Liquids in motion produce forces whenever the velocity or flow direction changes. The forces produced by changes in direction of fluid is called hydrodynamic forces and is equal to (density of fluid x discharge x change in flow velocity).
In underground pressurized pipelines, the configuration of pipelines causes unbalanced forces of hydrostatic and hydrodynamic and joint separation shall result if these forces are not properly balanced. In general, the unbalanced hydrostatic and hydrodynamic forces are called thrust forces. In normal applications of pressurized pipelines in wastewater works and waterworks, it is observed that the range of fluid velocity and discharge is quite limited. As such, the resulting unbalanced hydrodynamic forces induced are insignificant when compared with unbalanced hydrostatic forces and they are often neglected in the design of thrust blocks.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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