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  • 1
    Electronic Resource
    Electronic Resource
    Stability of axial flow in an annulus with a rotating inner cylinder (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2446-2455 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Flow between concentric cylinders with the inner cylinder rotating and an axial pressure gradient imposed in the annulus reveals a rich variety of flow regimes depending on the flow conditions. The occurrence of these flow regimes was studied experimentally by both visually and optically detecting the transition from one flow regime to another over a wide range of Taylor numbers for moderate axial Reynolds numbers. Seven flow regimes of toroidal vortices were identified, including Taylor vortices, wavy vortices, random wavy vortices, modulated wavy vortices, turbulent modulated wavy vortices, turbulent wavy vortices, and turbulent vortices. The toroidal vortices in these flow regimes look similar to the corresponding vortices when there is no axial flow, except that they translate with the axial flow at a speed slightly greater than the bulk axial velocity. Three flow regimes of helical vortices were observed at low Taylor numbers, including laminar helical vortices, stationary helical vortices, and wavy helical vortices. Depending on the flow parameters, the helical vortices had both positive and negative helix angles with respect to the bulk flow and appeared either stationary or moving downstream. Another flow regime consisting of the repeating sequential appearance of turbulent wavy vortices, turbulent helical vortices, and turbulent vortices was also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858485
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  • 2
    Electronic Resource
    Electronic Resource
    Near-wall streaky structure in a turbulent boundary layer on a cylinder (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2822-2824 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A near-wall streaky structure has been identified in a turbulent boundary layer on a cylinder in axial flow. A platinum wire looped around a cylinder moving in a tank of quiescent water was used to generate hydrogen bubbles near the wall of the cylinder. The streaks that were visualized correspond to high-speed streaks identified by Kline et al. [J. Fluid Mech. 30, 741 (1967)]. The appearance, motion, and spacing of the streaks appear similar to the streaky structure in a planar boundary layer, suggesting a similarity in the mechanism for the generation of turbulence in the boundary layers on a flat plate and on a cylinder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858172
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  • 3
    Electronic Resource
    Electronic Resource
    The thick, turbulent boundary layer on a cylinder: Mean and fluctuating velocities (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 3495-3505 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mean and fluctuating velocities in a turbulent boundary layer on a cylinder have been experimentally characterized for the case where the boundary layer is thick compared to the radius of transverse curvature. The mean velocity measurements suggest a mixed scaling for the "log law of the wall'' using the wall coordinate yUτ/ν and the ratio of the local boundary layer thickness to the radius of the cylinder δ/a. A relation for the slope and intercept of the log law of the wall as functions of δ/a based on empirical results and simple analysis is presented. Measurements of the Reynolds stress for δ/a of order 10 show that the Reynolds stress drops off much more quickly with distance from the wall than for a turbulent boundary layer on a flat plate. Both the Reynolds stress data and the turbulent intensity in the mean flow direction data are functions of the inverse radial distance from the center of the cylinder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865417
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  • 4
    Electronic Resource
    Electronic Resource
    The eddy viscosity in a turbulent boundary layer on a cylinder (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 4232-4233 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The eddy viscosity for a turbulent boundary layer on a cylinder was measured using hot-wire anemometry. Except near the wall, the eddy viscosity is roughly constant with a value corresponding to that estimated from the slope of the mean velocity profile. These results confirm that a constant eddy viscosity closure scheme is appropriate for the boundary layer on a cylinder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865716
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  • 5
    Electronic Resource
    Electronic Resource
    The structure of the turbulent boundary layer on a cylinder in axial flow (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2993-3005 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thick, turbulent boundary layer, which develops as a fluid flows parallel to a cylinder, has been experimentally characterized for the case where the boundary layer is thick compared to the radius of transverse curvature. Measurements of the turbulence intensity, velocity spectra, and intermittency are qualitatively similar to those for the planar boundary layer. Although measurements of wall shear stress using several different techniques have substantial scatter, the wall shear stress appears to be larger than that for the turbulent boundary layer on a flat plate at the same Reynolds number based on streamwise distance. The variable interval time averaging (VITA) and uv-quadrant techniques were used to detect the burst cycle near the wall. Conditionally averaged velocities were similar to those for a flat plate boundary layer indicating a similar burst cycle near the wall. However, the VITA frequency scaling indicates an interaction between the flow in the wall region and the outer flow. Flow visualization was used to observe the crossflow of structures in the boundary layer of a cylinder moving through a tank of quiescent water. Large-scale structures were observed moving from the outer region on one side of the cylinder to the outer region on the opposite side of the cylinder suggesting that the wall may be less important in controlling the size and motion of coherent structures in the cylindrical boundary layer than in the planar boundary layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866078
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  • 6
    Electronic Resource
    Electronic Resource
    Inertial particle motion in a Taylor Couette rotating filter (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 325-333 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In rotating filtration, which is based on supercritical cylindrical Couette flow with a rotating porous inner cylinder, the motion of particles in the suspension depends on both centrifugal sedimentation and transport due to the vortical motion of Taylor vortices. We have simulated the motion of dilute, rigid, spherical particles in Taylor Couette flow using computational particle tracking in an analytic velocity field for flow just above the transition to supercritical Taylor vortex flow. Neutrally buoyant particles follow fluid streamlines closely, but not exactly due to the curvature of the velocity field very near the particle. The motion of particles with a density greater than the fluid is primarily determined by the competition between the centrifugal sedimentation related to the primary cylindrical Couette flow and the secondary radial and axial transport of the Taylor vortex flow. As a result, particles that start near the outer edge of a vortex spiral inward toward a limit cycle orbit. Likewise, particles initially near the center of a vortex spiral outward toward the same limit cycle orbit. Even when a small radially inward throughflow is imposed, particles can remain trapped in retention zones that are away from the wall of the annulus. Consequently, the dynamics of the flow field result in particles tending to be transported away from the porous inner cylinder, thus contributing to the antiplugging character of rotating filter devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869882
