Verification Case 22
PRODUCT: AFT Impulse 9
TITLE: ImpVerify22.imp
REFERENCE: Liou, Jim C. P., Understanding Line Packing in Frictional Water Hammer, ASME, Journal of Fluids Engineering, August 2016, Vol. 138, Application Example
FLUID: Oil
ASSUMPTIONS: Closure is started at 20 seconds in both cases. Liou states valve Cv vs. time is known, but no curve is provided. It is assumed the valves close linearly over 60 or 180 seconds.
RESULTS:
DISCUSSION:
Liou states "Since the valve head loss is negligible relative to the pipe frictional head loss, the effective valve closure time is much shorter than the physical closure times. Therefore, an instantaneous closure of this valve can be assumed". This is essentially correct as an instantaneous closure results in essentially the same maximum head as the longer closure profiles. This is typically true for long pipelines with long communication times and insignificant valve head loss. Cv profiles should not be considered negligible if the closure time is greater than communication time or if the valve has significant head loss compared to pipe friction (major losses).
