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  • 1
    Electronic Resource
    Electronic Resource
    Inviscid two dimensional vortex dynamics and a soliton expansion of the sinh-Poisson equation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 1111-1119 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of inviscid, steady, two dimensional flows is examined for the case of a hyperbolic sine functional relation between the vorticity and the stream function. The 2-soliton solution of the sinh-Poisson equation with complex wavenumbers will reproduce the Mallier-Maslowe pattern, a row of counter-rotating vortices. A special 4-soliton solution is derived and the corresponding flow configuration is studied. By choosing special wavenumbers complex flows bounded by two rigid walls can result. A conjecture regarding the number of recirculation regions and the wavenumber of the soliton expansion is offered. The validity of the new solution is verified independently by direct differentiation with a computer algebra software. The circulation and the vorticity of these novel flow patterns are finite and are expressed in terms of well defined integrals. The questions of the linear stability and the nonlinear evolution of a finite amplitude disturbance of these steady vortices are left for future studies. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869636
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  • 2
    Electronic Resource
    Electronic Resource
    Wake and wake-induced shear-layer excitation in an annular jet (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3121-3134 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The wake and wake-induced structures in the initial region of an annular jet (with a center body truncated at the jet exit plane) are studied from the measurements of velocity correlation and conditional sampling. Both sets of structures are found to play an important role in momentum transports and Reynolds stress production. They are also found to be oriented in a quasi-two-dimensional orderly pattern. In the initial outer shear layer, a large-scale instability is induced by the shedding of the vortex-street-like wake structures from the center body. This wake-induced instability is associated with the formation of the induced coherent structures and the subsequent zigzag staggered pattern occupied by them and the inner wake structures on the quasi-two-dimensional orderly plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865963
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  • 3
    Electronic Resource
    Electronic Resource
    Velocity and spanwise vorticity measurements in an excited mixing layer of a plane jet (1996)
    Springer
    Experiments in fluids 20 (1996), S. 346-357 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The mixing layer of a plane jet was subjected to periodic weak excitation at two different frequencies corresponding to shear layer mode (St θ=0.012) and preferred mode (St D =0.36). The nozzle exit boundary layer was identical for the unexcited and excited flows. Measurements of mean velocity, longitudinal and lateral velocity fluctuations, Reynolds shear stress and spanwise component of fluctuating vorticity were made over a longitudinal distance x/D of 6 for both the unexcited and the excited flows. Even weak excitation was observed to influence the development of the mixing layer. Under shear layer mode of excitation, the width of the layer and longitudinal turbulence level decrease compared to the naturally developing (unexcited) flow whereas preferred mode of excitation results in increase in the width and turbulence levels. The rms spanwise vorticity showed an increase for shear layer mode of excitation whereas the preferred mode of excitation resulted in a decrease compared to the values in an unexcited flow. Spectra of velocity and vorticity fluctuations exhibited subharmonic peaks, suggesting the possible occurrence of vortex pairing in both unexpected and excited flows. The influence of excitation is found to decrease as x/D increases and is not significant at x/D=6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191016
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  • 4
    Electronic Resource
    Electronic Resource
    Near wall characteristics of flow over grooved circular cylinder (1991)
    Springer
    Experiments in fluids 10 (1991), S. 322-332 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation was made of the flow over a grooved circular cylinder of different aspect ratios. Based on the drag coefficient, Strouhal number and mean shear stress, three flow regimes of subcritical, critical and supercritical were found, all of which are below the subcritical Reynolds number of a smooth cylinder. Boundary layer characteristics within the different flow regimes were measured. The shift of the boundary layer away from the grooves and an estimated change in the virtual origin are used to establish the similarity of the flow characteristics of grooved and smooth cylinders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190248
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  • 5
    Electronic Resource
    Electronic Resource
    In the intermixing region behind circular cylinders with stepwise change of the diameter (1990)
    Springer
    Experiments in fluids 9 (1990), S. 213-221 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The flow within the intermixing region behind circular cylinders with stepwise change of the diameter of diameter ratio d/D of 0.5 has been examined. Based on the statistical analysis and conditional sampling of the velocity fluctuations and of flow visualization, the vortex wakes associated with the big and small cylinders have been established. Both wakes are found under the dominant primary mode, which corresponds to the vortex shedding Strouhal number of two dimensional cylinder, and the less dominant secondary mode. The Strouhal number of the secondary mode of the big vortex wake is higher than that of the primary mode and the opposite is found for the small vortex wake. Both vortex wakes and their modes are found convecting downstream and into region behind the other cylinder. Both wakes are observed to be different from that of two dimensional cylinder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190422
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  • 6
    Electronic Resource
    Electronic Resource
    Coherent structure interactions in an unexcited coaxial jet (1994)
    Springer
    Experiments in fluids 17 (1994), S. 147-157 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Based on a double triggering criterion, the axisymmetric and azimuthal structures within the initial region of an unexcited coaxial jet of mean velocity ratio of 0.3 (inner to outer) were recovered. Outer vortices, two trains of inner vortices and their amalgamation are found in the outer and inner mixing regions. Bifurcation of the amalgamated inner vortices occurs within the first two diameters of the jet and is responsible for the occurrence of the azimuthal structures in the inner jet region further downstream. Co-dominance of the symmetrical and azimuthal structures having different convection velocities is observed in the fully merged zone. Spatial separation between vortical structures and their relative vorticities are important parameters in affecting their convection velocities, growth and decay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190911
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of acoustic excitation on flow over a partially grooved circular cylinder (1995)
    Springer
    Experiments in fluids 19 (1995), S. 194-202 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation was carried out on the flow over a partially grooved circular cylinder over a Reynolds number range of 3 × 104 to 1.22 × 105 with and without acoustic excitation. Without excitation the flow over the smooth half of the cylinder was observed to shift to higher subcritical regime. The flow over the groove half, however, is shifted to supercritical or transcritical flow regime. With excitation, on the smooth half it is the separated laminar shear layer which locks in with the excitation frequency, resulting in the shift from subcritical to supercritical or transcritical regimes. On the groove half excitation is not effective for the flow within the transcritical regime. With excitation, the lift is found to reverse its direction while the drag is nearly the same.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189708
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  • 8
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    Effect of acoustic excitation on flow over a partially grooved circular cylinder (1995)
    Springer
    Details
    Publication Date: 1995-07-01
    Print ISSN: 0723-4864
    Electronic ISSN: 1432-1114
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 9
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    Near wall characteristics of flow over grooved circular cylinder (1991)
    Springer
    Details
    Publication Date: 1991-03-01
    Print ISSN: 0723-4864
    Electronic ISSN: 1432-1114
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 10
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    In the intermixing region behind circular cylinders with stepwise change of the diameter (1990)
    Springer
    Details
    Publication Date: 1990-06-01
    Print ISSN: 0723-4864
    Electronic ISSN: 1432-1114
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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