Features of laminar separation bubble subjected to varying adverse pressure gradients
This article describes the spatial development of a laminar separation bubble (LSB), its transition, and eventual breakdown under the influence of adverse pressure gradients (APGs) similar to those experienced by low-pressure turbine blades. The investigation combines a comprehensive experimental ap...
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Veröffentlicht in: | Physics of fluids (1994) 2023-12, Vol.35 (12) |
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description | This article describes the spatial development of a laminar separation bubble (LSB), its transition, and eventual breakdown under the influence of adverse pressure gradients (APGs) similar to those experienced by low-pressure turbine blades. The investigation combines a comprehensive experimental approach with a well-resolved large eddy simulation (LES). The streamwise pressure gradients were varied by manipulating the upper wall within the test section. The Reynolds number (Re), based on the plate length and inlet velocity, was 0.2 × 106 with a freestream turbulence intensity of 1.02%. The particle image velocimetry (PIV) and hotwire data were used to illustrate the vortex dynamics, growth of perturbations, and intermittency. The onset and end of transition progressively shift upstream, resulting in a reduction of the laminar shear layer length and bubble length with increasing APG. Interestingly, the flow features exhibit self-similarity in velocity profiles and the growth rate of velocity fluctuations when normalized against the bubble length. The formation of two-dimensional Kelvin–Helmholtz (K–H) rolls is apparent in the beginning, resulting in the selective amplification of frequency and exponential growth of fluctuations. Linear stability theory explains the most amplified frequency and phase speed of convective vortices, apart from the growth of disturbances. Analysis of LES data reveals intricate inviscid–viscous interactions that trigger shear layer breakdown. In brief, evolving perturbations within the braid region of vortices in the latter half interact with the advecting K–H rolls, culminating in the breakdown and the onset of turbulent flow downstream. |
doi_str_mv | 10.1063/5.0177593 |
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The investigation combines a comprehensive experimental approach with a well-resolved large eddy simulation (LES). The streamwise pressure gradients were varied by manipulating the upper wall within the test section. The Reynolds number (Re), based on the plate length and inlet velocity, was 0.2 × 106 with a freestream turbulence intensity of 1.02%. The particle image velocimetry (PIV) and hotwire data were used to illustrate the vortex dynamics, growth of perturbations, and intermittency. The onset and end of transition progressively shift upstream, resulting in a reduction of the laminar shear layer length and bubble length with increasing APG. Interestingly, the flow features exhibit self-similarity in velocity profiles and the growth rate of velocity fluctuations when normalized against the bubble length. The formation of two-dimensional Kelvin–Helmholtz (K–H) rolls is apparent in the beginning, resulting in the selective amplification of frequency and exponential growth of fluctuations. Linear stability theory explains the most amplified frequency and phase speed of convective vortices, apart from the growth of disturbances. Analysis of LES data reveals intricate inviscid–viscous interactions that trigger shear layer breakdown. In brief, evolving perturbations within the braid region of vortices in the latter half interact with the advecting K–H rolls, culminating in the breakdown and the onset of turbulent flow downstream.