The Experts below are selected from a list of 20520 Experts worldwide ranked by ideXlab platform
Guangyu Cao - One of the best experts on this subject based on the ideXlab platform.
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dynamic interaction of a downward Plane Jet and a cough Jet with respect to particle transmission an analytical and experimental study
Journal of Occupational and Environmental Hygiene, 2017Co-Authors: Guangyu Cao, Brandon E Boor, Shichao Liu, Atila NovoselacAbstract:ABSTRACTA cough Jet can travel beyond the breathing zone of the source person, and thus, infectious viral- and bacterial-laden particles can be transported from the source person to others in close proximity. To reduce the interpersonal transmission of coughed particles, the objective of this study was to analytically and experimentally investigate the performance of downward Plane Jets with various discharge velocities. Chamber measurements were conducted to examine the interaction between a transient cough Jet (discharge velocities of 12 m/sec and 16 m/sec) and a steady downward Plane Jet (discharge velocities from 1.0–8.5 m/sec) with respect to the transport of and human exposure to coughed particles. The results show that a relatively high-speed cough can easily penetrate a downward Plane Jet with a discharge velocity of less than 6 m/sec. A downward Plane Jet with a discharge velocity of 8.5 m/sec can bend the cough Jet to a certain extent. In this study, momentum comparison of the cough Jet and the ...
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Experimental study of the effect of turbulence intensities on the maximum velocity decay of an attached Plane Jet
Energy and Buildings, 2013Co-Authors: Guangyu Cao, Claudia Kandzia, Dirk Muller, Jorma Heikkinen, Risto Kosonen, Mika RuponenAbstract:Abstract The turbulent airflow partner downstream Jet slot is determined by the initial turbulent Jet properties, including, turbulence intensity, initial momentum flux and velocity profile. The objective of this experimental study is trying to quantitatively discover the effect of turbulence intensity of supply airflow on the Jet flow distribution of an attached Plane Jet. Our motivation proceeding our measurements is to achieve better understanding of room air flows and the influence of inlet diffusers (turbulence). Eleven conditions were measured in two test chambers where different types of slot diffusers were used to produce an attached air Jet with different turbulence intensities. All measurements are under isothermal conditions. The turbulence intensity of the Jet discharging from the slot was varying approximately from 1.0% to 14.0%. The results of this study reveal that turbulence intensity of the supplied air will affect significantly the maximum velocity decay of the attached Plane Jet. Measurement results show that the lower turbulence intensity of supply airflow will result in slower maximum velocity decay. A relatively stable turbulence level of the airflow at local maximum velocity has been found at relatively higher Reynolds numbers of 1333 and 2667, which is about 11% ± 4 in all measured cases. This study reveals a clear self-similarity characteristic of the turbulent airflow under conditions of different turbulence intensities and different Reynolds number.
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modelling and simulation of the near wall velocity of a turbulent ceiling attached Plane Jet after its impingement with the corner
Building and Environment, 2011Co-Authors: Guangyu Cao, Mika Ruponen, Risto Paavilainen, Jarek KurnitskiAbstract:At present, ceiling-mounted diffusers are very popular for indoor air distribution, particularly in offices, owing to greater efficiency in the distribution of the air supply and a more comfortable indoor environment. The objective of this study is to construct an effective model to design the indoor airflow of an attached Plane Jet after its impingement with the corner in a room. In this study, a full-scale test facility was set up to obtain detailed experimental data. One commercial CFD tool, CFX 11.0, was used to simulate the air velocity distribution of an attached Plane air Jet bounded by the ceiling and an insulated wall. One semi-empirical model was also constructed to predict the impingement Jet velocity. The results show that bout the semi-empirical model and CFX 11.0 were able to predict the maximum velocity of an impinging Jet at low Reynolds numbers, 1000 and 2000, with an inaccuracy of ±11%. However, the semi-empirical model could be more conveniently used to predict the maximum Jet velocity decay after its impingement the corner in a room than CFD simulation in terms of accuracy and the time required to design the indoor airflow pattern.
