Numerical study of vortex-breakdown over a slender wing in transonic flow at high incidence

Abstract The paper presents a study of the instability of the precessing vortex core in the model of the draft tube of a hydraulic turbine. The study was carried out using numerical modeling using various approaches: URANS, RSM, LES. The best agreement with the experimental data was shown by the RSM and LES methods with the modelling of the runner rotation by the sliding mesh method. In the regime under consideration, the precessing vortex rope is subject to instability, which leads to reconnection of its turns and the formation of an isolated vortex ring. Reconnection of the vortex core leads to aperiodic and intense pressure fluctuations recorded on the diffuser wall.

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Numerical Study of Axisymmetric Vortex Breakdown Flows in an Open Cylindrical Container with Rotating Bottom Wall.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.68.740 ◽

2002 ◽

Vol 68 (667) ◽

pp. 740-747

Author(s):

Yasunobu OGAWA ◽

Reima IWATSU

Keyword(s):

Vortex Breakdown ◽

Numerical Study ◽

Bottom Wall ◽

Cylindrical Container ◽

Axisymmetric Vortex

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Fan–Intake Interaction Under High Incidence

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4034701 ◽

2016 ◽

Vol 139 (4) ◽

Cited By ~ 14

Author(s):

Teng Cao ◽

Nagabhushana Rao Vadlamani ◽

Paul G. Tucker ◽

Angus R. Smith ◽

Michal Slaby ◽

...

Keyword(s):

Numerical Study ◽

Angle Of Incidence ◽

Inlet Distortion ◽

Distortion Level ◽

3D Geometry ◽

High Incidence ◽

Mach Number Distribution ◽

Unsteady Rans ◽

Bypass Ratio ◽

Insight Into

In this paper, we present an extensive numerical study on the interaction between the downstream fan and the flow separating over an intake under high incidence. The objectives of this investigation are twofold: (a) to gain qualitative insight into the mechanism of fan–intake interaction and (b) to quantitatively examine the effect of the proximity of the fan on the inlet distortion. The fan proximity is altered using the key design parameter, L/D, where D is the diameter of the intake, and L is the distance of the fan from the intake lip. Both steady and unsteady Reynolds-averaged numerical simulations (RANS) were carried out. For the steady calculations, a low-order fan model has been used, while a full 3D geometry has been used for the unsteady RANS. The numerical methodology is also thoroughly validated against the measurements for the intake-only and fan-only configurations on a high bypass ratio turbofan intake and fan, respectively. To systematically study the effect of fan on the intake separation and explore the design criteria, a simplified intake–fan configuration has been considered. In this fan–intake model, the proximity of the fan to the intake separation (L/D) can be conveniently altered without affecting other parameters. The key results indicate that, depending on L/D, the fan has either suppressed the level of the postseparation distortion or increased the separation-free operating range. At the lowest L/D (∼0.17), around a 5 deg increase in the separation-free angle of incidence was achieved. This delay in the separation-free angle of incidence decreased with increasing L/D. At the largest L/D (∼0.44), the fan was effective in suppressing the postseparation distortion rather than entirely eliminating the separation. Isentropic Mach number distribution over the intake lip for different L/D's revealed that the fan accelerates the flow near the casing upstream of the fan face, thereby decreasing the distortion level in the immediate vicinity. However, this acceleration effect decayed rapidly with increasing upstream distance from the fan-face.

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3-D Transonic Flow in a Compressor Cascade With Shock-Induced Corner Stall

Journal of Turbomachinery ◽

10.1115/1.1460913 ◽

2002 ◽

Vol 124 (3) ◽

pp. 358-366 ◽

Cited By ~ 27

Author(s):

Anton Weber ◽

Heinz-Adolf Schreiber ◽

Reinhold Fuchs ◽

Wolfgang Steinert

Keyword(s):

