Validation of single- and two-equation models for transient mixed flows: a laboratory test case

The numerical simulation of transient mixed flows requires suitable mathematical models that must be validated by comparison with experimental data. For this reason, a simple benchmark test case is proposed in this paper. A laboratory study was carried out in a circular conduit, specifically designed to induce a strong pipe filling bore and repeated regime transitions following the sudden opening of an internal gate. No gates or weirs were installed at the pipe ends, and ventilated conditions were guaranteed. Measurements of both pressure head and velocity are provided as supplementary material. The test case was simulated by using two finite volume shock-capturing schemes: a classic Preissmann slot model, and a recent two-equation model. In both cases, numerical results are in good agreement with experimental data, despite the low pressure wave celerity assumed to minimize spurious oscillations. When realistic celerity values are adopted, the two-equation model appears to be more robust in handling flow regime transitions.