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piv measurement of the attached Plane Jet velocity field at a high turbulence intensity level in a room
International Journal of Heat and Fluid Flow, 2010Co-Authors: Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Mika RuponenAbstract:The behaviour of an attached Plane Jet at high turbulence intensity (>20%) is not completely understood, especially at relatively low Reynolds numbers (<2000) in a room. This study focuses on the detailed mean and instantaneous Jet flow field using the particle image velocimetry (PIV) measurement technique in a full-scale climate chamber. Three isothermal conditions at different Reynolds numbers based on the Jet slot height and slot average velocity, 960, 1320 and 1680, were measured, having a turbulence intensity of 44%, 30% and 22%, respectively. The results show that the measured Jet velocity was able to match the earlier empirical turbulent Jet results when the turbulence intensity was of the order of 40%. Incomplete self-similarity occurs when the turbulence intensity is less than 30%. After a few slot heights downstream from the Jet slot, most of the data of the Jet at the Reynolds number 960 present self-similarity characteristics.
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particle image velocimetry piv application in the measurement of indoor air distribution by an active chilled beam
Building and Environment, 2010Co-Authors: Mika Ruponen, Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Olli SeppanenAbstract:Abstract We study the turbulent air flow behaviours of the attached Plane Jet discharged from an active chilled beam in a room using Particle Image Velocimetry (PIV). PIV is an innovative technology to study indoor air flow which began in the eighties of the last century for the measurement of whole air flow fields in fractions of a second. Here an experimental PIV system was built to reveal the structure of a turbulent attached Plane Jet in the entrainment process of the ambient air downstream from the Jet slot. For the particle seeding in the PIV experiments, a few different particles were tested with the attached Jet PIV application in a room. The results presented in this paper show the clear structure of the turbulent attached Plane Jet in the entrainment process after issuing from the chilled beam slot. The PIV visualisation results proved that the Jet will attach to the ceiling and become fully turbulent a short distance downstream from the slot. The Jet velocity vector fields show that the volume flow rate of the attached Plane Jet increases because of the large vortex mixing mechanism in the outer region of the Jet. In three measurement cases, the air Jet grows faster at a Reynolds number of 960 than at Reynolds numbers of 1320 and 1680. The calculated spreading angles in the cases with lower Reynolds numbers have similar values compared with the visualisation results.
Mika Ruponen - One of the best experts on this subject based on the ideXlab platform.
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experimental study of the effect of turbulence intensities on the maximum velocity decay of an attached Plane Jet
Energy and Buildings, 2013Co-Authors: Claudia Kandzia, Dirk Muller, Jorma Heikkinen, Risto Kosonen, Mika RuponenAbstract:Abstract The turbulent airflow partner downstream Jet slot is determined by the initial turbulent Jet properties, including, turbulence intensity, initial momentum flux and velocity profile. The objective of this experimental study is trying to quantitatively discover the effect of turbulence intensity of supply airflow on the Jet flow distribution of an attached Plane Jet. Our motivation proceeding our measurements is to achieve better understanding of room air flows and the influence of inlet diffusers (turbulence). Eleven conditions were measured in two test chambers where different types of slot diffusers were used to produce an attached air Jet with different turbulence intensities. All measurements are under isothermal conditions. The turbulence intensity of the Jet discharging from the slot was varying approximately from 1.0% to 14.0%. The results of this study reveal that turbulence intensity of the supplied air will affect significantly the maximum velocity decay of the attached Plane Jet. Measurement results show that the lower turbulence intensity of supply airflow will result in slower maximum velocity decay. A relatively stable turbulence level of the airflow at local maximum velocity has been found at relatively higher Reynolds numbers of 1333 and 2667, which is about 11% ± 4 in all measured cases. This study reveals a clear self-similarity characteristic of the turbulent airflow under conditions of different turbulence intensities and different Reynolds number.
