Experimental setup of entrapped air pockets model validation

In this paper analytical and experimental results are presented for the study of entrapped air pockets in a pipeline of irregular profile. The analytical results are obtained from a general model, presented by the authors in previous works, based on a liquid and pipe rigid approach and assuming for the gas a polytropic compression decompression behaviour. Laboratory results show, for a polytropic index n = 1.4, a very good agreement with theoretical results until the filling column reaches the highest point of the pipe. From that point, and due to the failure of the basic hypothesis, a well-defined air-water cross section interface, the discrepancies are relevant.