DEPARTMENT OF COMMERCE SINCLAIR WEEKS , Secretary WEATHER BUREAU F . W . REICHELDERFER , Chief MONTHLY WEATHER REVIEW
نویسندگان
چکیده
Simultaneous measurements of turbulent vertical velocity fluctuations at a height of 300 ft. measured by means of a fixed anemometer, small floating balloons, and airplane gust equipment at Brookhaven are presented. The resulting Eulerian (fixed anemometer) turbulence energy mectra are similar to the Lagrangian (balloon) spectra but "-with a displacement toward higher frequencies. The term Eulerian, in turbulence study, implies consideration of velocity fluctuations at a point or points fixed in space, as measured for example by one or more fixed anemometers or wind vanes. The term Lagrangian implies study of the fluctuations of individual fluid parcels ; these are very difficult to measure. In a sense, these two points of view of the turbulence phenomenon are closely related to the two most palpable physical manifestations of turbulence, first the irregular or random nature of the turbulent fluctuations and second the remarkable ability of fluid in a state of t,urbulence to disperse properties. Such problems of turbulence in the atmosphere as the effect of gusts on structures (towers, buildings, air-frames) lead to the Eulerian kind of analysis, whereas the Lagrangian form arises naturally in the highly important field of atmospheric diffusion. The irregular nature of turbulence early suggested, in fact imposed, a statistical rather than a deterministic approach to its study. Certain important quantities have emerged, with the development of this theory, that serve to characterize turbulence, chiefly the energy spectrum and the U. 8. Atomic Energy Oommission.
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