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Experimental study of the effect of turbulence intensities on the maximum velocity decay of an attached Plane Jet
Energy and Buildings, 2013Co-Authors: Guangyu Cao, Claudia Kandzia, Dirk Muller, Jorma Heikkinen, Risto Kosonen, Mika RuponenAbstract:Abstract The turbulent airflow partner downstream Jet slot is determined by the initial turbulent Jet properties, including, turbulence intensity, initial momentum flux and velocity profile. The objective of this experimental study is trying to quantitatively discover the effect of turbulence intensity of supply airflow on the Jet flow distribution of an attached Plane Jet. Our motivation proceeding our measurements is to achieve better understanding of room air flows and the influence of inlet diffusers (turbulence). Eleven conditions were measured in two test chambers where different types of slot diffusers were used to produce an attached air Jet with different turbulence intensities. All measurements are under isothermal conditions. The turbulence intensity of the Jet discharging from the slot was varying approximately from 1.0% to 14.0%. The results of this study reveal that turbulence intensity of the supplied air will affect significantly the maximum velocity decay of the attached Plane Jet. Measurement results show that the lower turbulence intensity of supply airflow will result in slower maximum velocity decay. A relatively stable turbulence level of the airflow at local maximum velocity has been found at relatively higher Reynolds numbers of 1333 and 2667, which is about 11% ± 4 in all measured cases. This study reveals a clear self-similarity characteristic of the turbulent airflow under conditions of different turbulence intensities and different Reynolds number.
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modelling and simulation of the near wall velocity of a turbulent ceiling attached Plane Jet after its impingement with the corner
Building and Environment, 2011Co-Authors: Guangyu Cao, Mika Ruponen, Risto Paavilainen, Jarek KurnitskiAbstract:At present, ceiling-mounted diffusers are very popular for indoor air distribution, particularly in offices, owing to greater efficiency in the distribution of the air supply and a more comfortable indoor environment. The objective of this study is to construct an effective model to design the indoor airflow of an attached Plane Jet after its impingement with the corner in a room. In this study, a full-scale test facility was set up to obtain detailed experimental data. One commercial CFD tool, CFX 11.0, was used to simulate the air velocity distribution of an attached Plane air Jet bounded by the ceiling and an insulated wall. One semi-empirical model was also constructed to predict the impingement Jet velocity. The results show that bout the semi-empirical model and CFX 11.0 were able to predict the maximum velocity of an impinging Jet at low Reynolds numbers, 1000 and 2000, with an inaccuracy of ±11%. However, the semi-empirical model could be more conveniently used to predict the maximum Jet velocity decay after its impingement the corner in a room than CFD simulation in terms of accuracy and the time required to design the indoor airflow pattern.
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piv measurement of the attached Plane Jet velocity field at a high turbulence intensity level in a room
International Journal of Heat and Fluid Flow, 2010Co-Authors: Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Mika RuponenAbstract:The behaviour of an attached Plane Jet at high turbulence intensity (>20%) is not completely understood, especially at relatively low Reynolds numbers (<2000) in a room. This study focuses on the detailed mean and instantaneous Jet flow field using the particle image velocimetry (PIV) measurement technique in a full-scale climate chamber. Three isothermal conditions at different Reynolds numbers based on the Jet slot height and slot average velocity, 960, 1320 and 1680, were measured, having a turbulence intensity of 44%, 30% and 22%, respectively. The results show that the measured Jet velocity was able to match the earlier empirical turbulent Jet results when the turbulence intensity was of the order of 40%. Incomplete self-similarity occurs when the turbulence intensity is less than 30%. After a few slot heights downstream from the Jet slot, most of the data of the Jet at the Reynolds number 960 present self-similarity characteristics.
