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71.
Abstract The response or a depth independent two layer flow to an underlying topographic irregularity is studied for flows in which the square of the internal Froude number exceeds the Rossby number. Irrespective of the magnitude of the Rossby number, rotation is important for such flows. The flow generally adjusts so that the thickness of the lower layer is nearly constant. However small anomalies from the constant thickness are found to extend to very large distances from the topography when the Rossby number exceeds unity. 相似文献
72.
利用2008年5月16日至2009年4月17日太湖地区多光谱旋转遮光辐射仪(multi—filter ro—tating shadow—band radiometer,简称MFRSR)的观测资料进行反演,得出415、500、615、675和870nm5个波段大气气溶胶光学厚度(aerosol optical depth,简称AOD)及各季节浑浊度系数和波长指数的统计结果。结果表明,5个波段AOD的最大值分别为1.9、1.6、1.3、1.2和1.0;它们谱分布的半宽度分别为0.90、0.70、0.55、0.45和0.25;AOD频率分布极大值处所对应的AOD值分别为0.750、0.550、0.475、0.425和0.425。5个波段AOD的平均值在春季最大,夏季次之,除870nm外,均为冬季最小。浑浊度系数变化范围为0~1.25,其中大于0.2的占97%以上,大于0.4的占66%以上。春季、夏季、秋季和冬季的波长指数变化范围分别为0~3.0、0~2.8、0.2~2.0和0.2~2.0,表明太湖地区大气污染较为严重,且受人为源的影响显著。相对于秋冬季,春夏季有较大粒径的气溶胶粒子存在。 相似文献
73.
Generation of cyclonic vortices in the middle layer of flow around a large mountain like Tibet and Rocky was investigated by means of a 3-D nonhydrostatic meteorological prognostic model. Special attention was paid to the effects of the earth’s rotation and stratification on the vortices detached successively from the slope of a high and large horizontal scale mountain. It was found the successive formation and detachment of such ‘von Karman-like vortices’ occurred in the flow regime at high Rossby numbers Ro and low Froude numbers Fr. It was successfully divided by the criterion of baroclinic instability. This means that if the condition is unstable baroclinically, a lee vortex is destabilized into a three-dimensional one, while under baroclinically stable conditions the lee vortex with vertical axis retains its standing structure and remains long lasting in the middle layer. 相似文献
74.
工厂化鱼类养殖智能系统的研究 总被引:4,自引:0,他引:4
为保证鱼类生长的环境始终处于最佳状态,作者根据狼鲈(Dicentrarchus labrar)的生理特点(耗氧率、氮的排泄率等)建立数学模型,并设计在工厂化水产养殖中采用生物转盘、臭氧(紫外线)消毒器等设备,构建在Windows2000 Visual Basic6.0下运行的环境调控软件包系统,通过计算机技术确定养殖污水处理设备(生物转盘)及增氧、消毒设备的数量及规格,将养殖环境控制在最佳状态。 相似文献
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77.
J. Boda 《地球物理与天体物理流体动力学》2013,107(1-4):77-90
Abstract The linear hydromagnetic stability of a non-constantly stratified horizontal fluid layer permeated by an azimuthal non-homogeneous magnetic field is investigated for various widths of the stably stratified part of the layer in the geophysical limit q→0 (q is the ratio of thermal and magnetic diffusivities). The choice of the strength of the magnetic field Bo is as in Soward (1979) (see also Soward and Skinner, 1988) and the equations for the disturbances are treated as in Fearn and Proctor (1983). It was found that convection is developed in the whole layer regardless of the width of its stably stratified part. The thermal instability penetrates essentially from the unstably stratified part of the layer into the stably stratified part for A ~ 1 (A characterises the ratio of the Lorentz and Coriolis forces). When the magnetic field is strong (A>1) the thermal convection is suppressed in the stably stratified part of the layer. However, in this case, it is replaced by the magnetically driven instability; which is fully developed in the whole layer. The thermal instabilities always propagate westward and exist for all the modes m. The magnetically driven instabilities propagate either westward or eastward according to the width of the stably and unstably stratified parts and exist only for the mode m=1. 相似文献
78.
Abstract Strong decay bounds are obtained for linearized perturbations to an unbounded, plane Couette flow in a parallel magnetic field. Finite conductivity and molecular viscosity are found to be stabilizing. Those modes decaying most slowly have the form of rolls aligned with the shear flow. The non-aligned rolls decay at an enhanced rate. Stability bounds at finite amplitude are obtained for flows bounded in one direction using energy methods. 相似文献
79.
Abstract We study a semi-analytical model of convection in a rapidly-rotating, differentially-heated annulus with sloping top and bottom lids. Rapid rotation leads to a preservation of relatively simple, two-dimensional (2-D) structure in the experimentally-observed flow, while temporal complexity increases with the Rayleigh number. The model is, therefore, two-dimensional; it exhibits a sequence of bifurcations from steadily-drifting, azimuthally-periodic convection columns, also called thermal Rossby waves, through vacillation and a period-doubling cascade, to aperiodic, weakly-turbulent solutions. Our semi-analytical results match to within a few percent previous numerical results with a limited-resolution 2-D model, and extend these results, due to the greater flexibility of the model presented here. Two types of vacillation are obtained, which we call, by analogy with classical nomenclature of the baroclinic annulus with moderate rotation rates, amplitude vacillation and tilted-trough vacillation. Their properties and dependence on the problem's nondimensional parameters are investigated. The period-doubling cascade for each type of vacillation is studied in some detail. 相似文献
80.