Free Span Vibrations of Submarine Pipelines in Steady Flows—Effect of Free-Stream Turbulence on Mean Drag Coefficients

Tørum, Alf; Anand, N.M.

doi:10.1115/1.3231212

Cited by 10 publications

(2 citation statements)

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“…The amplitude of upstream turbulence is of concern for several practical applications: the lift and drag of aircraft wings [ Hoffmann , 1991; Huang and Lee , 1999], the wind forces on buildings and structures [ Barriga et al , 1977; Zdravkovich and Carelas , 1997], air drag on automobiles [ Bearman , 1978], drag and heat transfer from turbine blades [ Fridman , 1997; Murawaski and Vafai , 2000], forces on underwater structures [ Torum and Anand , 1985], and the settling of particles suspended in fluids [ Brucato et al , 1998]. This report will focus on the first finding listed in Table 2, the increase of the viscous drag (skin friction) with an increase in the amplitude of the upstream turbulence, with application to the solar wind/magnetosphere flow problem.…”

Section: An Experiments Of Interest For Solar‐terrestrial Physicsmentioning

confidence: 99%

Role of solar wind turbulence in the coupling of the solar wind to the Earth's magnetosphere

2003

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[1] The correlation between the amplitude of the MHD turbulence in the upstream solar wind and the amplitude of the Earth's geomagnetic activity indices AE, AU, AL, Kp, ap, Dst, and PCI is explored. The amplitude of the MHD turbulence is determined by the fluctuation amplitude of the solar wind magnetic field. This ''turbulence effect'' in solar wind/magnetosphere coupling is more easily discerned when the interplanetary magnetic field (IMF) is northward, but the effect is also present when the IMF is southward. The magnitude of the effect is the same for northward and southward IMF, accounting for about 150 nT of the variability of the AE index. Tests are performed that conclude (1) that the turbulence effect is not caused by the turbulence amplitude acting as a proxy for jBj in the solar wind and (2) that reversals of the IMF from northward to southward in the turbulent fluctuations is not the cause of the correlations. An expression is derived for the total viscous-shear force on the surface of the magnetosphere; improved solar wind/ magnetosphere correlations result when this expression is used. With insight from fluidflow experiments, the turbulence effect is interpreted as an enhanced viscous coupling of the solar wind flow to the Earth's magnetosphere caused by an eddy viscosity that is controlled by the amplitude of MHD turbulence in the upstream solar wind: more upstream turbulence means more momentum transfer from the magnetosheath into the magnetosphere, resulting in more stirring of the magnetosphere, which produces enhanced geomagnetic activity indices.

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Section: An Experiments Of Interest For Solar‐terrestrial Physicsmentioning

confidence: 99%

Role of solar wind turbulence in the coupling of the solar wind to the Earth's magnetosphere

2003

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“…However, for a single circular section, very large oscillations (galloping) cannot be expected to occur [37,38]). Further, free stream turbulence intensity of up to 10% would not have a significant influence either on the oscillating lift coefficient or vortex-induced vibration of circular cylinders [39,40]. Hence, in the present case (where the turbulence intensity is 6.5%), the circular cylinder could be expected to undergo vortex-induced vibrations with an excitation level similar to that in a low turbulence environment.…”

Section: Mode and Mechanism Of Shedding At R/b=05mentioning

confidence: 78%

Influence of corner radius on the near wake structure of a transversely oscillating square cylinder

Kumar

Sohn

Gowda³

2009

J Mech Sci Technol

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The near wake flow field features of transversely oscillating square section cylinders with different corner radii were studied in an attempt to assess the influence of corner radius. The investigation was performed by using particle image velocimetry (PIV) technique in a water channel with a turbulence intensity of 6.5%. Five models were studied with r/B=0, 0.1, 0.2, 0.3 and 0.5 (r is the corner radius and B is the characteristic dimension of the body), and the body oscillation was limited to lock-in condition (at fe/fo=1.0; fe is the excitation frequency and fo is the vortex shedding frequency from a stationary cylinder at the same Re). The corner radius was found to significantly influence the flow features around the bodies. Except for r/B=0.5, for all the other cases of r/B ratios, cycle-to cycle variation in the mode of vortex shedding was observed in the case of oscillating cylinders inducing highly non-linear wake characteristics. Apart from variation in the shedding mode, changes in shedding cycle timing were also observed for sharp and rounded square cylinders. The hgher the r/B ratio, shedding in the near wake was found to be more uniform (lesser variation in shedding cycle timings). Another admissible shedding mechanism is newly identified to operate in the near wake of oscillating cylinders now being called as the 'passive shedding' mechanism. Results indicate that increasing the corner radius suppresses the possible instabilities of the cylinder.

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Vortex-Structure Interaction

Blevins¹

1995

Fluid Mechanics and Its Applications

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Free Span Vibrations of Submarine Pipelines in Steady Flows—Effect of Free-Stream Turbulence on Mean Drag Coefficients

Cited by 10 publications

References 0 publications

Role of solar wind turbulence in the coupling of the solar wind to the Earth's magnetosphere

Role of solar wind turbulence in the coupling of the solar wind to the Earth's magnetosphere

Influence of corner radius on the near wake structure of a transversely oscillating square cylinder

Vortex-Structure Interaction

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