Heat transfer in turbulent separated flows in the presence of high free-stream turbulence

Терехов, В. И.; Yarygina, Nadezhda I.; Zhdanov, R. F.

doi:10.1016/s0017-9310(03)00291-6

Cited by 60 publications

(30 citation statements)

References 25 publications

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“…The temperature profile minimum (caused by the flow separation) as well as the temperature maximum (caused by the flow reattachment) has moved further towards the diffuser inlet in the case of the non-rotating diffuser. Another important feature is the reduced length of the separated flow region (i.e., the length between separation and reattachment point) as the Re number increases; according to the results of other experiments conducted by Obi et al [14] and Terekhov et al [18], this phenomenon should be connected with the higher free-stream turbulence at higher Re numbers. Thus, the distance between separation and reattachment point of the non-rotating diffuser is (by Fig.…”

Section: Resultsmentioning

confidence: 87%

Heat Transfer Influenced by Turbulent Airflow Inside an Axially Rotating Diffuser

Bajcar

Širok

Hočevar

et al. 2007

Flow Turbulence Combust

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The paper presents a study of heat transfer between the turbulent airflow and the inner wall surface of an axial diffuser rotating around its longitudinal axis. Heat transfer was assessed through the measurement of a time-dependent temperature field of the diffuser inner wall surface. Measurements of the instantaneous flow velocity components were performed by a laser-Doppler anemometry system, which delivered information on mean velocity components as well as on the turbulence intensity. A significant increase of all three mean velocity components was observed near the rotating diffuser wall in comparison with a non-rotating diffuser. Temperature field measurements were carried out by means of infrared thermography. The experiment showed a significant dependence of the temperature field on the turbulent flowfield induced by diffuser rotation. A strong influence of the flow separation and reattachment on the temperature distribution was observed, while rotation was found to suppress the occurrence of flow separation from the diffuser wall. Properties of the velocity field such as turbulent kinetic energy were directly coupled with the temperature distribution in order to gain the information on how to enhance or reduce heat transfer by changing the integral parameters of the diffuser (e.g. rotation frequency or amount of flow).

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Section: Resultsmentioning

confidence: 87%

Heat Transfer Influenced by Turbulent Airflow Inside an Axially Rotating Diffuser

Bajcar

Širok

Hočevar

et al. 2007

Flow Turbulence Combust

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“…Diffusion coefficient D 1 Diameter of inlet tube D 2 Tube diameter behind expansion ER = (D 2 /D 1 ) 2 Degree of tube expansion S = (D 2 − D 1 )/2…”

Section: List Of Symbols Dmentioning

confidence: 99%

“…A sudden expansion in the tube or separated flow behind a back-facing step is the subject of numerous experimental and theoretical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Interest in this issue, together with important practical applications, is primarily caused by the fact that this problem is a classic one and is the most studied of a wide range of separated flows.…”

Section: Introductionmentioning

confidence: 99%

“…Interest in this issue, together with important practical applications, is primarily caused by the fact that this problem is a classic one and is the most studied of a wide range of separated flows. However, attempts to summarize the available literature data on parameters that define the flow and heat transfer in the separation region, such as the separation bubble length, maximal value of heat transfer, and its coordinates, have been unsuccessful [1,11,14]. In these studies, it is shown that flow prehistory and, particularly, the boundary layer thickness before separation have a strong influence on flow separation.…”

Section: Introductionmentioning

confidence: 99%

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Effect of dynamic and thermal prehistory on aerodynamic characteristics and heat transfer behind a sudden expansion in a round tube

Терехов

Bogatko

2016

Heat Mass Transfer

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“…1). The stepped nose of the model approximately 100 mm long formed a turbulent boundary layer approximately 10 mm thick with the velocity distributed as 1/7 [11]. Two models of identical size were used to measure the thermal and dynamic characteristics of the model.…”

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confidence: 99%

Thermal and dynamic characteristics of the separated flow behind a flat rib with different angles of alignment toward the flow

Терехов

Yarygina

Smulsky

2007

J Appl Mech Tech Phys

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Results of an experimental study of a turbulent flow past a flat rib with different angles of alignment toward the flow and with different rib heights are presented. The angle of rib alignment toward the flow is varied within ϕ = 50-90 • . Vortex formation is visualized, and the coordinates of the reattachment line are determined. It is demonstrated that a decrease in the angle ϕ forms a reattachment region and makes the flow behind the rib more three-dimensional. Pressure coefficients are measured in different longitudinal sections of the channel behind the rib with a varied angle of rib alignment ϕ. Temperature fields on the surface behind the rib are measured by means of an infrared imager and by thermocouples, and the corresponding heat-transfer coefficients are calculated. The effect of the angle of rib alignment toward the flow and the rib height on dynamic and thermal characteristics of the separated flow is analyzed.Introduction. Heat transfer in channels of various devices used in power engineering is often intensified with the help of various obstacles, e.g., flat ribs. In a separated flow, both upstream and downstream of the rib, generation of large-scale vortex structures and interaction of coherent structures with the wall promote intensification of heat transfer on the wall. At the same time, the presence of obstacles leads to an undesirable increase in pressure losses. Thus, the task is to increase heat transfer and simultaneously reduce pressure losses. To solve this problem, one has to study the physical mechanisms of controlling vortex formation in separated flows and carefully measure the dynamic and thermal characteristics in a system of ribs and behind a single obstacle, in particular, behind a single rib.Separated turbulent flow behind a flat obstacle aligned at an angle to the flow has some specific features, as compared to the flow behind an obstacle placed perpendicular to the flow. One of such features is a significant amplification of heat transfer [1][2][3][4]. This phenomenon is more and more widely used in engineering, for instance, for effective cooling of turbine blades or for increasing heat output in heat exchangers. As the obstacle is aligned at an angle to the free stream, the flow is three-dimensional. Numerical calculations of three-dimensional separated turbulent flows require large computational resources and do not ensure a necessary accuracy. In modeling oblique flows, a question arises whether there are regions and directions with invariant values of both dynamic and thermal characteristics, which is particularly important in the case of a single obstacle.There are few papers that describe experimental investigations of the flow structure behind a single obstacle aligned at an angle to the flow, and there are even fewer papers where the thermal characteristics under these conditions are studied. Hancock and McCluskey [5] considered the flow behind a rib aligned at an angle ϕ = 65 • to the flow and compared the results with the data for ϕ = 90 • . The components of the me...

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Heat transfer in turbulent separated flows in the presence of high free-stream turbulence

Cited by 60 publications

References 25 publications

Heat Transfer Influenced by Turbulent Airflow Inside an Axially Rotating Diffuser

Heat Transfer Influenced by Turbulent Airflow Inside an Axially Rotating Diffuser

Effect of dynamic and thermal prehistory on aerodynamic characteristics and heat transfer behind a sudden expansion in a round tube

Thermal and dynamic characteristics of the separated flow behind a flat rib with different angles of alignment toward the flow

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