Numerical investigation of the pressure-time method

The flow rate is a challenging hydrodynamic parameter to measure in order to determine turbine efficiency. The pressure-time method is a cost-effective alternative to estimate the flow rate. Its principle is based on the transformation of momentum into pressure during the deceleration of the liquid mass. Numerical simulations give valuable information to develop the method. One of the challenges in the numerical study of the pressure-time method is modelling the valve movement. In previous numerical studies, the dynamic mesh has been used for valve closure modelling. The dynamic mesh may lead to divergence, and re-meshing makes this method more time-consuming. In this paper, the valve closure is modelled considering immersed solid method. The results' sensitivity is studied by different time-step, grid, and boundary conditions at the inlet. It is shown that the result is independent of the time-step size smaller than 0.1 ms. Furthermore, it is observed that only the opening boundary condition at the inlet can predict the oscillation of variables during water hammer phenomenon. Then, the numerical results are validated with experimental data. Finally, the pressure-time method is applied to the data, and the flow rate is estimatedFunder: Elforsk; Svenska KraftnätSwedish Hydropower Centre—SV