. The roughness of the pipe acts as a barrier to the flow, as water molecules trap themselves on the surface of the pipe, resisting the flows movement. Therefore, as care has been taken to minimisze the effects of other potential energy loss factors, it can be assumed that all energy loss in this experiment is as a result of the relative roughness of the pipe and the equations for the frictional factor can be used (see equation 3 and 4). As this assumption is for an ideal setting, slight variations of the experimental and theoretical values of the friction factor can be accounted for, as well as through the effects of experimental error, which will be discussed shortly.
The values of a frictional factor were determined theoretically, through analysis of a moody chart. Values of Reynold’s' number were identified and used with the value of 0.0005 (See Appendix C 2.1), and relative roughness of the pipe to determine values of the frictional factor at different points (See Figure 3). As there was a strong relationship between the experimental and theoretical values of the frictional factor found (See Figure 4), it can be inferred that the calculations and theory used during this experiment isare correct. From visual inspection of Figure 4, there is a general exponential decrease of the friction factor with an increase of Reynold’s' number. It is to be noted that this does not mean, however, that there is a decrease in actual friction force with higher velocity/ higher Reynold’s' number.
Regardless of the strong relationship between experimental and theoretical values of frictional factors found errors during this experiment can account for any deviations. As values were obtained visually for both the volume of water gathered and the values of head on the monometers (h1 and h2), parallax error would have resulted. In addition, the time taken to fill a certain amount could have been automated through the use of a scale, as the density of water is known. These errors aforementioned would have accounted for the majority of the discrepancies between experimental and theoretical results found. Errors arising from the equipment itself, although minimal in comparison to those previously mentioned, still contribute to the overall error introduced. The tolerances of the piezometers, pump, diameter, and surface roughness would have aided in skewing the results.