Abstract
This paper is directed at the important contribution to fluid dynamics made by Johan Nikuradze. His seminal paper published in 1933 represents the gold standard of empty conduit permeability, for the flow of water through roughened pipes, even to this very day. We revisit in some detail the “inflection profile” in Nikuradze’s plot, which appears in the curve for his roughened data found in Figure 9 in that publication. In so doing, we show that the data points at low Reynolds number values, and particularly those surrounding the value of 3.4 approximately on the x-axis of his plot, do not represent the reported experimental results found in his tables of data. Furthermore, we also demonstrate that this discrepancy in his original paper is very problematic because it forms the basis for many subsequent scholarly works. As a result, this inflection profile has become erroneously embedded in conventional folklore concerning fluid flow in closed conduits and has enjoyed widespread acceptance as being a legitimate feature of fluid dynamics dogma. With the advent recently of Quinn’s Law, a novel approach to the understanding of fluid flow in closed conduits, we are able to articulate in a manner not heretofore possible, the significance of this discrepancy which is far too important to ignore.
Highlights
We begin by defining the problem in Nikuradze’z original publication [1].which is a replica of Nikuradze’s plot, there are many plotted points below a value of 3.6 on the x-axis
We have demonstrated that the plotted data points which define the inflection profile are not reported in his tables of data and, in addition, our measurements confirm that there is no inflection in the curve
We have provided our own measurements to bolster our challenge to the Nikuradze plot and by incorporating those measurements into the Quinn Fluid Flow Model (QFFM), we have established a unified frame of reference within which we compared
Summary
We begin by defining the problem in Nikuradze’z original publication [1]. As shown in Figure 1 which is a replica of Nikuradze’s plot, there are many plotted points below a value of 3.6 on the x-axis. He describes the inflection point as follows; “The critical Reynolds number for all degrees of relative roughness occurs at about the same position as for the smooth pipe, that is, between 2160 and 2500”. This range of Reynolds number corresponds to a range of values of 3.33 to 3.39 on the x-axis of figure 9, which identifies precisely the inflection point in the curve for the plotted data points that we cannot account for in his tables of reported data. We show three photographs of the experimental set up; Figure 2 is the fluidics module; Figure 3 is the spool of Teflon tubing; Figure 4 is the electronics module and computer control unit
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