The Numerical Simulation Of Local Head Losses In Common Pipes

In hydraulic engineering, the calculation of the local head losses when the flow passes through pipes in a sudden change is a common problem. In the actual engineering calculations, the local head loss coefficient in hydraulics book or hydraulic manual is constant, or a value calculated by a certain empirical formula, but the influence of the flow pattern to the coefficient isn't considered. However the actual local head loss coefficient changes along with Reynolds number, when the flow is at a high Reynolds number, the flow is in rough area, the local head loss coefficient can be regarded as only being concerned with its geometry, while the flow is at a low Reynolds number, using the same coefficient would make obvious error. But existing information and researches in the problem is less, so it is necessary to study it.In this paper, the three-dimensional k-εturbulent model was used to simulate eleven types of common pipe. By changing their geometry, the effect of the change of the pipeline geometry on the flow pattern and the local head losses was analyzed, the result of the analysis shows the change rule between the local head loss coefficient and the Reynolds number, and the change curve between the local head loss coefficient and the Reynolds number were drawn.For one pipe, the local head loss coefficient would gradually decrease and then tend to become a certain value along with Re, its change curve was similar to a power function, when its geometry (such as angle, diameter ratio, opening degree of gate valve, etc.) was changed, the greater the change in its size and the pipeline flow pattern was, the greater the local head loss coefficient was. For gate valve, the greater the opening degree was, the greater the local head loss was, and the smaller the change of the local head loss coefficient with Re was. Finally, the simulation results with the empirical values in hydraulic manual were compared.