Lumley 



appears likely that the techniques that change the structure of the turbulent 

 boundary layer offer the most promise. The limits of what can be done with 

 these techniques have still to be determined, however. 



REPLY TO THE DISCUSSION 



J. L. Lumley 



The Pennsylvania State University 

 University Park, Pennsylvania 



I wish to thank Professors Karlsson, Kistler and Eringen for their helpful 

 comments. I feel that in particular the preliminary data presented by Karlsson 

 indicates the caution with which one must use one's intuition in this very difficult 

 problem. The contribution by Eringen will be somewhat more difficult to assess 

 until turbulence dynamics have been worked out using the constitutive relations 

 he suggests. Since the turbulence dynamics of non-Newtonian media in general 

 are not understood, it is difficult to say whether constitutive relations fitting 

 within the framework of the simple fluid of Noll" are adequate, or whether a 

 locally orientable medium such as that proposed is required. The comments of 

 Kistler seem particularly germane to the paper of Vogel and Patterson and sug- 

 gest caution in the interpretation of their measurements in the near wake. 



-Noll. W., Archiv. Rat. Mech." Anal. _2, (1958), 197. 



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