LDA Investigation of the Flow Development Through Rotating U-Ducts

Cheah, S. C.; Iacovides, Hector; Jackson, Daniel M.; Ji, H.; Launder, B. E.

doi:10.1115/1.2836706

Cited by 86 publications

(18 citation statements)

References 6 publications

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“…To improve the performance of the CFD codes, a validation of the predictions is necessary and detailed measurements of the flow structure in the passages are required for comparison. Previous experiments to define the flow characteristics and to provide data for CFD evaluation have included LDV measurements in rotating and stationary two-pass passages by Cheah et al (1994) and Iacovides et al (1996). Liou and Chen (1997) recently performed LDV measurements of the developing flow through a smooth duct with a 180º straight-corner turn.…”

Section: Internal Cooling Of Turbine Bladesmentioning

confidence: 99%

PIV Investigation of the Flow Characteristics in an Internal Coolant Passage With Two Ducts Connected by a Sharp 180° Bend

Schabacker

Bölcs

Johnson

1998

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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A PIV study of the flow in a stationary model of a smooth two-pass internal coolant passage is presented, which focuses on the flow characteristics in the sharp 180º bend and downstream of the bend where the flow is redeveloping. Because PIV in its traditional conception only allows for the investigation of two-dimensional flow, a stereoscopic digital PIV system was assembled that measures all three velocity components simultaneously. The mean-velocity field and turbulence quantities of the flow are obtained from the PIV measurements. The model of the coolant passage consists of two square ducts, each having a length of 19 hydraulic diameters, which are connected by a sharp 180º bend with a rectangular outer wall. The measurements were obtained at one flow condition with a flow Reynolds number of 50,000. A strong secondary flow motion occurs in the bend of the smooth passage that consists of two counter rotating vortices, which impinge on the outer wall and influence the flow in the downstream leg. Both of the outer corners contain regions of recirculating flow. A separation bubble, about 1.5 hydraulic diameters long, occurs on the inner wall of the return pass. In the symmetry plane, the flow recovers from the bend effect within 10 hydraulic diameters.

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Section: Internal Cooling Of Turbine Bladesmentioning

confidence: 99%

PIV Investigation of the Flow Characteristics in an Internal Coolant Passage With Two Ducts Connected by a Sharp 180° Bend

Schabacker

Bölcs

Johnson

1998

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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“…3 and compared with the experimental data (Cheah et al, 1994). The results computed by using Launder±Sharma model are also included in the ®gure.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Thē ow Reynolds number based on the hydraulic diameter and bulk velocity is 100,000. The experimental study was carried out by Cheah et al (1994). Only the¯ow in the one half of the duct is computed because of the symmetry of ow con®guration.…”

Section: Numerical Resultsmentioning

confidence: 99%

Application of non-linear k -ω model to a turbulent flow inside a sharp U-bend

Song

Amano

2000

Computational Mechanics

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Simulation of the complex¯ow inside a sharp U-bend needs both re®ned turbulence models and higher order numerical discretization schemes. In the present study, a non-linear low-Reynolds number (low-Re) k±x model including the cubic terms was employed to predict the turbulent¯ow through a square cross-sectioned U-bend with a sharp curvature, R C /D = 0.65. In the turbulence model employed for the present study, the cubic terms are incorporated to represent the effect of extra strain-rates such as streamline curvature and threedimensionality on both turbulence normal and shear stresses. In order to accurately predict such complex ow®elds, a higher-order bounded interpolation scheme (Song et al., 1999) has been used to discretize all the transport equations. The calculated results by using both the non-linear k±x model and the linear low-Reynolds number k±e model (Launder and Sharma, 1974) have been compared with experimental data. It is shown that the present model produces satisfactory predictions of thē ow development inside the sharp U-bend and well captures the characteristics of the turbulence anisotropy within the duct core region and wall sub-layer.

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“…They employed three turbulence models k À e eddy viscosity model with one equation in the near wall region, a low-Re k À e eddy viscosity model, and a low-Re algebraic stress model. However, there are very limited numerical studies on the secondary flows inside rotating ducts oriented some angles with rotation axis [2,3,5,[9][10][11][12]. More recently, Hu et al [13] performed flow and heat transfer in the tip-turn region of a U-duct under rotating and non-rotating conditions with the passage with dimpled surface.…”

mentioning

confidence: 97%

“…Due to the lack of experimental data on local flow and heat transfer, it has neither been possible to gain a clear understanding of the hydrodynamics and thermal behavior in these complex passages nor to develop and validate numerical flow solvers that can be used for the simulation of blade cooling flows. Local heat transfer measurements for constant area U-bends can now be found in the literature [1][2][3][4][5]. Cooling flows through U-bends that involve a change in cross sectional area are present in blade cooling passages.…”

mentioning

confidence: 99%

Numerical study of the thermal development in a rotating cooling passage

et al. 2011

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In the present study, the fully developed turbulent secondary flows inside rotating square-upstream section and rectangular downstream section oriented at several angles with axis rotation are numerically simulated using the low Reynolds Non-linear k À x, k À e ReynoldsStress Model (RSM), and Large Eddy Simulation (LES) models. The two flat walls are heated (leading and trailing sides), while the outer wall and the splitter plate are thermally insulated. The simulation has been done at Re = 36,000 with different rotation numbers from Ro = -0.4 to Ro = 0.4, where negative Ro values refer to counter-clock wise and positive Ro values refer to clock wise sense of rotation. This enables to investigate the effects on the thermal development of the rotation numbers. The effects of minor modifications, in cross section area at the bend exit, on thermal development, under rotating conditions, can also be explored. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Previous studies have shown that the flow and heat transfer features through curved bends, even with a moderate curvature, cannot be accurately simulated. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method for achieving accurate computations. It is shown that the present RSM model produces satisfactory predictions of the flow development inside the sharp U-bend comparing with the experiments (Iacovides et al. 2006). In the present study, three turbulence models are used to predict Nusselt number distribution. The results were further compared with the LES computations and discussed the difference between the turbulence models and the LES as well.

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LDA Investigation of the Flow Development Through Rotating U-Ducts

Cited by 86 publications

References 6 publications

PIV Investigation of the Flow Characteristics in an Internal Coolant Passage With Two Ducts Connected by a Sharp 180° Bend

PIV Investigation of the Flow Characteristics in an Internal Coolant Passage With Two Ducts Connected by a Sharp 180° Bend

Application of non-linear k -ω model to a turbulent flow inside a sharp U-bend

Numerical study of the thermal development in a rotating cooling passage

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