Numerical Modeling of Water Hammer Phenomenon in Hydropower Pipelines - A Case Study of Keyal Khawar Hydropower Plant

Abstract

This study aimed at development and application of a numerical model; WHPANM (Water Hammer Phenomenon Analysis Numerical Model), to investigate the water hammer phenomenon in the penstock of the Keyal Khawar hydropower plant in Khyber Pakhtunkhwa, Pakistan. The model, written in Visual Basic, utilized the numerical method of characteristics to solve the momentum and continuity water hammer equations. Results indicated that using a 2.2 m diameter pipe resulted in a maximum and minimum pressure head of 1462 m and 1420 m. Increasing the diameter to 3.0 m decreased the maximum pressure head to 1448 m, while the minimum pressure head increased to 1422 m. Conversely, decreasing the diameter to 1.0 m led to a maximum and minimum pressure head of 1522 m and 1363 m, respectively. Regarding pipe length, a standard length of 900 m maintained maximum and minimum pressure heads at 1462 m and 1420 m, respectively. Extending length to 1400 m increased maximum pressure head to 1485 m. Conversely, shortening length to 300 m resulted in a decreased maximum pressure head of 1436 m, with minimum pressure head remaining constant at 1420 m. To prevent water hammer damage in high head hydropower plants, study recommends utilizing a 2.2 m diameter penstock pipe and coordinating valve closure times accordingly. The study suggests a systematic design approach, optimal penstock diameter, and less rigid pipe materials to mitigate water hammer effects. The WHPANM model demonstrated strong concordance with the original data generated by the commercial software employed by the consultant for the Kyal Khwar hydropower plant.