Transition of unsteady velocity profiles with reverse flow
This paper deals with the stability and transition to turbulence of wall-bounded unsteady velocity profiles with reverse flow. Such flows occur, for example, during unsteady boundary layer separation and in oscillating pipe flow. The main focus is on results from experiments in time-developing flow...
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| Veröffentlicht in: | Journal of fluid mechanics 1998-11, Vol.374, p.251-283 |
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| creator | DAS, DEBOPAM ARAKERI, JAYWANT H. |
| description | This paper deals with the stability and transition to turbulence
of wall-bounded
unsteady velocity profiles with reverse flow. Such flows occur, for example,
during
unsteady boundary layer separation and in oscillating pipe flow. The main
focus
is on results from experiments in time-developing flow in a long pipe,
which is
decelerated rapidly. The flow is generated by the controlled motion of
a piston. We
obtain analytical solutions for laminar flow in the pipe and in a two-dimensional
channel for arbitrary piston motions. By changing the piston speed and
the length
of piston travel we cover a range of values of Reynolds number and boundary
layer
thickness. The velocity profiles during the decay of the flow are unsteady
with reverse
flow near the wall, and are highly unstable due to their inflectional nature.
In the
pipe, we observe from flow visualization that the flow becomes unstable
with the
formation of what appears to be a helical vortex. The wavelength of the
instability
≃3δ where δ is the average
boundary layer thickness, the average being taken over the time the flow
is unstable. The
time of formation of the vortices scales with the average convective time
scale and is
≃39/(Δū/δ),
where
Δu=(umax−umin)
and umax, umin
and δ are the
maximum velocity, minimum velocity and boundary layer thickness respectively
at each instant
of time. The time to transition to turbulence is
≃33/(Δū/δ).
Quasi-steady linear
stability analysis of the velocity profiles brings out
two important results. First that the stability characteristics of velocity
profiles with
reverse flow near the wall collapse when scaled with the above variables.
Second that
the wavenumber corresponding to maximum growth does not change much during
the instability even though the velocity profile does change substantially.
Using the
results from the experiments and the stability analysis, we are able to
explain many
aspects of transition in oscillating pipe flow. We postulate that unsteady
boundary
layer separation at high Reynolds numbers is probably related to instability
of the
reverse flow region. |
| doi_str_mv | 10.1017/S0022112098002572 |
| format | Article |
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of wall-bounded
unsteady velocity profiles with reverse flow. Such flows occur, for example,
during
unsteady boundary layer separation and in oscillating pipe flow. The main
focus
is on results from experiments in time-developing flow in a long pipe,
which is
decelerated rapidly. The flow is generated by the controlled motion of
a piston. We
obtain analytical solutions for laminar flow in the pipe and in a two-dimensional
channel for arbitrary piston motions. By changing the piston speed and
the length
of piston travel we cover a range of values of Reynolds number and boundary
layer
thickness. The velocity profiles during the decay of the flow are unsteady
with reverse
flow near the wall, and are highly unstable due to their inflectional nature.
In the
pipe, we observe from flow visualization that the flow becomes unstable
with the
formation of what appears to be a helical vortex. The wavelength of the
instability
≃3δ where δ is the average
boundary layer thickness, the average being taken over the time the flow
is unstable. The
time of formation of the vortices scales with the average convective time
scale and is
≃39/(Δū/δ),
where
Δu=(umax−umin)
and umax, umin
and δ are the
maximum velocity, minimum velocity and boundary layer thickness respectively
at each instant
of time. The time to transition to turbulence is
≃33/(Δū/δ).
Quasi-steady linear
stability analysis of the velocity profiles brings out
two important results. First that the stability characteristics of velocity
profiles with
reverse flow near the wall collapse when scaled with the above variables.
Second that
the wavenumber corresponding to maximum growth does not change much during
the instability even though the velocity profile does change substantially.
