![]() It is a practice in engineering design that when a large object such as a ship, airplane, or building is to be made, a scale model is constructed and tested so that the performance of the large object can be calculated from the test results of the scale model.Lord Rayleigh has shown that it is a non-dimensional factor which governs all problems on fluid flow frictional resistance, and that similar non-dimensional constants exist for many other natural phenomena. The full implications of the Reynolds number were never realized by Reynolds who considered the ratio merely as a criterion for the critical velocity in pipe flow.For intermediate Reynolds numbers the flow is transitional - partly laminar and partly turbulent.For high Reynolds numbers the momentum of the fluid determines its behavior more than the viscosity and the flow is unsteady, churning, roiling, or turbulent and n = 2.For low Reynolds numbers the behavior of a fluid depends mostly on its viscosity and the flow is steady, smooth, viscous, or laminar and n = 1. ![]() The slope of the line of best fit on a log-log graph is the power ( n) relating the explanatory variable (flow speed) to the response variable (pressure gradient). Log-log graph of pressure gradient ( ∆ P/∆ d) vs. Compare pressure losses due to viscous friction with flow speed through a horizontal pipe. ![]() ![]()
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