Numerical investigation of the pipe length determination in branched systems by transient tests

The integration of the transient governing equations in the frequency domain yields models that are particularly suited for the inverse analysis in pressurized pipe networks. In these models, the pipe lengths can be considered as any other parameters, such as wave speeds, diameters or friction factors and hence can be estimated by the solution of the inverse problem, i.e. by a calibration. In this paper, a calibration procedure that considers the pipe length as parameters is introduced. Several aspects of the procedure are examined, such as the use of an appropriate frequency domain numerical model and optimization algorithm. The coupling of the admittance matrix method with a combination of genetic and Nelder-Mead algorithms is analyzed and tested on numerical data, considering both elastic and viscoelastic material pipes. The results of the presented numerical investigation allow to give some insights about the existence of the solution and to show that the outlined procedure can be used to successfully estimate the lengths of the pipe in a network.