Turbulent Transport 



W. V. R. MALKUS 



Woods Hole Oceanographic Institution. Woods Hole, Massachusetts 



Turbulence versus Turbulent Transport 



HOW often the word "turbulent" is used to mask ignorance of a 

 fluid dynamical process! A casual inspection has revealed apparent 

 disorder in space and time. The conclusion is that the process is a 

 random one. "Turbulent transport," on the other hand, suggests 

 that something has occurred as a consequence of the turbulence; 

 hence, such turbulence must have a certain average order and 

 cannot be completely random. I believe that almost all the tur- 

 bulence encountered in nature is transporting something. In fact, 

 I believe that the turbulence is there primarily to effect such 

 transport. 



In the fiuid world the most obvious turbulent transports are of 

 mass, momentum, and heat. Why does the geophysical fluid prefer 

 turbulent transport to the molecular processes of transport seen in 

 laboratory phenomena? The reason usually given is that the steady 

 laminar flows of the laboratory are stable against arbitrary disturb- 

 ances and return to their original configurations, but that large- 

 scale flows are unstable to disturbances and break up into "eddies." 

 Hence we may conclude that the resulting turbulence is the fluid's 

 way of reestablishing its stability. Though turbulent may seem to 

 many the very opposite of stable, fluids can and do achieve "sta- 

 tistical stability" by means of the turbulent transport of heat and 

 momentum. One explanation of the statistical stability achieved by 

 turbulent transport is that by redistributing heat and momentum 

 the fluid reduces the energy sources of the instabilities which led to 

 turbulence. However, any simple explanation of such a complicated 

 process as statistical stability must be treated as suspect. 



At the Woods Hole Oceanographic Institution I seek to isolate 



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