\nSiddharth Talapatra<\/td>\n<\/tr>\n
![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/07\/image1038.jpg\")
<\/a><\/h3>\nOutline<\/h3>\n
Our Project aims at applying advanced PIV techniques to measure near-wall flow structures over the rough surface in a turbulent channel flow.<\/p>\n
Goals<\/h3>\n\n- Study the geometric correlations between near wall flow structures and rough surface.<\/li>\n
- Study the correlations between the near wall flow structures\u00a0 and turbulent statistical quantities.<\/li>\n
- Provide theoretical foundation for developing reasonable wall-models in numerical simulations.<\/li>\n<\/ul>\n
Highlights<\/h3>\n\n- Near-wall optical measurement using index-matched fluid.<\/li>\n
- High resolution measurement to capture small scale turbulent motions.<\/li>\n
- Time-resolved measurement to capture the development of structures near the wall<\/li>\n
- 3D instantaneous measurement to resolve spanwise structure motions<\/li>\n<\/ul>\n
Introduction<\/h3>\n
Every surface is rough. We refer to rough surface in a hydrodynamic sense. In Fluid Mechanics we distinguish rough surface based on roughness Reynolds number k+<\/sup>= kut<\/sub>\/v <\/em>Where k is the roughness length scale, ut <\/sub><\/em>is the friction velocity, v is the kinetic viscosity, Generally:<\/p>\nk+<\/sup><5, hydrodynamically smooth
\n5< k+<\/sup><70, transitionally rough
\nk+<\/sup>>70, fully rough<\/p>\nThere are myriad prototypes of rough-wall flows in the nature and engineering applications. They appear in different geometries and large-ranging length scales. However, there are similarities in the external flow generated from these surfaces.<\/p>\n
Two major questions in rough-wall turbulence study.<\/p>\n
\n- \u00a0Study the relation between wall stress and roughness geometry.<\/li>\n
- \u00a0Study the influence zone of the roughness to the turbulence.<\/li>\n<\/ol>\n
Wall similarity hypothesis<\/strong> (Raupach et al. <\/em>1991, <\/em>Jim\u00e9nez 2004)
\nUnder well-characterized condition, i.e. sufficient separation among d<\/em>, k<\/em>, dv <\/sub><\/em>(d<\/em>\/k ><\/em>40, k\/dv <\/sub><\/em>>50-100), the influence of roughness to the turbulent motions is limited to roughness sublayer, typically within 2-5k <\/em>above the wall.<\/p>\nFacility<\/h3>\n
Our experiment facility is a bypass of the turbo-machinery facility in the Laboratory of Experimental Fluid Dynamics. The whole facility is filled with 62% by weight NaI solution which has the same refractive index as acrylic. This minimizes the reflection at the liquid-solid interface and enables us to investigate the flow phenomena very close to the wall. It also allows undistorted transmission of laser beam through the rough wall, which is crucial for Holographic measurements.<\/p>\n
![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/05\/Turbo-Machinery-and-Experiment-Bypass-1024x304.png\")
<\/a>Feature Highlights:<\/strong><\/p>\n\n- The facility equips with index-matched fluid to minimize the reflection on the rough surface.<\/li>\n
- The channels is made of transparent material. The test section can be accessed from different angles.<\/li>\n
- Four-insert design enables us to perform experiment under different surface conditions with modifying the main body of the channel.<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/05\/image1093.jpg\")
<\/a><\/p>\nSchematic of the By-pass Channel. The red mark is our field of interest, where we have a fully developed flow and transition effect from smooth-rough becomes negligible.<\/p>\n
Rough Surfaces:<\/strong><\/p>\nThe rough-surface is composed of uniformly closed-pack pyramids. This is a typical kind of 3d roughness with close length scales of all three directions.<\/p>\n
Roughness height k=0.457mm
\nPitch angle=20 degrees
