chapter 12 hydraulic transient design for pipeline systems

12.8 Chapter Twelve
HYDRAULIC TRANSIENT DESIGN FOR PIPELINE SYSTEMS
FIGURE 12.4 Geometric and hydraulic characteristics of typical control valves
ing Joukowsky's equation—Eq. (12.2) or Eq. (12.3). In this case the velocity difference
∆V � 0 � V o , where V o is the initial velocity of liquid in the pipe. Although Eq. (12.2)
applies across every wavelet, the effect of complete valve closure over a period of time
greater than 2L/a, where L is the distance along the pipe from the point of wave creation
to the location of the first pipe area change, can be beneficial. Actually, for a simple
pipeline the maximum head rise remains that from Eq. (12.3) for times of valve closure
t c � 2L/a, where L is the length of pipe. If the value of t c � 2L/a, then there can be a considerable
reduction of the peak pressure resulting from beneficial effects of negative wave
reflections from the open end or reservoir considered in the analysis. The phenomenon
can still be classified as waterhammer until the time of closure t c �� 2L/a, beyond which
time there are only inertial or incompressible deceleration effects, referred to as surging,
also known as rigid column analysis. Table 12.2 classifies four types of valve closure,
independent of type of valve.
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