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  • 7
    Electronic Resource
    Electronic Resource
    Pressure and shear stress measurements at the wall in a turbulent boundary layer on a cylinder (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 2732-2739 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fluctuating wall shear stress, wall pressure, and streamwise velocity were measured simultaneously in a cylindrical boundary layer at a momentum thickness Reynolds number of Reθ=2160 and a boundary layer thickness to cylinder radius ratio of δ/a=5 using a hot wire wall shear stress probe mounted just upstream of a hearing aid microphone and a hot wire velocity probe. Variable Interval Time Averaging (VITA) event detection on streamwise velocity indicates that streamwise accelerations are associated with positive wall pressure peaks and sudden increases in wall shear stress. Likewise, positive pressure peak events are associated with streamwise accelerations and sudden increases in wall shear stress. VITA detection on wall shear stress reveals that increasing wall shear stress corresponds to streamwise accelerations and small-amplitude pressure rises, not distinct intense pressure peaks. Detection of strong adverse and favorable instantaneous pressure gradients indicates that a shear layer at y+=13 coincides with a positive peak in the wall pressure, suggesting that a positive wall pressure peak event is the key wall pressure signature associated with the burst cycle. Measurements of the cross-correlation indicate that the pressure–shear stress relationship is about two times weaker than the pressure–velocity relation and about ten times weaker than the shear stress–velocity relation. Thus, a strong relationship exists between wall pressure and streamwise velocity as well as between wall shear stress and streamwise velocity, but the relationship between wall shear stress and wall pressure is quite weak. Because of the similarity of the near-wall structure of all wall-bounded turbulent flows, regardless of transverse curvature, these conclusions should be applicable to planar boundary layers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869384
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  • 8
    Electronic Resource
    Electronic Resource
    Spanwise structure of wall pressure on a cylinder in axial flow (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 151-161 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spanwise structure of wall pressure fluctuations was measured in an axisymmetric turbulent boundary layer on a cylinder parallel to the mean flow at a momentum thickness Reynolds number of 2530 and a boundary layer thickness to cylinder radius ratio of 4.81. The measurements were made using miniature hearing aid type condenser microphones with spanwise separations of 0°, 10°, 20°, 30°, 60°, and 90°. An improved wall pressure power spectrum was obtained at low frequencies by utilizing a two-point subtraction method to remove low frequency acoustic background noise of the wind tunnel. The spanwise correlations indicate that the spanwise coherent length of the wall pressure is 30° (78ν/uτ or 0.11δ). The spanwise coherence is weak and concentrated in a frequency band that is substantially lower than the most energetic frequency band of the wall pressure spectrum. A mode number–frequency decomposition of the wall pressure spectrum indicates that the greatest quantity of energy is in the circumferential modes nearest zero. Modes −4 to 4 contain most of the wall pressure energy. Conditional sampling by pressure peak and VITA detection schemes (where VITA was applied to wall pressure to detect strong pressure gradient events) indicate that the spanwise extent of the high pressure peaks and high wall pressure gradients is 60° (156ν/uτ or 0.22δ). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869909
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrodynamic stability of flow between rotating porous cylinders with radial and axial flow (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3687-3696 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linear stability analysis was carried out for axial flow between a rotating porous inner cylinder and a concentric, stationary, porous outer cylinder when radial flow is present for several radius ratios. The radial Reynolds number, based on the radial velocity at the inner cylinder and the inner radius, was varied from −15 to 15, and the axial Reynolds number based on the mean axial velocity and the annular gap was varied from 0 to 10. Linear stability analysis for axisymmetric perturbations results in an eigenvalue problem that was solved using a numerical technique based on the Runge–Kutta method combined with a shooting procedure. At a given radius ratio, the critical Taylor number at which Taylor vortices first appear for radial outflow decreases slightly for small positive radial Reynolds numbers and then increases as the radial Reynolds number becomes more positive. For radial inflow, the critical Taylor number increases as the radial Reynolds number becomes more negative. For a given radial Reynolds number, increasing the axial Reynolds number increases the critical Taylor number for transition very slightly. The critical wave velocity decreases slightly for small positive radial Reynolds numbers, but increases for larger positive and all negative radial Reynolds numbers. The perturbed velocities are very similar to those for no axial flow. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869506
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  • 10
    Electronic Resource
    Electronic Resource
    Hydrodynamic stability of viscous flow between rotating porous cylinders with radial flow (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 144-151 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linear stability analysis has been carried out for flow between porous concentric cylinders when radial flow is present. Several radius ratios with corotating and counter-rotating cylinders were considered. The radial Reynolds number, based on the radial velocity at the inner cylinder and the inner radius, was varied from −30 to 30. The stability equations form an eigenvalue problem that was solved using a numerical technique based on the Runge–Kutta method combined with a shooting procedure. The results reveal that the critical Taylor number at which Taylor vortices first appear decreases and then increases as the radial Reynolds number becomes more positive. The critical Taylor number increases as the radial Reynolds number becomes more negative. Thus, radially inward flow and strong outward flow have a stabilizing effect, while weak outward flow has a destabilizing effect on the Taylor vortex instability. Profiles of the relative amplitude of the perturbed velocities show that radially inward flow shifts the Taylor vortices toward the inner cylinder, while radially outward flow shifts the Taylor vortices toward the outer cylinder. The shift increases with the magnitude of the radial Reynolds number and as the annular gap widens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868077
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