T. Sundararajan, K. Srinivasan, Sarit K. Das","doi":"10.1080/14685248.2020.1849710","DOIUrl":"https://doi.org/10.1080/14685248.2020.1849710","url":null,"abstract":"Heated horizontal plane jets find wide applications in engineering appliances such as air curtains and discharge of industrial effluents. In the present study, experimental investigations are conducted on a heated horizontal plane jet with the Reynolds numbers in the transitional regime, using a hotwire anemometer. In the far to very far-field (20 < x/d < 100) centreline velocity decay and jet spread increases faster with the decrease of Reynolds number. This is because, with the increase of Reynolds number, the turbulent kinetic energy is distributed on a broadband of scales. As a result, larger scales, which are responsible for increased entrainment, get weaker. The shifting of the centre plane generally occurs in the far region for low Reynolds number jets. A comparison with the result of an isothermal jet at similar Reynolds numbers from the literature at identical conditions shows that the turbulence intensity is decreased due to heating. Centreline velocity decays slowly and half-width increases marginally for a heated jet when compared with an isothermal jet. The effect of heating is prominent for low Re jets. Spectral development shows a delayed transition due to heating. Probability density function plots reveal lack of equilibrium and presence of large-scale eddies in the flow field.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"22 1","pages":"26 - 47"},"PeriodicalIF":1.9,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/14685248.2020.1849710","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47445012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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