as affected by Resistance to Flow. 139 



Assuming equation (I) of my note to remain unaltered, 

 the analysis is the same as before. The question then arises 

 as to the significance of the " Ic" term in the expression for 

 R, and the following is the explanation which occurs to me. 

 During flow through the meter the film of fluid next the 

 walls has been demonstrated experimentally to be at rest 

 relative to the walls. Is it not possible that during flow this 

 film is in a state of strain, tind so possesses resilient energy? 

 This will not he indicated in any way by a difference in head 

 between the entrance and throat of the meter, but at the 

 same time it may furnish a store of energy which is being 

 continually drawn upon and replenished during flow. 

 I should say that I am not implying that my resistance 

 equation is general. In form it may not even be correct, in 

 spite of the good agreement between the analytical and 

 experimental curves, but what is more important is that it 

 indicates genuine abnormal values of C to be possible. 



There are two opposing views with regard to these 

 abnormal values of C. The one view is to look upon the 

 values of h, the manometer head, as having been affected by 

 errors of observation or by instrumental deficiencies. The 

 other view is that such abnormal values of C are due to the 

 incompleteness of our knowledge of the behaviour of actual 

 fluids in motion, so that when the usual incomplete analysis 

 is applied, the abnormal results follow. 1 take the latter view. 



The following * are the most recent results published 

 giving abnormal values of C, and are interesting as the first 

 record made of results on a Venturi flume. This is con- 

 structed on the same principle as a Venturi meter, with the 

 difference that the former possesses a free surface : — 



H. lit. G. 



•178 -025 '983 



•112 -010 1000 



•063 -002 1-036 



•038 --002 1-112 



•025 -003 1-211 



•017 --004 1-320 



•014 -001 1-384 



•010 — 1-411 



•0105 1-678 



•007 — 1-800 



H = head at entrance in feet of water. 

 H*==head at throat in feet of water. 



The authors of the paper give no analytical explanation 

 of these results, but state that they appear to be due to wave 

 formation. Yours truly, 



Mechanical Engineering: Dept., Wm. J. ^ A.LKER. 



College of Technology, Manchester. 

 21st March, 1921. 



* Engineering News Record, 1920, p, 452. 



