Heat transfer to reattached fluid flow downstream of a fence

Zukauskas, Algirdas; Pedisius, Antanas

doi:10.1007/bf01377568

Cited by 10 publications

(8 citation statements)

References 8 publications

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“…This free shear layer differs substantially from an ordinary mixing plane due to its high turbulence level [20], which also causes a gradual augmentation of its size at an increased distance from the rib [21]. This free shear layer differs substantially from an ordinary mixing plane due to its high turbulence level [20], which also causes a gradual augmentation of its size at an increased distance from the rib [21].…”

Section: Flow Over a Backward Facingmentioning

confidence: 95%

“…This free shear layer differs substantially from an ordinary mixing plane due to its high turbulence level [20], which also causes a gradual augmentation of its size at an increased distance from the rib [21]. The second part of the shear layer is carried away downstream, and contributes to the growth of a new subboundary layer reattached to the wall [21]. When subjected to the effects of stabilizing curvature and a strong interaction with the wall, the shear layer is substantially split into two fractions [21,22].…”

Section: Flow Over a Backward Facingmentioning

confidence: 99%

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Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts

2013

Journal of Heat Transfer

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The present study is geared toward quantifying the effects of imposed thermal boundary condition in cooling channel applications. In this regard, tests are conducted in a generic passage, with evenly distributed rib type perturbators at 90deg, with a 30% passage blockage ratio and pitch-to-height ratio of 10. Uniform heat-flux is imposed on the external side of the slab which provides Biot number and solid-to-fluid thermal conductivity ratio around I and 600, respectively. Through infrared thermometiy measurements over the wetted surface and via an energy balance within the solid, conjugate heat transfer coefficients are calculated over a single rib-pitch. The local heat extraction is demonstrated to be a strong function of the conduction effects, observed more dominantly in the rib vicinity. Moreover, the aero-thermal effects are investigated by comparing the flndings with analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. Furthermore, the results are contrasted with the iso-heat-flux wetted boundary condition test case. Neglecting the thermal boundary condition dependence, and thus the true thermal history of the boundary layer, is demonstrated to produce large errors in heat transfer predictions.

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Section: Flow Over a Backward Facingmentioning

confidence: 95%

“…This free shear layer differs substantially from an ordinary mixing plane due to its high turbulence level [20], which also causes a gradual augmentation of its size at an increased distance from the rib [21]. The second part of the shear layer is carried away downstream, and contributes to the growth of a new subboundary layer reattached to the wall [21]. When subjected to the effects of stabilizing curvature and a strong interaction with the wall, the shear layer is substantially split into two fractions [21,22].…”

Section: Flow Over a Backward Facingmentioning

confidence: 99%

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts

2013

Journal of Heat Transfer

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“…When the flow passes a rib obstacle, a free shear layer is formed at the sharp corner due to the interaction between the separated mainstream flow and the reverse flow in the recirculation region downstream. This free shear layer differs substantially from an ordinary mixing plane due to its high turbulence level [20], which also causes a gradual augmentation of its size at an increased distance from the rib [21]. In the region of flow reattachment, the separated shear layer curves sharply downward and impinges on the wall.…”

Section: Flow Over a Backward Facing Stepmentioning

confidence: 99%

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Cukurel¹,

Arts²

2012

Volume 1: Heat Transfer in Energy Systems; Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer;

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The present study is geared toward quantifying the effects of imposed thermal boundary condition in cooling channel applications. In this regard, tests are conducted in a generic passage, with evenly distributed rib type perturbators at 90 deg, with a 30% passage blockage ratio and pitch-to-height ratio of 10. Uniform heat-flux is imposed on the external side of the slab which provides Biot number and solid-to-fluid thermal conductivity ratio around 1 and 600, respectively. Through infrared thermometry measurements over the wetted surface and via an energy balance within the solid, conjugate heat transfer coefficients are calculated over a single rib-pitch. The local heat extraction is demonstrated to be a strong function of the conduction effects, observed more dominantly in the rib vicinity. Moreover, the aero-thermal effects are investigated by comparing the findings with analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. Furthermore, the results are contrasted with the iso-heat-flux wetted boundary condition test case. Neglecting the thermal boundary condition dependence, and thus the true thermal history of the boundary layer, is demonstrated to produce large errors in heat transfer predictions.

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“…In the region of flow reattachment, the separated shear layer curves sharply downward and impinges on the wall. When subjected to the effects of stabilizing curvature and a strong interaction with the wall, the shear layer is split into two fractions [16,17]. Since the energy of the first part does not suffice to overcome the strong adverse pressure gradient, it is deflected upstream; being reversed, it forms the recirculating flow region.…”

Section: Rib Roughened Channel Flow Fieldmentioning

confidence: 99%

“…Since the energy of the first part does not suffice to overcome the strong adverse pressure gradient, it is deflected upstream; being reversed, it forms the recirculating flow region. The second part of the shear layer is carried away downstream, and contributes to the growth of a new sub-boundary layer, as it reattaches to the wall [16].…”

Section: Rib Roughened Channel Flow Fieldmentioning

confidence: 99%

Film Cooling Extraction Effects on the Aero-Thermal Characteristics of Rib Roughened Cooling Channel Flow

Cukurel

Selcan

Arts

2012

Volume 4: Heat Transfer, Parts a and B

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The present study is geared towards quantifying the effects of film cooling holes on turbine internal cooling passages. In this regard, tests are conducted in a generic stationary model, with evenly distributed rib type perturbators at 90°, constituting a passage blockage ratio of H/Dh = 0.3 and pitch-to-height ratio of P/H = 10. The 1/3H diameter surface-perpendicular film cooling holes are employed at a distance of 5/3H downstream of the preceding rib. Through liquid crystal thermometry measurements, the aero-thermal effects of a change in suction ratio are contrasted for various configurations (Re = 40,000 SR = 0–6), and compared with the analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. At increased suction ratio, the size of the separation bubble downstream of the rib is observed to diminish, triggering globally an earlier reattachment, in addition to low-momentum hot fluid extraction via film cooling suction. Hence, in the presence of active flow extraction, higher overall heat transfer characteristics are observed throughout the channel. Moreover, the findings are generalized via friction factor and Nusselt number correlations, along with an analytical 20-pitch passage model. SR∼3.5 is observed to provide favorable characteristics of pitch-to-pitch uniform suction ratio, lack of hot fluid ingestion and to sustain the highest passage averaged heat transfer.

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Heat transfer to reattached fluid flow downstream of a fence

Abstract: Abstract. In this paper we present heat transfer experiments 6** performed at the reattachment of turbulent flows of fluids ~9, (Pr=

Cited by 10 publications

References 8 publications

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Local Heat Transfer Dependency on Thermal Boundary Condition in Ribbed Cooling Channel Geometries

Film Cooling Extraction Effects on the Aero-Thermal Characteristics of Rib Roughened Cooling Channel Flow

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