\nEquivalent sand roughness ks<\/sub>~1.5k<\/p>\n![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/05\/image719.jpg\")
<\/a>![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/05\/image16341.gif\")
<\/a>The acrylic roughness used in the experiment<\/span><\/p>\nApproaches<\/h3>\n
The approaches we applied or will apply in this project includes:<\/p>\n
\n- 2D PIV of high and low resolutions.<\/li>\n
- High speed PIV<\/li>\n
- High magnification stereo PIV<\/li>\n
- Holographic PIV (Currently by Siddharth Talapratra)<\/a><\/li>\n
- Tomographic PIV (Currently by Rinaldo Miorini)<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/06\/6001.png\")
<\/a><\/h3>\n![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/06\/6002.png\")
<\/a><\/p>\n![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/06\/6003.png\")
<\/a><\/p>\nResults<\/h3>\n
Basic flow condition calibration<\/i>
\n1st Stereo PIV experiment<\/i>
\n2nd Stereo PIV experiment<\/i><\/a>
\nHigh resolution PIV experiment<\/i><\/a>
\nHigh speed PIV experiment<\/i><\/a>
\nHolographic PIV experiment<\/i><\/a>
\nCoherent structures and associated subgrid-scale <\/i>(SGS<\/i>) energy transfer<\/a><\/p>\n![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/06\/7001.gif\")
<\/a>The sample plane is located at 35h from the leading edge of bottom rough-wall insert to guarantee well-developed self-similarity. <\/span><\/h3>\n![\"\"](\"https:\/\/engineering.jhu.edu\/lefd\/wp-content\/uploads\/2020\/06\/7002.png\")
<\/a>Publications<\/h3>\nJ. Hong, J. Katz, M. Schultz, 2011, Near-wall turbulence statistics and flow structures over three-dimensional roughness in a turbulent channel flow<\/a>,<\/em> Journal of Fluid Mechanics, vol.667, pp.1-37.<\/p>\nJ. Hong, J. Katz, C. Meneveau, M. Schultz, 2012, Coherent structures and associated subgrid-scale energy transfer in a rough-wall channel flow<\/a>,<\/em> Journal of Fluid Mechanics, 712, 92-128.<\/p>\nS. Talapatra, J. Katz, 2011, Volumetric 3D velocity measurements in the Roughness Sublayer of a channel flow using Microscopic Holographic PIV<\/em>, 9th International Symposium on Particle Image Velocimetry, Kobe, Japan.<\/p>\nJ. Hong, R. Miorini, J. Katz, M. Schultz, 2011, Investigation of Taylor’s hypothesis using time-resolved PIV data<\/em>, 9th International Symposium on Particle Image Velocimetry, Kobe, Japan.<\/p>\nJ. Hong, J. Katz, M. Schultz, 2010, Scale-dependent energy fluxes in a rough-wall turbulent channel flow<\/em><\/a>, In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers Digital Collection. Paper No: <\/span> FEDSM-ICNMM2010-30829, pp. 2095-2105;<\/p>\nS. Talapatra, J. Katz, 2010, Three dimensional volumetric velocity measurements in the inner part of a turbulent boundary layer over a rough wall using digital HPIV<\/em><\/a>, In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers Digital Collection. Paper No: <\/span> FEDSM-ICNMM2010-30813, pp. 193-201;<\/p>\nJ. Hong, J. Katz, M. Schultz, 2009, High resolution PIV measurement near a rough wall in an optically index-matched facility, 8th International Symposium on Particle Image Velocimetry, Melbourne, Australia.<\/p>\n
S. Talapatra, J. Hong, J. Katz, 2009, Digital microscopic holography to measure flow through rough walls, 8th International Symposium on Particle Image Velocimetry, Melbourne, Australia.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2008, Near-wall stereo PIV investigation of the turbulent channel flow over rough-walls, Proceedings of ASME 2008 Fluids Engineering Conference, Jacksonville, FL, USA.<\/p>\n
J. Hong, J. Katz, C. Meneveau, M. Schultz, 2011, Coherent structures and associated sub-grid scale energy transfer in a rough-wall turbulent channel flow, 64th Annual Meeting of the APS Division of Fluid Dynamics, Baltimore, MD, USA.<\/p>\n