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particle image velocimetry piv application in the measurement of indoor air distribution by an active chilled beam
Building and Environment, 2010Co-Authors: Mika Ruponen, Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Olli SeppanenAbstract:Abstract We study the turbulent air flow behaviours of the attached Plane Jet discharged from an active chilled beam in a room using Particle Image Velocimetry (PIV). PIV is an innovative technology to study indoor air flow which began in the eighties of the last century for the measurement of whole air flow fields in fractions of a second. Here an experimental PIV system was built to reveal the structure of a turbulent attached Plane Jet in the entrainment process of the ambient air downstream from the Jet slot. For the particle seeding in the PIV experiments, a few different particles were tested with the attached Jet PIV application in a room. The results presented in this paper show the clear structure of the turbulent attached Plane Jet in the entrainment process after issuing from the chilled beam slot. The PIV visualisation results proved that the Jet will attach to the ceiling and become fully turbulent a short distance downstream from the slot. The Jet velocity vector fields show that the volume flow rate of the attached Plane Jet increases because of the large vortex mixing mechanism in the outer region of the Jet. In three measurement cases, the air Jet grows faster at a Reynolds number of 960 than at Reynolds numbers of 1320 and 1680. The calculated spreading angles in the cases with lower Reynolds numbers have similar values compared with the visualisation results.
Jarek Kurnitski - One of the best experts on this subject based on the ideXlab platform.
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modelling and simulation of the near wall velocity of a turbulent ceiling attached Plane Jet after its impingement with the corner
Building and Environment, 2011Co-Authors: Guangyu Cao, Mika Ruponen, Risto Paavilainen, Jarek KurnitskiAbstract:At present, ceiling-mounted diffusers are very popular for indoor air distribution, particularly in offices, owing to greater efficiency in the distribution of the air supply and a more comfortable indoor environment. The objective of this study is to construct an effective model to design the indoor airflow of an attached Plane Jet after its impingement with the corner in a room. In this study, a full-scale test facility was set up to obtain detailed experimental data. One commercial CFD tool, CFX 11.0, was used to simulate the air velocity distribution of an attached Plane air Jet bounded by the ceiling and an insulated wall. One semi-empirical model was also constructed to predict the impingement Jet velocity. The results show that bout the semi-empirical model and CFX 11.0 were able to predict the maximum velocity of an impinging Jet at low Reynolds numbers, 1000 and 2000, with an inaccuracy of ±11%. However, the semi-empirical model could be more conveniently used to predict the maximum Jet velocity decay after its impingement the corner in a room than CFD simulation in terms of accuracy and the time required to design the indoor airflow pattern.
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piv measurement of the attached Plane Jet velocity field at a high turbulence intensity level in a room
International Journal of Heat and Fluid Flow, 2010Co-Authors: Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Mika RuponenAbstract:The behaviour of an attached Plane Jet at high turbulence intensity (>20%) is not completely understood, especially at relatively low Reynolds numbers (<2000) in a room. This study focuses on the detailed mean and instantaneous Jet flow field using the particle image velocimetry (PIV) measurement technique in a full-scale climate chamber. Three isothermal conditions at different Reynolds numbers based on the Jet slot height and slot average velocity, 960, 1320 and 1680, were measured, having a turbulence intensity of 44%, 30% and 22%, respectively. The results show that the measured Jet velocity was able to match the earlier empirical turbulent Jet results when the turbulence intensity was of the order of 40%. Incomplete self-similarity occurs when the turbulence intensity is less than 30%. After a few slot heights downstream from the Jet slot, most of the data of the Jet at the Reynolds number 960 present self-similarity characteristics.
