Localized loss, also known as minor loss or local pressure loss, refers to the pressure drop or decrease that occurs at specific points or components within a fluid flow system. These points of localized loss are typically associated with sudden changes in geometry, flow direction, or the presence of flow disturbances such as fittings, valves, bends, expansions, contractions, or other obstructions.
Unlike friction loss, which is primarily due to the overall pipe length and surface friction, localized losses are specific to certain locations or elements in the system. They result from changes in the flow profile, the generation of turbulence, vortices, or eddies, and additional energy dissipation in the fluid. The magnitude of localized losses depends on various factors, including the geometry and characteristics of the specific component or location, the flow velocity, fluid properties, and the smoothness of the surfaces. These losses are often quantified using experimentally derived coefficients or pressure loss correlations specific to the type of component or flow disturbance.
Accounting for localized losses is essential in system design, hydraulic calculations, and equipment selection. It helps ensure accurate estimation of pressure drops, determination of flow rates, and proper sizing and operation of components to maintain desired system performance. Various techniques, such as using smooth transitions, streamlined designs, or specific fittings designed to minimize localized losses, can be employed to mitigate their effects in fluid flow systems.