Using the
results from the experiments and the stability analysis, we are able to
explain many
aspects of transition in oscillating pipe flow. We postulate that unsteady
boundary
layer separation at high Reynolds numbers is probably related to instability
of the
reverse flow region.</description><identifier>ISSN: 0022-1120</identifier><identifier>EISSN: 1469-7645</identifier><identifier>DOI: 10.1017/S0022112098002572</identifier><identifier>CODEN: JFLSA7</identifier><language>eng</language><publisher>Cambridge: Cambridge University Press</publisher><subject>Exact sciences and technology ; Flows in ducts, channels, nozzles, and conduits ; Fluid dynamics ; Fundamental areas of phenomenology (including applications) ; Hydrodynamic waves ; Physics ; Transition to turbulence ; Turbulent flows, convection, and heat transfer</subject><ispartof>Journal of fluid mechanics, 1998-11, Vol.374, p.251-283</ispartof><rights>1998 Cambridge University Press</rights><rights>1998 INIST-CNRS</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c462t-9b09fa95a505f3a3bad5772085a1dcfdf80466250da3be27a82c1d62d19e5eab3</citedby></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://www.cambridge.org/core/product/identifier/S0022112098002572/type/journal_article$$EHTML$$P50$$Gcambridge$$H</linktohtml><link.rule.ids>164,314,776,780,27901,27902,55603</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=2421433$$DView record in Pascal Francis$$Hfree_for_read</backlink></links><search><creatorcontrib>DAS, DEBOPAM</creatorcontrib><creatorcontrib>ARAKERI, JAYWANT H.</creatorcontrib><title>Transition of unsteady velocity profiles with reverse flow</title><title>Journal of fluid mechanics</title><addtitle>J. Fluid Mech</addtitle><description>This paper deals with the stability and transition to turbulence
of wall-bounded
unsteady velocity profiles with reverse flow. Such flows occur, for example,
during
unsteady boundary layer separation and in oscillating pipe flow. The main
focus
is on results from experiments in time-developing flow in a long pipe,
which is
decelerated rapidly. The flow is generated by the controlled motion of
a piston. We
obtain analytical solutions for laminar flow in the pipe and in a two-dimensional
channel for arbitrary piston motions. By changing the piston speed and
the length
of piston travel we cover a range of values of Reynolds number and boundary
layer
thickness. The velocity profiles during the decay of the flow are unsteady
with reverse
flow near the wall, and are highly unstable due to their inflectional nature.
In the
pipe, we observe from flow visualization that the flow becomes unstable
with the
formation of what appears to be a helical vortex. The wavelength of the
instability
≃3δ where δ is the average
boundary layer thickness, the average being taken over the time the flow
is unstable. The
time of formation of the vortices scales with the average convective time
scale and is
≃39/(Δū/δ),
where
Δu=(umax−umin)
and umax, umin
and δ are the
maximum velocity, minimum velocity and boundary layer thickness respectively
at each instant
of time. The time to transition to turbulence is
≃33/(Δū/δ).
Quasi-steady linear
stability analysis of the velocity profiles brings out
two important results. First that the stability characteristics of velocity
profiles with
reverse flow near the wall collapse when scaled with the above variables.
Second that
the wavenumber corresponding to maximum growth does not change much during
the instability even though the velocity profile does change substantially.
Using the
results from the experiments and the stability analysis, we are able to
explain many
aspects of transition in oscillating pipe flow. We postulate that unsteady
boundary
layer separation at high Reynolds numbers is probably related to instability
of the
reverse flow region.</description><subject>Exact sciences and technology</subject><subject>Flows in ducts, channels, nozzles, and conduits</subject><subject>Fluid dynamics</subject><subject>Fundamental areas of phenomenology (including applications)</subject><subject>Hydrodynamic waves</subject><subject>Physics</subject><subject>Transition to turbulence</subject><subject>Turbulent flows, convection, and heat transfer</subject><issn>0022-1120</issn><issn>1469-7645</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1998</creationdate><recordtype>article</recordtype><recordid>eNp9kE1LwzAYx4MoOKcfwFsP4q2alyZpvcmmU5yIbl68hKxJNLNrZtJu7tubsuFF8PQ88H_hzw-AUwQvEET8cgIhxghhWOTxoxzvgR7KWJFyltF90OvktNMPwVEIcwgRgQXvgaupl3WwjXV14kzS1qHRUm2Sla5caZtNsvTO2EqHZG2bj8TrlfZBJ6Zy62NwYGQV9Mnu9sHr7c10cJeOn0b3g-txWmYMN2kxg4WRBZUUUkMkmUlFOccwpxKp0iiTw4wxTKGKmsZc5rhEimGFCk21nJE-ON_2xilfrQ6NWNhQ6qqStXZtEJjlGYI5ika0NZbeheC1EUtvF9JvBIKioyT-UIqZs125DKWsTKRR2vAbxBlGGSHRlm5tNvL5_pWl_xSME04FGz2Lh8nwcfhC30RXS3ZT5GLmrXrXYu5aX0dO_4z5AaT2hSQ</recordid><startdate>19981110</startdate><enddate>19981110</enddate><creator>DAS, DEBOPAM</creator><creator>ARAKERI, JAYWANT H.