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particle image velocimetry piv application in the measurement of indoor air distribution by an active chilled beam
Building and Environment, 2010Co-Authors: Mika Ruponen, Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Olli SeppanenAbstract:Abstract We study the turbulent air flow behaviours of the attached Plane Jet discharged from an active chilled beam in a room using Particle Image Velocimetry (PIV). PIV is an innovative technology to study indoor air flow which began in the eighties of the last century for the measurement of whole air flow fields in fractions of a second. Here an experimental PIV system was built to reveal the structure of a turbulent attached Plane Jet in the entrainment process of the ambient air downstream from the Jet slot. For the particle seeding in the PIV experiments, a few different particles were tested with the attached Jet PIV application in a room. The results presented in this paper show the clear structure of the turbulent attached Plane Jet in the entrainment process after issuing from the chilled beam slot. The PIV visualisation results proved that the Jet will attach to the ceiling and become fully turbulent a short distance downstream from the slot. The Jet velocity vector fields show that the volume flow rate of the attached Plane Jet increases because of the large vortex mixing mechanism in the outer region of the Jet. In three measurement cases, the air Jet grows faster at a Reynolds number of 960 than at Reynolds numbers of 1320 and 1680. The calculated spreading angles in the cases with lower Reynolds numbers have similar values compared with the visualisation results.
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experimental investigation of the velocity distribution of the attached Plane Jet after impingement with the corner in a high room
Energy and Buildings, 2010Co-Authors: Guangyu Cao, Mika Ruponen, Jarek KurnitskiAbstract:Supplying air into rooms properly without causing a sensation of draught is a challenging task. Airflow patterns and the air velocity of attached Plane Jets should be predicted and designed accurately before the airflow enters an occupied zone in different applications. The objective of this study is to identify the airflow patterns of attached Plane Jets and set up an efficient model to predict the maximum Jet velocity decay of an attached Plane Jet after its impingement with the corner in a high room. A full-scale test chamber was used to measure the Jet velocity with a Plane Jet supply device. The attached Plane Jet is bounded initially by the ceiling and the insulated wall after being discharged from the Jet slot. Three velocities from the slot, 0.5, 1.0, and 2.0 m/s, are used as the initial Jet velocities with three Reynolds numbers, 1000, 2000, and 4000, respectively. The results show that the behaviours of the attached Plane Jet differ from earlier studies carried out in a relatively low room. The virtual origin model setup in this study can be used to predict the maximum Jet velocity decay for Jet flow design with impingement in the corners of rooms.
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experimental investigation and modelling of a buoyant attached Plane Jet in a room
Applied Thermal Engineering, 2009Co-Authors: Guangyu Cao, Mika Ruponen, Jarek Kurnitski, Olli SeppanenAbstract:Abstract Buoyant attached Jets are widely used in various types of supply air devices especially in office buildings. This study focuses on a two-dimensional cooled attached Jet characteristic, including mean flow field structure, specification of the Jet regions and maximum velocity decay. A new superimposing model is derived to predict the maximum velocity decay and validated by measurement results. The measurement results demonstrate that the intermediate region of a buoyant Jet does exist when an inner layer extends downstream of the Jet slot. In addition, by assuming that the buoyant force is the main extra force on the Jet flow in the acceleration process, the superimposing model predicted the maximum velocity decay with precise accuracy in a Reynolds number range of 667–4000, based on slot heights of 20 and 30 mm and slot velocities of 0.50, 1.00 and 2.00 m/s. At a distance of 1000 mm from the slot, the velocity profile displays a self similarity character like an isothermal turbulent Jet. In the final region, where the buoyancy flux completely dominates the Jet, the Jet behaved like a plume with an unstable flow field.
Olli Seppanen - One of the best experts on this subject based on the ideXlab platform.
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particle image velocimetry piv application in the measurement of indoor air distribution by an active chilled beam
Building and Environment, 2010Co-Authors: Mika Ruponen, Guangyu Cao, Jarek Kurnitski, Markku Sivukari, Olli SeppanenAbstract:Abstract We study the turbulent air flow behaviours of the attached Plane Jet discharged from an active chilled beam in a room using Particle Image Velocimetry (PIV). PIV is an innovative technology to study indoor air flow which began in the eighties of the last century for the measurement of whole air flow fields in fractions of a second. Here an experimental PIV system was built to reveal the structure of a turbulent attached Plane Jet in the entrainment process of the ambient air downstream from the Jet slot. For the particle seeding in the PIV experiments, a few different particles were tested with the attached Jet PIV application in a room. The results presented in this paper show the clear structure of the turbulent attached Plane Jet in the entrainment process after issuing from the chilled beam slot. The PIV visualisation results proved that the Jet will attach to the ceiling and become fully turbulent a short distance downstream from the slot. The Jet velocity vector fields show that the volume flow rate of the attached Plane Jet increases because of the large vortex mixing mechanism in the outer region of the Jet. In three measurement cases, the air Jet grows faster at a Reynolds number of 960 than at Reynolds numbers of 1320 and 1680. The calculated spreading angles in the cases with lower Reynolds numbers have similar values compared with the visualisation results.
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experimental investigation and modelling of a buoyant attached Plane Jet in a room
Applied Thermal Engineering, 2009Co-Authors: Guangyu Cao, Mika Ruponen, Jarek Kurnitski, Olli SeppanenAbstract:Abstract Buoyant attached Jets are widely used in various types of supply air devices especially in office buildings. This study focuses on a two-dimensional cooled attached Jet characteristic, including mean flow field structure, specification of the Jet regions and maximum velocity decay. A new superimposing model is derived to predict the maximum velocity decay and validated by measurement results. The measurement results demonstrate that the intermediate region of a buoyant Jet does exist when an inner layer extends downstream of the Jet slot. In addition, by assuming that the buoyant force is the main extra force on the Jet flow in the acceleration process, the superimposing model predicted the maximum velocity decay with precise accuracy in a Reynolds number range of 667–4000, based on slot heights of 20 and 30 mm and slot velocities of 0.50, 1.00 and 2.00 m/s. At a distance of 1000 mm from the slot, the velocity profile displays a self similarity character like an isothermal turbulent Jet. In the final region, where the buoyancy flux completely dominates the Jet, the Jet behaved like a plume with an unstable flow field.
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experimental investigation and modeling of the attached Plane Jet velocity development characteristics in the transition process in a room
Hvac&r Research, 2009Co-Authors: Guangyu Cao, Mika Ruponen, Jarek Kurnitski, Olli SeppanenAbstract:Attached Plane Jets are widely used in room-air distribution solutions. The turbulent attached Plane Jet behavior in the transition process that determines the Jet behavior in the fully developed region is not completely understood, especially at relative low Reynolds numbers (<6000). This study focuses on obtaining the detailed Jet mean flowfield velocity data and Jet growing characteristics in the transition region. A virtual origin model was set up to predict the maximum Jet velocity decay, and the experiment was carried out to validate the model. In this experiment, three Reynolds numbers—1000, 2000, and 4000—were tested at different distances from 2 to 30 slot heights downstream of the Jet slot. The results are significantly different from the known theory for the third and fourth Jet zones definition. The experimental data show that after six slot heights downstream distance, most of the data start to fit closely the fully developed turbulent Jet velocity profiles and present self-preserving charact...
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Plane air Jet corner zone modelling in a room ventilated by an active chilled beam
International Journal of Ventilation, 2009Co-Authors: Guangyu Cao, Mika Ruponen, Jarek Kurnitski, Panu Mustakallio, Olli SeppanenAbstract:AbstractRecent studies have demonstrated the influence that air Jets in rooms ventilated by chilled beams have on draught-related thermal sensation. The most critical zone in which people often suffer draught sensation is located near a wall and close to the floor. To avoid the draught sensation, the critical velocities of the returning air Jet should be specified and determined before the Jet enters the occupied zone. In this study, the velocity of the attached Plane Jet was modelled and measured at six heights and at eight different distances from the wall. Results showed that the returning corner airflow reattaches to the floor surface with entrained ambient air after separation from the wall. The maximum returning air velocity was found to be close to the floor surface. Air in the rest of the room air was shown to move, rather than remain still. Moreover, the moving room air does enforce free shear at the free boundary of the attached Jet. This new model could be applied to estimate the possibility of...
