Numerical Analysis of Pipeline Equipment Effect on Water Hammer Using Characteristic Method

Abstract

In this attempt effect of pipeline equipment behavior was considered on water hammer numerically. The effect includes opening / closing of the shut off valves, loss of coefficient of the outlet bypass pipe for the air chamber, elasticity of the pipeline and loss coefficient due to friction. In order to study the behavior, mass and momentum conservation equations were solved numerically using characteristic method during transient conditions. As a water hammer phenomena accompanies with large pressure gradient, so the pipeline equipment behavior and their effect were analyzed with respect to the maximum pressure occurrence. For a pipeline of 5000 m length, 1 m diameter, 1 m3/s discharge and 100 m height between upstream and downstream, the following result were concluded: 1-If the moment of inertia of the pump impeller increases by 400 percent, the maximum pressure occurred by the water hammer will decrease by 9 percent. 2-During on and off of the shut off valve, 80 percent of pressure increase due to water hammer was created during the last 15 percent of valve closure. 3-If pressure wave velocity increases by 75 percent, then the maximum pressure generated due to the water hammer will increase by 27 percent. 4-If the loss coefficient of the by pass line of the air chamber decreases by 90 percent, then the maximum pressure due to the water hammer will decrease by 20 percent. 5-If the pipeline Moody friction coefficient increases by 92 percent, the maximum pressure due to the water hammer will increase by 66 percent.