Experimental and numerical investigations of water hammer analysis in pipeline with two different materials and their combined configuration

Water conductor system in hydro power plants experience water hammer or hydraulic transient events regularly and may cause damage of civil and mechanical components. Recently developed viscoelastic pipes such as Glass Reinforced Fibre Plastic (GRP) have been started in use to replace metallic pipes in hydro power and water supply plants. However, studies on combinations of metallic-viscoelastic pipeline behaviour for water hammer conditions are limited especially for varied diameter and combinations of different pipe materials. In this paper, the response of water hammer pressure in metallic-viscoelastic pipeline is investigated experimentally and numerically. Two different pipe materials i.e. Mild Steel (MS) and GRP and their metallic-viscoelastic pipe configuration was used to investigate and analyze the water hammer pressure generation and compared with pressure developed in single material pipeline. An experimental setup was designed and fabricated to carry out the water hammer test. The numerical simulation was carried out by using the method of characteristics (MOC). The GRP pipeline was found more effective to reduce the water hammer pressure and a combination of GRP + MS pipeline (GRP for initial reach having low pressure and MS for later reach having high pressure) in the plants, where GRP pipeline alone cannot be used due to manufacturing limitations of pressure and size, can be used to reduce transient pressure in the water conductor system.