S. Talapatra, J. Katz, 2011, Measurements of the 3D flow structures within the roughness sublayer using Microscopic Holographic PIV, 64th Annual Meeting of the APS Division of Fluid Dynamics, Baltimore, MD, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2010, Roughness signature in the outer-layer of a turbulent boundary layer, 63rd Annual Meeting of the APS Division of Fluid Dynamics, Long beach, CA, USA.<\/p>\n
S. Talapatra, J. Katz, 2010, Resolving the 3D velocity field inside a Roughness Sublayer in a turbulent channel flow using HPIV, Long beach, CA, USA.<\/p>\n
J. Katz, J. Hong, C. Meneveau, M. Schultz, 2010, Subgrid scale (SGS) flow structures and energy flux in a rough-wall channel flow, 63rd Annual Meeting of the APS Division of Fluid Dynamics, Long beach, CA, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2009, Near-wall flow structures over 3D roughness in a turbulent channel flow, International Union of Theoretical and Applied Mechanics (IUTAM) symposium on “The physics of wall-bounded turbulent flows on rough walls”, Cambridge, UK.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2009, Turbulence statistics over 3D roughness in a turbulent channel flow, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
S. Talapatra, J. Hong, J. Katz, 2009, Near-wall measurement in turbulent flow over rough wall using microscopic HPIV, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
J. Katz, J. Hong, M. Schultz, 2009, Flow structures and effects of spatial resolution on turbulence Statistics in rough wall turbulent channel flow, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2008, Experimental investigation of near-wall flow structures in a rough-wall turbulent channel flow, 61st Annual Meeting of the APS Division of Fluid Dynamics, San Antonio, TX, USA.<\/p>\n
S. Talapatra, J. Hong, Y. Lu, J. Katz, 2008, Microscopic holography for flow over rough plate, 61st Annual Meeting of the APS Division of Fluid Dynamics, San Antonio, TX, USA.<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Rough Wall Turbulence People Graduate Student Jiarong Hong Siddharth Talapatra Collaborator Mike Schultz Project Supervisor Joseph Katz Project Engineer Yury Ronzhes Outline Our Project aims at applying advanced PIV techniques to measure near-wall flow structures over the rough surface in … Continue reading
- \n
- Study the geometric correlations between near wall flow structures and rough surface.<\/li>\n
- Study the correlations between the near wall flow structures\u00a0 and turbulent statistical quantities.<\/li>\n
- Provide theoretical foundation for developing reasonable wall-models in numerical simulations.<\/li>\n<\/ul>\n
Highlights<\/h3>\n
- \n
- Near-wall optical measurement using index-matched fluid.<\/li>\n
- High resolution measurement to capture small scale turbulent motions.<\/li>\n
- Time-resolved measurement to capture the development of structures near the wall<\/li>\n
- 3D instantaneous measurement to resolve spanwise structure motions<\/li>\n<\/ul>\n
Introduction<\/h3>\n
Every surface is rough. We refer to rough surface in a hydrodynamic sense. In Fluid Mechanics we distinguish rough surface based on roughness Reynolds number k+<\/sup>= kut<\/sub>\/v <\/em>Where k is the roughness length scale, ut <\/sub><\/em>is the friction velocity, v is the kinetic viscosity, Generally:<\/p>\n
k+<\/sup><5, hydrodynamically smooth
\n5< k+<\/sup><70, transitionally rough
\nk+<\/sup>>70, fully rough<\/p>\nThere are myriad prototypes of rough-wall flows in the nature and engineering applications. They appear in different geometries and large-ranging length scales. However, there are similarities in the external flow generated from these surfaces.<\/p>\n
Two major questions in rough-wall turbulence study.<\/p>\n
- \n
- \u00a0Study the relation between wall stress and roughness geometry.<\/li>\n