</description><identifier>ISSN: 1070-6631</identifier><identifier>EISSN: 1089-7666</identifier><identifier>DOI: 10.1063/5.0177593</identifier><identifier>CODEN: PHFLE6</identifier><language>eng</language><publisher>Melville: American Institute of Physics</publisher><subject>Amplification ; Breakdown ; Fluid dynamics ; Fluid flow ; Large eddy simulation ; Low pressure ; Particle image velocimetry ; Perturbation ; Phase velocity ; Physics ; Pressure gradients ; Reynolds number ; Rolls ; Self-similarity ; Separation ; Shear layers ; Turbine blades ; Turbulence intensity ; Velocity distribution ; Vortices</subject><ispartof>Physics of fluids (1994), 2023-12, Vol.35 (12)</ispartof><rights>Author(s)</rights><rights>2023 Author(s). Published under an exclusive license by AIP Publishing.</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c292t-af9eff280b7cce556b2b5ea80ed535b70e40a071f5c11c27c37ba9bd9771d7a53</citedby><cites>FETCH-LOGICAL-c292t-af9eff280b7cce556b2b5ea80ed535b70e40a071f5c11c27c37ba9bd9771d7a53</cites><orcidid>0009-0004-0625-2425 ; 0000-0002-5993-3513</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,776,780,790,4498,27901,27902</link.rule.ids></links><search><creatorcontrib>Kumar, Ravi</creatorcontrib><creatorcontrib>Sarkar, S.</creatorcontrib><title>Features of laminar separation bubble subjected to varying adverse pressure gradients</title><title>Physics of fluids (1994)</title><description>This article describes the spatial development of a laminar separation bubble (LSB), its transition, and eventual breakdown under the influence of adverse pressure gradients (APGs) similar to those experienced by low-pressure turbine blades. The investigation combines a comprehensive experimental approach with a well-resolved large eddy simulation (LES). The streamwise pressure gradients were varied by manipulating the upper wall within the test section. The Reynolds number (Re), based on the plate length and inlet velocity, was 0.2 × 106 with a freestream turbulence intensity of 1.02%. The particle image velocimetry (PIV) and hotwire data were used to illustrate the vortex dynamics, growth of perturbations, and intermittency. The onset and end of transition progressively shift upstream, resulting in a reduction of the laminar shear layer length and bubble length with increasing APG. Interestingly, the flow features exhibit self-similarity in velocity profiles and the growth rate of velocity fluctuations when normalized against the bubble length. The formation of two-dimensional Kelvin–Helmholtz (K–H) rolls is apparent in the beginning, resulting in the selective amplification of frequency and exponential growth of fluctuations. Linear stability theory explains the most amplified frequency and phase speed of convective vortices, apart from the growth of disturbances. Analysis of LES data reveals intricate inviscid–viscous interactions that trigger shear layer breakdown. In brief, evolving perturbations within the braid region of vortices in the latter half interact with the advecting K–H rolls, culminating in the breakdown and the onset of turbulent flow downstream.</description><subject>Amplification</subject><subject>Breakdown</subject><subject>Fluid dynamics</subject><subject>Fluid flow</subject><subject>Large eddy simulation</subject><subject>Low pressure</subject><subject>Particle image velocimetry</subject><subject>Perturbation</subject><subject>Phase velocity</subject><subject>Physics</subject><subject>Pressure gradients</subject><subject>Reynolds number</subject><subject>Rolls</subject><subject>Self-similarity</subject><subject>Separation</subject><subject>Shear layers</subject><subject>Turbine blades</subject><subject>Turbulence intensity</subject><subject>Velocity distribution</subject><subject>Vortices</subject><issn>1070-6631</issn><issn>1089-7666</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2023</creationdate><recordtype>article</recordtype><recordid>eNp9kE1LAzEQhoMoWD8O_oOAJ4Wtk8Qkm6MUv6DgRc8hyU7KlnZ3TbIF_71b27OnmcMz78s8hNwwmDNQ4kHOgWktjTghMwa1qbRS6nS_a6iUEuycXOS8BgBhuJqRrxd0ZUyYaR_pxm3bziWacXDJlbbvqB-93yDNo19jKNjQ0tOdSz9tt6Ku2WHKSIfpPE8ZdJVc02JX8hU5i26T8fo4L6ee58_FW7X8eH1fPC2rwA0vlYsGY-Q1eB0CSqk89xJdDdhIIb0GfAQHmkUZGAtcB6G9M74xWrNGOykuye0hd0j994i52HU_pm6qtLw2NeOq1nvq7kCF1OecMNohtdvpCcvA7q1ZaY_WJvb-wObQlj8F_8C_PCltmA</recordid><startdate>202312</startdate><enddate>202312</enddate><creator>Kumar, Ravi</creator><creator>Sarkar, S.