The purpose of the review is to provide a very rough feeling about what geophysical fluid dynamics is. After general introductory remarks, some particular topics in geophysical fluid dynamics are reviewed rather in detail. The topics selected here are mostly not standard ones, as found in a standard text book, but such that provide a very vivid view on what is actually going on in this field.

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Although the CFD applications in the auto companies are being accelerated, many calculational problems remain unsolved in terms of turbulence model, calculational method including boundary conditions, etc. This review paper describes the basic treatments of turbulence model in the CFD calculations and the recent trend of their application of the flow around automobile body. The computational problems we face today are also discussed.

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We have recognized that internal gravity waves play crucially important roles in controlling momentum cycles in the atmosphere. Internal gravity waves generated in the troposphere propagate upward to the middle atmosphere and release the radiation stress interacting with mean flow. Theoretical elucidations of the waves are given together with the observational evidences measured by the MU radar. Importance of internal gravity waves is also described in understanding ozone hole dynamics in the polar stratosphere.

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Velocity measurement and visualization of the mixing layer of water flow were made in order to examine a possibility of recognizing vortices from a streakline picture. Both cases with and without external excitation were tried. The cross-stream component of velocity fluctuation was measured along the center line of the mixing layer, and the spectrum and the autocorrelation were obtained. The dye was injected into the fluid at the splitter plate of the mixing layer, and the video image and 35 mm photograph were taken. The images in the 35 mm film were digitized and processed by the use of an image analyser (LUZEX 2D). A combination of certain image processing functions and a criterion for identifying isolated vortices proved to be useful for educing vortices in the twodimensional mixing layer, especially in the excited case where vortices were arranged regularly.

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The behavior of a pure plume in stratified cross-flows was experimentally investigated in a strongly nonlinear range using flow visualization techniques. First, flow patterns were classified into four regimes according to the densimetric Froude number. Second, time-averaged features of the plume were examined and compared with previous results. Third, effects of a bottom wall and a wall boundary layer on the behavior of the plume were discussed. In addition, the period of intermittently generated thermals was estimated.

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The complex function method is applied for the screen printing flow, assuming that the printing ink is highly viscous and Newtonian.
The screen printing flow may be expressed through the Taylor flow. The pressure distribution and the vorticity distribution are obtained easier than the boundary value method by G. I. Taylor. We found that the location of the maximum pressure line of the Taylor flow is different from the previous analysis.
A new flow which may express the screen printing better is obtained by placing a sink at the origin of the Taylor flow.
The theoretical pressure distribution obtained for the new model shows a good agreement with the experimental results obtained by us. As far as the result is concerned, the viscosity of the printing ink changes uniformly under a given shear condition, which matches with the empirical results.

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