Michael Gauding - One of the best experts on this subject based on the ideXlab platform.
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on new scaling laws in a temporally evolving turbulent Plane Jet using lie symmetry analysis and direct numerical simulation corrigendum
Journal of Fluid Mechanics, 2018Co-Authors: Hamed Sadeghi, Martin Oberlack, Michael GaudingAbstract:A temporally evolving turbulent Plane Jet is studied both by direct numerical simulation (DNS) and Lie symmetry analysis. The DNS is based on a high-order scheme to solve the Navier–Stokes equations for an incompressible fluid. Computations were conducted at Reynolds number , where is defined based on the initial Jet thickness, , and the initial centreline velocity, . A symmetry approach, known as the Lie group, is used to find symmetry transformations, and, in turn, group invariant solutions, which are also denoted as scaling laws in turbulence. This approach, which has been extensively developed to create analytical solutions of differential equations, is presently applied to the mean momentum and two-point correlation equations in a temporally evolving turbulent Plane Jet. The symmetry analysis of these equations allows us to derive new invariant (self-similar) solutions for the mean flow and higher moments of the velocities in the Jet flow. The current DNS validates the consequence of Lie symmetry analysis and therefore confirms the establishment of novel scaling laws in turbulence. It is shown that the classical scaling law for the mean velocity is a specific form of the current scaling (which has a more general form); however, the scaling for the second and higher moments (such as Reynolds stresses) has a completely different structure compared to the classical scaling. While the failure of the classical scaling for the second moments of the fluctuating velocities has been noted from the Jet data for many years, the DNS results nicely match with the present self-similar relations derived from Lie symmetry analysis. Key ingredients for the present results, in particular for the scaling laws of the higher moments, are symmetries, which are of a purely statistical nature. i.e. these symmetries are admitted by the moment equations, however, they are not observed by the original Navier–Stokes equations.
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on new scaling laws in a temporally evolving turbulent Plane Jet using lie symmetry analysis and direct numerical simulation corrigendum
Journal of Fluid Mechanics, 2018Co-Authors: Hamed Sadeghi, Martin Oberlack, Michael GaudingAbstract:A temporally evolving turbulent Plane Jet is studied both by direct numerical simulation (DNS) and Lie symmetry analysis. The DNS is based on a high-order scheme to solve the Navier–Stokes equations for an incompressible fluid. Computations were conducted at Reynolds number $\mathit{Re}_{0}=8000$ , where $\mathit{Re}_{0}$ is defined based on the initial Jet thickness, $\unicode[STIX]{x1D6FF}_{0.5}(0)$ , and the initial centreline velocity, $\overline{U}_{1}(0)$ . A symmetry approach, known as the Lie group, is used to find symmetry transformations, and, in turn, group invariant solutions, which are also denoted as scaling laws in turbulence. This approach, which has been extensively developed to create analytical solutions of differential equations, is presently applied to the mean momentum and two-point correlation equations in a temporally evolving turbulent Plane Jet. The symmetry analysis of these equations allows us to derive new invariant (self-similar) solutions for the mean flow and higher moments of the velocities in the Jet flow. The current DNS validates the consequence of Lie symmetry analysis and therefore confirms the establishment of novel scaling laws in turbulence. It is shown that the classical scaling law for the mean velocity is a specific form of the current scaling (which has a more general form); however, the scaling for the second and higher moments (such as Reynolds stresses) has a completely different structure compared to the classical scaling. While the failure of the classical scaling for the second moments of the fluctuating velocities has been noted from the Jet data for many years, the DNS results nicely match with the present self-similar relations derived from Lie symmetry analysis. Key ingredients for the present results, in particular for the scaling laws of the higher moments, are symmetries, which are of a purely statistical nature. i.e. these symmetries are admitted by the moment equations, however, they are not observed by the original Navier–Stokes equations.