- \u00a0Study the influence zone of the roughness to the turbulence.<\/li>\n<\/ol>\n
Wall similarity hypothesis<\/strong> (Raupach et al. <\/em>1991, <\/em>Jim\u00e9nez 2004)
\nUnder well-characterized condition, i.e. sufficient separation among d<\/em>, k<\/em>, dv <\/sub><\/em>(d<\/em>\/k ><\/em>40, k\/dv <\/sub><\/em>>50-100), the influence of roughness to the turbulent motions is limited to roughness sublayer, typically within 2-5k <\/em>above the wall.<\/p>\nFacility<\/h3>\n
Our experiment facility is a bypass of the turbo-machinery facility in the Laboratory of Experimental Fluid Dynamics. The whole facility is filled with 62% by weight NaI solution which has the same refractive index as acrylic. This minimizes the reflection at the liquid-solid interface and enables us to investigate the flow phenomena very close to the wall. It also allows undistorted transmission of laser beam through the rough wall, which is crucial for Holographic measurements.<\/p>\n
<\/a>Feature Highlights:<\/strong><\/p>\n- \n
- The facility equips with index-matched fluid to minimize the reflection on the rough surface.<\/li>\n
- The channels is made of transparent material. The test section can be accessed from different angles.<\/li>\n
- Four-insert design enables us to perform experiment under different surface conditions with modifying the main body of the channel.<\/li>\n<\/ul>\n<\/a><\/p>\n
Schematic of the By-pass Channel. The red mark is our field of interest, where we have a fully developed flow and transition effect from smooth-rough becomes negligible.<\/p>\n
Rough Surfaces:<\/strong><\/p>\n
The rough-surface is composed of uniformly closed-pack pyramids. This is a typical kind of 3d roughness with close length scales of all three directions.<\/p>\n
Roughness height k=0.457mm
\nPitch angle=20 degrees
\nEquivalent sand roughness ks<\/sub>~1.5k<\/p>\n<\/a><\/a>The acrylic roughness used in the experiment<\/span><\/p>\nApproaches<\/h3>\n
The approaches we applied or will apply in this project includes:<\/p>\n
- \n
- 2D PIV of high and low resolutions.<\/li>\n
- High speed PIV<\/li>\n
- High magnification stereo PIV<\/li>\n
- Holographic PIV (Currently by Siddharth Talapratra)<\/a><\/li>\n
- Tomographic PIV (Currently by Rinaldo Miorini)<\/li>\n<\/ul>\n
<\/a><\/h3>\n<\/a><\/p>\n<\/a><\/p>\nResults<\/h3>\n
Basic flow condition calibration<\/i>
\n1st Stereo PIV experiment<\/i>
\n2nd Stereo PIV experiment<\/i><\/a>
\nHigh resolution PIV experiment<\/i><\/a>
\nHigh speed PIV experiment<\/i><\/a>
\nHolographic PIV experiment<\/i><\/a>
\nCoherent structures and associated subgrid-scale <\/i>(SGS<\/i>) energy transfer<\/a><\/p>\n<\/a>The sample plane is located at 35h from the leading edge of bottom rough-wall insert to guarantee well-developed self-similarity. <\/span><\/h3>\n<\/a>Publications<\/h3>\nJ. Hong, J. Katz, M. Schultz, 2011, Near-wall turbulence statistics and flow structures over three-dimensional roughness in a turbulent channel flow<\/a>,<\/em> Journal of Fluid Mechanics, vol.667, pp.1-37.<\/p>\n
J. Hong, J. Katz, C. Meneveau, M. Schultz, 2012, Coherent structures and associated subgrid-scale energy transfer in a rough-wall channel flow<\/a>,<\/em> Journal of Fluid Mechanics, 712, 92-128.<\/p>\n
S. Talapatra, J. Katz, 2011, Volumetric 3D velocity measurements in the Roughness Sublayer of a channel flow using Microscopic Holographic PIV<\/em>, 9th International Symposium on Particle Image Velocimetry, Kobe, Japan.<\/p>\n
J. Hong, R. Miorini, J. Katz, M. Schultz, 2011, Investigation of Taylor’s hypothesis using time-resolved PIV data<\/em>, 9th International Symposium on Particle Image Velocimetry, Kobe, Japan.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2010, Scale-dependent energy fluxes in a rough-wall turbulent channel flow<\/em><\/a>, In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers Digital Collection. Paper No: <\/span> FEDSM-ICNMM2010-30829, pp. 2095-2105;<\/p>\n
