Concept of Flow Potential and Flow Resistance

• Consider the flow of water from one reservoir to another as shown in Fig. 35.3. The two reservoirs A and B are maintained with constant levels of water. The difference between these two levels is as shown in the figure. Therefore water flows from reservoir A to reservoir B .

Fig 35.3 Flow of liquid from one reservoir to another

• Application of Bernoulli's equation between two points A and B at the free surfaces in the two reservoirs gives

	(35.10)

where is the loss of head in the course of flow from A to B .

• Therefore, Eq. (35.10) states that under steady state, the head causing flow becomes equal to the total loss of head due to the flow.
  
• Considering the possible hydrodynamic losses, the total loss of head can be written in terms of its different components as
  

				(35.11)
	Loss of heat at entry to the pipe from reservoir A	Friction loss in pipe over its length L	Exit loss to the reservoir B

where, V is the average velocity of flow in the pipe.