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THEORY OF TURBULENCE 29tions, A. Ingersoll, from the Jet Propulsion Laboratory in California,presented some results from the Jupiter (Voyager) satellites and theirimplications for continuum mechanics. His talk captured the sense ofdiscovery and new physics that characterized the meeting.Ingersoll showed a spectacular series of slides and movies of Jupiter'satmosphere as observed by Voyager 1. The simple empirics of theplanet's atmosphere are astounding: Jupiter's atmosphere is very large(with linear scalelengths about eleven times larger than the Earth),rotates faster (with a 9-hour period), and is characterized by verylarge-scalevortex structures (some the size of the Earth!), which arevery stable (the Great Red Spot was first observed 200 years ago) andare imbedded in a highly regular zonal flow. Figure 2 shows a cylindricalprojection of the whole surface of Jupiter—the zonal bands havecounterrotating flow in an almost textbook example of "trade winds."Ingersoll showed slide after slide of similar phenomena.Figure 3 shows structures in the wake of the Red Spot; Figure 4shows the regular atmospheric waves in a polar projection of Jupiter;and Figure 5 shows an incredible picture of a three-dimensional helicalwake in the atmosphere.Perhaps most surprising was the movie that Ingersoll showed of theatmospheric motions taken over a several-week period. By assemblingpictures of the planet taken every 9 hours by the satellite as itapproached Jupiter, the "weather" on the planet was recorded in amotion picture that forces even the most jaded observer to conclude thatsomething extraordinary is going on—the evidence for ordered, largescalemotion is unavoidable.As Ingersoll and others have pointed out, the evidence from Jupiterhas very far-reaching implications for fluid mechanics. Here is a fluidwith an astronomical Reynolds number (on the order of 10 5 to 10 6 ). Inthis range it is almost universally assumed that all fluid flow will berandomized and totally disordered. Yet, here is a large example of theopposite fluid evolution. Ingersoll concluded his talk with a refreshingresponse to a quite defensive question from a physicist threatened bythese implications: "Everything about Jupiter is astounding."BROADER IMPLICATIONSThe most recent theoretical work on the formation of large-scalestructure in turbulence (see Fusion, Dec. 1979, p. 24) is clearly divisiblein terms of the approach taken to the initial formation of vortex motion.The most common approach, a direct continuation of von Karman'soriginal work, assumes from the beginning that the vortices exist, and
Figure 2. Cylindrical projection of the Jovian atmosphere: This montage of photographs fromthe Voyager satellite shows dramatically the large-scale wavelike features on the planet. Theregular spacing of the cyclonic and anticyclonic storms, the fixed-wavelength ripples in thelatitudinal winds, and the latitudinally stratified flow are all striking. A length scale can beestimated by comparing the size of the Earth to the Great Red Spot, whose diameter is aboutthree times that of the Earth.Figure 3. Smaller-scale motions in the Jovian atmosphere: The atmosphere of Jupiter remainshighly structured on the smallest scales observable by Voyager. Here a magnification of the areasouthwest of the Great Red Spot is shown, in the wake generated by the storm. The highlyconvoluted flow is a beautiful example of structured turbulent flow in a high-Reynolds-numberfluid.30
Page 2 and 3: EDITORIALSTAFFEditorDr. Steven Bard
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