This is the final published version of the article (version of record). It first appeared online via APS at http://journals.aps.org/pre/abstract/10.1103/PhysRevE.94.043103. Please refer to any applicable terms of use of the publisher. University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms PHYSICAL REVIEW E 94, 043103 (2016) Connections between centrifugal, stratorotational, and radiative instabilities in viscous Taylor-Couette flow The "Rayleigh line" μ = η 2 , where μ = o / i and η = r i /r o are respectively the rotation and radius ratios between inner (subscript i) and outer (subscript o) cylinders, is regarded as marking the limit of centrifugal instability (CI) in unstratified inviscid Taylor-Couette flow, for both axisymmetric and nonaxisymmetric modes. Nonaxisymmetric stratorotational instability (SRI) is known to set in for anticyclonic rotation ratios beyond that line, i.e., η 2 < μ < 1 for axially stably stratified Taylor-Couette flow, but the competition between CI and SRI in the range μ < η 2 has not yet been addressed. In this paper, we establish continuous connections between the two instabilities at finite Reynolds number Re, as previously suggested by Le Bars and Le Gal [Phys. Rev. Lett. 99, 064502 (2007)], making them indistinguishable at onset. Both instabilities are also continuously connected to the radiative instability at finite Re. These results demonstrate the complex impact viscosity has on the linear stability properties of this flow. Several other qualitative differences with inviscid theory were found, among which are the instability of a nonaxisymmetric mode localized at the outer cylinder without stratification and the instability of a mode propagating against the inner cylinder rotation with stratification. The combination of viscosity and stratification can also lead to a "collision" between (axisymmetric) Taylor vortex branches, causing the axisymmetric oscillatory state already observed in past experiments. Perhaps more surprising is the instability of a centrifugal-like helical mode beyond the Rayleigh line, caused by the joint effects of stratification and viscosity. The threshold μ = η 2 seems to remain, however, an impassable instability limit for axisymmetric modes, regardless of stratification, viscosity, and even disturbance amplitude.

Air-inlet design and resulting thrust performance of Microwave Rocket at 10 km altitude and a flight Mach number of 2 were computed using CFD and the influence of plenum area size was examined. The results showed that, the partial filling rate was found to monotonically increase with the area ratio of plenum to thrust tube, though aerodynamic drag was increased with the ratio. Optimum area ratio was found about 1.0, and 85% of the maximum thrust was obtained when the range was between 0.60 and 2.0.