Seyer and Metzner 



I am not very familiar with the equations of fluid dynamics, having recently 

 entered the field to apply a new measurement technique we have developed. With 

 this technique we have thus far measured, I believe for the first time, the instan- 

 taneous thickness and velocity profile for the laminar region at the wall in tur- 

 bulent pipe flow. I would judge that the equations presented in this and the pre- 

 ceding paper are largely either empirical or semiempirical (the form specified 

 by some theory, but the constants fitted to experiment) and that, therefore, ac- 

 curate time-continuous experimental data on the stress and rate of strain rela- 

 tionships for these fluids is required — possibly to verify the theoretical form of 

 the equations and certainly to provide the constants which would determine the 

 detailed behaviour of the fluid. This paper indicates that the standard hot wire 

 or hot probe results for fluid velocity are highly questionable due to expected 

 but unknown effects of the non -Newtonian fluid on the probe. When one further 

 considers that in Newtonian flow corrections are frequently necessary which 

 were not originally expected, such as, for example, the effect of small-scale- 

 turbulence intensity on the heat transfer veiocity relationship. Furthermore all 

 probes tend to disturb the flow for measurements near a wall, which may be the 

 region where drag reduction occurs with these unique solutions. Our new tech- 

 nique involves the instantaneous introduction of a very fine dye tracer at any 

 angle to the flow, including perpendicular, without disturbing the flow. It will 

 permit continuous and accurate determinations of the liquid strain rate (velocity 

 profiles). I would welcome suggestions as to experimental conditions. 



REPLY TO DISCUSSION 



A. B. Metzner 



Professor Hummel correctly emphasizes the inconsistencies between the 

 several approaches available at the present time for interpretation of the turbu- 

 lent drag reduction effects noted in viscoelastic fluids. The suggestion that 

 local strain rate measurements in such turbulent systems would be of much in- 

 terest is obviously a good one, and he is to be encouraged to both carry out such 

 studies, if he has an interest in them, or make the details of his experimental 

 technique available to others who may have an interest in it. 



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