Transonic Flow ◽

Numerical Study ◽

Reverse Flow ◽

Boundary Layer Separation ◽

Ring Vortex ◽

Blade Surface ◽

Compressor Cascade ◽

Complex Flow ◽

Flow Angle ◽

Blade Passage

An experimental and numerical study of the transonic flow through a linear compressor cascade with endwalls was conducted. The cascade with a low aspect ratio of 1.34 was tested at an inlet Mach number of 1.09 and a Reynolds number of 1.9×106. Detailed flow visualizations on the surfaces and five-hole probe measurements inside the blading and in the wake region showed clearly a three-dimensional boundary layer separation on the blade surface and the sidewall, and a severe corner stall induced by a strong 3-D shock system at blade passage entrance. The experimental data have been used to validate and improve the 3-D Navier-Stokes code TRACE. Results showed an excellent resolution of the complex flow field. Surface pressure distributions on the entire blade surface and the endwalls, flow angle and total pressure contours within the blade passage and the wake are compared with the experimental results. An analysis of the secondary flow of this highly staggered cascade did not show the classical corner vortex. Instead, a severe flow deviation and partly reverse flow near the walls is seen. The flow solver helped to identify a weak ring vortex that originates from the passage sidewall. Surface oil flow pictures on the blade contour and the sidewall are in qualitatively good agreement to numerical surface streaklines. A considerable improvement of the numerical results could be achieved by a gradual grid refinement, especially in the corner region and by successive code development.

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Numerical study of vortex breakdown

Applied Numerical Mathematics ◽

10.1016/0168-9274(86)90034-6 ◽

1986 ◽

Vol 2 (3-5) ◽

pp. 291-302 ◽

Cited By ~ 14

Author(s):

M. Hafez ◽

G. Kuruvila ◽

M.D. Salas

Keyword(s):

Vortex Breakdown ◽

Numerical Study

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A Numerical Study of Vortex Breakdown in Turbulent Swirling Flows

Journal of Fluids Engineering ◽

10.1115/1.483247 ◽

1999 ◽

Vol 122 (1) ◽

pp. 179-183 ◽

Cited By ~ 10

Author(s):

Robert E. Spall ◽

Blake M. Ashby

Keyword(s):

Reynolds Stress ◽

Stokes Equations ◽

Vortex Breakdown ◽

Numerical Study ◽

Reynolds Stress Model ◽

Navier Stokes ◽

Stress Model ◽

Mean Flow ◽

Navier Stokes Equations ◽

The Mean

Solutions to the incompressible Reynolds-averaged Navier–Stokes equations have been obtained for turbulent vortex breakdown within a slightly diverging tube. Inlet boundary conditions were derived from available experimental data for the mean flow and turbulence kinetic energy. The performance of both two-equation and full differential Reynolds stress models was evaluated. Axisymmetric results revealed that the initiation of vortex breakdown was reasonably well predicted by the differential Reynolds stress model. However, the standard K-ε model failed to predict the occurrence of breakdown. The differential Reynolds stress model also predicted satisfactorily the mean azimuthal and axial velocity profiles downstream of the breakdown, whereas results using the K-ε model were unsatisfactory. [S0098-2202(00)01601-1]

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Vortex Breakdown in an Enclosed Cylinder With a Partially Rotating Bottom-Wall

Journal of Fluids Engineering ◽

10.1115/1.2969427 ◽

2008 ◽

Vol 130 (11) ◽

Author(s):

P. Yu ◽

T. S. Lee ◽

Y. Zeng ◽

H. T. Low

Keyword(s):

Aspect Ratio ◽

Vortex Breakdown ◽

Numerical Study ◽

Axisymmetric Flow ◽

Rotating Disk ◽

Bottom Wall ◽

Cylindrical Chamber ◽

Noticeable Effect ◽

Disk Radius ◽

Boundary Curves

A numerical study of the axisymmetric flow in a cylindrical chamber of height H is presented, which is driven by a bottom disk rotating at angular velocity Ω. However, unlike most previous studies, the present rotating disk is of smaller radius than the bottom-wall. The boundary curves for the onset of vortex breakdown are presented using different definitions of the nondimensional parameters, depending on whether the cylinder radius R or the disk radius rd is used as the length scale. The study shows that the boundary curves are best correlated when presented in terms of the Reynolds number Ωrd2∕υ, aspect ratio H∕R, and cylinder-to-disk ratio R∕rd. The cylinder-to-disk ratio R∕rd up to 1.6 is found to have noticeable effect on vortex breakdown; this is attributed to the change of effective aspect ratio. The contours of streamline, angular momentum, and azimuthal vorticity are presented and compared with those of whole bottom-wall rotation.

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