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Impulse and momentum
Published in J.N. Fawcett, J.S. Burdess, Basic Mechanics with Engineering Applications, 2012
The absolute angular momentum of the body is equal to IGθ˙ plus the moment of the linear momentum vector, p = mυG, about Q.
Angular momentum transfer in direct numerical simulations of a laboratory model of a tropical cyclone
Published in Geophysical & Astrophysical Fluid Dynamics, 2022
Anna Evgrafova, Andrei Sukhanovskii
The absolute angular momentum per unit mass m, is defined in cylindrical geometry by where r is the radius from the axis of rotation, is the system rotation rate and is the azimuthal component of velocity. The absolute angular momentum is a sum of angular momentum of solid body rotation () and relative angular momentum (). Note that advective transfer of angular momentum by axisymmetric flows, in case of initial solid body rotation, can not provide local values of m higher than (Read 1986).
Mean flow generation due to longitudinal librations of sidewalls of a rotating annulus
Published in Geophysical & Astrophysical Fluid Dynamics, 2020
Michael V. Kurgansky, Torsten Seelig, Marten Klein, Andreas Will, Uwe Harlander
Finally, we briefly discuss the unstable case with ϵ > 0.28 that was studied in detail by Ghasemi et al. (2016, 2018) by direct numerical simulations. They found that the maximum azimuthal mean flow scales with ∼. A phenomenological explanation was given how absolute angular momentum of the bulk flow is mixed and changed due to the propagation of Görtler vortices into the bulk, causing a new global and steady vortex. The radial turbulent transport of the azimuthal momentum has been identified as the main forcing for the mean flow. However, so far a clear understanding of the mechanism that drives the mean flow for the subcritical case was lacking. Precisely this gap has been addressed and closed by the theoretical analysis of the present study in conjunction with the theory-supporting laboratory measurements. From (33) we know that in the subcritical regime, the maximum azimuthal velocity scales with . The findings for the stable and unstable cases are summarised in figure 6 where we plot the maximum mean flow velocity shown in figure 5(a) as a function of ϵ and indicate the separation between the sub- and supercritical cases by a thick blue vertical line. The scaling by Ghasemi et al. (2016) is given by the orange curve. For the proportionality constant we used . We find a good agreement between theory and experiment in the subcritical range that scales with . For the supercritical case we see that our present laboratory experiments support the slightly lower -scaling recently reported by Ghasemi et al. (2016), although with a slightly different proportionality prefactor.
Characteristics of the convective bursts and their relationship with the rapid intensification of Super Typhoon Maria (2018)
Published in Atmospheric and Oceanic Science Letters, 2020
Jian HENG, Shuai YANG, Yuanfa GONG, Jianfeng GU, Haiwen LIU
The intensifying radially lower-level inflow and upper-level outflow move the absolute angular momentum surfaces inwards (Stern et al. 2015) and speed up the RMW contraction (Figure 3(a,b)), thereby accelerating RI. The accompanying upright developments of the updrafts lead to the vertical alignment of the TC center under moderately low VWS conditions, which are beneficial to RI (Munsell et al. 2017; Chen, Xue, and Fang 2018).