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No description available.

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To investigate the generation of mesoscale gravity waves from upper-tropospheric jet-front systems, five different life cycles of baroclinic waves are simulated with a high-resolution mesoscale model (MM5 with 10-km grid spacing). The baroclinicity (and the growth rates) of the baroclinic waves differs significantly among these five experiments as a result of using different tropospheric static stability and tropopause geometry for the initial two-dimensional baroclinic jet. After a short initial adjustment, the baroclinic waves in each experiment grow nearly linearly for as long as five days before the final nonlinear growth stage. Vertically propagating mesoscale gravity waves are generated universally in the exit region of the upper-tropospheric jet streaks near the tropopause level at the later stage of quasi-linear growth and the early stage of nonlinear growth of baroclinic waves. The synoptic environments of gravity waves are consistent with previous studies of typical mesoscale gravity waves. The low-stratospheric gravity waves generated from the upper-level jet streak in these experiments have a horizontal wavelength of 75-175 km and an intrinsic frequency 3-10 times of the Coriolis parameter. The intrinsic frequency of these gravity waves appears to be directly correlated with the growth rate and the strength of the baroclinic waves. In general, the faster the growth rate of the baroclinic waves, the higher the intrinsic frequency of the gravity waves. Similar frequencies of the gravity waves are found in experiments with smaller quasi-linear growth rates of baroclinic waves but with significantly different initial tropospheric static stability and tropopause geometry. The residuals of the nonlinear balance equation are used to assess the flow imbalance. It is also suggested that growth of imbalance is directly related to the growth rate of baroclinic waves and thus the frequency of primary gravity waves of interest. Diagnosis of flow imbalance suggests that balance adjustment, as a generalization of geostrophic adjustment, may be responsible for the generation of the gravity waves in the upper-tropospheric jet-front systems.

Turbulent liquid sheets have been proposed to protect solid structures in fusion power plants by attenuating damaging radiation. For the High-Yield Lithium-Injection Fusion Energy (HYLIFE-II) inertial fusion energy (IFE) power plant concept, arrays of molten-salt sheets form a sacrificial barrier between the fusion event and the chamber first wall while permitting target injection and ignition. Thick liquid protection can help make fusion energy commercially attractive by reducing chamber size and prolonging chamber lifetime. Establishing an experimental design database for this basic building block flow will provide valuable information about various thick liquid protection schemes and allow reactor designers to establish acceptable tolerances between chamber components. Turbulent water sheets issuing downwards into ambient air were studied experimentally at Reynolds numbers of 53,000 ??0,000 and Weber numbers of 2,900 ??,000 based on average velocity and the short dimension of the nozzle exit ( and delta). Initial conditions were quantified by the streamwise (x) and transverse (z) velocity components using laser-Doppler velocimetry just upstream of the nozzle exit. Characterization of the mean free-surface position and free-surface fluctuations, or surface ripple, and estimation of the amount of mass ejected as droplets from the free surface were quantified in the near-field (within 25 and delta of the nozzle exit). Surface ripple and mean sheet geometry were determined directly from planar laser-induced fluorescence visualizations of the free surface. The droplets due to the turbulent breakup of the jet, termed here the hydrodynamic source term, were measured using a simple collection technique to within 1 and delta of the nominal free surface of the jet. The influence of various passive flow control techniques such as removing low-momentum fluid at the free surface (boundary-layer cutting) on sheet geometry, surface ripple, and turbulent breakup were also quantified. The data obtained in this research will allow designers of inertial fusion energy systems to identify the parameter ranges necessary for successful implementation of the thick liquid wall protection system.

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