ISSN:0309-1929    

DOI:10.1080/03091927908243757

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Laboratory experiments on mixing in stratified fluids are examined in the light of some simple energy arguments applied to an analysis of mixing at density interfaces. It is shown that as the stability of the flow, as measured by an overall Richardson numberRio, increases, the velocity interface becomes considerably thicker than the density interface. This mismatch in interface thickness provides the extra kinetic energy required for mixing in these strongly stratified flows. The behaviour of the flux Richardson numberRfas a function ofRiois also discussed. It is found that the results from a number of different experiments are quite similar, and thatRfincreases from zero asRiodoes, reaches a maximum value (0.2 & plusmn; 0.05) and then decreases again with further increase inRio. Finally, some recent ideas of Posmentier (1977) on the formation of interfaces in a stratified, turbulent flow are compared with observations.

ISSN:0309-1929    

DOI:10.1080/03091927908243758

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The efficiency shown by topographic obstacles in triggering the occurrence of disturbances which can grow and develop as independent eddies is intimately connected to both the rotation and the stratification of the basic, ‘unperturbed’, atmospheric state. The presence of temperature gradients makes the basic state baroclinically unstable; conversion of available potential energy of the basic state into kinetic energy of the disturbance is made possible if a perturbation strong enough and of the appropriate scale is applied. Steep, large scale obstacles embedded in the atmospheric flow very often provide just such a perturbation, acting, therefore, as sources of systems which can develop and influence the weather of regions even very distant from the obstacle itself. The detailed phenomenology of lee cyclogenesis and its numerical modelling still represent a challenge to dynamic meteorology; a review of the most significant results in this field will be presented and some of them will be discussed in some more detail.

ISSN:0309-1929    

DOI:10.1080/03091927908243759

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The study of the mechanisms controlling the stratification in closed fluid regions is an important branch of geophysical fluid dynamics. Part of this subject can be handled with a simple linear model, consisting of a buoyancy layer at the non-horizontal boundaries of a container and an advective-diffusive interior coupled by volume continuity. The model is valid under the following conditions: firstly, the buoyancy-frequency characterizing the solution must be sufficiently large to give rise to a flow pattern of boundary layer type and, secondly, the non-horizontal walls must not have too large thermal conductivity.

ISSN:0309-1929    

DOI:10.1080/03091927908243760

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

There are fundamental differences between the mechanics of entrainment in river plumes and two-layer channel flow. Entrainment of seawater to a river plume is seen to occur predominantly in a frontal region. A simple theory for the energetics of frontal entrainment is applied to river discharge in a wide fjord with a seaward narrows. The salinity of the plume depends onW/BandB/Ho, whereWis the width of the narrows,Bis the river width andHois the river thickness. The theory contains two constants which are determined from laboratory experiments. From laboratory observations, active plume entrainment is estimated to extend to 7 (H + B) seaward. The theory supports the conjecture that river plume entrainment can be simulated in distorted laboratory models as long asB/Ho≫ 1 in the laboratory.

ISSN:0309-1929    

DOI:10.1080/03091927908243761

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The effect of Soret and Dufour cross-transport phenomena, together with adiabatic and compressibility corrections are studied in the stability analysis of horizontal binary gas layers heated from below or above. Our predictions may be of relevance in micrometeorology to explain some of the fatures of local atmospheric circulation.

ISSN:0309-1929    

DOI:10.1080/03091927908243762

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091927908243763

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The stability of a zonal flow with uniform vertical shear and planetary scale latitudinal variation to perturbations of ultra-long wavelength is examined analytically by means of the Planetary Geostrophic (PG) equations (Phillips' (1963) Quasi-Geostrophic equations of type 2).

ISSN:0309-1929    

DOI:10.1080/03091927908243764

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The small perturbation of a steady, two-dimensional horizontal stream of a moist inviscid, Boussinesq fluid is treated analytically by use of an asymptotic method when a certain parameter ε is small and numerically by use of an iterative method for general values of ε. This parameter is a measure of the difference between dry and wet adiabats in the model atmosphere, which is absolutely stable and which contains a moist layer near the ground. Vapour condenses (evaporates) where the vertical displacement of a fluid particle exceeds the ascent condensation level and the vertical motion is upward (downward). The condensation of vapour and release of latent heat are nonlinear phenomena which are treated, but otherwise the equations of motion and boundary conditions are linearized. We limit our attention to an airflow of uniform properties over a mountain ridge. The hydrostatic approximation is made. As a result, the horizontal wavelengths must be long compared to the vertical ones and lee waves are absent. Moisture is found to reduce the drag on the mountain substantially.

ISSN:0309-1929    

DOI:10.1080/03091927908243765

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A horizontal cylinder is traversed horizontally normal to its longitudinal axis in density stratified brine, and the lee waves which are produced over a range of model velocities are viewed with a six mirror Mach Zehnder interferometer which allows the density distribution to be evaluated. At the lowest model velocities, viscous effects limit the number of visible waves to no more than three. The viscous internal wave theory of Chang and Stevenson is extended and used to calculate lee waves over a ridge. Although the linear theory does not include the no-slip condition at the lower boundary and does not include the upstream wake, which is clearly visible in the experiments, the way in which the waves attenuate away from the model is reproduced quite well by the theory. The viscous results will be compared with the standard inviscid calculations.

ISSN:0309-1929    

DOI:10.1080/03091927908243766

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor