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<br />, <br />I <br />--------', <br />L <br />~~-C--".-t <br />----~ <br />, <br /> <br />CHAPTER 2. EQUATIONS FOR STEADY GRADUALLY VARIED FLOW <br /> <br />Section 2.01. The On~Dimensional Energy Equation <br /> <br />'. <br /> <br />Water at rest exerts a hydrostatic pressure upon the solid bounda- <br />ries which contain it and, like a solid body at rest, possesses a cer- <br />tain potential energy due to the vertical height of that solid boundary <br />above some datum such as mean sea level. If the pressure on the water <br /> <br />surface is atmospheric (i.e., the water has a 'free' surface and is not <br /> <br />confined by the roof of a pipe). the total energy at each point is the <br /> <br /> <br />potential energy plus the pressure energy due to the weight of water <br /> <br /> <br />above that point. Should this water begin to flow. part of the total <br /> <br /> <br />energy would be converted to kinetic energy, and part of it used to <br /> <br /> <br />overcome friction and other losses. Water surface profile computation <br /> <br /> <br />is based on application of an analytical procedure to calculate quantities <br /> <br /> <br />for each of these energy components. The principles of conservation <br /> <br /> <br />of energy and conservation of mass are involved in the analytical pro- <br /> <br /> <br />cedure. <br /> <br />The basic relationship describing the conservation of energy of <br /> <br /> <br />any mass being moved between two points is: <br /> <br />E2 + WORK = El + 6E <br /> <br />(2-1 ) <br /> <br />where: <br /> <br />El = the total energy at pOint 1 <br /> <br />2.01 <br />