</creator><general>Cambridge University Press</general><scope>BSCLL</scope><scope>IQODW</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>8FD</scope><scope>H8D</scope><scope>L7M</scope></search><sort><creationdate>19981110</creationdate><title>Transition of unsteady velocity profiles with reverse flow</title><author>DAS, DEBOPAM ; ARAKERI, JAYWANT H.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c462t-9b09fa95a505f3a3bad5772085a1dcfdf80466250da3be27a82c1d62d19e5eab3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1998</creationdate><topic>Exact sciences and technology</topic><topic>Flows in ducts, channels, nozzles, and conduits</topic><topic>Fluid dynamics</topic><topic>Fundamental areas of phenomenology (including applications)</topic><topic>Hydrodynamic waves</topic><topic>Physics</topic><topic>Transition to turbulence</topic><topic>Turbulent flows, convection, and heat transfer</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>DAS, DEBOPAM</creatorcontrib><creatorcontrib>ARAKERI, JAYWANT H.</creatorcontrib><collection>Istex</collection><collection>Pascal-Francis</collection><collection>CrossRef</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Journal of fluid mechanics</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>DAS, DEBOPAM</au><au>ARAKERI, JAYWANT H.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Transition of unsteady velocity profiles with reverse flow</atitle><jtitle>Journal of fluid mechanics</jtitle><addtitle>J. Fluid Mech</addtitle><date>1998-11-10</date><risdate>1998</risdate><volume>374</volume><spage>251</spage><epage>283</epage><pages>251-283</pages><issn>0022-1120</issn><eissn>1469-7645</eissn><coden>JFLSA7</coden><abstract>This paper deals with the stability and transition to turbulence
of wall-bounded
unsteady velocity profiles with reverse flow. Such flows occur, for example,
during
unsteady boundary layer separation and in oscillating pipe flow. The main
focus
is on results from experiments in time-developing flow in a long pipe,
which is
decelerated rapidly. The flow is generated by the controlled motion of
a piston. We
obtain analytical solutions for laminar flow in the pipe and in a two-dimensional
channel for arbitrary piston motions. By changing the piston speed and
the length
of piston travel we cover a range of values of Reynolds number and boundary
layer
thickness. The velocity profiles during the decay of the flow are unsteady
with reverse
flow near the wall, and are highly unstable due to their inflectional nature.
In the
pipe, we observe from flow visualization that the flow becomes unstable
with the
formation of what appears to be a helical vortex. The wavelength of the
instability
≃3δ where δ is the average
boundary layer thickness, the average being taken over the time the flow
is unstable. The
time of formation of the vortices scales with the average convective time
scale and is
≃39/(Δū/δ),
where
Δu=(umax−umin)
and umax, umin
and δ are the
maximum velocity, minimum velocity and boundary layer thickness respectively
at each instant
of time. The time to transition to turbulence is
≃33/(Δū/δ).
Quasi-steady linear
stability analysis of the velocity profiles brings out
two important results. First that the stability characteristics of velocity
profiles with
reverse flow near the wall collapse when scaled with the above variables.
Second that
the wavenumber corresponding to maximum growth does not change much during
the instability even though the velocity profile does change substantially.
Using the
results from the experiments and the stability analysis, we are able to
explain many
aspects of transition in oscillating pipe flow. We postulate that unsteady
boundary
layer separation at high Reynolds numbers is probably related to instability
of the
reverse flow region.</abstract><cop>Cambridge</cop><pub>Cambridge University Press</pub><doi>10.1017/S0022112098002572</doi><tpages>33</tpages></addata></record> |
| fulltext | fulltext |
| identifier | ISSN: 0022-1120 |
| ispartof | Journal of fluid mechanics, 1998-11, Vol.374, p.251-283 |
| issn | 0022-1120 1469-7645 |
| language | eng |
| recordid | cdi_proquest_miscellaneous_26841081 |
| source | Cambridge University Press Journals Complete |
| subjects | Exact sciences and technology Flows in ducts, channels, nozzles, and conduits Fluid dynamics Fundamental areas of phenomenology (including applications) Hydrodynamic waves Physics Transition to turbulence Turbulent flows, convection, and heat transfer |
| title | Transition of unsteady velocity profiles with reverse flow |
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