</creator><general>American Institute of Physics</general><scope>AAYXX</scope><scope>CITATION</scope><scope>8FD</scope><scope>H8D</scope><scope>L7M</scope><orcidid>https://orcid.org/0009-0004-0625-2425</orcidid><orcidid>https://orcid.org/0000-0002-5993-3513</orcidid></search><sort><creationdate>202312</creationdate><title>Features of laminar separation bubble subjected to varying adverse pressure gradients</title><author>Kumar, Ravi ; Sarkar, S.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c292t-af9eff280b7cce556b2b5ea80ed535b70e40a071f5c11c27c37ba9bd9771d7a53</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2023</creationdate><topic>Amplification</topic><topic>Breakdown</topic><topic>Fluid dynamics</topic><topic>Fluid flow</topic><topic>Large eddy simulation</topic><topic>Low pressure</topic><topic>Particle image velocimetry</topic><topic>Perturbation</topic><topic>Phase velocity</topic><topic>Physics</topic><topic>Pressure gradients</topic><topic>Reynolds number</topic><topic>Rolls</topic><topic>Self-similarity</topic><topic>Separation</topic><topic>Shear layers</topic><topic>Turbine blades</topic><topic>Turbulence intensity</topic><topic>Velocity distribution</topic><topic>Vortices</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Kumar, Ravi</creatorcontrib><creatorcontrib>Sarkar, S.</creatorcontrib><collection>CrossRef</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Physics of fluids (1994)</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Kumar, Ravi</au><au>Sarkar, S.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Features of laminar separation bubble subjected to varying adverse pressure gradients</atitle><jtitle>Physics of fluids (1994)</jtitle><date>2023-12</date><risdate>2023</risdate><volume>35</volume><issue>12</issue><issn>1070-6631</issn><eissn>1089-7666</eissn><coden>PHFLE6</coden><abstract>This article describes the spatial development of a laminar separation bubble (LSB), its transition, and eventual breakdown under the influence of adverse pressure gradients (APGs) similar to those experienced by low-pressure turbine blades. The investigation combines a comprehensive experimental approach with a well-resolved large eddy simulation (LES). The streamwise pressure gradients were varied by manipulating the upper wall within the test section. The Reynolds number (Re), based on the plate length and inlet velocity, was 0.2 × 106 with a freestream turbulence intensity of 1.02%. The particle image velocimetry (PIV) and hotwire data were used to illustrate the vortex dynamics, growth of perturbations, and intermittency. The onset and end of transition progressively shift upstream, resulting in a reduction of the laminar shear layer length and bubble length with increasing APG. Interestingly, the flow features exhibit self-similarity in velocity profiles and the growth rate of velocity fluctuations when normalized against the bubble length. The formation of two-dimensional Kelvin–Helmholtz (K–H) rolls is apparent in the beginning, resulting in the selective amplification of frequency and exponential growth of fluctuations. Linear stability theory explains the most amplified frequency and phase speed of convective vortices, apart from the growth of disturbances. Analysis of LES data reveals intricate inviscid–viscous interactions that trigger shear layer breakdown. In brief, evolving perturbations within the braid region of vortices in the latter half interact with the advecting K–H rolls, culminating in the breakdown and the onset of turbulent flow downstream.</abstract><cop>Melville</cop><pub>American Institute of Physics</pub><doi>10.1063/5.0177593</doi><tpages>21</tpages><orcidid>https://orcid.org/0009-0004-0625-2425</orcidid><orcidid>https://orcid.org/0000-0002-5993-3513</orcidid></addata></record> |
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subjects | Amplification Breakdown Fluid dynamics Fluid flow Large eddy simulation Low pressure Particle image velocimetry Perturbation Phase velocity Physics Pressure gradients Reynolds number Rolls Self-similarity Separation Shear layers Turbine blades Turbulence intensity Velocity distribution Vortices |
title | Features of laminar separation bubble subjected to varying adverse pressure gradients |
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