ABSTRACT
By either integrating the microscopic momentum equations or applying a momentum balance to a "slug" of fluid in the center of the conduit as was done for tube flow, a relationship can be determined between flow rate and driving force for laminar flow in a conduit with a noncircular cross section. The effect of geometry on the flow field for turbulent flows is much less pronounced than for laminar flows. This is because the majority of the energy dissipation or flow resistance occurs within the boundary layer which, in typical turbulent flows, occupies a relatively narrow region of the total flow field near the boundary. The most reliable method is to measure the total pressure drop through a long run of pipe both with and without the fitting, at the same flow rate, and determine the fitting loss by difference.
