Loss of Energy due to Sudden Enlargement

Consider a pipe of cross-sectional area A₁and carrying a liquid of specific weight . It is connected to another pipe of larger cross-sectional area A₂(A₂>A₁). Since there is a sudden change in the cross-sectional area of flow passage, the liquid emerging from smaller pipe is unable to follow the abrupt change in boundary (Fig. 1). Consequently, the flow separates from the boundary, forming turbulent eddies that results in the loss of energy to be ultimately dissipated as heat. If p₁, V₁and p₂, V₂ respectively, are the pressures and velocities of flow of liquid in the narrower and wider pipe, then by continuity equation, the discharge is,

                                        
                                          Fig. 1: Flow through sudden enlargement in a pipe.