*Article* **Experimental and Numerical Analysis of a Water Emptying Pipeline Using Different Air Valves**

### **Oscar E. Coronado-Hernández 1,2,\*, Vicente S. Fuertes-Miquel 2, Mohsen Besharat 3,4 and Helena M. Ramos 4**


### Academic Editor: Arjen Y. Hoekstra

Received: 5 December 2016; Accepted: 3 February 2017; Published: 8 February 2017

**Abstract:** The emptying procedure is a common operation that engineers have to face in pipelines. This generates subatmospheric pressure caused by the expansion of air pockets, which can produce the collapse of the system depending on the conditions of the installation. To avoid this problem, engineers have to install air valves in pipelines. However, if air valves are not adequately designed, then the risk in pipelines continues. In this research, a mathematical model is developed to simulate an emptying process in pipelines that can be used for planning this type of operation. The one-dimensional proposed model analyzes the water phase propagation by a new rigid model and the air pockets effect using thermodynamic formulations. The proposed model is validated through measurements of the air pocket absolute pressure, the water velocity and the length of the emptying columns in an experimental facility. Results show that the proposed model can accurately predict the hydraulic characteristic variables.

**Keywords:** air-water; air pocket; air valve; hydraulic model; pipeline; emptying; water supply; water hammer
