Loss of Energy due to Gradual Contraction or Enlargement

The energy loss due to sudden contraction of enlargement can be minimized substantially by gradual decrease or increase in area of cross-section of the flow because the dissipation of energy due to turbulent eddies will be eliminated. In such case, the head loss is expressed as,

                                                                                (8)

where V₁ and V₂ are the mean velocities at the inlet and outlet; k is the loss coefficient whose value depends on the angle of convergence/divergence and cross-sectional areas at the upstream and downstream respectively.

Loss of Energy in Bends

The bends are provided in a flow passage to change the direction of the flow. This causes the loss of energy due to flow separation from the boundary and subsequent formation of turbulent eddies. In general, the head loss may be expressed as,

                                                                                           (9)