Rigid model for transient flow in pressurized pipe system containing trapped air mass

The mathematical analysis shows that,with disregarding local head losses and by means of different simplified rigid models,the calculated results of the maximum pressure in a pressurized pipe system containing trapped air mass are equal to and independent of the initial length of the water-column.However,the calculation examples in this paper indicate that,if the initial water-column length is relatively short or the volume of the trapped gas is very small,the calculation error may be significant and even leads to a false conclusion.Therefore a complete rigid model is then presented in this paper,along with its theoretical limitation and suitable application terms.