Effects of Surge Tank Geometry on the Water Hammer Phenomenon: Numerical Investigation

Abstract

A surge tank, as one of the most common control facilities, is applied to control head pressure levels in long pressurized pipelines during the water hammer occurrence. The cost-effective operation of surge tanks is highly affected by their characteristics (i.e., surge tank diameter and inlet diameter of surge tanks) and can effectively reduce the repercussion of water hammers. This investigation utilized the method of characteristics (MOC) in order to simulate the behavior of transient flow at the surge tank upstream and the head pressure fluctuations regime for the hydraulic system of a hydropower dam. Firstly, the MOC model was validated by experimental observations. The various types of boundary conditions (i.e., sure tank, reservoir, branch connection of three pipes, series pipes, and downstream valve) were applied to investigate the simultaneous effects of the surge tank properties. In this way, all the simulations of water hammer equations were conducted for nine various combinations of surge tank diameter (D) and inlet diameter of surge tank (d). The results of this study indicated that for the surge tank design with D = 6 m and d = 3.4 m, head pressure fluctuations reached the minimum level in the large section of the pipeline which is the surge tank upstream. Additionally, the occurrence of the water hammer phenomenon was probable in the initial section of the pipeline.

Study on Influence of Flow Inertia of Pressure Pipe on Critical Stable Sectional Area of Surge Tank

“…In the process of calculating the analytical formula of the critical stable section area of the surge tank, all the formulas for calculating the critical stable section area of the surge tank including Thoma's formula and E/N correction formula ignore the influence of the flow inertia in the pressure pipe (expressed by the time constant of the flow inertia in the pressure pipe Te) [1][2][3] . To analyze the influence of Te on the critical stable section area of the surge tank, after considering Te being the inertia time constant of the flow in the pressure pipe, a fifth-order analytical model of the hydraulic turbine generator set with the surge tank is derived.…”