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  • 1
    Electronic Resource
    Electronic Resource
    Numerical and experimental results for developing curved channel flow (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1473-1476 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-dimensional finite-volume simulations of the spatial development of centrifugally unstable flow in a curved channel have been performed, and compared with detailed hot-wire measurements. Both approaches revealed spatially developing streamwise vortex pairs at the concave wall, which gave rise to regions of alternating negative and positive streamwise perturbation velocities. The computational box size was chosen large enough so that the flow was allowed to naturally select the spanwise wave number. The computed velocity field was found to be in excellent agreement with the experimentally determined one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857982
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the curved wall jet influenced by system rotation and self-similar suction or blowing (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 3048-3059 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we use local nonparallel linear stability theory to study the jet on a concave and convex wall with spanwise system rotation and self-similar suction or blowing. It is found for low negative rotation, i.e. the Coriolis force counteracts the centrifugal force, that the critical Goertler number Go is increased for both the concave and convex wall jet. For the convex wall jet the critical Go is increased up to eight times compared with the nonrotation case. In this region of negative rotation, the principle of exchange of instabilities does not hold for the convex wall jet. For high negative and positive rotation the flow is destabilized on both types of walls. Suction stabilizes the concave wall jet while the convex wall jet is destabilized. For blowing, the concave wall jet is destabilized to a certain limit and then stabilized for increased blowing. The convex wall jet is stabilized for blowing. The combined effects of curvature, system rotation, and self-similar suction or blowing show that the highest critical Go can be increased for the rotating concave wall jet for both suction and blowing. For the rotating convex wall jet the highest critical Go is increased for suction and decreased for blowing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868681
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Görtler vortices in wall jet flow on a rotating cylinder (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 2238-2248 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot-wire anemometry, smoke visualization and nonlinear calculations were used to study the wall jet on a cylinder with rotation. It was found that streamwise vortices are amplified in convex wall jet flow without rotation and that the maximum amplitude was higher than for the concave case. Furthermore, the transition region was located downstream compared with the concave wall jet. Rotation was found to destabilize the convex wall jet, i.e., the transition region appeared upstream compared with nonrotation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869745
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  • 4
    Electronic Resource
    Electronic Resource
    Experiments on instabilities in curved channel flow (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1666-1676 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are reported from hot-wire measurements in a narrow gap, curved air channel with a spanwise aspect ratio of 29. The Reynolds numbers (Re) covered a range from 2 to 6.5 times the critical Re, i.e., the Re for which the flow becomes centrifugally unstable according to linear stability theory. For the lowest Re studied, the measurements showed a regular flow pattern of streamwise vortices, whereas at higher Re interaction occurred between vortex pairs. The streamwise disturbance velocity increased rapidly near the inlet section, thereafter the disturbance amplitude overshot before it finally reached a saturated level of the nonlinear stage. At even higher Re a secondary instability in the form of traveling waves appeared on top of the primary instability and was found to be localized between one pair of vortices at the inflow region from the concave wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858388
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Experiments on streamwise vortices in curved wall jet flow (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 2978-2988 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot-wire anemometry and smoke visualizations are used to study the jet on a concave wall. The measurements were performed in the region 91〈Go〈198, where Go is the Görtler number. It is found that streamwise vortices are amplified on the concave wall. The growth of vortices is dependent on the initial amplitude, i.e. the highest initial amplitude gives the maximum strength of vortices. The amplification occurs in the laminar region while the time-averaged strength of vortices decreases further downstream in the transition region. No merging or splitting of vortex pairs was found. Regular oscillations of the time signal occur at higher Görtler numbers before breakdown. Smoke visualization shows that the horseshoe mode appears with a streamwise wave length of the same order as the triggered spanwise wave length. The streamwise velocity fluctuations indicating the secondary instability were found to coincide better with the total shear distribution rather than streamwise velocity gradients in the spanwise or wall normal directions. Power spectra show distinct peaks at different frequencies. At streamwise positions near the start of curvature, the filtered root-mean-square (rms) levels of the streamwise velocity component around 95 Hz, corresponding to the horseshoe mode, show maximum amplitude between different vortex pairs. The filtered frequency around 22 Hz, which is the dominating frequency further downstream, shows maximum amplitude further away from the wall, where the velocity profile has an inflectional character. However, as the flow proceeds downstream the maximum at 22 Hz moves against the wall. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868675
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  • 6
    Electronic Resource
    Electronic Resource
    Secondary instability and breakdown to turbulence in curved channel flow (1993)
    Springer
    Flow, turbulence and combustion 51 (1993), S. 9-14 
    Details
    ISSN: 1573-1987
    Keywords: curved channel flow ; secondary instability ; transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of curvature on laminar channel flow is studied experimentally, with a focus on secondary instability of the counter-rotating longitudinal vortices set up by the centrifugal force. It is shown that two types of secondary instability, with distinctly different frequencies, are at hand simultaneously, and their spatial distribution and growth are determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082506
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