S. Talapatra, J. Katz, 2010, Three dimensional volumetric velocity measurements in the inner part of a turbulent boundary layer over a rough wall using digital HPIV<\/em><\/a>, In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers Digital Collection. Paper No: <\/span> FEDSM-ICNMM2010-30813, pp. 193-201;<\/p>\n
J. Hong, J. Katz, M. Schultz, 2009, High resolution PIV measurement near a rough wall in an optically index-matched facility, 8th International Symposium on Particle Image Velocimetry, Melbourne, Australia.<\/p>\n
S. Talapatra, J. Hong, J. Katz, 2009, Digital microscopic holography to measure flow through rough walls, 8th International Symposium on Particle Image Velocimetry, Melbourne, Australia.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2008, Near-wall stereo PIV investigation of the turbulent channel flow over rough-walls, Proceedings of ASME 2008 Fluids Engineering Conference, Jacksonville, FL, USA.<\/p>\n
J. Hong, J. Katz, C. Meneveau, M. Schultz, 2011, Coherent structures and associated sub-grid scale energy transfer in a rough-wall turbulent channel flow, 64th Annual Meeting of the APS Division of Fluid Dynamics, Baltimore, MD, USA.<\/p>\n
S. Talapatra, J. Katz, 2011, Measurements of the 3D flow structures within the roughness sublayer using Microscopic Holographic PIV, 64th Annual Meeting of the APS Division of Fluid Dynamics, Baltimore, MD, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2010, Roughness signature in the outer-layer of a turbulent boundary layer, 63rd Annual Meeting of the APS Division of Fluid Dynamics, Long beach, CA, USA.<\/p>\n
S. Talapatra, J. Katz, 2010, Resolving the 3D velocity field inside a Roughness Sublayer in a turbulent channel flow using HPIV, Long beach, CA, USA.<\/p>\n
J. Katz, J. Hong, C. Meneveau, M. Schultz, 2010, Subgrid scale (SGS) flow structures and energy flux in a rough-wall channel flow, 63rd Annual Meeting of the APS Division of Fluid Dynamics, Long beach, CA, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2009, Near-wall flow structures over 3D roughness in a turbulent channel flow, International Union of Theoretical and Applied Mechanics (IUTAM) symposium on “The physics of wall-bounded turbulent flows on rough walls”, Cambridge, UK.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2009, Turbulence statistics over 3D roughness in a turbulent channel flow, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
S. Talapatra, J. Hong, J. Katz, 2009, Near-wall measurement in turbulent flow over rough wall using microscopic HPIV, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
J. Katz, J. Hong, M. Schultz, 2009, Flow structures and effects of spatial resolution on turbulence Statistics in rough wall turbulent channel flow, 62nd Annual Meeting of the APS Division of Fluid Dynamics, Minneapolis, MN, USA.<\/p>\n
J. Hong, J. Katz, M. Schultz, 2008, Experimental investigation of near-wall flow structures in a rough-wall turbulent channel flow, 61st Annual Meeting of the APS Division of Fluid Dynamics, San Antonio, TX, USA.<\/p>\n
S. Talapatra, J. Hong, Y. Lu, J. Katz, 2008, Microscopic holography for flow over rough plate, 61st Annual Meeting of the APS Division of Fluid Dynamics, San Antonio, TX, USA.<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Rough Wall Turbulence People Graduate Student Jiarong Hong Siddharth Talapatra Collaborator Mike Schultz Project Supervisor Joseph Katz Project Engineer Yury Ronzhes Outline Our Project aims at applying advanced PIV techniques to measure near-wall flow structures over the rough surface in … Continue reading
- Tomographic PIV (Currently by Rinaldo Miorini)<\/li>\n<\/ul>\n